Abstract
The NEWS-G collaboration is searching for light dark matter candidates using a spherical proportional counter. Light gases, such as hydrogen, helium, and neon, are used as targets, providing access in the 0.1–10 GeV mass range. First results obtained with SEDINE, a 60 cm in diameter detector, in the Underground Laboratory of Modane yielded a 90% confidence level upper limit of 4.4⋅ 1037 cm2 on the nucleon-dark matter interaction cross-section for a candidate with 0.5 GeV mass. Recent developments in several aspects of the detector instrumentation are presented, along with the construction of a new, 140 cm in diameter, detector with new compact shielding.
Highlights
37Ar 2.82 keV peak Before correction 37Ar 2.82 keV peak After correction (b) physics results of the NEWS-G collaboration were obtained using the SEDINE detector, a 60 cm in diameter spherical proportional counter, operating at LSM. These results demonstrate the potential of spherical proportional counters in the search of low-mass DM candidates
These improvements, together with the developments in sensor design, are expected to lead to substantial improvements in the sensitivity for light DM candidates
Summary
The spherical proportional counter, presented in figure 1, is a novel gaseous detector [13,14,15]. The spherical proportional counter, presented, is a novel gaseous detector [13,14,15] It consists of a grounded spherical shell which acts as the cathode and a small spherical anode, the sensor, supported at the centre by a grounded metallic rod, to which the high voltage is applied and from which the signal is read-out. The spherical proportional counter exhibits the following key features: a) very low energy thresholds, down to single ionisation electron detection, thanks to small sensor capacitance and high gain operation; b) small number of read-out channels; c) background rejection and fiducialisation through pulse shape analysis; d) simple and robust construction with radiopure materials; e) variety of light target gases, allowing optimisation. Sibility to vary the operational pressure and high voltage, providing additional handles to disentangle potential signals from unknown backgrounds
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