Results on Low-Mass Weakly Interacting Massive Particles from an 11 kg-day Target Exposure of DAMIC at SNOLAB. (arXiv:2007.15622v2 [astro-ph.CO] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Aguilar_Arevalo_A/0/1/0/all/0/1">A. Aguilar-Arevalo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Amidei_D/0/1/0/all/0/1">D. Amidei</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Baxter_D/0/1/0/all/0/1">D. Baxter</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cancelo_G/0/1/0/all/0/1">G. Cancelo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vergara_B/0/1/0/all/0/1">B.A. Cervantes Vergara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chavarria_A/0/1/0/all/0/1">A.E. Chavarria</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+DOlivo_J/0/1/0/all/0/1">J.C. D'Olivo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Estrada_J/0/1/0/all/0/1">J. Estrada</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Favela_Perez_F/0/1/0/all/0/1">F. Favela-Perez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gaior_R/0/1/0/all/0/1">R. Gaior</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Guardincerri_Y/0/1/0/all/0/1">Y. Guardincerri</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hoppe_E/0/1/0/all/0/1">E.W. Hoppe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hossbach_T/0/1/0/all/0/1">T.W. Hossbach</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kilminster_B/0/1/0/all/0/1">B. Kilminster</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lawson_I/0/1/0/all/0/1">I. Lawson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lee_S/0/1/0/all/0/1">S.J. Lee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Letessier_Selvon_A/0/1/0/all/0/1">A. Letessier-Selvon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Matalon_A/0/1/0/all/0/1">A. Matalon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mitra_P/0/1/0/all/0/1">P. Mitra</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Overman_C/0/1/0/all/0/1">C.T. Overman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Piers_A/0/1/0/all/0/1">A. Piers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Privitera_P/0/1/0/all/0/1">P. Privitera</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ramanathan_K/0/1/0/all/0/1">K. Ramanathan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rocha_J/0/1/0/all/0/1">J. Da Rocha</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sarkis_Y/0/1/0/all/0/1">Y. Sarkis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Settimo_M/0/1/0/all/0/1">M. Settimo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Smida_R/0/1/0/all/0/1">R. Smida</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Thomas_R/0/1/0/all/0/1">R. Thomas</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tiffenberg_J/0/1/0/all/0/1">J. Tiffenberg</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Traina_M/0/1/0/all/0/1">M. Traina</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vilar_R/0/1/0/all/0/1">R. Vilar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Virto_A/0/1/0/all/0/1">A.L. Virto</a>
We present constraints on the existence of weakly interacting massive
particles (WIMPs) from an 11 kg-day target exposure of the DAMIC experiment at
the SNOLAB underground laboratory. The observed energy spectrum and spatial
distribution of ionization events with electron-equivalent energies $>$200
eV$_{rm ee}$ in the DAMIC CCDs are consistent with backgrounds from natural
radioactivity. An excess of ionization events is observed above the analysis
threshold of 50 eV$_{rm ee}$. While the origin of this low-energy excess
requires further investigation, our data exclude spin-independent WIMP-nucleon
scattering cross sections $sigma_{chi-n}$ as low as $3times 10^{-41}$ cm$^2$
for WIMPs with masses $m_{chi}$ from 7 to 10 GeV$c^{-2}$ . These results are
the strongest constraints from a silicon target on the existence of WIMPs with
$m_{chi}$$<$9 GeV$c^{-2}$ and are directly relevant to any dark matter
interpretation of the excess of nuclear-recoil events observed by the CDMS
silicon experiment in 2013.
We present constraints on the existence of weakly interacting massive
particles (WIMPs) from an 11 kg-day target exposure of the DAMIC experiment at
the SNOLAB underground laboratory. The observed energy spectrum and spatial
distribution of ionization events with electron-equivalent energies $>$200
eV$_{rm ee}$ in the DAMIC CCDs are consistent with backgrounds from natural
radioactivity. An excess of ionization events is observed above the analysis
threshold of 50 eV$_{rm ee}$. While the origin of this low-energy excess
requires further investigation, our data exclude spin-independent WIMP-nucleon
scattering cross sections $sigma_{chi-n}$ as low as $3times 10^{-41}$ cm$^2$
for WIMPs with masses $m_{chi}$ from 7 to 10 GeV$c^{-2}$ . These results are
the strongest constraints from a silicon target on the existence of WIMPs with
$m_{chi}$$<$9 GeV$c^{-2}$ and are directly relevant to any dark matter
interpretation of the excess of nuclear-recoil events observed by the CDMS
silicon experiment in 2013.
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