Tien Shan data on inelastic proton-air cross section at 10 PeV [HEAP]


New data on the absolute value on the inelastic proton-air cross section at 10 PeV are presented. Conclusion is made about the growth with energy of the inelastic proton-air cross section according to comparisons with experimental data were obtained at the Tien Shan complex array on various components of extensive air showers: hadrons, Cherenkov light and electrons with many different calculated models of cosmic rays interactions at the atmosphere. The analysis showed that the rise conforms to 7-9 % per one order of the energy from 0.2 TeV (accelerators with fixed targets) to 10 PeV (EAS cosmic rays). That corresponds to around 350 mb at 1 PeV and 380 mb at 10 PeV of primary cosmic rays. These data corresponds better to the QGSJET-II-04 model version.

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N. Nesterova
Thu, 22 Feb 18

Comments: 4 pages, 3 figures. arXiv admin note: substantial text overlap with arXiv:1506.04291

Projected WIMP sensitivity of the LUX-ZEPLIN (LZ) dark matter experiment [IMA]


LUX-ZEPLIN (LZ) is a next generation dark matter direct detection experiment that will operate 4850 feet underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA. Using a two-phase xenon detector with an active mass of 7 tonnes, LZ will search primarily for low-energy interactions with Weakly Interacting Massive Particles (WIMPs), which are hypothesized to make up the dark matter in our galactic halo. In this paper, the projected WIMP sensitivity of LZ is presented based on the latest background estimates and simulations of the detector. For a 1000 live day run using a 5.6 tonne fiducial mass, LZ is projected to exclude at 90% confidence level spin-independent WIMP-nucleon cross sections above $1.6 \times 10^{-48}$ cm$^{2}$ for a 40 $\mathrm{GeV}/c^{2}$ mass WIMP. Additionally, a $5\sigma$ discovery potential is projected reaching cross sections below the existing and projected exclusion limits of similar experiments that are currently operating. For spin-dependent WIMP-neutron(-proton) scattering, a sensitivity of $2.7 \times 10^{-43}$ cm$^{2}$ ($8.1 \times 10^{-42}$ cm$^{2}$) for a 40 $\mathrm{GeV}/c^{2}$ mass WIMP is expected. With construction well underway, LZ is on track for underground installation at SURF in 2019 and will start collecting data in 2020.

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D. Akerib, C. Akerlof, S. Alsum, et. al.
Mon, 19 Feb 18

Comments: 14 pages, 11 figures

How blind are underground and surface detectors to strongly interacting Dark Matter? [CL]


Above a critical dark matter-nucleus scattering cross section any terrestrial direct detection experiment loses sensitivity to dark matter, since the Earth crust, atmosphere, and potential shielding layers start to block off the dark matter particles. This critical cross section is commonly determined by describing the average energy loss of the dark matter particles analytically. However, this treatment overestimates the stopping power of the Earth crust. Therefore the obtained bounds should be considered as conservative. We perform Monte Carlo simulations to determine the precise value of the critical cross section for various direct detection experiments and compare them to other dark matter constraints in the low mass regime. In this region we find parameter space where typical underground and surface detectors are completely blind to dark matter. This “hole” in the parameter space can hardly be closed with an increase in the detector exposure. Dedicated surface or high-altitude experiments may be the only way to directly probe this part of the parameter space.

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T. Emken and C. Kouvaris
Wed, 14 Feb 18

Comments: 12 pages, 7 figures

Discriminating WIMP-nucleus response functions in present and future XENON-like direct detection experiments [CL]


The standard interpretation of direct-detection limits on dark matter involves particular assumptions of the underlying WIMP-nucleus interaction, such as, in the simplest case, the choice of a Helm form factor that phenomenologically describes an isoscalar spin-independent interaction. In general, the interaction of dark matter with the target nuclei may well proceed via different mechanisms, which would lead to a different shape of the corresponding nuclear structure factors as a function of the momentum transfer $q$. We study to what extent different WIMP-nucleus responses can be differentiated based on the $q$-dependence of their structure factors (or “form factors”). We assume an overall strength of the interaction consistent with present spin-independent limits and consider an exposure corresponding to XENON1T-like, XENONnT-like, and DARWIN-like direct detection experiments. We find that, as long as the interaction strength does not lie too much below current limits, the DARWIN settings allow a conclusive discrimination of many different response functions based on their $q$-dependence, with immediate consequences for elucidating the nature of dark matter.

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A. Fieguth, M. Hoferichter, P. Klos, et. al.
Wed, 14 Feb 18

Comments: 10 pages, 7 figures

Future Ground-based Wide Field of View Air Shower Detectors [HEAP]


Extensive air shower (EAS) arrays directly sample the shower particles that reach the observation altitude. They are wide field of view (FoV) detectors able to view the whole sky simultaneously and continuously. In fact, EAS arrays have an effective FoV of about 2 sr and operate with a duty cycle of $\sim$100\%. This capability makes them well suited to study extended sources, such as the Galactic diffuse emission and measure the spectra of Galactic sources at the highest energies (near or beyond 100 TeV). Their sensitivity in the sub-TeV/TeV energy domain cannot compete with that of Cherenkov telescopes, but the wide FoV is ideal to perform unbiased sky surveys, discover transients or explosive events (GRBs) and monitor variable or flaring sources such as Active Galactic Nuclei (AGN). An EAS array is able to detect at the same time events induced by photons and charged cosmic rays, thus studying the connection between these two messengers of the non-thermal Universe. Therefore, these detectors are, by definition, multi-messenger instruments.
Wide FoV telescopes are crucial for a multi-messenger study of the Gravitational Wave events due to their capability to survey simultaneously all the large sky regions identified by LIGO and VIRGO, looking for a possible correlated $\gamma$-ray emission.
In this contribution we summarize the scientific motivations which push the construction of new wide FoV air shower detectors and introduce the future instruments currently under installation. Finally, we emphasize the need of an EAS array in the Southern hemisphere to monitor the Inner Galaxy and face a number of important open problems.

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G. Sciascio
Wed, 14 Feb 18

Comments: 19 pages, Invited talk, XII Multifrequency Behaviour of High Energy Cosmic Sources Workshop, 12-17 June, 2017, Palermo, Italy

The discreet charm of higgsino dark matter – a pocket review [CL]


We give a brief review of the current constraints and prospects for detection of higgsino dark matter in low-scale supersymmetry. In the first part we argue, after performing a survey of all potential dark matter particles in the MSSM, that the (nearly) pure higgsino is the only candidate emerging virtually unscathed from the wealth of observational data of recent years. In doing so by virtue of its gauge quantum numbers and electroweak symmetry breaking only, it maintains at the same time a relatively high degree of model-independence. In the second part we properly review the prospects for detection of a higgsino-like neutralino in direct underground dark matter searches, collider searches, and indirect astrophysical signals. We provide estimates for the typical scale of the superpartners and fine tuning in the context of traditional scenarios where the breaking of supersymmetry is mediated at about the scale of Grand Unification and where strong expectations for a timely detection of higgsinos in underground detectors are closely related to the measured 125 GeV mass of the Higgs boson at the LHC.

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K. Kowalska and E. Sessolo
Tue, 13 Feb 18

Comments: 28 pages, 7 figures. Contribution to the special issue “New Physics Landmarks: Dark Matter and Neutrino Masses” of Advances in High Energy Physics

Model-independent constraints on dark matter annihilation in dwarf spheroidal galaxies [CL]


We present a general, model-independent formalism for determining bounds on the production of photons in dwarf spheroidal galaxies via dark matter annihilation, applicable to any set of assumptions about dark matter particle physics or astrophysics. As an illustration, we analyze gamma-ray data from the Fermi Large Area Telescope to constrain a variety of nonstandard dark matter models, several of which have not previously been studied in the context of dwarf galaxy searches.

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K. Boddy, J. Kumar, D. Marfatia, et. al.
Tue, 13 Feb 18

Comments: 14 pages, 10 figures, 1 table. The unnormalized background distribution for each dwarf is available in an ancillary file