| 11. |
- Athron, Peter, et al.
(författare)
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SpecBit, DecayBit and PrecisionBit : GAMBIT modules for computing mass spectra, particle decay rates and precision observables
- 2018
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 78:1
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Tidskriftsartikel (refereegranskat)abstract
- We present the GAMBIT modules SpecBit, DecayBit and PrecisionBit. Together they provide a new framework for linking publicly available spectrum generators, decay codes and other precision observable calculations in a physically and statistically consistent manner. This allows users to automatically run various combinations of existing codes as if they are a single package. The modular design allows software packages fulfilling the same role to be exchanged freely at runtime, with the results presented in a common format that can easily be passed to downstream dark matter, collider and flavour codes. These modules constitute an essential part of the broader GAMBIT framework, a major new software package for performing global fits. In this paper we present the observable calculations, data, and likelihood functions implemented in the three modules, as well as the conventions and assumptions used in interfacing them with external codes. We also present 3-BIT-HIT, a command-line utility for computing mass spectra, couplings, decays and precision observables in the MSSM, which shows how the three modules can easily be used independently of GAMBIT.
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| 12. |
- Athron, Peter, et al.
(författare)
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Status of the scalar singlet dark matter model
- 2017
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 77:8
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Tidskriftsartikel (refereegranskat)abstract
- One of the simplest viable models for dark matter is an additional neutral scalar, stabilised by a symmetry. Using the GAMBIT package and combining results from four independent samplers, we present Bayesian and frequentist global fits of this model. We vary the singlet mass and coupling along with 13 nuisance parameters, including nuclear uncertainties relevant for direct detection, the local dark matter density, and selected quark masses and couplings. We include the dark matter relic density measured by Planck, direct searches with LUX, PandaX, SuperCDMS and XENON100, limits on invisible Higgs decays from the Large Hadron Collider, searches for high-energy neutrinos from dark matter annihilation in the Sun with IceCube, and searches for gamma rays from annihilation in dwarf galaxies with the Fermi-LAT. Viable solutions remain at couplings of order unity, for singlet masses between the Higgs mass and about 300 GeV, and at masses above 1 TeV. Only in the latter case can the scalar singlet constitute all of dark matter. Frequentist analysis shows that the low-mass resonance region, where the singlet is about half the mass of the Higgs, can also account for all of dark matter, and remains viable. However, Bayesian considerations show this region to be rather fine-tuned.
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| 13. |
- Baltz, Edward A., et al.
(författare)
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Pre-launch estimates for GLAST sensitivity to Dark Matter annihilation signals
- 2008
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; 0807:013
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the sensitivity of the Gamma-ray Large Area Space Telescope (GLAST) for indirectly detecting weakly interacting massive particles (WIMPs) through the γ-ray signal that their pair annihilation produces. WIMPs are among the favorite candidates for explaining the compelling evidence that about 80% of the mass in the Universe is non-baryonic dark matter (DM). They are serendipitously motivated by various extensions of the standard model of particle physics such as supersymmetry and universal extra dimensions (UED). With its unprecedented sensitivity and its very large energy range (20 MeV to more than 300 GeV) the main instrument on board the GLAST satellite, the Large Area Telescope (LAT), will open a new window of discovery. As our estimates show, the LAT will be able to detect an indirect DM signature for a large class of WIMP models given a cuspy profile for the DM distribution. Using the current state of the art Monte Carlo and event reconstruction software developed within the LAT collaboration, we present preliminary sensitivity studies for several possible sources inside and outside the Galaxy. We also discuss the potential of the LAT to detect UED via the electron/positron channel. Diffuse background modeling and other background issues that will be important in setting limits or seeing a signal are presented
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| 14. |
- Berg, Marcus, et al.
(författare)
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Neutralino Dark Matter in BMSSM Effective Theory
- 2009
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :08
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Tidskriftsartikel (refereegranskat)abstract
- We study thermal neutralino dark matter in an effective field theory extension of the MSSM, called ``Beyond the MSSM'' (BMSSM) in Dine, Seiberg and Thomas (2007). In this class of effective field theories, the field content of the MSSM is unchanged, but the little hierarchy problem is alleviated by allowing small corrections to the Higgs/higgsino part of the Lagrangian. We perform parameter scans and compute the dark matter relic density. The light higgsino LSP scenario is modified the most; we find new regions of parameter space compared to the standard MSSM. This involves interesting interplay between the WMAP dark matter bounds and the LEP chargino bound. We also find some changes for gaugino LSPs, partly due to annihilation through a Higgs resonance, and partly due to coannihilation with light top squarks in models that are ruled in by the new effective terms.
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| 15. |
- Bergström, Lars, et al.
(författare)
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Complementarity of direct dark matter detection and indirect detection through gamma rays
- 2011
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 83:4, s. 045024-
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Tidskriftsartikel (refereegranskat)abstract
- We show, by using an extensive sample of viable supersymmetric models as templates, that indirect detection of dark matter through gamma rays may have a large potential for identifying the nature of dark matter. This is, in particular, true also for models that give too weak dark matter-nucleon scattering cross sections to be probed by present and planned direct detection experiments. Also models with a mass scale too high to be accessible at CERN's LHC accelerator may show up in next-generation imaging Cherenkov telescope arrays. Based on our findings, we therefore suggest to view indirect searches as genuine particle physics experiments, complementing other strategies to probe so far unknown regions in the parameter space of e.g. supersymmetric models, and propose a new approach that would make use of telescopes dedicated for dark matter searches. As a concrete example for the potential of such an approach, we consider an array of imaging air Cherenkov telescopes, the Dark Matter Array (DMA), and show that such an experiment could extend present-day limits by several orders of magnitude, reaching a large class of models that would remain undetected in both direct detection experiments and searches at the LHC. In addition, in a sizable part of the parameter space, signals from more than one type of dark matter detection experiment would be possible, something that may eventually be necessary in order to identify the dark matter candidate.
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| 16. |
- Bergström, Lars, 1952-, et al.
(författare)
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Gamma-ray and Radio Constraints of High Positron Rate Dark Matter Models Annihilating into New Light Particles
- 2009
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 79:8, s. 081303-
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Tidskriftsartikel (refereegranskat)abstract
- The possibility of explaining the positron and electron excess recently found by the PAMELA and ATIC collaborations in terms of dark matter (DM) annihilation has attracted considerable attention. Models surviving bounds from, e.g, antiproton production generally fall into two classes, where either DM annihilates directly with a large branching fraction into light leptons, or, as in the recent models of Arkani-Hamed et al., and of Nomura and Thaler, the annihilation gives low-mass (pseudo)scalars or vectors $\phi$ which then decay into $\mu^+\mu^-$ or $e^+e^-$. While the constraints on the first kind of models have recently been treated by several authors, we study here specifically models of the second type which rely on an efficient Sommerfeld enhancement in order to obtain the necessary boost in the annihilation cross section. We compute the photon flux generated by QED radiative corrections to the decay of $\phi$ and show that this indeed gives a rather spectacular broad peak in $E^2d\sigma/dE$, that for these extreme values of the cross section violate gamma-ray observations of the Galactic center for DM density profiles steeper than that of Navarro, Frenk and White. The most stringent constraint comes from the comparison of the predicted synchrotron radiation in the central part of the Galaxy with radio observations of Sgr A*. For the most commonly adopted DM profiles, the models that provide a good fit to the PAMELA and ATIC data are ruled out, unless there are physical processes that boost the local anti-matter fluxes more than one order of magnitude, while not affecting the gamma-ray or radio fluxes.
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| 17. |
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| 18. |
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| 19. |
- Bertoli, Gabriele, 1983-
(författare)
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Search for Supersymmetry in Monojet Final States with the ATLAS Experiment
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Large Hadron Collider is the most powerful particle accelerator built to date. The LHC is a proton–proton and heavy ion collider, in 2015 it operated at an un- precedented center of mass energy of sqrt(s) = 13 TeV. This thesis presents the results of the search for physics beyond the Standard Model of particle physics in a compressed supersymmetric squark–neutralino model. The present work uses an experimental sig- nature with a single high energetic jet and large missing transverse energy, so called monojet signature. The search is carried out using an integrated luminosity of 3.2 inverse femtobarn recorded by the ATLAS experiment in 2015. No significant excess compared to the Standard Model prediction has been observed thus a 95% CL limit has been set on the production of squark pairs with the subsequent decay ~q -> q + chi01 (q = u, d, c, s). Squark masses up to 608 GeV are excluded for m(~q) - m(chi01) = 5 GeV significantly improving earlier results.The Tile Calorimeter is the ATLAS hadronic calorimeter covering the central region of the detector. It is designed to measure hadrons, jets, tau particles and missing energy. In order to accurately be able to properly reconstruct these physical objects a careful description of the electronic noise is required. This thesis presents the work done in updating, monitoring and studying the noise calibration constants used in the processing of data and the identification of hadronic jets. These studies showed an unexpected variation over time of the cell noise and further investigation led to discover that the tile noise filter was not behaving as expected in some situations in approximately 5% of the detector cells.
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| 20. |
- Blennow, Mattias, 1980-, et al.
(författare)
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Neutrinos from WIMP annihilations in the Sun including neutrino oscillations
- 2011
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Ingår i: The Proceedings of the 22nd International Conference on Neutrino Physics and Astrophysics. - : Elsevier. ; , s. 37-38
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Konferensbidrag (refereegranskat)abstract
- The prospects to detect neutrinos from the Sun arising from dark matter annihilations in the core of the Sun are reviewed. Emphasis is placed on new work investigating the effects of neutrino oscillations on the expected neutrino fluxes.
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