Recommendations of the LHC Dark Matter Working Group: Comparing LHC searches for heavy mediators of dark matter production in visible and invisible decay channels [CL]

Weakly-coupled TeV-scale particles may mediate the interactions between normal matter and dark matter. If so, the LHC would produce dark matter through these mediators, leading to the familiar ‘mono-X’ search signatures, but the mediators would also produce signals without missing momentum via the same vertices involved in their production. This document from the LHC Dark Matter Working Group suggests how to compare searches for these two types of signals in case of vector and axial-vector mediators, based on a workshop that took place on September 19/20, 2016 and subsequent discussions. These suggestions include how to extend the spin-1 mediated simplified models already in widespread use to include lepton couplings. This document also provides analytic calculations of the relic density in the simplified models and reports an issue that arose when ATLAS and CMS first began to use preliminary numerical calculations of the dark matter relic density in these models.

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A. Albert, M. Backovic, A. Boveia, et. al.
Fri, 17 Mar 17

Comments: 19 pages, 4 figures


Directional Sensitivity In Light-Mass Dark Matter Searches With Single-Electron Resolution Ionization Detectors [CL]

We present a method for using solid state detectors with directional sensitivity to dark matter interactions to detect low-mass Weakly Interacting Massive Particles (WIMPs) originating from galactic sources. In spite of a large body of literature for high-mass WIMP detectors with directional sensitivity, there is no available technique to cover WIMPs in the mass range <1 GeV. We argue that single-electron resolution semiconductor detectors allow for directional sensitivity once properly calibrated. We examine commonly used semiconductor material response to these low-mass WIMP interactions.

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F. Kadribasic, N. Mirabolfathi, K. Nordlund, et. al.
Fri, 17 Mar 17

Comments: N/A

The Novel ABALONE Photosensor Technology [CL]

The patented and proven ABALONE Photosensor Technology (Daniel Ferenc, U.S. Patent 9,064,678, 2010) has the capability of opening new horizons in the fields of fundamental physics, functional medical imaging, and nuclear security. This article discusses our new technology and overviews the unprecedented performance of ABALONE Photosensors, produced in the custom designed production line at UC Davis and continuously tested since 2013. In conclusion, the modern ABALONE Technology is far superior to prior art in performance, robustness and the capacity for integration into large area detector shells. It is about two orders of magnitude more cost effective while being mass-producible with a relatively low investment.

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D. Ferenc, A. Chang and M. Ferenc
Thu, 16 Mar 17

Comments: 16 pages, 7 figures, Submitted for publication to Nuclear Instruments And Methods In Physics Research A on March 12, 2017 (Ms. Ref. No.: NIMA-D-17-00243)

Powerful Solar Signatures of Long-Lived Dark Mediators [HEAP]

Dark matter capture and annihilation in the Sun can produce detectable high-energy neutrinos, providing a probe of the dark matter-proton scattering cross section. We consider the case when annihilation proceeds via long-lived dark mediators, which allows gamma rays to escape the Sun and reduces the attenuation of neutrinos. For gamma rays, there are exciting new opportunities, due to detailed measurements of GeV solar gamma rays with Fermi, and unprecedented sensitivities in the TeV range with HAWC and LHAASO. For neutrinos, the enhanced flux, particularly at higher energies ($\sim$TeV), allows a more sensitive dark matter search with IceCube and KM3NeT. We show that these search channels can be extremely powerful, potentially improving sensitivity to the dark matter spin-dependent scattering cross section by several orders of magnitude relative to present searches for high-energy solar neutrinos, as well as direct detection experiments.

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R. Leane, K. Ng and J. Beacom
Thu, 16 Mar 17

Comments: 16 pages, 8 figures

Global constraints on absolute neutrino masses and their ordering [CL]

Within the standard three-neutrino framework, the absolute neutrino masses and their ordering (either normal, NO, or inverted, IO) are currently unknown. However, the combination of current data coming from oscillation experiments, neutrinoless double beta decay searches, and cosmological surveys, can provide interesting constraints for such unknowns in the sub-eV mass range, down to O(0.1) eV in some cases. We discuss current limits on absolute neutrino mass observables by performing a global data analysis, that includes the latest results from oscillation experiments, neutrinoless double beta decay bounds from the KamLAND-Zen experiment, and constraints from representative combinations of Planck measurements and other cosmological data sets. In general, NO appears to be somewhat favored with respect to IO at the level of ~2 sigma, mainly by neutrino oscillation data (especially atmospheric), corroborated by cosmological data in some cases. Detailed constraints are obtained via the chi^2 method, by expanding the parameter space either around separate minima in NO and IO, or around the absolute minimum in any ordering. Implications for upcoming oscillation and non-oscillation neutrino experiments, including beta-decay searches, are also discussed.

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F. Capozzi, E. Valentino, E. Lisi, et. al.
Tue, 14 Mar 17

Comments: 17 pages, including 3 tables and 11 figures

A Reappraisal on Dark Matter Co-annihilating with a Top/Bottom Partner [CL]

We revisit the calculation of relic density of dark matter particles co-annihilating with a top or bottom partner, by properly including the QCD bound-states (onia) effects of the colored partners, as well as the relevant electroweak processes which become important in the low mass region. We carefully set up the complete framework that incorporates the relevant contributions and investigate their effects on the cosmologically preferred mass spectrum, which turn out to be comparable in size to those coming from the Sommerfeld enhancement. We apply the calculation to three scenarios: bino-stop and bino-sbottom co-annihilations in supersymmetry, and a vector dark matter co-annihilating with a fermionic top partner. In addition, we confront our analysis of the relic abundance with recent direct detection experiments and, in the case of bino-sbottom co-annihilation, collider searches at the LHC.

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W. Keung, I. Low and Y. Zhang
Fri, 10 Mar 17

Comments: 19 pages, 6 figures

Correlation of AOT with Relative Frequency of Air Showers with energy 10^{15} – 10^{16} eV by Yakutsk Data [IMA]

Long-term series of measurement of spectral transparency of the atmosphere (\lambda = 430 nm) and atmospheric optical thickness (AOT) measured by multimode photometer CE 318 in the region of Yakutsk array are analyzed. Correlation of AOT with intensity of air showers with small energies 10^{15} – 10^{16} eV is found. The variability of aerosol composition of the atmosphere during the registration period of the Cherenkov light should be taken into account since it may affect the quality of determining characteristics of air showers.

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S. Knurenko and I. Petrov
Tue, 7 Mar 17

Comments: XXV ECRS 2016 Proceedings – eConf C16-09-04.3

Collective neutrino oscillations and neutrino wave packets [CL]

Effects of decoherence by wave packet separation on collective neutrino oscillations in dense neutrino gases are considered. We estimate the length of the wave packets of neutrinos produced in core collapse supernovae and the expected neutrino coherence length, and then proceed to consider the decoherence effects within the density matrix formalism of neutrino flavour transitions. First, we demonstrate that for neutrino oscillations in vacuum the decoherence effects are described by a damping term in the equation of motion of the density matrix of a neutrino as a whole (as contrasted to that of the fixed-momentum components of the neutrino density matrix). Next, we consider neutrino oscillations in ordinary matter and dense neutrino backgrounds, both in the adiabatic and non-adiabatic regimes. In the latter case we study two specific models of adiabaticity violation — one with short-term and another with extended non-adiabaticity. It is demonstrated that, while in the adiabatic case a damping term is present in the equation of motion of the neutrino density matrix (just like in the vacuum oscillation case), no such term in general appears in the non-adiabatic regime.

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E. Akhmedov, J. Kopp and M. Lindner
Thu, 2 Mar 17

Comments: LaTeX, 38 pages

The Dark Side of MSW: Solar Neutrinos as a Probe of Dark Matter-Neutrino Interactions [CL]

Sterile neutrinos at the eV scale have long been studied in the context of anomalies in short baseline neutrino experiments. Their cosmology can be made compatible with our understanding of the early Universe provided the sterile neutrino sector enjoys a nontrivial dynamics with exotic interactions, possibly providing a link to the Dark Matter (DM) puzzle. Interactions between DM and neutrinos have also been proposed to address the long-standing “missing satellites” problem in the field of large scale structure formation. Motivated by these considerations, in this paper we discuss realistic scenarios with light steriles coupled to DM. We point out that within this framework active neutrinos acquire an effective coupling to DM that manifests itself as a new matter potential in the propagation within a medium of asymmetric DM. Assuming that at least a small fraction of DM has been captured by the Sun, we show that a sizable fraction of the parameter space of these scenarios can be probed by solar neutrino experiments, especially in the regime of small couplings and light mediators where all other probes become inefficient. In the latter regime these scenarios behave as familiar $3+1$ models in all channels except for solar data, where a Dark MSW effect takes place. Solar Dark MSW is characterized by sizable modifications of the most energetic $^8$B and CNO neutrinos, whereas the other fluxes remain largely unaffected.

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F. Capozzi, I. Shoemaker and L. Vecchi
Wed, 1 Mar 17

Comments: 19 pages, 6 figures

First Demonstration of a Scintillating Xenon Bubble Chamber for Dark Matter and CE$ν$NS Detection [CL]

A 30-gram xenon bubble chamber, operated at Northwestern University in June and November 2016, has for the first time observed simultaneous bubble nucleation and scintillation by nuclear recoils in liquid xenon. This chamber is instrumented with a CCD camera for near-IR bubble imaging, a solar-blind PMT to detect 175-nm xenon scintillation light, and a piezoelectric acoustic transducer to detect the ultrasonic emission from a growing bubble. The time-of-nucleation determined from the acoustic signal is used to correlate specific scintillation pulses with bubble-nucleating events. The observed single- and multiple-bubble rates when exposed to a $^{252}$Cf neutron source indicate that, for a thermodynamic “Seitz” threshold of 8.3 keV, the minimum nuclear recoil energy required to nucleate a bubble is between 11 and 25 keV. This is consistent with the observed scintillation spectrum for bubble-nucleating events. We see no evidence for bubble nucleation by gamma rays at the thresholds studied, setting a 90% CL upper limit of $6.3\times10^{-7}$ bubbles per gamma interaction at a 4.2-keV thermodynamic threshold. This indicates stronger gamma discrimination than in CF$_3$I bubble chambers, supporting the hypothesis that scintillation production suppresses bubble nucleation by electron recoils, while nuclear recoils nucleate bubbles as usual. These measurements establish the noble-liquid bubble chamber as a promising new technology for WIMP and CE$\nu$NS detection.

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D. Baxter, C. Chen, M. Crisler, et. al.
Wed, 1 Mar 17

Comments: 5 pages, 4 figures

Terrestrial Effects on Dark Matter-Electron Scattering Experiments [CL]

A well-studied possibility is that dark matter may reside in a sector secluded from the Standard Model, except for the so-called photon portal: kinetic mixing between the ordinary and dark photons. Such interactions can be probed at dark matter direct detection experiments, and new experimental techniques involving detection of dark matter-electron scattering offer new sensitivity to sub-GeV dark matter. Typically however it is implicitly assumed that the dark matter is not altered as it traverses the Earth to arrive at the detector. In this paper we study in detail the effects of terrestrial stopping on dark photon models of dark matter, and find that they significantly reduce the sensitivity of XENON10 and DAMIC. In particular we find that XENON10 only excludes masses in the range (5-3000) MeV while DAMIC only probes (20-50) MeV. Their corresponding cross section sensitivity is reduced to a window of cross sections between $(5\times 10^{-38}-10^{-30})~{\rm cm}^{2}$ for XENON10 and a small window around $\sim 10^{-31}~{\rm cm}^{2}$ for DAMIC. We also examine implications for a future DAMIC run.

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T. Emken, C. Kouvaris and I. Shoemaker
Tue, 28 Feb 17

Comments: 6 pages, 4 figures

Dark Matter Search Results from the PICO-60 C$_3$F$_8$ Bubble Chamber [CEA]

New results are reported from the operation of the PICO-60 dark matter detector, a bubble chamber filled with 52 kg of C$_3$F$_8$ located in the SNOLAB underground laboratory. As in previous PICO bubble chambers, PICO-60 C$_3$F$_8$ exhibits excellent electron recoil and alpha decay rejection, and the observed multiple-scattering neutron rate indicates a single-scatter neutron background of less than 1 event per month. A blind analysis of an efficiency-corrected 1167-kg-day exposure at a 3.3-keV thermodynamic threshold reveals no single-scattering nuclear recoil candidates, consistent with the predicted background. These results set the most stringent direct-detection constraint to date on the WIMP-proton spin-dependent cross section at 3.4 $\times$ 10$^{-41}$ cm$^2$ for a 30-GeV$\thinspace$c$^{-2}$ WIMP, more than one order of magnitude improvement from previous PICO results.

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C. Amole, M. Ardid, I. Arnquist, et. al.
Mon, 27 Feb 17

Comments: 6 pages, 6 figures

Cosmic Ray RF detection with the ASTRONEU array [CL]

Results will be shown from the ASTRONEU array developed and operated in the outskirts of Patras, Greece. An array of 9 scintillator detectors and 3 antennas were deployed to study Extensive Air Showers (EAS) as a tool for calibrating an underwater neutrino telescope, possible other applications in muon tomography, education purposes, and last but not least, the detection of air showers via their electromagnetic signature. This is the first stage of a total of 24 scintillator counters and 6 RF antennas to complete the array. In this work, results with regard to the electromagnetic detection of showers will be shown. The method of operation and analysis will be presented. The purpose of this project was to demonstrate the adequacy of the method to detect cosmic events even in the presence of high urban electromagnetic background, using noise filters, timing, signal polarization, and eventual comparison with well understood event reconstruction using the scintillator detectors. The results indicate that cosmic showers were detected and the method can be used for the complete array.

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I. Manthos, I. Gkialas, G. Bourlis, et. al.
Tue, 21 Feb 17

Comments: 18 pages, 11 figures

Search for Astrophysical Tau Neutrinos with IceCube [HEAP]

High-energy (TeV-PeV) cosmic neutrinos are expected to be produced in extremely energetic astrophysical sources such as active galactic nuclei. The IceCube Neutrino Observatory at the South Pole has recently detected a diffuse astrophysical neutrino flux. While the flux is consistent with all flavors of neutrinos being present, identification of tau neutrinos within the flux is yet to occur. Although tau neutrino production is thought to be low at the source, an equal fraction of neutrinos are expected at Earth due to averaged neutrino oscillations over astronomical distances. Above a few hundred TeV, tau neutrinos become resolvable in IceCube with negligible background from cosmic-ray induced atmospheric neutrinos. Identification of tau neutrinos within the observed flux is crucial to precise measurement of its flavor content, which could serve to test fundamental neutrino properties over extremely long baselines, and possibly shed light on new physics beyond the Standard Model. We present the analysis method and results from a recent search for astrophysical tau neutrinos in three years of IceCube data.

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D. Xu and IceCube. Collaboration
Mon, 20 Feb 17

Comments: 6 pages, 7 figures, proceedings, the 38th International Conference on High Energy Physics

Two-Higgs-Doublet-Portal Dark-Matter Models in Light of Direct Search and LHC Data [CL]

We explore simple Higgs-portal models of dark matter (DM) with spin 1/2, 3/2, and 1, respectively, applying to them constraints from the LUX and PandaX-II direct detection experiments and from LHC measurements on the 125-GeV Higgs boson. With only one Higgs doublet, we find that the spin-1/2 DM having a purely scalar coupling to the Higgs doublet is viable only in a narrow range of mass near the Higgs pole, whereas the vector DM is still allowed if its mass is also close to the Higgs pole or exceeds 1.4 TeV, both in line with earlier analyses. Moreover, the spin-3/2 DM is in a roughly similar situation to the spin-1/2 DM, but has even more restricted surviving parameter space. We also consider the two-Higgs-doublet extension of each of the preceding models, assuming that the expanded Yukawa sector is that of the two-Higgs-doublet model of type II. We show that in these two-Higgs-doublet-portal models significant portions of the DM mass regions excluded in the simplest scenarios by the direct search bounds can be recovered due to suppression of the DM effective interactions with nucleons at some ratios of the $CP$-even Higgs bosons’ couplings to the up and down quarks. Some parts of the regained parameter space can yield a DM-nucleon scattering cross-section that is far less than its current experimental limit or even goes below the neutrino-background floor.

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C. Chang, X. He and J. Tandean
Fri, 17 Feb 17

Comments: 24 pages, 10 figures. arXiv admin note: text overlap with arXiv:1609.03551

New constraints and discovery potential of sub-GeV dark matter with xenon detectors [CL]

Existing xenon dark matter (DM) direct detection experiments can probe the DM-nucleon interaction of DM with a sub-GeV mass through a search for bremsstrahlung from the recoiling xenon atom. We show that LUX’s constraints on sub-GeV DM, which utilise the scintillation (S1) and ionisation (S2) signals, are approximately three orders of magnitude more stringent than previous xenon constraints in this mass range, derived from the XENON10 and XENON100 S2-only searches. The new LUX constraints provide the most stringent direct detection constraints for DM particles with a mass below 0.5 GeV. In addition, the bremsstrahlung signal in LUX and its successor LZ maintain the discrimination between background and signal events so that an unambiguous discovery of sub-GeV DM is possible. We show that LZ has the potential to reconstruct the DM mass with 20% accuracy for particles lighter than 0.5 GeV.

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C. McCabe
Fri, 17 Feb 17

Comments: 6 pages, 3 figures

Photon emission and atomic collision processes in two-phase argon doped with xenon and nitrogen [CL]

We present a comprehensive analysis of photon emission and atomic collision processes in two-phase argon doped with xenon and nitrogen. The dopants are aimed to convert the VUV emission of pure Ar to the UV emission of the Xe dopant in the liquid phase and to the near UV emission of the N2 dopant in the gas phase. Such a mixture is relevant to two-phase dark matter and low energy neutrino detectors, with enhanced photon collection efficiency for primary and secondary scintillation signals. Based on this analysis, we show that the recently proposed hypothesis of the enhancement of the excitation transfer from Ar to N2 species in the two-phase mode is either incorrect or needs assumption about a new extreme mechanism of excitation transfer coming into force at lower temperatures, in particular that of the resonant excitation transfer via ArN2 compound (van der Waals molecule).

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A. Buzulutskov
Tue, 14 Feb 17

Comments: 6 pages, 1 figure, 1 table

The ALP miracle: unified inflaton and dark matter [CL]

We propose a scenario where both inflation and dark matter are described by a single axion-like particle (ALP) in a unified manner. In a class of the minimal axion hilltop inflation, the effective masses at the maximum and mimimum of the potential have equal magnitude but opposite sign, so that the ALP inflaton is light both during inflation and in the true vacuum. After inflation, most of the ALPs decay and evaporate into plasma through a coupling to photons, and the remaining ones become dark matter. We find that the observed CMB and matter power spectrum as well as the dark matter abundance point to an ALP of mass $m_\phi = {\cal O}(0.01)$eV and the axion-photon coupling $g_{\phi \gamma \gamma} ={\cal O}(10^{-11})$GeV$^{-1}$: the ALP miracle. The suggested parameter region is within the reach of the next generation axion helioscope, IAXO. Furthermore, thermalized ALPs contribute to hot dark matter and its abundance is given in terms of the effective number of extra neutrino species, $\Delta N_{\rm eff} \simeq 0.03$, which can be tested by the future CMB experiments. We also discuss a case with multiple ALPs, where the coupling to photons can be enhanced in the early Universe by an order of magnitude or more, which enlarges the parameter space for the ALP miracle. The heavy ALPs decay and/or evaporate into the standard model particles and reheats the Universe, and they can be searched for in various experiments such as SHiP.

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R. Daido, F. Takahashi and W. Yin
Mon, 13 Feb 17

Comments: 29 pages, 9 figures

Dark Matter "Transporting" Mechanism Explaining Positron Excesses [CL]

We propose a novel mechanism to explain the positron excesses, which are observed by satellite-based telescopes including PAMELA and AMS-02, in dark matter (DM) scenarios. The novelty behind the proposal is that it makes direct use of DM around the Galactic Center where DM populates most densely, allowing us to avoid tensions from cosmological and astrophysical measurements. The key ingredients of this mechanism include DM annihilation into unstable states with a very long laboratory-frame life time and their “retarded” decay near the Earth to electron-positron pair(s) possibly with other (in)visible particles. We argue that this sort of explanation is not in conflict with relevant constraints from big bang nucleosynthesis and cosmic microwave background. Regarding the resultant positron spectrum, we provide a generalized source term in the associated diffusion equation, which can be readily applicable to any type of two-“stage” DM scenarios wherein production of Standard Model particles occurs at completely different places from those of DM annihilation. We then conduct a data analysis with the recent AMS-02 data to validate our proposal.

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D. Kim, J. Park and S. Shin
Mon, 13 Feb 17

Comments: 5 pages, 3 figures

3D simulation for Cherenkov emissions in Extensive Air Showers [IMA]

The development of a 3-dimensional simulation for Cherenkov photon emissions in Extensive Air Showers (EAS) is reported in this paper. CORSIKA is the most widely used Monte-Carlo generator for the description of EAS, but it is not recommended to calculate Cherenkov light emissions for EAS at ultra high energies due to the enormous amount of data storage and running time required. The presented BinTheSky is a framework to simulate the Cherenkov light emissions using the spatial information produced by Monte-Carlo generators. The light is emitted in the shower, propagated and attenuated to the ground. The framework enables one to calculate the light spatial, timing and directional distributions at the ground or at a given altitude, whereas the usual approach of Ultra High Energy Cosmic Ray experiments relies on the simulation of the longitudinal shower development and on parametrizations of the transverse shower distributions.

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J. Espadanal and P. Goncalves
Mon, 13 Feb 17

Comments: N/A

New Physics and Atmospheric Neutrino Trident Production with PINGU and ORCA [CL]

We propose to use atmospheric neutrinos as a powerful probe of new physics beyond the Standard Model via neutrino trident production. The final state with double muon tracks simultaneously produced from the same vertex is a distinctive signal at large Cherenkov detectors such as PINGU and ORCA. We calculate the expected event numbers of trident production in the Standard Model. In order to illustrate the potential of this process to probe new physics we obtain the sensitivity of PINGU and ORCA on new vector/scalar bosons with coupling to muon neutrinos.

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S. Ge, M. Lindner and W. Rodejohann
Mon, 13 Feb 17

Comments: 5 pages, 8 figures

First On-Site True Gamma-Ray Imaging-Spectroscopy of Contamination near Fukushima Plant [CL]

We have developed an Electron Tracking Compton Camera (ETCC), which provides a well-defined Point Spread Function (PSF) by reconstructing a direction of each gamma as a point and realizes simultaneous measurement of brightness and spectrum of MeV gamma-rays for the first time. Here, we present the results of our on-site pilot gamma-imaging-spectroscopy with ETCC at three contaminated locations in the vicinity of the Fukushima Daiichi Nuclear Power Plants in Japan in 2014. The obtained distribution of brightness (or emissivity) with remote-sensing observations is unambiguously converted into the dose distribution. We confirm that the dose distribution is consistent with the one taken by conventional mapping measurements with a dosimeter physically placed at each grid point. Furthermore, its imaging spectroscopy, boosted by Compton-edge-free spectra, reveals complex radioactive features in a quantitative manner around each individual target point in the background-dominated environment. Notably, we successfully identify a “micro hot spot” of residual caesium contamination even in an already decontaminated area. These results show that the ETCC performs exactly as the geometrical optics predicts, demonstrates its versatility in the field radiation measurement, and reveals potentials for application in many fields, including the nuclear industry, medical field, and astronomy.

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D. Tomono, T. Mizumoto, A. Takada, et. al.
Fri, 10 Feb 17

Comments: 19 pages, 7 figures, 2 tables

Establishment of Imaging Spectroscopy of Nuclear Gamma-Rays based on Geometrical Optics [CL]

Since the discovery of nuclear gamma-rays, its imaging has been limited to pseudo imaging, such as Compton Camera (CC) and coded mask. Pseudo imaging does not keep physical information (intensity, or brightness in Optics) along a ray, and thus is capable of no more than qualitative imaging of bright objects. To attain quantitative imaging, cameras that realize geometrical optics is essential, which would be, for nuclear MeV gammas, only possible via complete reconstruction of the Compton process. Recently we have revealed that “Electron Tracking Compton Camera” (ETCC) provides a well-defined Point Spread Function (PSF). The information of an incoming gamma is kept along a ray with the PSF and that is equivalent to geometrical optics. Here we present an imaging-spectroscopic measurement with the ETCC. Our results highlight the intrinsic difficulty with CCs in performing accurate imaging, and show that the ETCC surmounts this problem. The imaging capability also helps the ETCC suppress the noise level dramatically by ~3 orders of magnitude without a shielding structure. Furthermore, full reconstruction of Compton process with the ETCC provides spectra free of Compton edges. These results mark the first proper imaging of nuclear gammas based on the genuine geometrical optics.

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T. Tanimori, Y. Mizumura, A. Takada, et. al.
Fri, 10 Feb 17

Comments: 22 pages, 8 figures

Flashes of Hidden Worlds at Colliders [CL]

(This is a general physics level overview article about hidden sectors, and how they motivate searches for long-lived particles. Intended for publication in Physics Today.)
Searches for new physics at the Large Hadron Collider have so far come up empty, but we just might not be looking in the right place. Spectacular bursts of particles appearing seemingly out of nowhere could shed light on some of nature’s most profound mysteries.

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D. Curtin and R. Sundrum
Thu, 9 Feb 17

Comments: Comment: 8 pages, 5 figures. Submitted to Physics Today

The gluon condensation at high energy hadron collisions [CL]

We report that the saturation/CGC model of gluon distribution is unstable under action of the chaotic solution in a nonlinear QCD evolution equation, and it evolves to the distribution with a sharp peak at the critical momentum. We find that this gluon condensation is caused by a new kind of shadowing-antishadowing effects, and it leads to a series of unexpected effects in high energy hadron collisions including astrophysical events. For example, the extremely intense fluctuations in the transverse-momentum and rapidity distributions of the gluon jets present the gluon-jet bursts; a sudden increase of the proton-proton cross sections may fill the GZK suppression; the blocking QCD evolution will restrict the maximum available energy of the hadron-hadron colliders.

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W. Zhu and J. Lan
Thu, 9 Feb 17

Comments: 45 pages, 19 figures, to be published in Nucl. Phys. B

A 100-ps Multi-Time over Threshold Data Acquisition System for Cosmic Ray Detection [CL]

High-energy cosmic rays are one of the primary sources of information for scientists investigating the elementary properties of matter. The need to study cosmic rays, with energies thousands of times larger than those encountered in particle accelerators, led to the development of modern detection hardware and experimental methodologies. We present a low power, low complexity data acquisition (DAQ) system with 100 ps resolution, suitable for particle and radiation detection experiments. The system uses a Multiple-Time-over-Threshold (MToT) technique for the treatment of the output signal of Photo Multiplier Tubes (PMTs). The use of three thresholds compensates for the slewing effects and offers a more accurate measurement of the PMT pulses’ width. For the evaluation of the pulse the system uses comparators and a Time-to-Digital (TDC) converter, whereas the pulses are time-stamped using the GPS signal. The prototype card is analyzed for its noise behavior and is tested to verify its performance. The system has been designed for the HEllenic LYceum Cosmic Observatories Network (HELYCON) Extensive Air Showers (EAS) detector.

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K. Georgakopoulou, C. Spathis, G. Bourlis, et. al.
Mon, 6 Feb 17

Comments: 23 pages, 12 figures

Study of radiation background at various high altitude locations in preparation for rare event search in cosmic rays [CL]

Various phenomenological models presented over the years have hinted at the possible presence of strangelets, which are nuggets of Strange Quark Matter (SQM), in cosmic rays. One way to search for such rare events is through the deployment of large area Nuclear Track Detector (NTD) arrays at high mountain altitudes. Before the deployment of any such array can begin, a detailed study of the radiation background is essential. Also a proper understanding of the response of detectors exposed to extreme weather conditions is necessary. With that aim, pilot studies were carried out at various high altitude locations in India such as Darjeeling (2200 m a.m.s.l), Ooty (2200 m a.m.s.l) and Hanle (4500 m a.m.s.l). Small arrays of CR-39 as well as high threshold Polyethylene Terephthalate (PET) detectors were given open air exposures for periods ranging from three months to two years. The findings of such studies are reported in this paper.

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R. Bhattacharyya, S. Dey, S. Ghosh, et. al.
Fri, 3 Feb 17

Comments: 5 pages, 6 figures

New neutrino physics and the altered shapes of solar neutrino spectra [SSA]

Neutrinos coming from the Sun’s core are now measured with a high precision, and fundamental neutrino oscillations parameters are determined with a good accuracy. In this work, we estimate the impact that a new neutrino physics model, the so-called generalized Mikheyev-Smirnov-Wolfenstein (MSW) oscillation mechanism, has on the shape of some of leading solar neutrino spectra, some of which will be partially tested by the next generation of solar neutrino experiments. In these calculations, we use a high-precision standard solar model in good agreement with helioseismology data. We found that the neutrino spectra of the different solar nuclear reactions of the proton-proton chains and carbon-nitrogen-oxygen cycle have quite distinct sensitivities to the new neutrino physics. The $HeP$ and $^8B$ neutrino spectra are the ones for which their shapes are more affected when neutrinos interact with quarks in addition to electrons. The shape of the $^{15}O$ and $^{17}F$ neutrino spectra are also modified, although in these cases the impact is much smaller. Finally, the impact in the shape of the $PP$ and $^{13}N$ neutrino spectra is practically negligible.

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I. Lopes
Fri, 3 Feb 17

Comments: 14 pages;7 figures, Phys. Rev. D

Probing Leptophilic Dark Sectors with Hadronic Processes [CL]

We study vector portal dark matter models where the mediator couples only to leptons. In spite of the lack of tree-level couplings to colored states, radiative effects generate interactions with quark fields that could give rise to a signal in current and future experiments. We identify such experimental signatures: scattering of nuclei in dark matter direct detection; resonant production of lepton-antilepton pairs at the Large Hadron Collider; and hadronic final states in dark matter indirect searches. Furthermore, radiative effects also generate an irreducible mass mixing between the vector mediator and the $Z$ boson, severely bounded by ElectroWeak Precision Tests. We use current experimental results to put bounds on this class of models, accounting for both radiatively induced and tree-level processes. Remarkably, the former often overwhelm the latter.

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F. DEramo, B. Kavanagh and P. Panci
Thu, 2 Feb 17

Comments: 10 pages, 3 figures

Lensing substructure quantification in RXJ1131-1231: A 2 keV lower bound on dark matter thermal relict mass [CEA]

We study the substructure content of the strong gravitational lens RXJ1131-1231 through a forward modelling approach that relies on generating an extensive suite of realistic simulations. The statistics of the substructure population of halos depends on the properties of dark matter. We use a merger tree prescription that allows us to stochastically generate substructure populations whose properties depend on the dark matter particle mass. These synthetic halos are then used as lenses to produce realistic mock images that have the same features, e.g. luminous arcs, quasar positions, instrumental noise and PSF, as the data. By analysing the data and the simulations in the same way, we are able to constrain models of dark matter statistically using Approximate Bayesian Computing (ABC) techniques. This method relies on constructing summary statistics and distance measures that are sensitive to the signal being targeted. We find that using the HST data for \RXJ we are able to rule out a warm dark matter thermal relict mass below 2 keV at the 2$\sigma$ confidence level.

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S. Birrer, A. Amara and A. Refregier
Thu, 2 Feb 17

Comments: 23 pages, to be submitted to JCAP, comments welcome

DAMA annual modulation and mirror Dark Matter [CL]

The DAMA experiment using ultra low background NaI(Tl) crystal scintillators has measured an annual modulation effect in the keV region which satisfies all the peculiarities of an effect induced by Dark Matter particles. In this paper we analyze this annual modulation effect in terms of mirror Dark Matter, an exact duplicate of ordinary matter from parallel hidden sector, which chemical composition is dominated by mirror helium while it can also contain significant fractions of heavier elements as Carbon and Oxygen. Dark mirror atoms are considered to interact with the target nuclei in the detector via Rutherford-like scattering induced by kinetic mixing between mirror and ordinary photons, both being massless. In the present analysis we consider various possible scenarios for the mirror matter chemical composition. For all the scenarios, the relevant ranges for the kinetic mixing parameter have been obtained taking also into account various existing uncertainties in nuclear and particle physics quantities.

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R. Cerulli, P. Villar, F. Cappella, et. al.
Tue, 31 Jan 17

Comments: 30 pages, 16 figures, 3 tables, version in publication on Eur. Phys. J. C

Neutrino Lines from Majoron Dark Matter [CL]

Models with spontaneously broken global lepton number can lead to a pseudo-Goldstone boson as a long-lived dark matter candidate. Here we revisit the case of singlet majoron dark matter and discuss multiple constraints. For masses above MeV, this model could lead to a detectable flux of monochromatic mass-eigenstate neutrinos, which have flavor ratios that depend strongly on the neutrino mass hierarchy. We provide a convenient parametrization for the loop-induced majoron couplings to charged fermions that allows us to discuss three-generation effects such as lepton flavor violation. These couplings are independent of the low-energy neutrino parameters but can be constrained by the majoron decays into charged fermions.

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C. Garcia-Cely and J. Heeck
Thu, 26 Jan 17

Comments: 13 pages

Cosmic Ray Antiprotons at High Energies [CL]

Cosmic ray antiprotons provide a powerful tool to probe dark matter annihilations in our galaxy. The sensitivity of this important channel is, however, diluted by sizable uncertainties in the secondary antiproton background. In this work, we improve the calculation of secondary antiproton production with a particular focus on the high energy regime. We employ the most recent collider data and identify a substantial increase of antiproton cross sections with energy. This increase is driven by the violation of Feynman scaling as well as by an enhanced strange hyperon production. The updated antiproton production cross sections are made publicly available for independent use in cosmic ray studies. In addition, we provide the correlation matrix of cross section uncertainties for the AMS-02 experiment. At high energies, the new cross sections improve the compatibility of the AMS-02 data with a pure secondary origin of antiprotons in cosmic rays.

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M. Winkler
Fri, 20 Jan 17

Comments: 26 pages, 9 figures. Ancillary files: antiproton cross section tables, cross section uncertainties of the antiproton flux, correlation matrix of cross section uncertainties for AMS-02

Investigating the influence of diffractive interactions on ultra – high energy extensive air showers [CL]

The understanding of the basic properties of the ultra – high energy extensive air showers is strongly dependent on the description of the hadronic interactions in a energy range beyond that probed by the LHC. One of the uncertainties present in the modeling of the air showers is the treatment of diffractive interactions, which are dominated by non – perturbative physics and usually described by phenomenological models. These interactions are expect to affect the development of the air showers, since they provide a way of transporting substantial amounts of energy deep in the atmosphere, modifying the global characteristics of the shower profile. In this paper we investigate the impact of the diffractive interactions in the observables that can be measured in hadronic collisions at high energies and ultra – high energy cosmic ray interactions. We consider three distinct phenomenological models for the treatment of diffractive physics and estimate the influence of these interactions on the elasticity, number of secondaries, longitudinal air shower profiles and muon densities for proton – air and iron – air collisions at different primary energies. Our results demonstrate that the diffractive events has a non – negligible effect on the observables and that the distinct approaches for these interactions, present in the phenomenological models, are an important source of theoretical uncertainty for the description of the extensive air showers.

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L. Arbeletche, V. Goncalves and M. Muller
Fri, 20 Jan 17

Comments: 19 pages, 11 figures

Dark Photons from Captured Inelastic Dark Matter Annihilation: Charged Particle Signatures [CL]

The dark sector may contain a dark photon that kinetically mixes with the Standard Model photon, allowing dark matter to interact weakly with normal matter. In previous work we analyzed the implications of this scenario for dark matter capture by the Sun. Dark matter will gather in the core of the Sun and annihilate to dark photons. These dark photons travel outwards from the center of the Sun and may decay to produce positrons that can be detected by the Alpha Magnetic Spectrometer (AMS-02) on the ISS. We found that the dark photon parameter space accessible to this analysis is largely constrained by strong limits on the spin-independent WIMP-nucleon cross section from direct detection experiments. In this paper we build upon previous work by considering the case where the dark sector contains two species of Dirac fermion that are nearly degenerate in mass and couple inelastically to the dark photon. We find that for small values of the mass splitting $\Delta \sim 100 ~\kev$, the predicted positron signal at AMS-02 remains largely unchanged from the previously considered elastic case while constraints from direct detection are relaxed, leaving a region of parameter space with dark matter mass $100 ~\gev \lesssim m_X \lesssim 10 ~\tev$, dark photon mass $1 ~\mev \lesssim m_{A’} \lesssim 100 ~\mev$, and kinetic mixing parameter $10^{-9} \lesssim \varepsilon \lesssim 10^{-8}$ that is untouched by supernova observations and fixed target experiments but where an inelastic dark sector may still be discovered using existing AMS-02 data.

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J. Smolinsky and P. Tanedo
Fri, 13 Jan 17

Comments: 18 pages, 5 figures

Radio detection of extensive air showers [IMA]

Radio detection of extensive air showers initiated in the Earth’s atmosphere has made tremendous progress in the last decade. Today, radio detection is routinely used in several cosmic-ray observatories. The physics of the radio emission in air showers is well-understood, and analysis techniques have been developed to determine the arrival direction, the energy and an estimate for the mass of the primary particle from the radio measurements. The achieved resolutions are competitive with those of more traditional techniques. In this article, I shortly review the most important achievements and discuss the potential for future applications.

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T. Huege
Thu, 12 Jan 17

Comments: To appear in NIM A as part of the proceedings of the RICH2016 conference, Bled, Slovenia

FRB 121102 Casts New Light on the Photon Mass [HEAP]

The photon mass, $m_\gamma$, can in principle be constrained using measurements of the dispersion measures (DMs) of fast radio bursts (FRBs), once the FRB redshifts are known. The DM of the repeating FRB 121102 is known to $< 1$\%, a host galaxy has now been identified with high confidence,and its redshift, $z$, has now been determined with high accuracy: $z = 0.19273(8)$. Taking into account the plasma contributions to the DM from the Intergalactic medium (IGM) and the Milky Way, we use the data on FRB 121102 to derive the constraint $m_\gamma \lesssim 2.2 \times 10^{-14}$ eV c$^{-2}$ ($3.9 \times 10^{-50}$ kg). Since the plasma and photon mass contributions to DMs have different redshift dependences, they could in principle be distinguished by measurements of more FRB redshifts, enabling the sensitivity to $m_\gamma$ to be improved.

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L. Bonetti, J. Ellis, N. Mavromatos, et. al.
Thu, 12 Jan 17

Comments: 8 pages, 1 figure

On the coherent emission of radio frequency radiation from high energy particle showers [IMA]

Extended Air Showers produced by cosmic rays impinging on the earth atmosphere irradiate radio frequency radiation through different mechanisms. Upon certain conditions, the emission has a coherent nature, with the consequence that the emitted power is not proportional to the energy of the primary cosmic rays, but to the energy squared. The effect was predicted in 1962 by Askaryan and it is nowadays experimentally well established and exploited for the detection of ultra high energy cosmic rays.
In this paper we discuss in details the conditions for coherence, which in literature have been too often taken for granted, and calculate them analytically, finding a formulation which comprehends both the coherent and the incoherent emissions. We apply the result to the Cherenkov effect, obtaining the same conclusions derived by Askaryan, and to the geosynchrotron radiation.

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E. Conti and G. Sartori
Tue, 10 Jan 17

Comments: 9 pages, 2 figures. Submitted to International Journal of Modern Physics D. arXiv admin note: substantial text overlap with arXiv:1511.03562

Dark Matter Search in Space: Combined Analysis of Cosmic Ray Antiproton-to-Proton Flux Ratio and Positron Flux Measured by AMS-02 [CL]

Dark matter search in space has been carried out for many years. Measurements of cosmic ray photons, charged antiparticles and neutrinos are useful tools for dark matter indirect search. The antiparticle energy spectra of cosmic rays have several exciting features such as the unexpected positron excess at $E\sim$ 10 — 500\,GeV and the remarkably flattening antiproton/proton at $E\sim$ 60–450\,GeV precisely measured by the AMS-02 experiment, which can not be explained simultaneously by secondary production in interstellar medium. In this work, we report a combined analysis of cosmic ray antiproton and positron spectra arising from dark matter on the top of a secondary production in a spatial-dependent propagation model. We discuss the systematics from antiproton production cross section using the two latest Monte Carlo generators, \textit{i.e.} EPOS LHC and QGSJET-II-04, respectively. We compare their results. In the case of EPOS LHC, we find that the dark matter pair annihilating into $\tau$ leptons channel with 100\% branching ratio is the only possible one channel scenario to explain data. On the other hand, there is not a single possible channel in the case of QGSJET-II-04m. We also propose possible two-channel scenarios based on these two Monte Carlo generators.

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J. Feng and H. Zhang
Tue, 10 Jan 17

Comments: 8 pages, 6 figures, 2 tables

KM3NeT-ORCA: Oscillation Research with Cosmics in the Abyss [CL]

KM3NeT, currently under construction in the abysses of the Mediterranean Sea, is a distributed research infrastructure that will host a km3-scale neutrino telescope (ARCA) for high-energy neutrino astronomy, and a megaton scale detector (ORCA) for neutrino oscillation studies of atmospheric neutrinos. ORCA is optimised for a measurement of the mass hierarchy, providing a sensitivity of 3{\sigma} after 3-4 years. It will also measure the atmospheric mixing parameters $\Delta m_{32}^2$ and $\theta_{23}$ with a precision comparable to the NOvA and T2K experiments using both the muon neutrino disappearance and tau neutrino appearance channels. It will provide a measurement of the tau neutrino appearance rate with better than 10% precision, a crucial ingredient for tests of unitarity. It will probe the octant of the mixing angle $\theta_{23}$ via matter resonance effects on neutrinos and antineutrinos crossing the core and mantle, which are largely independent on the CP phase. The observation of neutrino oscillations over a wide range of baselines and energies will provide broad sensitivity to new physics such as non-standard neutrino interactions (NSI) and sterile neutrinos.

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P. Coyle
Fri, 6 Jan 17

Comments: 27th International Conference on Neutrino Physics and Astrophysics (Neutrino 2016)

Search for Electronic Recoil Event Rate Modulation with 4 Years of XENON100 Data [CEA]

We report on a search for electronic recoil event rate modulation signatures in the XENON100 data accumulated over a period of 4 years, from January 2010 to January 2014. A profile likelihood method, which incorporates the stability of the XENON100 detector and the known electronic recoil background model, is used to quantify the significance of periodicity in the time distribution of events. There is a weak modulation signature at a period of $431^{+16}_{-14}$ days in the low energy region of $(2.0-5.8)$ keV in the single scatter event sample, with a global significance of $1.9\,\sigma$, however no other more significant modulation is observed. The expected annual modulation of a dark matter signal is not compatible with this result. Single scatter events in the low energy region are thus used to exclude the DAMA/LIBRA annual modulation as being due to dark matter electron interactions via axial vector coupling at $5.7\,\sigma$.

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XENON. collaboration, E. Aprile, J. Aalbers, et. al.
Wed, 4 Jan 17

Comments: 6 pages, 5 figures

Cosmic particles [HEAP]

Since more than a century we investigate cosmic particles coming from the Universe with the aim of understanding their nature, their origin and how they are accelerated. So far, cosmic rays have provided many impressive results, giving birth to the particle physics and extending our vision of the Universe over a wide range of energies. In this contribution an overview of the most recent result is given. This field remains extremely active with new experiments and instruments opening new perspective for the research at the edge between astrophysics and particle physics.

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M. Settimo
Fri, 30 Dec 16

Comments: 10 pages, 7 figures. Proceeding of the ICHEP 2016, Chicago, 3-10 August 2016. To be published in PoS

Hot dense magnetized spinor matter in particle and astroparticle physics: the role of boundaries [CL]

We study the influence of boundaries on chiral effects in hot dense relativistic spinor matter in a strong magnetic field which is orthogonal to the boundaries. The most general set of boundary conditions ensuring the confinement of matter within the boundaries is employed. We find that the chiral magnetic effect disappears, whereas the chiral separation effect stays on, becoming dependent on temperature and on a choice of boundary conditions. As temperature increases from zero to large values, a stepped-shape behaviour of the chiral separation effect as a function of chemical potential is changed to a smooth one. A choice of the boundary condition can facilitate either amplification or diminution of the chiral separation effect; in particular, the effect can persist even at zero chemical potential, if temperature is finite. This points at a significant role of boundaries for physical systems with hot dense magnetized spinor matter, i.e. compact astrophysical objects (neutron stars and magnetars), relativistic heavy-ion collisions, novel materials known as the Dirac and Weyl semimetals.

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Y. Sitenko
Fri, 30 Dec 16

Comments: 7 pages; based on a plenary talk at the XVI Odessa Gamow International Conference-School “Astronomy and beyond: Astrophysics, Cosmology, Cosmomicrophysics, Astroparticle Physics, Radioastronomy and Astrobiology”, 14-20 August 2016, Odessa, Ukraine. arXiv admin note: text overlap with arXiv:1606.08241

Alternative dark matter candidates: Axions [CL]

The axion is arguably one of the best motivated candidates for dark matter. For a decay constant greater than about 10^9 GeV, axions are dominantly produced non-thermally in the early universe and hence are “cold”, their velocity dispersion being small enough to fit to large scale structure. Moreover, such a large decay constant ensures the stability at cosmological time scales and its behaviour as a collisionless fluid at cosmological length scales. Here, we review the state of the art of axion dark matter predictions and of experimental efforts to search for axion dark matter in laboratory experiments.

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A. Ringwald
Fri, 30 Dec 16

Comments: 6 pages, 2 figures, contribution to the proceedings of the Neutrino Oscillation Workshop 2016, 4 – 11 September, 2016, Otranto, Lecce, Italy

Multi-Dimensional Effective Field Theory Analysis for Direct Detection of Dark Matter [CEA]

The scattering of dark matter particles off nuclei in direct detection experiments can be described in terms of a multi-dimensional effective field theory (EFT). A new systematic analysis technique is developed using the EFT approach and Bayesian inference methods to exploit, when possible, the energy-dependent information of the detected events, experimental efficiencies, and backgrounds. Highly-dimensional likelihoods are calculated over the mass of the Weakly Interacting Massive Particle (WIMP) and multiple EFT coupling coefficients, which can then be used to set limits on these parameters and choose models (EFT operators) that best fit the direct detection data. Expanding the parameter space beyond the standard spin-independent isoscalar cross-section and WIMP mass reduces tensions between previously published experiments. Combining these experiments to form a single joint likelihood leads to stronger limits than when each experiment is considered on its own. Simulations using two non-standard operators (3 and 8) are used to test the proposed analysis technique in up to five dimensions and demonstrate the importance of using multiple likelihood projections when determining constraints on WIMP mass and EFT coupling coefficients. In particular, this shows that an explicit momentum dependence in dark matter scattering can be identified.

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H. Rogers, D. Cerdeno, P. Cushman, et. al.
Fri, 30 Dec 16

Comments: 20 pages, 11 figures

Triple parton scatterings in proton-nucleus collisions at high energies [CL]

A generic expression to compute triple parton scattering (TPS) cross sections in high-energy proton-nucleus (pA) collisions is derived as a function of the corresponding single-parton cross sections and an effective parameter encoding the transverse parton profile of the proton. The TPS cross sections are enhanced by a factor of $9\,A\approx 2000$ in pPb compared to those in proton-nucleon collisions at the same center-of-mass energy. Estimates for triple charm ($c\overline{c}$) and bottom ($b\overline{b}$) production in pPb collisions at LHC and FCC energies are presented based on next-to-next-to-leading order (NNLO) calculations for $c\overline{c}, b\overline{b}$ single-parton cross sections. At $\sqrt{s_{NN}} = 8.8$ TeV, about 10% of the pPb events have three $c\overline{c}$ pairs produced in separate partonic interactions. At $\sqrt{s_{NN}} = 63$ TeV, the pPb cross sections for triple-J$/\psi$ and triple-$b\overline{b}$ are ${\cal O}$(1–10 mb). In the most energetic cosmic-ray collisions observed on earth, TPS $c\overline{c}$-pair cross sections equal the total p-Air inelastic cross section.

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D. dEnterria and A. Snigirev
Wed, 28 Dec 16

Comments: 6 pages, 4 figures. arXiv admin note: text overlap with arXiv:1612.05582

Results from the DM-Ice17 Dark Matter Experiment at the South Pole [CL]

DM-Ice is a phased experimental program using low-background NaI(Tl) crystals with the aim to unambiguously test the claim of dark matter detection by the DAMA experiments. DM-Ice17, consisting of 17 kg of NaI(Tl), has been continuously operating at a depth of 2457 m in the South Pole ice for over five years, demonstrating the feasibility of a low-background experiment in the Antarctic ice. Studies of low and high energy spectra, an annual modulation analysis, and a WIMP exclusion limit based on the physics run of DM-Ice17 are presented. We also discuss the plan and projected sensitivity of a new joint physics run, COSINE-100, with upgraded detectors at the Yangyang Underground Laboratory in Korea.

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J. Jo and Ice. Collaboration-DM
Fri, 23 Dec 16

Comments: Contribution to the Proceedings of the 38th International Conference on High Energy Physics, ICHEP 2016, Chicago, IL, USA

Dielectric Haloscopes to Search for Axion Dark Matter: Theoretical Foundations [CL]

We study the underlying theory of dielectric haloscopes, a new way to detect dark matter axions. When an interface between different dielectric media is inside a magnetic field, the oscillating axion field acts as a source of electromagnetic waves, which emerge in both directions perpendicular to the surface. The emission rate can be boosted by multiple layers judiciously placed to achieve constructive interference and by a large transverse area. Starting from the axion-modified Maxwell equations, we calculate the efficiency of this new dielectric haloscope approach. This technique could potentially search the unexplored high-frequency range of 10–100 GHz (axion mass 40–400 $\mu$eV), where traditional cavity resonators have difficulties reaching the required volume.

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A. Millar, G. Raffelt, J. Redondo, et. al.
Thu, 22 Dec 16

Comments: 72 pages, 34 figures

Connecting Leptonic Unitarity Triangle to Neutrino Oscillation with CP Violation in Vacuum and in Matter [CL]

Leptonic unitarity triangle (LUT) provides fundamental means to geometrically describe CP violation in neutrino oscillation. In this work, we use LUT to present a new geometrical interpretation of the vacuum oscillation probability, and derive a compact new oscillation formula in terms of only 3 independent parameters of the corresponding LUT. Then, we systematically study matter effects in the geometrical formulation of neutrino oscillation with CP violation. Including nontrivial matter effects, we derive a very compact new oscillation formula by using the LUT formulation. We further demonstrate that this geometrical formula holds well for applications to neutrino oscillations in matter, including the long baseline experiments T2K, MINOS, NOvA, and DUNE.

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H. He and X. Xu
Wed, 21 Dec 16

Comments: PRD Final Version (9pp, 5 Figs). All results/conclusions un-changed. Further added new Fig.5 for analysis of LBL experiment DUNE. Only minor rewording to clarify the Importance of this work

Constraints on leptophilic dark matter from the AMS-02 experiment [CL]

The annihilation of dark matter particles in the galactic halo of the Milky Way may lead to cosmic ray signatures that can be probed by the AMS-02 experiment, which has measured the composition and fluxes of charged cosmic rays with unprecedented precision. Given the absence of characteristic spectral features in the electron and positron fluxes measured by AMS-02, we derive upper limits on the dark matter annihilation cross section for leptophilic dark matter models. Our limits are based on a new background model that describes all recent measurements of the energy spectra of cosmic ray positrons and electrons. For thermal dark matter relics, we can exclude dark matter masses below about 100 GeV. We include the radiation of electroweak gauge bosons in the dark matter annihilation process and compute the antiproton signal that can be expected within leptophilic dark matter models.

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L. Cavasonza, H. Gast, M. Kramer, et. al.
Wed, 21 Dec 16

Comments: 7 pages, 3 figures, 1 table