Search

In this paper, we present a re-analysis of SuperCDMS data using a profile likelihood approach to search for sub-GeV dark matter particles (DM) through two inelastic scattering channels: bremsstrahlung radiation and the Migdal effect. By considering possible inelastic scattering channels, experimental sensitivity can be extended to DM masses that would otherwise be undetectable through the DM-nucleon elastic scattering channel, given the energy threshold of current experiments. We exclude DM masses down to $220~\textrm{MeV}/c^2$ at $2.7 \times 10^{-30}~\textrm{cm}^2$ via the bremsstrahlung channel. The Migdal channel search excludes DM masses down to $30~\textrm{MeV}/c^2$ at $5.0 \times 10^{-30}~\textrm{cm}^2$., Comment: This paper is being withdrawn due to an error in data selection during the analysis. Although incorrect, the limits are roughly representative of the sensitivity. The new corrected version of the result will be uploaded once ready

Recent results from the SENSEI experiment show that a cut on event clustering can reduce low-energy excesses in their eV-sensitive calorimeter. This hints at the role of surrounding uninstrumented surfaces in producing backgrounds. Charged particles crossing dielectric boundaries are well known to produce low-energy radiation. In particular, transition radiation, secondary electron emission, and sputtering may contribute to the spectrum, morphology, and rate of events observed in eV-sensitive detectors. The rich phenomenology and high yields of these surface processes will complicate comparisons of low-threshold dark matter detectors both to each other and to background models., Comment: 4 pages, 2 figures

XENON1T recently reported an excess of low-energy electron recoil events that may be attributable to either new physics or to the radioactive decay of tritium. It is likely that hydrogen is not be effectively removed by the hot zirconium getters deployed in the detector. Cosmogenic activation of the xenon underground is found to be insufficient to describe the observed excess, although gases diffusing out of detector materials from cosmogenic activation on surface may contribute. Changes in the operation of gas purification systems for XENON1T and other liquid nobel gas detectors could both confirm the tritium hypothesis and remove it from the detector., Comment: Corrected equation 1. Typo corrections. Removed possibility that XENON1T doesn't contain a Hydrogen Removal Unit

In their recent preprint [arXiv:2002.06937], Kurinsky, Baxter, Kahn, and Krnjaic assume an unphysical ionization yield for plasmon excitations in order to claim a possible dark matter signal. Their proposed signal is not possible based on known physics, but their proposed detection method warrants further investigation., Comment: 2 pages

The Super Cryogenic Dark Matter Search experiment (SuperCDMS) at the Soudan Underground Laboratory studied energy loss associated with Frenkel defect formation in germanium crystals at mK temperatures using in situ $^{210}$Pb sources. We examine the spectrum of $^{206}$Pb nuclear recoils near its expected 103 keV endpoint energy and determine an energy loss of $\left(6.08\pm0.18\right)$ %, which we attribute to defect formation. From this result and using TRIM simulations, we extract the first experimentally determined average displacement threshold energy of $\left(19.7^{+0.6}_{-0.5}\right)$ eV for germanium. This has implications for the analysis thresholds of future germanium-based dark matter searches., Comment: 4 Figures, Two data files, One data release description file

Proposed dark matter detectors with eV-scale sensitivities will detect a large background of atomic (nuclear) recoils from coherent photon scattering. This background climbs steeply below $\sim10$~eVnr, far exceeding the declining rate of low-energy Compton recoils. The upcoming generation of dark matter detectors will not be limited by this background, but further development of eV-scale and sub-eV detectors will require the use of low-$Z$ target materials, such as helium, to avoid a large rate of coherent photon scattering, or highly efficient methods to reject photons when they scatter., Comment: 2 pages, 1 figure

This report, based on the Dark Sectors workshop at SLAC in April 2016, summarizes the scientific importance of searches for dark sector dark matter and forces at masses beneath the weak-scale, the status of this broad international field, the important milestones motivating future exploration, and promising experimental opportunities to reach these milestones over the next 5-10 years., Comment: 66 pages, 15 figures, 3 tables. Workshop website and agenda: http://www-conf.slac.stanford.edu/darksectors2016/ https://indico.cern.ch/event/507783/ Editors: J. Alexander, M. Battaglieri, B. Echenard, R. Essig, M. Graham, E. Izaguirre, J. Jaros, G. Krnjaic, J. Mardon, D. Morrissey, T. Nelson, M. Perelstein, M. Pyle, A. Ritz, P. Schuster, B. Shuve, N. Toro, R. Van De Water

The $^9$Be$(\gamma,n)^8$Be reaction is enhanced by a near threshold $1/2^+$ state. Contradictions between existing measurements of this reaction cross-section affect calculations of astrophysical r-process yields, dark matter detector calibrations, and the theory of the nuclear structure of $^9$Be. Select well-documented radioisotope $^9$Be$(\gamma,n)$ source yield measurements have been reanalyzed, providing a set of high-accuracy independently measured cross sections. A Breit-Wigner fit of these corrected measurements yields $E_R=1738.8\pm1.9$ keV, $\Gamma_\gamma=0.771\pm0.021$ eV, and $\Gamma_n=268\pm15$ keV for the $1/2^+$ state. A virtual $1/2^+$ state is excluded with 99.3\% confidence., Comment: 7 pages, 4 figures, 4 tables

Dark matter detectors require calibrations of their energy scale and efficiency to detect nuclear recoils in the $1-50$ keV range. Most calibrations use neutron scattering and require MCNP or Geant4 simulations of neutron propagation through the detector. For most nuclei heavier than $^{16}$O, these simulations' libraries ignore the contribution of resolved resonances to the neutron elastic differential cross-section. For many isotopes and neutron energies of importance to dark matter detection, this invalid assumption can severely distort simulated nuclear recoil spectra. The correct angular distributions can be calculated from the resonance parameters using R-matrix formalism. A set of neutron scattering libraries with high resolution angular distributions for MCNP and Geant4 of $^{19}$F, $^{40}$Ar, $^{50,52}$Cr, $^{56}$Fe, $^{136}$Xe, and $^{206,207,208}$Pb is presented. An MCNPX library for simulating the production of low-energy neutrons in the $^9$Be$(\gamma,n)^8$Be reaction is also presented. Example dark matter detector calibrations are simulated with the new libraries showing how detector sensitivity could be overestimated by factors of two by relying on existing MCNP and Geant4 libraries., Comment: 4 pages, 3 figures

The space of E-infinity structures on an simplicial operad C is the limit of a tower of fibrations, so its homotopy is the abutment of a Bousfield-Kan fringed spectral sequence. The spectral sequence begins (under mild restrictions) with the stable cohomotopy of the graded right Gamma-module formed by the homotopy groups of C ; the fringe contains an obstruction theory for the existence of E-infinity structures on C. This formulation is very flexible: applications extend beyond structures on classical ring spectra to examples (in references) in motivic homotopy theory., Comment: 33 pages

We show that the poset of non-trivial partitions of 1,2,...,n has a fundamental homology class with coefficients in a Lie superalgebra. Homological duality then rapidly yields a range of known results concerning the integral representations of the symmetric groups S_n and S_{n+1} on the homology and cohomology of this partially-ordered set., Comment: Published by Algebraic and Geometric Topology at http://www.maths.warwick.ac.uk/agt/AGTVol4/agt-4-41.abs.html