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1.	Ade, P. A. R., et al. (author) A Constraint on Primordial B-modes from the First Flight of the Spider Balloon-borne Telescope 2022 In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 927:2 Journal article (peer-reviewed)abstract We present the first linear polarization measurements from the 2015 long-duration balloon flight of SPIDER, which is an experiment that is designed to map the polarization of the cosmic microwave background (CMB) on degree angular scales. The results from these measurements include maps and angular power spectra from observations of 4.8% of the sky at 95 and 150 GHz, along with the results of internal consistency tests on these data. While the polarized CMB anisotropy from primordial density perturbations is the dominant signal in this region of sky, Galactic dust emission is also detected with high significance. Galactic synchrotron emission is found to be negligible in the SPIDER bands. We employ two independent foreground-removal techniques to explore the sensitivity of the cosmological result to the assumptions made by each. The primary method uses a dust template derived from Planck data to subtract the Galactic dust signal. A second approach, which constitutes a joint analysis of SPIDER and Planck data in the harmonic domain, assumes a modified-blackbody model for the spectral energy distribution of the dust with no constraint on its spatial morphology. Using a likelihood that jointly samples the template amplitude and r parameter space, we derive 95% upper limits on the primordial tensor-to-scalar ratio from Feldman-Cousins and Bayesian constructions, finding r < 0.11 and r < 0.19, respectively. Roughly half the uncertainty in r derives from noise associated with the template subtraction. New data at 280 GHz from SPIDER´s second flight will complement the Planck polarization maps, providing powerful measurements of the polarized Galactic dust emission.
2.	Ade, Peter, et al. (author) The Simons Observatory : science goals and forecasts 2019 In: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :2 Journal article (peer-reviewed)abstract The Simons Observatory (SO) is a new cosmic microwave background experiment being built on Cerro Toco in Chile, due to begin observations in the early 2020s. We describe the scientific goals of the experiment, motivate the design, and forecast its performance. SO will measure the temperature and polarization anisotropy of the cosmic microwave background in six frequency bands centered at: 27, 39, 93, 145, 225 and 280 GHz. The initial con figuration of SO will have three small-aperture 0.5-m telescopes and one large-aperture 6-m telescope, with a total of 60,000 cryogenic bolometers. Our key science goals are to characterize the primordial perturbations, measure the number of relativistic species and the mass of neutrinos, test for deviations from a cosmological constant, improve our understanding of galaxy evolution, and constrain the duration of reionization. The small aperture telescopes will target the largest angular scales observable from Chile, mapping approximate to 10% of the sky to a white noise level of 2 mu K-arcmin in combined 93 and 145 GHz bands, to measure the primordial tensor-to-scalar ratio, r, at a target level of sigma(r) = 0.003. The large aperture telescope will map approximate to 40% of the sky at arcminute angular resolution to an expected white noise level of 6 mu K-arcmin in combined 93 and 145 GHz bands, overlapping with the majority of the Large Synoptic Survey Telescope sky region and partially with the Dark Energy Spectroscopic Instrument. With up to an order of magnitude lower polarization noise than maps from the Planck satellite, the high-resolution sky maps will constrain cosmological parameters derived from the damping tail, gravitational lensing of the microwave background, the primordial bispectrum, and the thermal and kinematic Sunyaev-Zel'dovich effects, and will aid in delensing the large-angle polarization signal to measure the tensor-to-scalar ratio. The survey will also provide a legacy catalog of 16,000 galaxy clusters and more than 20,000 extragalactic sources.
3.	Bambi, Cosimo, et al. (author) Testing the rotational nature of the supermassive object M87from the circularity and size of its first image 2019 In:* Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 100:4 Journal article (peer-reviewed)abstract The Event Horizon Telescope (EHT) collaboration has recently released the first image of a black hole (BH), opening a new window onto tests of general relativity in the strong field regime. In this paper, we derive constraints on the nature of M87* (the supermassive object at the center of the galaxy M87), exploiting the fact that its shadow appears to be highly circular, and using measurements of its angular size. We first consider the simple case where M87* is assumed to be a Kerr BH. We find that the inferred circularity of M87* excludes Kerr BHs with observation angle theta(obs) greater than or similar to 45 degrees for dimensionless rotational parameter 0.95 less than or similar to a() <= 1 whereas the observation angle is unbounded for a() less than or similar to 0.9. We then consider the possibility that M87* might be a superspinar, i.e., an object described by the Kerr solution and spinning so fast that it violates the Kerr bound by having vertical bar a()vertical bar > 1. We find that, within certain regions of parameter space, the inferred circularity and size of the shadow of M87 do not exclude the possibility that this object might be a superspinar.
4.	Baum, Sebastian, 1990- (author) Dark Matter, Ancient Rocks, a Band of Higgs Bosons, and a Big Collider : or, Models of New Physics and Some Ways to Probe Them 2019 Doctoral thesis (other academic/artistic)abstract The past ~ 50 years have seen a remarkable success of particle physics. In the 1970s, the Standard Model was formulated and in 2012 its final ingredient, the Higgs boson, was discovered at the Large Hadron Collider (LHC). The Standard Model describes virtually all particle physics observable in the laboratory. However, despite this success, the Standard Model has a number of shortcomings. Some problems stem from its mathematical structure, most famously the hierarchy problem. Further, the Standard Model fails to describe the composition of our Universe, for example, it cannot explain the observed Dark Matter. Thus, the need for physics beyond the Standard Model is clear. A long series of experiments has been conducted to search for this new physics. Alas, these experiments came up empty handed.This thesis discusses two lines of work: 1) Arguably, the Higgs sector of the Standard Model is its least constrained part and simultaneously intimately related to many of the Standard Model's shortcomings. We discuss models extending the Higgs sector, both in a general and in a supersymmetric setting, and how they can be probed at the LHC. 2) A century after the first evidence for Dark Matter emerged, we still don't know what it is made up of. We discuss some models for Dark Matter, including axions and a particular model for Weakly Interacting Massive Particle (WIMP) Dark Matter. Then, we present some methods to search for WIMP Dark Matter, focusing on paleo-detectors, a proposed method where one would search for the traces of WIMP-nucleus interactions left in ancient minerals.
5.	Baum, Sebastian, et al. (author) Dark matter capture, subdominant WIMPs, and neutrino observatories 2017 In: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 95:4 Journal article (peer-reviewed)abstract Weakly interacting massive particles (WIMPs), which are among the best motivated dark matter (DM) candidates, could make up all or only a fraction of the total DM budget. We consider a scenario in which WIMPs are a subdominant DM component; such a scenario would affect both current direct and indirect bounds on the WIMP-nucleon scattering cross section. In this paper we focus on indirect searches for the neutrino flux produced by annihilation of subdominant WIMPs captured by the Sun or the Earth via either spin-dependent or spin-independent scattering. We derive the annihilation rate and the expected neutrino flux at neutrino observatories. In our computation, we include an updated chemical composition of the Earth with respect to the previous literature, leading to an increase of the Earth's capture rate for spin-dependent scattering by a factor of 3. Results are compared with current bounds from Super-Kamiokande and IceCube. We discuss the scaling of bounds from both direct and indirect detection methods with the WIMP abundance.
6.	Baum, Sebastian, et al. (author) Dark Matter implications of DAMA/LIBRA-phase2 results 2019 In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 789, s. 262-269 Journal article (peer-reviewed)abstract Recently, the DAMA/LIBRA collaboration released updated results from their search for the annual modulation signal from Dark Matter (DM) scattering in the detector. Besides approximately doubling the exposure of the DAMA/LIBRA data set, the updated photomultiplier tubes of the experiment allow a lower recoil energy threshold of I keV electron equivalent compared to the previous threshold of 2 keV electron equivalent. We study the compatibility of the observed modulation signal with DM scattering. Due to a conspiracy of multiple effects, the new data at low recoil energies is very powerful for testing the DM hypothesis. We find that canonical (isospin conserving) spin-independent DM-nucleon interactions are no longer a good fit to the observed modulation signal in the standard halo model. The canonical spin independent case is disfavored by the new data, with best fit points of a DM mass of similar to 8 GeV, disfavored by 5.2 sigma, or a mass of similar to 54GeV, disfavored by 2.5 sigma. Allowing for isospin violating spin independent interactions, we find a region with a good fit to the data with suppressed effective couplings to iodine for DM masses of similar to 10 GeV. We also consider spin-dependent DM-nucleon interactions, which yield good fits for similar DM masses of similar to 10 GeV or similar to 45 GeV.
7.	Baum, Sebastian, et al. (author) Determining dark matter properties with a XENONnT/LZ signal and LHC Run 3 monojet searches 2018 In: Physical Review D. - 2470-0010 .- 2470-0029. ; 97:8 Journal article (peer-reviewed)abstract We develop a method to forecast the outcome of the LHC Run 3 based on the hypothetical detection of O(100) signal events at XENONnT. Our method relies on a systematic classification of renormalizable single-mediator models for dark matter-quark interactions and is valid for dark matter candidates of spin less than or equal to one. Applying our method to simulated data, we find that at the end of the LHC Run 3 only two mutually exclusive scenarios would be compatible with the detection of O(100) signal events at XENONnT. In the first scenario, the energy distrib ution of the signal events is featureless, as for canonical spin-independent interactions. In this case, if a monojet signal is detected at the LHC, dark matter must have spin 1/2 and interact with nucleons through a unique velocity-dependent operator. If a monojet signal is not detected, dark matter interacts with nucleons through canonical spin-independent interactions. In a second scenario, the spectral distribution of the signal events exhibits a bump at nonzero recoil energies. In this second case, a monojet signal can be detected at the LHC Run 3; dark matter must have spin 1/2 and interact with nucleons through a unique momentum-dependent operator. We therefore conclude that the observation of O(100) signal events at XENONnT combined with the detection, or the lack of detection, of a monojet signal at the LHC Run 3 would significantly narrow the range of possible dark matter-nucleon interactions. As we argued above, it can also provide key information on the dark matter particle spin.
8.	Baum, Sebastian (author) Exploring particle physics beyond the Standard Model 2017 Licentiate thesis (other academic/artistic)abstract The standard model of particle physics (SM) is arguably the best tested theory of physics, providing an accurate description of virtually all high energy particle physics phenomena observable in the laboratory. However, the SM also has a number of shortcomings: some of more theoretical nature such as the fine-tuning problem of the Higgs or the strong-CP problem, and some of more phenomenological nature such as not allowing for a satisfying implementation of neutrino masses and the lack of a suitable candidate for the observed dark matter of the Universe.The SM’s shortcomings have motivated the development of a large number of beyond the SM (BSM) particle physics models. However, no (conclusive) evidence for any BSM model has been found to date. The papers included in this thesis study different approaches to search for BSM physics:In [I], we studied bounds on weakly interacting massive particle (WIMP) DM models arising from the absence of neutrino signals from DM capture and subsequent DM pair-annihilation in dense astrophysical objects such as the Sun or the Earth. We interpreted these bounds in a model independent fashion, focusing in particular on the scaling of the bounds for the case where WIMPs comprise only a sub-dominant component of the DM. We also used a chemical composition of the Earth updated with respect to the previous literature, strengthening the bound on spin-dependent interactions from capture and annihilation in the Earth by approximately a factor 3.In [II], we studied the collider phenomenology of one particular BSM model, the next-to-minimal supersymmetric standard model (NMSSM). In particular, we focused on 1) the impact of the presence of the 125 GeV SM-like Higgs boson on the NMSSM parameter space, 2) the identification of NMSSM specific search channels at the LHC which allow to effectively probe the NMSSM parameter space allowed by more conventional searches, and 3) an in-depth study of one of these search channels, the mono-Higgs signature. As shown in [II], this channel allows to probe the low tan β , large m_A regime which is difficult to probe with conventional searches, and in contrast to many conventional Higgs searches, the reach of the mono-Higgs channel improves significantly with the increased luminosity expected to be collected at the LHC in current and future runs.
9.	Baum, Sebastian, et al. (author) NMSSM Higgs boson search strategies at the LHC and the mono-Higgs signature in particular 2017 In: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 95:11 Journal article (peer-reviewed)abstract We study the collider phenomenology of the extended Higgs sector of the next-to-minimal supersymmetric Standard Model (NMSSM). The region of NMSSM parameter space favored by a 125 GeV SM-like Higgs and naturalness generically features a light Higgs and neutralino spectrum as well as a large O(1) coupling between the Higgs doublets and the NMSSM singlet fields. In such regimes, the heavier Higgs bosons can decay dominantly into lighter Higgs bosons and neutralinos. We study the prospects of observing such decays at the 13 TeV LHC, focusing on mono-Higgs signatures as probes of such regions of parameter space. We present results for the mono-Higgs reach in a framework easily applicable to other models featuring similar decay topologies. In the NMSSM, we find that the mono-Higgs channel can probe TeV scale Higgs bosons and has sensitivity even in the low tan beta, large m(A) regime that is difficult to probe in the MSSM. Unlike for many conventional Higgs searches, the reach of the mono-Higgs channel will improve significantly with the increased luminosity expected to be collected at the LHC in the ongoing and upcoming runs.
10.	Baum, Sebastian, et al. (author) Paleodetectors for Galactic supernova neutrinos 2020 In: Physical Review D. - : American Physical Society (APS). - 2470-0010 .- 2470-0029. ; 101:10 Journal article (peer-reviewed)abstract Paleodetectors are a proposed experimental technique in which one would search for traces of recoiling nuclei in ancient minerals. Natural minerals on Earth are as old as O(1) Gyr and, in many minerals, the damage tracks left by recoiling nuclei are also preserved for timescales long compared to 1 Gyr once created. Thus, even reading out relatively small target samples of order 100 g, paleodetectors would allow one to search for very rare events thanks to the large exposure, epsilon similar to 100 g Gyr = 10(5) t yr. Here, we explore the potential of paleodetectors to measure nuclear recoils induced by neutrinos from Galactic core collapse supernovae. We find that they would not only allow for a direct measurement of the average core collapse supernova rate in the Milky Way, but would also contain information about the time dependence of the local supernova rate over the past similar to 1 Gyr. Since the supernova rate is thought to be directly proportional to the star formation rate, such a measurement would provide a determination of the local star formation history. We investigate the sensitivity of paleodetectors to both a smooth time evolution and an enhancement of the core collapse supernova rate on relatively short timescales, as would be expected for a starburst period in the local group.
11.	Baum, Sebastian, et al. (author) Searching for dark matter with paleo-detectors 2020 In: Physics Letters B. - : ELSEVIER. - 0370-2693 .- 1873-2445. ; 803 Journal article (peer-reviewed)abstract A large experimental program is underway to extend the sensitivity of direct detection experiments, searching for interaction of Dark Matter with nuclei, down to the neutrino floor. However, such experiments are becoming increasingly difficult and costly due to the large target masses and exquisite background rejection needed for the necessary improvements in sensitivity. We investigate an alternative approach to the detection of Dark Matter-nucleon interactions: Searching for the persistent traces left by Dark Matter scattering in ancient minerals obtained from much deeper than current underground laboratories. We estimate the sensitivity of paleo-detectors, which extends far beyond current upper limits for a wide range of Dark Matter masses. The sensitivity of our proposal also far exceeds the upper limits set by Snowden-Ifft et al. more than three decades ago using ancient Mica in an approach similar to paleo-detectors.
12.	Baum, Sebastian, et al. (author) Searching for Dark Matter with Paleo-Detectors Other publication (other academic/artistic)abstract A large experimental program is underway to extend the sensitivity of direct detection experiments, searching for interactions of Dark Matter with nuclei, down to the neutrino floor. However, such experiments are becoming increasingly difficult and costly due to the large target masses and exquisite background rejection needed for the necessary improvements in sensitivity. We investigate an alternative approach to the detection of Dark Matter--nucleon interactions: Searching for the persistent traces left by Dark Matter scattering in ancient minerals obtained from much deeper than current underground laboratories. We estimate the sensitivity of paleo-detectors, which extends far beyond current upper limits for a wide range of Dark Matter masses.
13.	Baum, Sebastian, et al. (author) The NMSSM is within reach of the LHC : mass correlations & decay signatures 2019 In: Journal of High Energy Physics (JHEP). - : SPRINGER. - 1126-6708 .- 1029-8479. ; :4 Journal article (peer-reviewed)abstract The Next-to-Minimal Supersymmetric Standard Model (NMSSM), the singlet extension of the MSSM which fixes many of the MSSM's shortcomings, is shown to be within reach of the upcoming runs of the Large Hadron Collider (LHC). A systematic treatment of the various Higgs decay channels and their interplay has been lacking due to the seemingly large number of free parameters in the NMSSM's Higgs sector. We demonstrate that due to the SM-like nature of the observed Higgs boson, the NMSSM's Higgs and neutralino sectors have highly correlated masses and couplings and can effectively be described by four physically intuitive parameters: the physical masses of the two CP-odd states and their mixing angle, and tan , which plays a minor role. The heavy Higgs bosons in the NMSSM have large branching ratios into pairs of lighter Higgs bosons or a light Higgs and a Z boson. Search channels arising via these Higgs cascades are unique to models like the NMSSM with a Higgs sector larger than that of the MSSM. In order to cover as much of the NMSSM parameter space as possible, one must combine conventional search strategies employing decays of the additional Higgs bosons into pairs of SM particles with Higgs cascade channels. We demonstrate that such a combination would allow a significant fraction of the viable NMSSM parameter space containing additional Higgs bosons with masses below 1 TeV to be probed at future runs of the LHC.
14.	Bergman, A. S., et al. (author) 280 GHz Focal Plane Unit Design and Characterization for the SPIDER-2 Suborbital Polarimeter 2018 In: Journal of Low Temperature Physics. - : Springer Science and Business Media LLC. - 0022-2291 .- 1573-7357. ; 193:5-6, s. 1075-1084 Journal article (peer-reviewed)abstract We describe the construction and characterization of the 280 GHz bolometric focal plane units (FPUs) to be deployed on the second flight of the balloon-borne SPIDER instrument. These FPUs are vital to SPIDER's primary science goal of detecting or placing an upper limit on the amplitude of the primordial gravitational wave signature in the cosmic microwave background (CMB) by constraining the B-mode contamination in the CMB from Galactic dust emission. Each 280 GHz focal plane contains a 16 x 16 grid of corrugated silicon feedhorns coupled to an array of aluminum-manganese transition-edge sensor (TES) bolometers fabricated on 150 mm diameter substrates. In total, the three 280 GHz FPUs contain 1530 polarization-sensitive bolometers (765 spatial pixels) optimized for the low loading environment in flight and read out by time-division SQUID multiplexing. In this paper, we describe the mechanical, thermal, and magnetic shielding architecture of the focal planes and present cryogenic measurements which characterize yield and the uniformity of several bolometer parameters. The assembled FPUs have high yields, with one array as high as 95% including defects from wiring and readout. We demonstrate high uniformity in device parameters, finding the median saturation power for each TES array to be similar to 3 pW at 300 mK with a less than 6% variation across each array at 1 sigma. These focal planes will be deployed alongside the 95 and 150 GHz telescopes in the SPIDER-2 instrument, slated to fly from McMurdo Station in Antarctica in December 2018.
15.	Collaboration, The Theia, et al. (author) Theia: Faint objects in motion or the new astrometry frontier 2017 In: arXiv.org. ; , s. 01348-1707 Journal article (peer-reviewed)
16.	Coogan, Adam, et al. (author) Efficient gravitational wave template bank generation with differentiable waveforms 2022 In: Physical Review D. - 2470-0010 .- 2470-0029. ; 106:12 Journal article (peer-reviewed)abstract The most sensitive search pipelines for gravitational waves from compact binary mergers use matched filters to extract signals from the noisy data stream coming from gravitational wave detectors. Matched-filter searches require banks of template waveforms covering the physical parameter space of the binary system. Unfortunately, template bank construction can be a time-consuming task. Here we present a new method for efficiently generating template banks that utilizes automatic differentiation to calculate the parameter space metric. Principally, we demonstrate that automatic differentiation enables accurate computation of the metric for waveforms currently used in search pipelines, whilst being computationally cheap. Additionally, by combining random template placement and a Monte Carlo method for evaluating the fraction of the parameter space that is currently covered, we show that search-ready template banks for frequency-domain waveforms can be rapidly generated. Finally, we argue that differentiable waveforms offer a pathway to accelerating stochastic placement algorithms. We implement all our methods into an easy-to-use python package based on the jax framework, diffbank, to allow the community to easily take advantage of differentiable waveforms for future searches.
17.	de Salas, Pablo Fernández, et al. (author) On the estimation of the local dark matter density using the rotation curve of the Milky Way 2019 In: Journal of Cosmology and Astroparticle Physics. - : IOP PUBLISHING LTD. - 1475-7516. ; :10 Journal article (peer-reviewed)abstract The rotation curve of the Milky Way is commonly used to estimate the local dark matter density rho(DM,circle dot). However, the estimates are subject to the choice of the distribution of baryons needed in this type of studies. In this work we explore several Galactic mass models that differ in the distribution of baryons and dark matter, in order to determine rho(DM,circle dot). For this purpose we analyze the precise circular velocity curve measurement of the Milky Way up to similar to 25 kpc from the Galactic centre obtained from Gaia DR2 [1]. We find that the estimated value of rho(DM,circle dot) stays robust to reasonable changes in the spherical dark matter halo. However, we show that rho(DM,circle dot) is affected by the choice of the model for the underlying baryonic components. In particular, we find that rho(DM,circle dot) is mostly sensitive to uncertainties in the disk components of the Galaxy. We also show that, when choosing one particular baryonic model, the estimate of rho(DM,circle dot) has an uncertainty of only about 10% of its best-fit value, but this uncertainty gets much bigger when we also consider the variation of the baryonic model. In particular, the rotation curve method does not allow to exclude the presence of an additional very thin component, that can increase rho(DM,circle dot) by more than a factor of 8 (the thin disk could even be made of dark matter). Therefore, we conclude that exclusively using the rotation curve of the Galaxy is not enough to provide a robust estimate of rho(DM,circle dot). For all the models that we study without the presence of an additional thin component, our resulting estimates of the local dark matter density take values in the range rho(DM,circle dot) similar or equal to 0.3-0.4 GeV/cm(3), consistent with many of the estimates in the literature.
18.	Drukier, Andrzej K., et al. (author) Paleo-detectors : Searching for Dark Matter with Ancient Minerals 2019 In: Physical Review D. Particles and fields. - : AMER PHYSICAL SOC. - 0556-2821 .- 1089-4918. ; 99:4 Journal article (peer-reviewed)abstract We explore paleo-detectors as an approach to the direct detection of weakly interacting massive particle (WIMP) dark matter radically different from conventional detectors. Instead of instrumenting a (large) target mass in a laboratory in order to observe WIMP-induced nuclear recoils in real time, the approach is to examine ancient minerals for traces of WIMP-nucleus interactions recorded over timescales as large as 1 Gyr. Here, we discuss the paleo-detector proposal in detail, including background sources and possible target materials. In order to suppress backgrounds induced by radioactive contaminants such as uranium, we propose to use minerals found in marine evaporites or in ultrabasic rocks. We estimate the sensitivity of paleo-detectors to spin-independent and spin-dependent WIMP-nucleus interactions. The sensitivity to low-mass WIMPs with masses mχ≲10 GeV extends to WIMP-nucleon cross sections many orders of magnitude smaller than current upper limits. For heavier WIMPs with masses mχ≳30 GeV cross sections a factor of a few to ∼100 smaller than current upper limits can be probed by paleo-detectors.
19.	Duivenvoorden, Adriaan, et al. (author) CMB B-mode non-Gaussianity I : Optimal bispectrum estimator and Fisher Forecasts Other publication (other academic/artistic)
20.	Duivenvoorden, Adriaan J., et al. (author) CMB B-mode non-Gaussianity : Optimal bispectrum estimator and Fisher forecasts 2020 In: Physical Review D. - 1550-7998 .- 1550-2368. ; 102:2 Journal article (peer-reviewed)abstract Upcoming cosmic microwave background (CMB) data can be used to explore harmonic 3-point functions that involve the B-mode component of the CMB polarization signal. We focus on bispectra describing the non-Gaussian correlation of the B-mode field and the CMB temperature anisotropies (T) and/or E-mode polarization, i.e., (TTB), (EEB), and (TER). Such bispectra probe violations of the tensor consistency relation: the model-independent behavior of cosmological correlation functions that involve a large-wavelength tensor mode (gravitational wave). An observed violation of the tensor consistency relation would exclude a large number of inflation models. We describe a generalization of the Komatsu-Spergel-Wandelt (KSW) bispectrum estimator that allows statistical inference on this type of primordial non-Gaussianity with data of the CMB temperature and polarization anisotropies. The generalized estimator shares its statistical properties with the existing KSW estimator and retains the favorable numerical scaling with angular resolution. In this paper, we derive the estimator and present a set of Fisher forecasts. We show how the forecasts scale with various experimental parameters such as minimum and maximum multipole moments, relevant for, e.g., the upcoming ground-based Simons Observatory experiment and proposed LiteBIRD satellite experiment. We comment on possible contaminants due to secondary cosmological and astrophysical sources.
21.	Duivenvoorden, Adriaan Judocus, 1991- (author) Probing the early Universe with B-mode polarization : The Spider instrument, optical modelling and non-Gaussianity 2019 Doctoral thesis (other academic/artistic)abstract One of the main goals of modern observational cosmology is to constrain or detect a stochastic background of primordial gravitational waves. The existence of such a background is a generic prediction of the inflationary paradigm: the leading explanation for the universe's initial perturbations. A detection of the gravitational wave signal would provide strong evidence for the paradigm and would amount to an indirect probe of an energy scale far beyond that of conventional physics. Several dedicated experiments search for the signal by performing highly accurate measurements of a unique probe of the primordial gravitational wave background: the B-mode signature in the polarization of the cosmic microwave background (CMB) radiation. A part of this thesis is devoted to one of these experiments: the balloon-borne Spider instrument. The analysis of the first dataset, obtained in two (95 and 150 GHz) frequency bands during a January 2015 Antarctic flight, is described, along with details on the characterisation of systematic signal and the calibration of the instrument. The case of systematic signal due to poorly understood optical properties is treated in more detail. In the context of upcoming experiments, a study of systematic optical effects is presented as well as a numerically efficient method to consistently propagate such effects through an analysis pipeline. This is achieved by a `beam convolution' algorithm capable of simulating the contribution from the entire sky, weighted by the optical response, to the instrument's time-ordered data. It is described how the algorithm can be employed to forecast the performance of upcoming CMB experiments. In the final part of the thesis, an additional use of upcoming B-mode data is described. Constraints on the non-Gaussian correlation between the large-angular-scale B-mode field and the CMB temperature or E-mode anisotropies on small angular scales constitute a rigorous consistency check of the inflationary paradigm. An efficient statistical estimation procedure, a generalised bispectrum estimator, is derived and the constraining power of upcoming CMB data is explored.
22.	Edwards, Thomas D. P., et al. (author) Digging for dark matter : Spectral analysis and discovery potential of paleo-detectors 2019 In: Physical Review D. Particles and fields. - : AMER PHYSICAL SOC. - 0556-2821 .- 1089-4918. ; 99:4 Journal article (peer-reviewed)abstract Paleo-detectors are a recently proposed method for the direct detection of dark matter (DM). In such detectors, one would search for the persistent damage features left by DM–nucleus interactions in ancient minerals. Initial sensitivity projections have shown that paleo-detectors could probe much of the remaining weakly interacting massive particle (WIMP) parameter space. In this paper, we improve upon the cut-and-count approach previously used to estimate the sensitivity by performing a full spectral analysis of the background- and DM-induced signal spectra. We consider two scenarios for the systematic errors on the background spectra: (i) systematic errors on the normalization only, and (ii) systematic errors on the shape of the backgrounds. We find that the projected sensitivity is rather robust to imperfect knowledge of the backgrounds. Finally, we study how well the parameters of the true WIMP model could be reconstructed in the hypothetical case of a WIMP discovery.
23.	Filippini, J. P., et al. (author) In-Flight Gain Monitoring of SPIDER's Transition-Edge Sensor Arrays 2022 In: Journal of Low Temperature Physics. - : Springer Science and Business Media LLC. - 0022-2291 .- 1573-7357. ; 209:3-4, s. 649-657 Journal article (peer-reviewed)abstract Experiments deploying large arrays of transition-edge sensors (TESs) often require a robust method to monitor gain variations with minimal loss of observing time. We propose a sensitive and non-intrusive method for monitoring variations in TES responsivity using small square waves applied to the TES bias. We construct an estimator for a TES's small-signal power response from its electrical response that is exact in the limit of strong electrothermal feedback. We discuss the application and validation of this method using flight data from SPIDER, a balloon-borne telescope that observes the polarization of the cosmic microwave background with more than 2000 TESs. This method may prove useful for future balloon- and space-based instruments, where observing time and ground control bandwidth are limited.
24.	Freese, Katherine, et al. (author) Chain early dark energy : A Proposal for solving the Hubble tension and explaining today's dark energy 2021 In: Physical Review D. - : American Physical Society (APS). - 2470-0010 .- 2470-0029. ; 104:8 Journal article (peer-reviewed)abstract We propose a new model of early dark energy (EDE) as a possible solution to the Hubble tension in cosmology, the apparent discrepancy between local measurements of the Hubble constant H-0 similar or equal to 74 km s(-1) Mpc(-1) and H-0 similar or equal to 67 km s(-1) Mpc(-1) inferred from the cosmic microwave background (CMB). In chain EDE, the universe undergoes a series of first order phase transitions, starting at a high energy vacuum in a potential, and tunneling down through a chain of every lower energy metastable minima. As in all EDE models, the contribution of the vacuum energy to the total energy density of the universe is initially negligible, but reaches similar to 10% around matter-radiation equality, before cosmological data require it to redshift away quickly-at least as fast as radiation. We indeed obtain this required behavior with a series of N tunneling events, and show that for N > 600 the phase transitions are rapid enough to allow fast percolation and thereby avoid large scale anisotropies in the CMB. We construct a specific example of chain EDE featuring a scalar field in a quasiperiodic potential (a tilted cosine), which is ubiquitous in axion physics and, therefore, carries strong theoretical motivation. Interestingly, the energy difference between vacua can be roughly the size of today's dark energy (milli-electron-volt scale). Therefore, the end result of chain EDE could provide a natural explanation of dark energy, if the tunneling becomes extremely slow in the final step before the field reaches zero (or negative) energy. We discuss a simple mechanism which can stop the scalar field in the desired minimum. Thus chain EDE offers the exciting prospect to explain EDE and dark energy by the same scalar field.
25.	Freese, Katherine, et al. (author) Colloquium : Annual modulation of dark matter 2013 In: Reviews of Modern Physics. - : American Physical Society. - 0034-6861 .- 1539-0756. ; 85:4, s. 1561-1581 Journal article (peer-reviewed)abstract Direct detection experiments, which are designed to detect the scattering of dark matter off nuclei in detectors, are a critical component in the search for the Universe's missing matter. This Colloquium begins with a review of the physics of direct detection of dark matter, discussing the roles of both the particle physics and astrophysics in the expected signals. The count rate in these experiments should experience an annual modulation due to the relative motion of the Earth around the Sun. This modulation, not present for most known background sources, is critical for solidifying the origin of a potential signal as dark matter. The focus is on the physics of annual modulation, discussing the practical formulas needed to interpret a modulating signal. The dependence of the modulation spectrum on the particle and astrophysics models for the dark matter is illustrated. For standard assumptions, the count rate has a cosine dependence with time, with a maximum in June and a minimum in December. Well-motivated generalizations of these models, however, can affect both the phase and amplitude of the modulation. Shown is how a measurement of an annually modulating signal could teach us about the presence of substructure in the galactic halo or about the interactions between dark and baryonic matter. Although primarily a theoretical review, the current experimental situation for annual modulation and future experimental directions is briefly discussed.
26.	Freese, Katherine, 1957-, et al. (author) Dark matter and gravitational waves from a dark big bang 2023 In: Physical Review D. - : American Physical Society (APS). - 2470-0010 .- 2470-0029. ; 107:8 Journal article (peer-reviewed)abstract The hot big bang is often considered as the origin of all matter and radiation in the Universe. Primordial nucleosynthesis provides strong evidence that the early Universe contained a hot plasma of photons and baryons with a temperature T>MeV. However, the earliest probes of dark matter originate from much later times around the epoch of structure formation. In this work we describe a scenario in which dark matter (and possibly dark radiation) can be formed around or even after primordial nucleosynthesis in a second big bang, which we dub the “dark big bang.” The latter occurs through a phase transition in the dark sector that transforms dark vacuum energy into a hot dark plasma of particles; in this paper we focus on a first-order phase transition for the dark big bang. The correct dark matter abundance can be set by dark matter cannibalism or by pair annihilation within the dark sector followed by a thermal freeze-out. Alternatively ultraheavy “dark-zilla” dark matter can originate directly from bubble collisions during the dark big bang. We will show that the dark big bang is consistent with constraints from structure formation and the cosmic microwave background if it occurred when the Universe was less than one month old, corresponding to a temperature in the visible sector above O(keV). While the dark matter evades direct and indirect detection, the dark big bang gives rise to striking gravity wave signatures to be tested at pulsar timing array experiments. Furthermore, the dark big bang allows for realizations of self-interacting and/or warm dark matter, which suggest exciting discovery potential in future small-scale structure observations.
27.	Freese, Katherine, et al. (author) Dark matter collisions with the human body 2012 In: Physics Letters B. - 0370-2693 .- 1873-2445. ; 717:1-3, s. 25-28 Journal article (peer-reviewed)abstract We investigate the interactions of Weakly Interacting Massive Particles (WIMPs) with nuclei in the human body. We are motivated by the fact that WIMPS are excellent candidates for the dark matter in the Universe. Our estimates use a 70 kg human and a variety of WIMP masses and cross-sections. The contributions from individual elements in the body are presented and it is found that the dominant contribution is from scattering off of oxygen (hydrogen) nuclei for the spin-independent (spin-dependent) interactions. For the case of 60 GeV WIMPs, we find that, of the billions of WIMPs passing through a human body per second, roughly similar to 10 WIMPs hit one of the nuclei in the human body in an average year, if the scattering is at the maximum consistent with current bounds on WIMP interactions. We also study the 10-20 GeV WIMPs with much larger cross-sections that best fit the DAMA, COGENT, and CRESST data sets and find much higher rates: in this case as many as 10(5) WIMPs hit a nucleus in the human body in an average year, corresponding to almost one a minute. Though WIMP interactions are a source of radiation in the body, the annual exposure is negligible compared to that from other natural sources (including radon and cosmic rays), and the WIMP collisions are harmless to humans.
28.	Freese, Katherine, et al. (author) Dark stars : a review 2016 In: Reports on progress in physics (Print). - : Institute of Physics Publishing (IOPP). - 0034-4885 .- 1361-6633. ; 79:6 Research review (peer-reviewed)abstract Dark stars are stellar objects made (almost entirely) of hydrogen and helium, but powered by the heat from dark matter annihilation, rather than by fusion. They are in hydrostatic and thermal equilibrium, but with an unusual power source. Weakly interacting massive particles (WIMPs), among the best candidates for dark matter, can be their own antimatter and can annihilate inside the star, thereby providing a heat source. Although dark matter constitutes only <= 0.1% of the stellar mass, this amount is sufficient to power the star for millions to billions of years. Thus, the first phase of stellar evolution in the history of the Universe may have been dark stars. We review how dark stars come into existence, how they grow as long as dark matter fuel persists, and their stellar structure and evolution. The studies were done in two different ways, first assuming polytropic interiors and more recently using the MESA stellar evolution code; the basic results are the same. Dark stars are giant, puffy (similar to 10 AU) and cool (surface temperatures similar to 10 000 K) objects. We follow the evolution of dark stars from their inception at similar to 1M(circle dot) as they accrete mass from their surroundings to become supermassive stars, some even reaching masses >10(6)M(circle dot) and luminosities >10(10)L(circle dot), making them detectable with the upcoming James Webb Space Telescope. Once the dark matter runs out and the dark star dies, it may collapse to a black hole; thus dark stars may provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation may exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The current review briefly discusses dark stars existing today, but focuses on the early generation of dark stars.
29.	Freese, Katherine, et al. (author) Have pulsar timing arrays detected the hot big bang: Gravitational waves from strong first order phase transitions in the early Universe 2022 In: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 106:10 Journal article (peer-reviewed)abstract The origins of matter and radiation in the universe lie in a hot big bang. We present a number of well-motivated cosmologies in which the big bang occurs through a strong first-order phase transition - either at the end of inflation, after a period of kination ("kination-induced big bang"), or after a second period of vacuum domination in the early Universe ("supercooled big bang"); we also propose a "dark big bang"where only the dark matter in the Universe is created in a first-order phase transition much after inflation. In all of these scenarios, the resulting gravitational radiation can explain the tentative signals reported by the NANOGrav, Parkes, and European Pulsar Timing Array experiments if the reheating temperature of the hot big bang, and correspondingly the energy scale of the false vacuum, falls in the range T∗∼ρvac1/4=MeV-100 GeV. All of the same models at higher reheating temperatures will be of interest to upcoming ground- and space-based interferometer searches for gravitational waves at larger frequency.
30.	Freese, Katherine, et al. (author) MSSM A-funnel and the galactic center excess : prospects for the LHC and direct detection experiments 2016 In: Journal of High Energy Physics (JHEP). - : Springer-Verlag New York. - 1126-6708 .- 1029-8479. ; :4 Journal article (peer-reviewed)abstract The pseudoscalar resonance or "A-funnel" in the Minimal Supersymmetric Standard Model (MSSM) is a widely studied framework for explaining dark matter that can yield interesting indirect detection and collider signals. The well-known Galactic Center excess (GCE) at GeV energies in the gamma ray spectrum, consistent with annihilation of a less than or similar to 40 GeV dark matter particle, has more recently been shown to be compatible with significantly heavier masses following reanalysis of the background. In this paper, we explore the LHC and direct detection implications of interpreting the GCE in this extended mass window within the MSSM A-funnel framework. We find that compatibility with relic density, signal strength, collider constraints, and Higgs data can be simultaneously achieved with appropriate parameter choices. The compatible regions give very sharp predictions of 200-600 GeV CP-odd/even Higgs bosons at low tan beta at the LHC and spin-independent cross sections approximate to 10(-11) pb at direct detection experiments. Regardless of consistency with the GCE, this study serves as a useful template of the strong correlations between indirect, direct, and LHC signatures of the MSSM A-funnel region.
31.	Freese, Katherine, et al. (author) Natural Chain Inflation 2022 In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 829 Journal article (peer-reviewed)abstract In Chain Inflation the universe tunnels along a series of false vacua of ever-decreasing energy. The main goal of this paper is to embed Chain Inflation in high energy fundamental physics. We begin by illustrating a simple effective formalism for calculating Cosmic Microwave Background (CMB) observables in Chain Inflation. Density perturbations seeding the anisotropies emerge from the probabilistic nature of tunneling (rather than from quantum fluctuations of the inflation). To obtain the correct normalization of the scalar power spectrum and the scalar spectral index, we find an upper limit on the scale of inflation at horizon crossing of CMB scales, V-*(1/4) < 10(12) GeV. We then provide an explicit realization of chain inflation, in which the inflaton is identified with an axion in supergravity. The axion enjoys a perturbative shift symmetry which is broken to a discrete remnant by instantons. The model, which we dub 'natural chain inflation' satisfies all cosmological constraints and can be embedded into a standard Lambda CDM cosmology. Our work provides a major step towards the ultraviolet completion of chain inflation in string theory.
32.	Freese, Katherine, et al. (author) Neutrino point source searches for dark matter spikes 2022 In: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; 2022:08, s. 065- Journal article (peer-reviewed)abstract Any dark matter spikes surrounding black holes in our Galaxy are sites of signif-icant dark matter annihilation, leading to a potentially detectable neutrino signal. In this paper we examine 10 - 105M (R) black holes associated with dark matter spikes that formed in early minihalos and still exist in our Milky Way Galaxy today, in light of neutrino data from the ANTARES [1] and IceCube [2] detectors. In various regions of the sky, we determine the minimum distance away from the solar system that a dark matter spike must be in order to have not been detected as a neutrino point source for a variety of representative dark matter annihilation channels. Given these constraints on the distribution of dark matter spikes in the Galaxy, we place significant limits on the formation of the first generation of stars in early minihalos - stronger than previous limits from gamma-ray searches in Fermi Gamma -Ray Space Telescope data. The larger black holes considered in this paper may arise as the remnants of Dark Stars after the dark matter fuel is exhausted; thus neutrino observations may be used to constrain the properties of Dark Stars. The limits are particularly strong for heavier WIMPs. For WIMP masses ti 5 TeV, we show that & LE; 10% of minihalos can host first stars that collapse into BHs larger than 103M (R).
33.	Freese, Katherine (author) Status of dark matter in the universe 2017 In: International Journal of Modern Physics D. - 0218-2718. ; 26:6 Research review (peer-reviewed)abstract Over the past few decades, a consensus picture has emerged in which roughly a quarter of the universe consists of dark matter. I begin with a review of the observational evidence for the existence of dark matter: rotation curves of galaxies, gravitational lensing measurements, hot gas in clusters, galaxy formation, primordial nucleosynthesis and Cosmic Microwave Background (CMB) observations. Then, I discuss a number of anomalous signals in a variety of data sets that may point to discovery, though all of them are controversial. The annual modulation in the DAMA detector and/or the gamma-ray excess seen in the Fermi Gamma Ray Space Telescope from the Galactic Center could be due to WIMPs; a 3.5 keV X-ray line from multiple sources could be due to sterile neutrinos; or the 511 keV line in INTEGRAL data could be due to MeV dark matter. All of these would require further confirmation in other experiments or data sets to be proven correct. In addition, a new line of research on dark stars is presented, which suggests that the first stars to exist in the universe were powered by dark matter heating rather than by fusion: the observational possibility of discovering dark matter in this way is discussed.
34.	Freese, Katherine, 1957-, et al. (author) The Gravitational Wave Spectrum of Chain Inflation Other publication (other academic/artistic)abstract Chain inflation is an alternative to slow-roll inflation in which the inflaton tunnels along a large number of consecutive minima in its potential. In this work we perform the first comprehensive calculation of the gravitational wave spectrum of chain inflation. In contrast to slow-roll inflation the latter does not stem from quantum fluctuations of the gravitational field during inflation, but rather from the bubble collisions during the first-order phase transitions associated with vacuum tunneling. Our calculation is performed within an effective theory of chain inflation which builds on an expansion of the tunneling rate capturing most of the available model space. The effective theory can be seen as chain inflation's analogue of the slow-roll expansion in rolling models of inflation. We show that chain inflation produces a very characteristic double-peak spectrum: a faint high-frequency peak associated with the gravitational radiation emitted during inflation, and a strong low-frequency peak associated with the graceful exit from chain inflation (marking the transition to the radiation-dominated epoch). There exist very exciting prospects to test the gravitational wave signal from chain inflation at the aLIGO-aVIRGO-KAGRA network, at LISA and /or at pulsar timing array experiments. A particularly intriguing possibility we point out is that chain inflation could be the source of the stochastic gravitational wave background recently detected by NANOGrav, PPTA, EPTA and CPTA. We also show that the gravitational wave signal of chain inflation is often accompanied by running/ higher running of the scalar spectral index to be tested at future Cosmic Microwave Background experiments.
35.	Freese, Katherine, et al. (author) The Higgs boson can delay reheating after inflation 2018 In: Journal of Cosmology and Astroparticle Physics. - : IOP PUBLISHING LTD. - 1475-7516. ; :5 Journal article (peer-reviewed)abstract The Standard Model Higgs boson, which has previously been shown to develop an effective vacuum expectation value during inflation, can give rise to large particle masses during inflation and reheating, leading to temporary blocking of the reheating process and a lower reheat temperature after inflation. We study the effects on the multiple stages of reheating: resonant particle production (preheating) as well as perturbative decays from coherent oscillations of the inflaton field. Specifically, we study both the cases of the inflaton coupling to Standard Model fermions through Yukawa interactions as well as to Abelian gauge fields through a Chern-Simons term. We find that, in the case of perturbative inflaton decay to SM fermions, reheating can be delayed due to Higgs blocking and the reheat temperature can decrease by up to an order of magnitude. In the case of gauge-reheating, Higgs-generated masses of the gauge fields can suppress preheating even for large inflatongauge couplings. In extreme cases, preheating can be shut down completely and must be substituted by perturbative decay as the dominant reheating channel. Finally, we discuss the distribution of reheat temperatures in different Hubble patches, arising from the stochastic nature of the Higgs VEV during inflation and its implications for the generation of both adiabatic and isocurvature fluctuations.
36.	Gambrel, A. E., et al. (author) The XFaster Power Spectrum and Likelihood Estimator for the Analysis of Cosmic Microwave Background Maps 2021 In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 922:2 Journal article (peer-reviewed)abstract We present the XFaster analysis package, a fast, iterative angular power spectrum estimator based on a diagonal approximation to the quadratic Fisher matrix estimator. It uses Monte Carlo simulations to compute noise biases and filter transfer functions and is thus a hybrid of both Monte Carlo and quadratic estimator methods. In contrast to conventional pseudo-Cℓ–based methods, the algorithm described here requires a minimal number of simulations and does not require them to be precisely representative of the data to estimate accurate covariance matrices for the bandpowers. The formalism works with polarization-sensitive observations and also data sets with identical, partially overlapping, or independent survey regions. The method was first implemented for the analysis of BOOMERanG data and also used as part of the Planck analysis. Here we describe the full, publicly available analysis package, written in Python, as developed for the analysis of data from the 2015 flight of the Spider instrument. The package includes extensions for self-consistently estimating null spectra and estimating fits for Galactic foreground contributions. We show results from the extensive validation of XFaster using simulations and its application to the Spider data set.
37.	Gariazzo, Stefano, et al. (author) Neutrino mass and mass ordering : no conclusive evidence for normal ordering 2022 In: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; 2022:10 Journal article (peer-reviewed)abstract The extraction of the neutrino mass ordering is one of the major challenges in particle physics and cosmology, not only for its implications for a fundamental theory of mass generation in nature, but also for its decisive role in the scale of future neutrinoless double beta decay experimental searches. It has been recently claimed that current oscillation, beta decay and cosmological limits on the different observables describing the neutrino mass parameter space provide robust decisive Bayesian evidence in favor of the normal ordering of the neutrino mass spectrum [1]. We further investigate these strong claims using a rich and wide phenomenology, with different sampling techniques of the neutrino parameter space. Contrary to the findings of Jimenez et al. [1], no decisive evidence for the normal mass ordering is found. Neutrino mass ordering analyses must rely on priors and parameterizations that are ordering-agnostic: robust results should be regarded as those in which the preference for the normal neutrino mass ordering is driven exclusively by the data, while we find a difference of up to a factor of 33 in the Bayes factors among the different priors and parameterizations exploited here. An ordering-agnostic prior would be represented by the case of parameterizations sampling over the two mass splittings and a mass scale, or those sampling over the individual neutrino masses via normal prior distributions only. In this regard, we show that the current significance in favor of the normal mass ordering should be taken as 2.7σ (i.e. moderate evidence), mostly driven by neutrino oscillation data. Let us stress that, while current data favor NO only mildly, we do not exclude the possibility that this may change in the future. Eventually, upcoming oscillation and cosmological data may (or may not) lead to a more significant exclusion of IO.
38.	Gerbino, Martina, et al. (author) A novel approach to quantifying the sensitivity of current and future cosmological datasets to the neutrino mass ordering through Bayesian hierarchical modeling 2017 In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 775, s. 239-250 Journal article (peer-reviewed)abstract We present a novel approach to derive constraints on neutrino masses, as well as on other cosmological parameters, from cosmological data, while taking into account our ignorance of the neutrino mass ordering. We derive constraints from a combination of current as well as future cosmological datasets on the total neutrino mass M-nu and on the mass fractions f(nu),i = m(i)/M-nu (where the index i = 1, 2, 3 indicates the three mass eigenstates) carried by each of the mass eigenstates m(i), after marginalizing over the (unknown) neutrino mass ordering, either normal ordering (NH) or inverted ordering (IH). The bounds on all the cosmological parameters, including those on the total neutrino mass, take therefore into account the uncertainty related to our ignorance of the mass hierarchy that is actually realized in nature. This novel approach is carried out in the framework of Bayesian analysis of a typical hierarchical problem, where the distribution of the parameters of the model depends on further parameters, the hyperparameters. In this context, the choice of the neutrino mass ordering is modeled via the discrete hyperparameter h(type), which we introduce in the usual Markov chain analysis. The preference from cosmological data for either the NH or the IH scenarios is then simply encoded in the posterior distribution of the hyper-parameter itself. Current cosmic microwave background (CMB) measurements assign equal odds to the two hierarchies, and are thus unable to distinguish between them. However, after the addition of baryon acoustic oscillation (BAO) measurements, a weak preference for the normal hierarchical scenario appears, with odds of 4 : 3 from Planck temperature and large-scale polarization in combination with BAO (3 : 2 if small-scale polarization is also included). Concerning next-generation cosmological experiments, forecasts suggest that the combination of upcoming CMB (COrE) and BAO surveys (DESI) may determine the neutrino mass hierarchy at a high statistical significance if the mass is very close to the minimal value allowed by oscillation experiments, as for NH and a fiducial value of M-nu = 0.06 eV there is a 9 : 1 preference of normal versus inverted hierarchy. On the contrary, if the sum of the masses is of the order of 0.1 eV or larger, even future cosmological observations will be inconclusive. The innovative statistical strategy exploited here represents a very simple, efficient and robust tool to study the sensitivity of present and future cosmological data to the neutrino mass hierarchy, and a sound competitor to the standard Bayesian model comparison. The unbiased limit on M-nu we obtain is crucial for ongoing and planned neutrinoless double beta decay searches.
39.	Gerbino, Martina, et al. (author) Impact of neutrino properties on the estimation of inflationary parameters from current and future observations 2017 In: Physical Review D. - 2470-0010 .- 2470-0029. ; 95:4 Journal article (peer-reviewed)abstract We study the impact of assumptions about neutrino properties on the estimation of inflationary parameters from cosmological data, with a specific focus on the allowed contours in the n(s)/r plane, where n(s) is the scalar spectral index and r is the tensor-to-scalar ratio. We study the following neutrino properties: (i) the total neutrino mass M-i = Sigma(i)m(i) (where the index i = 1, 2, 3 runs over the three neutrino mass eigenstates); (ii) the number of relativistic degrees of freedom N-eff at the time of recombination; and (iii) the neutrino hierarchy. Whereas previous literature assumed three degenerate neutrino masses or two massless neutrino species (approximations that clearly do not match neutrino oscillation data), we study the cases of normal and inverted hierarchy. Our basic result is that these three neutrino properties induce < 1 sigma shift of the probability contours in the n(s)/r plane with both current or upcoming data. We find that the choice of neutrino hierarchy (normal, inverted, or degenerate) has a negligible impact. However, the minimal cutoff on the total neutrino mass M-v,M-min = 0 that accompanies previous works using the degenerate hierarchy does introduce biases in the n(s)/r plane and should be replaced by M-v,M-min = 0.059 eV as required by oscillation data. Using current cosmic microwave background (CMB) data from Planck and Bicep/Keck, marginalizing over the total neutrino mass M-v and over r can lead to a shift in the mean value of ns of similar to 0.3 sigma toward lower values. However, once baryon acoustic oscillation measurements are included, the standard contours in the n(s)/r plane are basically reproduced. Larger shifts of the contours in the n(s)/r plane (up to 0.8 sigma) arise for nonstandard values of N-eff. We also provide forecasts for the future CMB experiments Cosmic Origins Explorer (COrE, satellite) and Stage-IV (ground-based) and show that the incomplete knowledge of neutrino properties, taken into account by a marginalization over M-v, could induce a shift of similar to 0.4 sigma toward lower values in the determination of ns (or a similar to 0.8 sigma shift if one marginalizes over N-eff). Comparison to specific inflationary models is shown. Imperfect knowledge of neutrino properties must be taken into account properly, given the desired precision in determining whether or not inflationary models match the future data.
40.	Giusarma, Elena, et al. (author) Improvement of cosmological neutrino mass bounds 2016 In: Physical Review D. - 2470-0010. ; 94:8 Journal article (peer-reviewed)abstract The most recent measurements of the temperature and low-multipole polarization anisotropies of the cosmic microwave background from the Planck satellite, when combined with galaxy clustering data from the Baryon Oscillation Spectroscopic Survey in the form of the full shape of the power spectrum, and with baryon acoustic oscillation measurements, provide a 95% confidence level (C.L.) upper bound on the sum of the three active neutrinos Sigma m(nu) < 0.183 eV, among the tightest neutrino mass bounds in the literature, to date, when the same data sets are taken into account. This very same data combination is able to set, at similar to 70% C.L., an upper limit on Sigma m(nu) of 0.0968 eV, a value that approximately corresponds to the minimal mass expected in the inverted neutrino mass hierarchy scenario. If high-multipole polarization data from Planck is also considered, the 95% C.L. upper bound is tightened to Sigma m(nu) < 0.176 eV. Further improvements are obtained by considering recent measurements of the Hubble parameter. These limits are obtained assuming a specific nondegenerate neutrino mass spectrum; they slightly worsen when considering other degenerate neutrino mass schemes. Low-redshift quantities, such as the Hubble constant or the reionization optical depth, play a very important role when setting the neutrino mass constraints. We also comment on the eventual shifts in the cosmological bounds on Sigma m(nu) when possible variations in the former two quantities are addressed.
41.	Giusarma, Elena, et al. (author) Scale-dependent galaxy bias, CMB lensing-galaxy cross-correlation, and neutrino masses 2018 In: Physical Review D. - 2470-0010 .- 2470-0029. ; 98:12 Journal article (peer-reviewed)abstract One of the most powerful cosmological data sets when it comes to constraining neutrino masses is represented by galaxy power spectrum measurements, P-gg(k). The constraining power of P-gg(k) is however severely limited by uncertainties in the modeling of the scale-dependent galaxy bias b(k). In this work we present a new proof-of-principle for a method to constrain b(k) by using the cross-correlation between the cosmic microwave background (CMB) lensing signal and galaxy maps (C-l(kappa g)) using a simple but theoretically well-motivated parametrization for b(k). We apply the method using C-l(kappa g) measured by cross-correlating Planck lensing maps and the Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 11 (DR11) CMASS galaxy sample, and P-gg(k) measured from the BOSS DR12 CMASS sample. We detect a nonzero scale-dependence at moderate significance, which suggests that a proper modeling of b(k) is necessary in order to reduce the impact of nonlinearities and minimize the corresponding systematics. The accomplished increase in constraining power of P-gg(k) is demonstrated by determining a 95% confidence level upper bound on the sum of the three active neutrino masses M-nu of M-nu < 0.19 eV. This limit represents a significant improvement over previous bounds with comparable data sets. Our method will prove especially powerful and important as future large-scale structure surveys will overlap more significantly with the CMB lensing kernel providing a large cross-correlation signal.
42.	Gualtieri, R., et al. (author) SPIDER : CMB Polarimetry from the Edge of Space 2018 In: Journal of Low Temperature Physics. - : Springer Science and Business Media LLC. - 0022-2291 .- 1573-7357. ; 193:5-6, s. 1112-1121 Journal article (peer-reviewed)abstract SPIDER is a balloon-borne instrument designed to map the polarization of the millimeter-wave sky at large angular scales. Spider targets the B-mode signature of primordial gravitational waves in the cosmic microwave background (CMB), with a focus on mapping a large sky area with high fidelity at multiple frequencies. SPIDER's first long-duration balloon (LDB) flight in January 2015 deployed a total of 2400 antenna-coupled transition-edge sensors (TESs) at 90 GHz and 150 GHz. In this work we review the design and in-flight performance of the SPIDER instrument, with a particular focus on the measured performance of the detectors and instrument in a space-like loading and radiation environment. SPIDER's second flight in December 2018 will incorporate payload upgrades and new receivers to map the sky at 285 GHz, providing valuable information for cleaning polarized dust emission from CMB maps.
43.	Hagstotz, Steffen, et al. (author) Bounds on light sterile neutrino mass and mixing from cosmology and laboratory searches 2021 In: Physical Review D. - 2470-0010 .- 2470-0029. ; 104:12 Journal article (peer-reviewed)abstract We present a consistent framework to set limits on properties of light sterile neutrinos coupled to all three active neutrinos using a combination of the latest cosmological data and terrestrial measurements from oscillations, β-decay, and neutrinoless double-β-decay (0νββ) experiments. We directly constrain the full 3+1 active-sterile mixing matrix elements \|Uα4\|2, with α∈(e,μ,τ), and the mass-squared splitting Δm241≡m24−m21. We find that results for a 3+1 case differ from previously studied 1+1 scenarios where the sterile is coupled to only one of the neutrinos, which is largely explained by parameter space volume effects. Limits on the mass splitting and the mixing matrix elements are currently dominated by the cosmological datasets. The exact results are slightly prior dependent, but we reliably find all matrix elements to be constrained below \|Uα4\|2≲10−3. Short-baseline neutrino oscillation hints in favor of eV-scale sterile neutrinos are in serious tension with these bounds, irrespective of prior assumptions. We also translate the bounds from the cosmological analysis into constraints on the parameters probed by laboratory searches, such as mβ or mββ, the effective mass parameters probed by β-decay and 0νββ searches, respectively. When allowing for mixing with a light sterile neutrino, cosmology leads to upper bounds of mβ<0.09 eV and mββ<0.07 eV at 95% CL, more stringent than the limits from current laboratory experiments.
44.	Ilie, Cosmin, et al. (author) Supermassive Dark Star candidates seen by JWST 2023 In: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 120:30 Journal article (peer-reviewed)abstract The first generation of stars in the universe is yet to be observed. There are two leading theories for those objects that mark the beginning of the cosmic dawn: hydrogen burning Population III stars and Dark Stars, made of hydrogen and helium but powered by dark matter heating. The latter can grow to become supermassive (M⋆ ∼ 106M⊙) and extremely bright (L ∼ 109L⊙). We show that each of the following three objects—JADES-GS-z13-0, JADES-GS-z12-0, and JADES-GS-z11-0 (at redshifts z ∈ [11, 14])—are consistent with a Supermassive Dark Star interpretation, thus identifying the first Dark Star candidates.
45.	Jacobsen, Sunniva, et al. (author) Constraining Axion-Like Particles with HAWC Observations of TeV Blazars Other publication (other academic/artistic)abstract Axion-like particles (ALPs) are a broad class of pseudo-scalar bosons that generically arise from broken symmetries in extensions of the standard model. In many scenarios, ALPs can mix with photons in regions with high magnetic fields. Photons from distant sources can mix with ALPs, which then travel unattenuated through the Universe, before they mix back to photons in the Milky Way galactic magnetic field. Thus, photons can traverse regions where their signals would normally be blocked or attenuated. In this paper, we study TeV -ray observations from distant blazars, utilizing the significant -ray attenuation expected from such signals to look for excess photon fluxes that may be due to ALP-photon mixing. We find no such excesses among a stacked population of seven blazars and constrain the ALP-photon coupling constant to fall below for ALP masses below 300 neV. These results are competitive with, or better than, leading terrestrial and astrophysical constraints in this mass range.
46.	Jacobsen, Sunniva, et al. (author) Constraining axion-like particles with HAWC observations of TeV blazars 2023 In: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; 2023:10 Journal article (peer-reviewed)abstract Axion-like particles (ALPs) are a broad class of pseudo-scalar bosons that generically arise from broken symmetries in extensions of the standard model. In many scenarios, ALPs can mix with photons in regions with high magnetic fields. Photons from distant sources can mix with ALPs, which then travel unattenuated through the Universe, before they mix back to photons in the Milky Way galactic magnetic field. Thus, photons can traverse regions where their signals would normally be blocked or attenuated. In this paper, we study TeV γ-ray observations from distant blazars, utilizing the significant γ-ray attenuation expected from such signals to look for excess photon fluxes that may be due to ALP-photon mixing. We find no such excesses among a stacked population of seven blazars and constrain the ALP-photon coupling constant to fall below ∼4.5×10-11 GeV-1 for ALP masses below 300 neV. These results are competitive with, or better than, leading terrestrial and astrophysical constraints in this mass range.
47.	Jacobsen, Sunniva (author) Constraining the Dark Matter Parameter Space 2022 Licentiate thesis (other academic/artistic)abstract The nature of dark matter (DM) is one of the greatest mysteries of modern physics. Itmakes up 25% of the total energy-matter content in the Universe, and is essential forexplaining the large-scale structures we observe in the Universe. Little is known aboutthe nature of dark matter, and the number of possible theories is vast. However, themost popular dark matter candidates either solve other, unrelated problems of physics orappear naturally in theories beyond the Standard Model (BSM). Two such candidates areWeakly Interacting Massive Particles (WIMPs) and Axion-like Particles (ALPs). Thisthesis is based on two papers which study the properties of these two DM candidates andthe possible signals they may leave in detectors at Earth, and in the γ-ray spectrum ofdistant astrophysical sources.Paper I focuses on a class of WIMPs called "inelastic DM" in which the DM particle musttransfer onto a higher-mass state when it interacts with SM particles. In this paper, wehave studied whether such a model can explain the discrepancy between the claimed DMsignal in DAMA and the lack of one in other direct detection experiments.Paper II focuses on the general class of ALPs, and uses data from the HAWC observatoryto study whether the observed γ-ray spectra at very high energies from distant blazarsare in conflict with the expected spectra from different ALP models.
48.	Jacobsen, Sunniva, et al. (author) Inelastic dark matter scattering off Thallium cannot save DAMA 2021 In: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :10 Journal article (peer-reviewed)abstract We study the compatibility of the observed DAMA modulation signal with inelas-tic scattering of dark matter (DM) off of the 0.1% Thallium (Tl) dopant in DAMA. In this work we test whether there exist regions of parameter space where the Tl interpretation gives a good fit to the most recent data from DAMA, and whether these regions are compatible with the latest constraints from other direct detection experiments. Previously, Chang et al. in 2010 [1], had proposed the Tl interpretation of the DAMA data, and more recently (in 2019) the DAMA/LIBRA collaboration [2] found regions in parameter space of Tl inelastic scattering that differ by more than 10o-from a no modulation hypothesis. We have expanded upon their work by testing whether the regions of parameter space where inelastic DM-Tl scattering gives a good fit to the most recent DAMA data survive the constraints placed by the lack of a DM signal in XENON1T and CRESST-II. In addition, we have tested how these regions change with the main sources of uncertainty: the Tl quenching factor, which has never been measured directly, and the astrophysical uncertainties in the DM distribution. We conclude that inelastic DM scattering off Tl cannot explain the DAMA data in light of null results from other experiments.
49.	Jacobsen, Sunniva, 1994- (author) Probes of New Physics : Signatures of new particles in extreme objects and ground-based experiments 2024 Doctoral thesis (other academic/artistic)abstract The Standard Model (SM) of particle physics is one of the greatest successes of the 20th century. It offers a beautiful description of the elementary par- ticles and their interactions based on symmetries and the breaking of them. Despite its success, the SM is regarded as incomplete both because it does not explain certain observed phenomena and because it exhibits fine-tuning prob- lems. This thesis explores how particles beyond the SM (BSM) interact with SM particles, and the signals we should expect from them. In particular, the classes of hypothetical, new particles denoted as "Weakly Interacting Massive Particles" (WIMPs) and "Axion-like Particles" (ALPs) are studied.This thesis consists of three papers, which all contribute to the search for new particles beyond the SM in different ways. The first paper focuses on a class of WIMPs called "inelastic DM" in which the DM particle must transfer onto a higher-mass state when it scatters off SM particles. In this paper, we have studied whether such a model can explain the discrepancy between the claimed DM signal in DAMA and the lack of one in other direct detection experiments. The second paper of this thesis focuses on ALPs and their signals in the γ-ray spectra of distant sources. ALPs and photons can oscillate in the presence of external magnetic fields, such as the ones that are expected to be present in the jets of blazars (active galactic nuclei). These oscillations should lead to an increased flux in the TeV spectra of these sources. In this paper we used data from the HAWC observatory to study whether the observed γ-ray spectra of these sources were in conflict with the expected spectra for different ALP models.The last paper in this thesis does not involve any new particles beyond the SM, but investigates whether current models of the isotropic gamma-ray back- ground (IGRB) is consistent with observations. Since searches for new par- ticles depend heavily on our understanding of astrophysical phenomena and the SM processes that take place, studies of these are important. The IGRB consists of all the diffuse γ-ray emission that cannot be assigned to individ- ual point sources. In this paper, we calculated the expected contribution to the IGRB from resolved blazars and found that this introduces an emerging tension between blazar models and observations.
50.	Katherine, Freese, et al. (author) Neutrino point source searches for dark matter spikes Other publication (other academic/artistic)abstract Any dark matter spikes surrounding black holes in our Galaxy are sites of significant dark matter annihilation, leading to a potentially detectable neutrino signal. In this paper we examine 10−105M⊙ black holes associated with dark matter spikes that formed in early minihalos and still exist in our Milky Way Galaxy today, in light of neutrino data from the ANTARES and IceCube detectors. In various regions of the sky, we determine the minimum distance away from the solar system that a dark matter spike must be in order to have not been detected as a neutrino point source for a variety of representative dark matter annihilation channels. Given these constraints on the distribution of dark matter spikes in the Galaxy, we place significant limits on the formation of the first generation of stars in early minihalos -- stronger than previous limits from gamma-ray searches in Fermi Gamma-Ray Space Telescope data. The larger black holes considered in this paper may arise as the remnants of Dark Stars after the dark matter fuel is exhausted; thus neutrino observations may be used to constrain the properties of Dark Stars. The limits are particularly strong for heavier WIMPs. For WIMP masses ∼5TeV, we show that ≲10% of minihalos can host first stars that collapse into BHs larger than 103M⊙.

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Type of publication: journal article (74); other publication (6); doctoral thesis (5); licentiate thesis (3); research review (2)

Type of content: peer-reviewed (76); other academic/artistic (14)

Author/Editor: Freese, Katherine (75); Gerbino, Martina (10); Gudmundsson, Jón E. (8); Li, S. (7); Galloway, M. (7); Song, X. (7); show more...; Huang, Z. (7); Tucker, C. (7); Ade, P. A. R. (7); Bock, J. J. (7); Bond, J. R. (7); Chiang, H. C. (7); Eriksen, H. K. (7); Fraisse, A. A. (7); Jones, W. C. (7); Netterfield, C. B. (7); Racine, B. (7); Wehus, I. K. (7); Amiri, M. (7); Benton, S. J. (7); Bergman, A. S. (7); Bryan, S. A. (7); Contaldi, C. R. (7); Farhang, M. (7); Filippini, J. P. (7); Gambrel, A. E. (7); Gandilo, N. N. (7); Halpern, M. (7); Hartley, J. (7); Hasselfield, M. (7); Hilton, G. (7); Holmes, W. (7); Hristov, V. V. (7); Irwin, K. D. (7); Kuo, C. L. (7); Kermish, Z. D. (7); Megerian, K. (7); Moncelsi, L. (7); Morford, T. A. (7); Nagy, J. M. (7); Nolta, M. (7); Padilla, I. L. (7); Rahlin, A. S. (7); Reintsema, C. (7); Ruhl, J. E. (7); Ruud, T. M. (7); Shariff, J. A. (7); Soler, J. D. (7); Trangsrud, A. (7); Tucker, R. S. (7); show less...

University: Stockholm University (88); Royal Institute of Technology (30); Lund University (2); Chalmers University of Technology (2); Uppsala University (1)

Language: English (90)

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