arXiv subjects

A. Kamaha

Publications and source records attributed to A. Kamaha.

6 recordsLinked to original sources

arXiv2021

Investigating the XENON1T Low-Energy Electronic Recoil Excess Using NEST

The search for dark matter, the missing mass of the Universe, is one of the most active fields of study within particle physics. The XENON1T experiment recently observed a 3.5$σ$ excess potentially consistent with dark matter, or with solar axions. Here, we will use the Noble Element Simulation Technique (NEST) software to simulate the XENON1T detector, reproducing the excess. We utilize different detector efficiency and energy reconstruction models, but they primarily impact sub-keV energies and cannot explain the XENON1T excess. However, using NEST, we can reproduce their excess in multiple, unique ways, most easily via the addition of 31$\pm$11 $^{37}Ar$ decays. Furthermore, this results in new, modified background models, reducing the significance of the excess to $\le2.2σ$ at least using non-Profile Likelihood Ratio (PLR) methods. This is independent confirmation that the excess is a real effect, but potentially explicable by known physics. Many cross-checks of our $^{37}Ar$ hypothesis are presented.

hep-ex↗

arXiv2019

Precision laser-based measurements of the single electron response of SPCs for the NEWS-G light dark matter search experiment

Spherical Proportional Counters (SPCs) are a novel gaseous detector technology employed by the NEWS-G low-mass dark matter search experiment for their high sensitivity to single electrons from ionization. In this paper, we report on the first characterization of the single electron response of SPCs with unprecedented precision, using a UV-laser calibration system. The experimental approach and analysis methodology are presented along with various direct applications for the upcoming next phase of the experiment at SNOLAB. These include the continuous monitoring of the detector response and electron drift properties during dark matter search runs, as well as the experimental measurement of the trigger threshold efficiency. We measure a mean ionization energy of $\mathrm{W}=27.6\pm0.2~\mathrm{eV}$ in $\mathrm{Ne + CH_4}$ $(2\%)$ for 2.8 keV X-rays, and demonstrate the feasibility of performing similar precision measurements at sub-keV energies for future gas mixtures to be used for dark matter searches at SNOLAB.

physics.ins-det↗

arXiv2017

First results from the NEWS-G direct dark matter search experiment at the LSM

New Experiments With Spheres-Gas (NEWS-G) is a direct dark matter detection experiment using Spherical Proportional Counters (SPCs) with light noble gases to search for low-mass Weakly Interacting Massive Particles (WIMPs). We report the results from the first physics run taken at the Laboratoire Souterrain de Modane (LSM) with SEDINE, a 60 cm diameter prototype SPC operated with a mixture of $\mathrm{Ne}+\mathrm{CH}_{4}$ (0.7 %) at 3.1 bars for a total exposure of $9.7\;\mathrm{kg\cdot days}$. New constraints are set on the spin-independent WIMP-nucleon scattering cross-section in the sub-$\mathrm{GeV/c^2}$ mass region. We exclude cross-sections above $4.4 \times \mathrm{10^{-37}\;cm^2}$ at 90 % confidence level (C.L.) for a 0.5 $\mathrm{GeV/c^2}$ WIMP. The competitive results obtained with SEDINE are promising for the next phase of the NEWS-G experiment: a 140 cm diameter SPC to be installed at SNOLAB by summer 2018.

astro-ph.IM↗

arXiv2017

Final Results of the PICASSO Dark Matter Search Experiment

The PICASSO dark matter search experiment operated an array of 32 superheated droplet detectors containing 3.0 kg of C$_{4}$F$_{10}$ and collected an exposure of 231.4 kgd at SNOLAB between March 2012 and January 2014. We report on the final results of this experiment which includes for the first time the complete data set and improved analysis techniques including \mbox{acoustic} localization to allow fiducialization and removal of higher activity regions within the detectors. No signal consistent with dark matter was observed. We set limits for spin-dependent interactions on protons of $σ_p^{SD}$~=~1.32~$\times$~10$^{-2}$~pb (90\%~C.L.) at a WIMP mass of 20 GeV/c$^{2}$. In the spin-independent sector we exclude cross sections larger than $σ_p^{SI}$~=~4.86~$\times$~10$^{-5 }$~pb~(90\% C.L.) in the region around 7 GeV/c$^{2}$. The pioneering efforts of the PICASSO experiment have paved the way forward for a next generation detector incorporating much of this technology and experience into larger mass bubble chambers.

hep-ex↗

arXiv2012

Constraints on Low-Mass WIMP Interactions on 19F from PICASSO

Recent results from the PICASSO dark matter search experiment at SNOLAB are reported. These results were obtained using a subset of 10 detectors with a total target mass of 0.72 kg of 19F and an exposure of 114 kgd. The low backgrounds in PICASSO allow recoil energy thresholds as low as 1.7 keV to be obtained which results in an increased sensitivity to interactions from Weakly Interacting Massive Particles (WIMPs) with masses below 10 GeV/c^2. No dark matter signal was found. Best exclusion limits in the spin dependent sector were obtained for WIMP masses of 20 GeV/c^2 with a cross section on protons of sigma_p^SD = 0.032 pb (90% C.L.). In the spin independent sector close to the low mass region of 7 GeV/c2 favoured by CoGeNT and DAMA/LIBRA, cross sections larger than sigma_p^SI = 1.41x10^-4 pb (90% C.L.) are excluded.

hep-ex↗

arXiv2010

New Insights into Particle Detection with Superheated Liquids

We report new results obtained in calibrations of superheated liquid droplet detectors used in dark matter searches with different radiation sources (n,$α$,$γ$). In particular, detectors were spiked with alpha-emitters located inside and outside the droplets. It is shown that the responses are different, depending on whether alpha particles or recoil nuclei create the signals. The energy thresholds for $α$-emitters are compared with test beam measurements using mono-energetic neutrons, as well as with theoretical predictions. Finally a model is presented which describes how the observed intensities of particle induced acoustic signals can be related to the dynamics of bubble growth in superheated liquids. An improved understanding of the bubble dynamics is an important first step in obtaining better discrimination between particle types interacting in detectors of this kind.

physics.ins-det↗