Prospects of type-II seesaw at future colliders in light of the DAMPE $e^+ e^-$ excess [CL]

The DAMPE $e^+ e^-$ excess at around 1.4 TeV could be explained in the type-II seesaw model with a scalar dark mater $D$ which is stabilized by a discrete $Z_2$ symmetry. The simplest scenario is the annihilation $DD \to H^{++} H^{–}$ followed by the subsequent decay $H^{\pm\pm} \to e^\pm e^\pm$, with both the DM and triplet scalars roughly 3 TeV with a small mass splitting. In addition to the Drell-Yan process at future 100 TeV hadron colliders, the doubly-charged components could also be produced at lepton colliders like ILC and CLIC in the off-shell mode, and mediate lepton flavor violating processes $e^+ e^- \to \ell_i^\pm \ell_j^\mp$ (with $i \neq j$). A wide range of parameter space of the type-II seesaw could be probed, which are well below the current stringent lepton flavor constraints.

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Y. Sui and Y. Zhang
Tue, 12 Dec 17

Comments: 8 pages, 5 figures

An algorithm to resolve γ-rays from charged cosmic rays with DAMPE [CL]

The DArk Matter Particle Explorer (DAMPE), also known as Wukong in China, launched on December 17, 2015, is a new high energy cosmic ray and {\gamma}-ray satellite-borne observatory in space. One of the main scientific goals of DAMPE is to observe GeV-TeV high energy {\gamma}-rays with accurate energy, angular, and time resolution, to indirectly search for dark matter particles and for the study of high energy astrophysics. Due to the comparatively higher fluxes of charged cosmic rays with respect to {\gamma}-rays, it is challenging to identify {\gamma}-rays with sufficiently high efficiency minimizing the amount of charged cosmic ray contamination. In this work we present a method to identify {\gamma}-rays in DAMPE data based on Monte Carlo simulations, using the powerful electromagnetic/hadronic shower discrimination provided by the calorimeter and the veto detection of charged particles provided by the plastic scintillation detector. Monte Carlo simulations show that after this selection the number of electrons and protons that contaminate the selected {\gamma}-ray events at $\sim10$ GeV amounts to less than 1% of the selected sample. Finally, we use flight data to verify the effectiveness of the method by highlighting known {\gamma}-ray sources in the sky and by reconstructing preliminary light curves of the Geminga pulsar.

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Z. Xu, K. Duan, Z. Shen, et. al.
Mon, 11 Dec 17

Comments: 15 pages,16 figures

Flavor Structure of the Cosmic-Ray Electron/Positron Excesses at DAMPE [HEAP]

The Dark Matter Particle Explorer (DAMPE) satellite detector newly announced its first result for measuring the cosmic-ray electron/positron (CRE) energy spectrum up to 4.6TeV, including a peak-like event excess around 1.4TeV. We observe a sizable hidden excess in the DAMPE CRE spectrum over a fairly wide region (0.6-1.1)TeV, which has a non-peak-like structure. We find that this new excess can be explained by a set of 1.4TeV $\mu^\pm$ events with subsequent decays into $e^\pm$ plus neutrinos. To explain this new excess together with the 1.4TeV peak, we show that the flavor structure of the original lepton final-state produced by the dark matter (DM) annihilations (or other mechanism) should have a composition ratio $N_e : (N_\mu + \frac {1}{6} N_\tau) \approx 1:12.7$. We point out some simple realizations, including the simplest case, $N_e : N_\mu : N_\tau \approx 1:12.7:0$. We further discuss the implications for the flavor-related DM model buildings.

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S. Ge and H. He
Fri, 8 Dec 17

Comments: 6 pages, 3 figures

A Simple Testable Model of Baryon Number Violation: Baryogenesis, Dark Matter, Neutron-Antineutron Oscillation and Collider Signals [CL]

We study a simple TeV-scale model of baryon number violation which explains the observed proximity of the dark matter and baryon abundances. The model has constraints arising from both low and high-energy processes, and in particular, predicts a sizeable rate for the neutron-antineutron ($n-\bar{n}$) oscillation at low energy and the monojet signal at the LHC. We find an interesting complementarity among the constraints arising from the observed baryon asymmetry, ratio of dark matter and baryon abundances, $n-\bar{n}$ oscillation lifetime and the LHC monojet signal. There are regions in the parameter space where the $n-\bar{n}$ oscillation lifetime is found to be more constraining than the LHC constraints, which illustrates the importance of the next-generation $n-\bar{n}$ oscillation experiments.

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R. Allahverdi, P. Dev and B. Dutta
Fri, 8 Dec 17

Comments: 8 pages, 4 figures

Muon detector for the COSINE-100 experiment [CL]

The COSINE-100 dark matter search experiment has started taking physics data with the goal of performing an independent measurement of the annual modulation signal observed by DAMA/LIBRA. A muon detector was constructed by using plastic scintillator panels in the outermost layer of the shield surrounding the COSINE-100 detector. It is used to detect cosmic ray muons in order to understand the impact of the muon annual modulation on dark matter analysis. Assembly and initial performance test of each module have been performed at a ground laboratory. The installation of the detector in Yangyang Underground Laboratory (Y2L) was completed in the summer of 2016. Using three months of data, the muon underground flux was measured to be 328 $\pm$ 1(stat.)$\pm$ 10(syst.) muons/m$^2$/day. In this report, the assembly of the muon detector and the results from the analysis are presented.

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100. Collaboration-COSINE, H. Prihtiadi, G. Adhikari, et. al.
Thu, 7 Dec 17

Comments: 11 pages, 19 figures

Design and Construction of the DEAP-3600 Dark Matter Detector [IMA]

The Dark matter Experiment using Argon Pulse-shape discrimination (DEAP) has been designed for a direct detection search for particle dark matter using a single-phase liquid argon target. The projected cross section sensitivity for DEAP-3600 to the spin-independent scattering of Weakly Interacting Massive Particles (WIMPs) on nucleons is $10^{-46}~\rm{cm}^{2}$ for a 100 GeV/$c^2$ WIMP mass with a fiducial exposure of 3 tonne-years. This paper describes the physical properties and construction of the DEAP-3600 detector.

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P. Amaudruz, M. Baldwin, M. Batygov, et. al.
Thu, 7 Dec 17

Comments: 70 pages, 24 figures, to be submitted to Astroparticle Physics Journal

Backgrounds and pulse shape discrimination in the ArDM liquid argon TPC [CL]

The ArDM experiment completed a single-phase commissioning run in 2015 with an active liquid argon target of nearly one tonne in mass. The analysis of the data and comparison to simulations allowed for a test of the crucial detector properties and confirmed the low background performance of the setup. The statistical rejection power for electron recoil events using the pulse shape discrimination method was estimated using data from a Cf-252 neutron calibration source. Electron and nuclear recoil band profiles were found to be well described by Gaussian distributions. Employing such a model we derive values for the electron recoil statistical rejection power of more than 10$^8$ in the tonne-scale liquid argon target for events with more than 50 detected photons at a 50% acceptance for nuclear recoils. The Rn-222 emanation rate of the ArDM cryostat at room temperature was found to be 65.6$\pm$0.4 $\mu$Hz/l, and the Ar-39 specific activity from the employed atmospheric argon to be 0.95$\pm$0.05 Bq/kg. The cosmic muon flux at the Canfranc underground site was determined to be between 2 and 3.5$\times 10^{-3}m^{2}s^{-1}$ . These results pave the way for the next physics run of ArDM in the double-phase operational mode.

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ArDM. Collaboration, J. Calvo, C. Cantini, et. al.
Thu, 7 Dec 17

Comments: 17 pages, 10 figures