Atomic limits in the search for galactic dark matter

Sørensen, P.

doi:10.1103/physrevd.91.083509

Cited by 43 publications

(46 citation statements)

References 57 publications

(48 reference statements)

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“…Below 0.8 keV nr our quenching model starts to deviate from a pure Lindhard model due to the adiabatic correction factor F AC . The corresponding best-fit value of the adiabatic energy scale factor ξ = 0.16 keV nr is seen to be in good agreement with kinematic threshold predictions recently made for germanium [33]. As discussed above, ξ lies well below our triggering threshold of ∼ 0.8 keV ee .…”

Section: Resultssupporting

confidence: 90%

Measurement of the low-energy quenching factor in germanium using anY88/Bephotoneutron source

et al. 2016

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We employ an 88 Y/Be photoneutron source to derive the quenching factor for neutron-induced nuclear recoils in germanium, probing recoil energies from a few hundred eVnr to 8.5 keVnr. A comprehensive Monte Carlo simulation of our setup is compared to experimental data employing a Lindhard model with a free electronic energy loss k and an adiabatic correction for sub-keVnr nuclear recoils. The best fit k = 0.179±0.001 obtained using a Monte Carlo Markov Chain (MCMC) ensemble sampler is in good agreement with previous measurements, confirming the adequacy of the Lindhard model to describe the stopping of few-keV ions in germanium crystals at a temperature of ∼77 K. This value of k corresponds to a quenching factor of 13.7 % to 25.3 % for nuclear recoil energies between 0.3 keVnr and 8.5 keVnr, respectively.

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Section: Resultssupporting

confidence: 90%

Measurement of the low-energy quenching factor in germanium using anY88/Bephotoneutron source

et al. 2016

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“…This high stopping power can cause 1) a high fraction of the 210 Pb energy to be dissipated as heat, decreasing the Lindhard factor, and 2) a high argon dimer decay rate through non-radiative channels, strengthening the Birks saturation. The SRIM simulations, however, under-predict the amount of quenching, possibly due to Lindhard model breaking down for Pb recoils at low energies, as suggested in [19].…”

mentioning

confidence: 93%

First measurement of surface nuclear recoil background for argon dark matter searches

Stanford

Westerdale

et al. 2017

Phys. Rev. D

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One major background in direct searches for weakly interacting massive particles (WIMPs) comes from the deposition of radon progeny on detector surfaces. The most dangerous surface background is the 206 Pb recoils produced by 210 Po decays. In this letter, we report the first characterization of this background in liquid argon. The scintillation signal of low energy Pb recoils is measured to be highly quenched in argon, and we estimate that the 103 keV 206 Pb recoil background will produce a signal equal to that of a ∼5 keV (30 keV) electron recoil ( 40 Ar recoil). In addition, we demonstrate that this dangerous 210 Po surface background can be suppressed, using pulse shape discrimination methods, by a factor of ∼100 or higher, which can make argon dark matter detectors near background-free and enhance their potential for discovery of medium-and high-mass WIMPs. We also discuss the impact on other low background experiments. Noble liquid detectors have demonstrated exceptional sensitivity in direct searches for weakly interacting massive particles (WIMPs), a popular candidate for dark matter. Over the past decade, xenon-based experiments including XENON100 [1] and LUX [2] have achieved the highest sensitivities in this field. Recently, argon-based experiments have also developed key technologies necessary for sensitive WIMP searches, as demonstrated by the DarkSide-50 experiment [3,4]. The DEAP-3600 experiment [5], which is being commissioned at SNOLAB, is expected to achieve a higher dark matter sensitivity than that of current xenon experiments, especially for high-mass WIMPs. With the powerful pulse shape discrimination (PSD) capability of argon, argon dark matter searches at multi-tonne scales can be free of electron recoil backgrounds from solar neutrinos [6] and from radioactive decays of radon progeny and 85 Kr [7], all of which compromise the sensitivity of xenon experiments.Due to the low expected interaction rate between WIMP dark matter and ordinary matter, it is critical for WIMP search experiments to achieve a very low background rate, especially for nuclear recoil background that can mimic a WIMP interaction. One such nuclear recoil background can result from the exposure of detector surfaces to radon that is naturally present in the environment, specifically in air and in ground water. Through the following decay sequence,

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“…For sub-GeV DM particles, nuclear recoil energies are below O(0.1) keV. The scintillation and ionisation yield for such small energies have not yet been measured in liquid xenon, but theoretical arguments predict the resulting signals to be very small [56]. We conservatively neglect this contribution and assume that only electronic energy contributes to the S1 and S2 signals, such that pdf(S1,S2|E R , E EM ) = pdf(S1,S2|E EM ) and the integration over E R in eq.…”

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confidence: 99%

Directly Detecting Sub-GeV Dark Matter with Electrons from Nuclear Scattering

2018

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Dark matter (DM) particles with mass in the sub-GeV range are an attractive alternative to heavier weakly interacting massive particles, but direct detection of such light particles is challenging. If, however, DM-nucleus scattering leads to ionization of the recoiling atom, the resulting electron may be detected even if the nuclear recoil is unobservable. We demonstrate that including this effect significantly enhances direct detection sensitivity to sub-GeV DM. Existing experiments set world-leading limits, and future experiments may probe the cross sections relevant for thermal freeze-out.

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Atomic limits in the search for galactic dark matter

Cited by 43 publications

References 57 publications

Measurement of the low-energy quenching factor in germanium using anY88/Bephotoneutron source

Measurement of the low-energy quenching factor in germanium using anY88/Bephotoneutron source

First measurement of surface nuclear recoil background for argon dark matter searches

Directly Detecting Sub-GeV Dark Matter with Electrons from Nuclear Scattering

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