# Towards a medium-scale axion helioscope and haloscope [CL]

We discuss the physics case for and the concept of a medium-scale axion helioscope with sensitivities in the axion-photon coupling a few times better than CERN Axion Solar Telescope (CAST). Search for an axion-like particle with these couplings is motivated by several persistent astrophysical anomalies. We present early conceptual design, existing infrastructure, projected sensitivity and timeline of such a helioscope (Troitsk Axion Solar Telescope Experiment, TASTE) to be constructed in the Institute for Nuclear Research, Troitsk, Russia. The proposed instrument may be also used for the search of dark-matter halo axions.

V. Anastassopoulos, F. Avignone, A. Bykov, et. al.
Thu, 29 Jun 17
32/44

Comments: 38 pages, 15 figures, JINST style

# The HAYSTAC Axion Search Analysis Procedure [IMA]

We describe in detail the analysis procedure used to derive the first limits from the Haloscope at Yale Sensitive to Axion CDM (HAYSTAC), a microwave cavity search for cold dark matter (CDM) axions with masses above $20\ \mu\text{eV}$. We have introduced several significant innovations to the axion search analysis pioneered by the Axion Dark Matter eXperiment (ADMX), including optimal filtering of the individual power spectra that constitute the axion search dataset and a consistent maximum likelihood procedure for combining and rebinning these spectra. These innovations enable us to obtain the axion-photon coupling $|g_\gamma|$ excluded at any desired confidence level directly from the statistics of the combined data.

B. Brubaker, L. Zhong, S. Lamoreaux, et. al.
Tue, 27 Jun 17
16/58

|

# The DArk Matter Particle Explorer mission [IMA]

The DArk Matter Particle Explorer (DAMPE), one of the four scientific space science missions within the framework of the Strategic Pioneer Program on Space Science of the Chinese Academy of Sciences, is a general purpose high energy cosmic-ray and gamma-ray observatory, which was successfully launched on December 17th, 2015 from the Jiuquan Satellite Launch Center. The DAMPE scientific objectives include the study of galactic cosmic rays up to $\sim 10$ TeV and hundreds of TeV for electrons/gammas and nuclei respectively, and the search for dark matter signatures in their spectra. In this paper we illustrate the layout of the DAMPE instrument, and discuss the results of beam tests and calibrations performed on ground. Finally we present the expected performance in space and give an overview of the mission key scientific goals.

DAMPE. collaboration
Tue, 27 Jun 17
46/58

Comments: 45 pages, including 29 figures and 6 tables

|

# Dark Matter, Neutrino mass, Cutoff for Cosmic-Ray Neutrino, and Higgs Boson Invisible Decay from a Neutrino Portal Interaction [CL]

We study an effective theory beyond the standard model (SM) where either of two additional gauge singlets, a Majorana fermion and a real scalar, constitute all or some fraction of dark matter. The only additional interaction to the SM is via a dimension-five lepton number preserving operator: a neutrino portal interaction. We point out that this interaction (i) generates the neutrino mass radiatively, (ii) gives a cutoff for the cosmic-ray neutrino, and (iii) induces the testable Higgs boson invisible decay in the future lepton colliders, such as the CEPC, ILC, and CLIC. In particular, there are two correlated phenomena. If the dark matter is detected in XENON1T, XENONnT, LZ, DARWIN, or PandaX in future, the Higgs invisible decay is within the reach of the future lepton colliders. If a high energy cutoff of cosmic-ray neutrino, which may account for the non-detection of GZK neutrinos or Glashow resonance, is generated due to its annihilation with the cosmic background neutrino, the Higgs invisible decay can be searched for in these colliders. Moreover, the scale for one of the neutrino masses is predicted. The UV completion and the fine tuning, as well as the constraints from collider physics, cosmology, and astronomy are discussed.

W. Yin
Thu, 22 Jun 17
12/68

# Performance measurement of HARPO: a Time Projection Chamber as a gamma-ray telescope and polarimeter [IMA]

We analyse the performance of a gas time projection chamber (TPC) as a high-performance gamma-ray telescope and polarimeter in the e$^+$e$^-$ pair creation regime. We use data collected at a gamma-ray beam of known polarisation. The TPC provides two orthogonal projections $(x,z)$ and $(y,z)$ of the tracks induced by each conversion in the gas volume. We use a simple vertex finder in which vertices and pseudo-tracks exiting from them are identified.
We study the various contributions to the single-photon angular resolution using Monte Carlo simulations and compare them with the experimental data and find that they are in excellent agreement. The distribution of the azimutal angle of pair conversions shows a bias due to the non-cylindrical-symmetric structure of the detector. This bias would average out for a long duration exposure on a space mission, but for this pencil-beam characterisation we have ensured its accurate simulation by a double systematics control scheme, data taking with the detector rotated at several angles with respect to the beam polarisation direction and systematics control with a non-polarised beam.
We measure, for the first time, the polarisation asymmetry of a linearly polarised gamma-ray beam in the low energy pair creation regime. This sub-GeV energy range is critical for cosmic sources as their spectra are power laws which fall quickly as a function of increasing energy.
This work could pave the way to extending polarised gamma-ray astronomy beyond the MeV energy regime.

P. Gros, S. Amano, D. Attie, et. al.
Wed, 21 Jun 17
7/64

|

# Measurement of low energy ionization signals from Compton scattering in a CCD dark matter detector [CL]

An important source of background in direct searches for low-mass dark matter particles are the energy deposits by small-angle scattering of environmental $\gamma$ rays. We report detailed measurements of low-energy spectra from Compton scattering of $\gamma$ rays in the bulk silicon of a charge-coupled device (CCD). Electron recoils produced by $\gamma$ rays from $^{57}$Co and $^{241}$Am radioactive sources are measured between 60 eV and 4 keV. The observed spectra agree qualitatively with theoretical predictions, and characteristic spectral features associated with the atomic structure of the silicon target are accurately measured for the first time. A theoretically-motivated parametrization of the data that describes the Compton spectrum at low energies for any incident $\gamma$-ray flux is derived. The result is directly applicable to background estimations for low-mass dark matter direct-detection experiments based on silicon detectors, in particular for the DAMIC experiment down to its current energy threshold.

K. Ramanathan, A. Kavner, A. Chavarria, et. al.
Wed, 21 Jun 17
22/64

An important source of background in direct searches for low-mass dark matter particles are the energy deposits by small-angle scattering of environmental $\gamma$ rays. We report detailed measurements of low-energy spectra from Compton scattering of $\gamma$ rays in the bulk silicon of a charge-coupled device (CCD). Electron recoils produced by $\gamma$ rays from $^{57}$Co and $^{241}$Am radioactive sources are measured between 60 eV and 4 keV. The observed spectra agree qualitatively with theoretical predictions, and characteristic spectral features associated with the atomic structure of the silicon target are accurately measured for the first time. A theoretically-motivated parametrization of the data that describes the Compton spectrum at low energies for any incident $\gamma$-ray flux is derived. The result is directly applicable to background estimations for low-mass dark matter direct-detection experiments based on silicon detectors, in particular for the DAMIC experiment down to its current energy threshold.