| 1. |
- Aalbers, J., et al.
(author)
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A next-generation liquid xenon observatory for dark matter and neutrino physics
- 2023
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In: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 50:1
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Research review (peer-reviewed)abstract
- The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector.
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| 2. |
- Aartsen, M. G., et al.
(author)
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IceCube-Gen2 : the window to the extreme Universe
- 2021
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In: Journal of Physics G. - : Institute of Physics Publishing (IOPP). - 0954-3899 .- 1361-6471. ; 48:6
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Journal article (peer-reviewed)abstract
- The observation of electromagnetic radiation from radio to gamma-ray wavelengths has provided a wealth of information about the Universe. However, at PeV (10(15) eV) energies and above, most of the Universe is impenetrable to photons. New messengers, namely cosmic neutrinos, are needed to explore the most extreme environments of the Universe where black holes, neutron stars, and stellar explosions transform gravitational energy into non-thermal cosmic rays. These energetic particles have millions of times higher energies than those produced in the most powerful particle accelerators on Earth. As neutrinos can escape from regions otherwise opaque to radiation, they allow an unique view deep into exploding stars and the vicinity of the event horizons of black holes. The discovery of cosmic neutrinos with IceCube has opened this new window on the Universe. IceCube has been successful in finding first evidence for cosmic particle acceleration in the jet of an active galactic nucleus. Yet, ultimately, its sensitivity is too limited to detect even the brightest neutrino sources with high significance, or to detect populations of less luminous sources. In this white paper, we present an overview of a next-generation instrument, IceCube-Gen2, which will sharpen our understanding of the processes and environments that govern the Universe at the highest energies. IceCube-Gen2 is designed to: (a) Resolve the high-energy neutrino sky from TeV to EeV energies (b) Investigate cosmic particle acceleration through multi-messenger observations (c) Reveal the sources and propagation of the highest energy particles in the Universe (d) Probe fundamental physics with high-energy neutrinos IceCube-Gen2 will enhance the existing IceCube detector at the South Pole. It will increase the annual rate of observed cosmic neutrinos by a factor of ten compared to IceCube, and will be able to detect sources five times fainter than its predecessor. Furthermore, through the addition of a radio array, IceCube-Gen2 will extend the energy range by several orders of magnitude compared to IceCube. Construction will take 8 years and cost about $350M. The goal is to have IceCube-Gen2 fully operational by 2033. IceCube-Gen2 will play an essential role in shaping the new era of multi-messenger astronomy, fundamentally advancing our knowledge of the high-energy Universe. This challenging mission can be fully addressed only through the combination of the information from the neutrino, electromagnetic, and gravitational wave emission of high-energy sources, in concert with the new survey instruments across the electromagnetic spectrum and gravitational wave detectors which will be available in the coming years.
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| 3. |
- Abdullahi, Asli M., et al.
(author)
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The present and future status of heavy neutral leptons
- 2023
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In: Journal of Physics G. - : Institute of Physics Publishing (IOPP). - 0954-3899 .- 1361-6471. ; 50:2
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Journal article (peer-reviewed)abstract
- The existence of nonzero neutrino masses points to the likely existence of multiple Standard Model neutral fermions. When such states are heavy enough that they cannot be produced in oscillations, they are referred to as heavy neutral leptons (HNLs). In this white paper, we discuss the present experimental status of HNLs including colliders, beta decay, accelerators, as well as astrophysical and cosmological impacts. We discuss the importance of continuing to search for HNLs, and its potential impact on our understanding of key fundamental questions, and additionally we outline the future prospects for next-generation future experiments or upcoming accelerator run scenarios.
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| 4. |
- Abraham, Roshan Mammen, et al.
(author)
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Tau neutrinos in the next decade : from GeV to EeV
- 2022
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In: Journal of Physics G. - : Institute of Physics Publishing (IOPP). - 0954-3899 .- 1361-6471. ; 49:11
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Journal article (peer-reviewed)abstract
- Tau neutrinos are the least studied particle in the standard model. This whitepaper discusses the current and expected upcoming status of tau neutrino physics with attention to the broad experimental and theoretical landscape spanning long-baseline, beam-dump, collider, and astrophysical experiments. This whitepaper was prepared as a part of the NuTau2021 Workshop.
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| 5. |
- Addazi, A., et al.
(author)
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New high-sensitivity searches for neutrons converting into antineutrons and/or sterile neutrons at the HIBEAM/NNBAR experiment at the European Spallation Source
- 2021
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In: Journal of Physics G. - : Institute of Physics Publishing (IOPP). - 0954-3899 .- 1361-6471. ; 48:7
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Journal article (peer-reviewed)abstract
- The violation of baryon number, , is an essential ingredient for the preferential creation of matter over antimatter needed to account for the observed baryon asymmetry in the Universe. However, such a process has yet to be experimentally observed. The HIBEAM/NNBAR program is a proposed two-stage experiment at the European Spallation Source to search for baryon number violation. The program will include high-sensitivity searches for processes that violate baryon number by one or two units: free neutron–antineutron oscillation () via mixing, neutron–antineutron oscillation via regeneration from a sterile neutron state (), and neutron disappearance (n → n'); the effective process of neutron regeneration () is also possible. The program can be used to discover and characterize mixing in the neutron, antineutron and sterile neutron sectors. The experiment addresses topical open questions such as the origins of baryogenesis and the nature of dark matter, and is sensitive to scales of new physics substantially in excess of those available at colliders. A goal of the program is to open a discovery window to neutron conversion probabilities (sensitivities) by up to three orders of magnitude compared with previous searches. The opportunity to make such a leap in sensitivity tests should not be squandered. The experiment pulls together a diverse international team of physicists from the particle (collider and low energy) and nuclear physics communities, while also including specialists in neutronics and magnetics.
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| 6. |
- Akeroyd, A. G., et al.
(author)
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Slight excess at 130 GeV in search for a charged Higgs boson decaying to a charm quark and a bottom quark at the Large Hadron Collider
- 2022
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In: Journal of Physics G. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 49:8
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Journal article (peer-reviewed)abstract
- Searches for a charged Higgs boson (H-+/-) decaying to a charm quark and a bottom quark (H +/- -> cb) have been carried out at the Large Hadron Collider (LHC) in the decay of top quarks (t -> H(+/-)b). In a recent search by the ATLAS collaboration (with all run II data, 139 fb(-1)) a local excess of around 3 sigma has been observed, which is best fitted by a charged Higgs boson with a mass (m(H)+/-) of around 130 GeV and a product of branching ratios (BRs) given by BR(t -> H(+/-)b) x BR(H-+/- -> cb) = 0.16% +/- 0.06%. In the context of two-Higgs-doublet models (2HDM) with independent Yukawa couplings for H-+/- we present the parameter space for which this excess (assuming it to be genuine) can be accommodated, taking into account the limits from LHC searches for H-+/- -> cs and H-+/- -> tau nu at m(H)+/- = 130 GeV and the constraint from b -> s gamma. It is then shown that such an excess cannot be explained in 2HDMs with natural flavour conservation, but can be accommodated in the flipped three-Higgs-doublet model (3HDM) and in the aligned 2HDM (A2HDM). Upcoming searches with 139 fb(-1) in the channels H-+/- -> cb (CMS), H-+/- -> cs (ATLAS/CMS) and H-+/- -> tau nu (ATLAS/CMS) will determine if the excess is the first sign of an H-+/- with m(H)+/- = 130 GeV.
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| 7. |
- Akeroyd, A. G., et al.
(author)
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The decay A(0) -> h(0)Z(*) in the inverted hierarchy scenario and its detection prospects at the large hadron collider
- 2023
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In: Journal of Physics G. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 50:9
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Journal article (peer-reviewed)abstract
- Searches are being carried out at the large hadron collider (LHC) for the decay of the CP-odd scalar (A(0)) in two-Higgs-doublet models (2HDMs) with natural flavour conservation (NFC) in the channel A(0) -> h(0)Z (with m(h)(0) = 125 GeV and Z on-shell). In the absence of any signal, limits on the parameter space of [tan beta, cos(beta - alpha), mA0] in each 2HDM are derived for m(A)(0) > 225 GeV. In this work, we consider the scenario of inverted hierarchy with m(h)(0) < 125 GeV and m(H)(0) = 125 GeV in which the decay A(0) -> h(0)Z(*) (i.e. including the case of an off-shell Z) can have a large branching ratio in the 2HDM (Type I) for m(A)(0) < 225 GeV. We calculate the signal cross section sigma(gg -> A(0)) ' BR(A(0) -> h(0)Z (*)) ' BR(h(0) -> b<(b)over bar>) in the 2HDM (Type I) with NFC and compare its magnitude with the cross section for the case of normal hierarchy (m(h)(0) = 125 GeV) that is currently being searched for at the LHC. For the experimentally unexplored region m(A)(0) < 225 GeV it is shown that the above cross section for signal events in the scenario of inverted hierarchy can be of the order of a few picobarns. Such sizeable cross sections are several orders of magnitude larger than the cross sections for the case of normal hierarchy, thus motivating an extension of the ongoing searches for A(0) -> h(0)Z(*) to probe the scenario of inverted hierarchy.
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| 8. |
- Alimena, Juliette, et al.
(author)
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Searching for long-lived particles beyond the Standard Model at the Large Hadron Collider
- 2020
-
In: Journal of Physics G. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 47:9
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Journal article (peer-reviewed)abstract
- Particles beyond the Standard Model (SM) can generically have lifetimes that are long compared to SM particles at the weak scale. When produced at experiments such as the Large Hadron Collider (LHC) at CERN, these long-lived particles (LLPs) can decay far from the interaction vertex of the primary proton-proton collision. Such LLP signatures are distinct from those of promptly decaying particles that are targeted by the majority of searches for new physics at the LHC, often requiring customized techniques to identify, for example, significantly displaced decay vertices, tracks with atypical properties, and short track segments. Given their non-standard nature, a comprehensive overview of LLP signatures at the LHC is beneficial to ensure that possible avenues of the discovery of new physics are not overlooked. Here we report on the joint work of a community of theorists and experimentalists with the ATLAS, CMS, and LHCb experiments-as well as those working on dedicated experiments such as MoEDAL, milliQan, MATHUSLA, CODEX-b, and FASER-to survey the current state of LLP searches at the LHC, and to chart a path for the development of LLP searches into the future, both in the upcoming Run 3 and at the high-luminosity LHC. The work is organized around the current and future potential capabilities of LHC experiments to generally discover new LLPs, and takes a signature-based approach to surveying classes of models that give rise to LLPs rather than emphasizing any particular theory motivation. We develop a set of simplified models; assess the coverage of current searches; document known, often unexpected backgrounds; explore the capabilities of proposed detector upgrades; provide recommendations for the presentation of search results; and look towards the newest frontiers, namely high-multiplicity 'dark showers', highlighting opportunities for expanding the LHC reach for these signals.
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| 9. |
- Andrews, Harry Arthur, et al.
(author)
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Novel tools and observables for jet physics in heavy-ion collisions
- 2020
-
In: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 47:6
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Journal article (peer-reviewed)abstract
- Studies of fully-reconstructed jets in heavy-ion collisions aim at extracting thermodynamical and transport properties of hot and dense QCD matter. Recently, a plethora of new jet substructure observables have been theoretically and experimentally developed that provide novel precise insights on the modifications of the parton radiation pattern induced by a QCD medium. This report, summarizing the main lines of discussion at the 5th Heavy Ion Jet Workshop and CERN TH institute 'Novel tools and observables for jet physics in heavy-ion collisions' in 2017, presents a first attempt at outlining a strategy for isolating and identifying the relevant physical processes that are responsible for the observed medium-induced jet modifications. These studies combine theory insights, based on the Lund parton splitting map, with sophisticated jet reconstruction techniques, including grooming and background subtraction algorithms.
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| 10. |
- Basu, Sumit, et al.
(author)
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Multiplicity and pseudo-rapidity density distributions of charged particles produced in pp, pA and AA collisions at RHIC & LHC energies
- 2020
-
In: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 48:2
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Journal article (peer-reviewed)abstract
- Multiplicity and pseudorapidity (η) density (dN ch/dη) distributions of charged hadrons provide key information towards understanding the particle production mechanisms and initial conditions of high-energy heavy-ion collisions. However, detector constraints limit the η-range across which charged particle measurements can be carried out. Extrapolating the measured distributions to large η-range by parameterizing measured distributions and by using calculations from event generators, we characterize the production of charged particles over the full kinematic range. In the present study, we use three different ans atze to obtain quantitative descriptions of the shape of pseudorapidity distributions of charged hadrons produced in pp, p-A, and A-A collisions for beam energies (s NN) ranging from a few GeV to a few TeV corresponding to RHIC and LHC energies. We study the limiting fragmentation behavior in these collisions and report evidence for participant-scaling violations in high-energy collisions at the TeV scale. We additionally examine measured pseudorapidity distributions to constrain models describing initial conditions of particle production. We predict the centrality dependence of charged particle multiplicity distributions at FAIR and NICA energies and give an estimation of charged particle multiplicity at η = 0 for the proposed HE-LHC and FCC energies.
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