New measurement of the scintillation efficiency of low-energy nuclear recoils in liquid xenon

Abstract

Particle detectors that use liquid xenon (LXe) as detection medium are among the leading technologies in the search for dark matter weakly interacting massive particles (WIMPs). A key enabling element has been the low-energy detection threshold for recoiling nuclei produced by the interaction of WIMPs in LXe targets. In these detectors, the nuclear recoil energy scale is based on the LXe scintillation signal and thus requires knowledge of the relative scintillation efficiency of nuclear recoils, L eff . The uncertainty in L eff at low energies is the largest systematic uncertainty in the reported results from LXe WIMP searches at low masses. In the context of the XENON Dark Matter project, a new LXe scintillation detector has been designed and built specifically for the measurement of L eff at low energies, with an emphasis on maximizing the scintillation light detection efficiency to obtain the lowest possible energy threshold. We report new measurements of L eff at low energies performed with this detector. Our results suggest a L eff which slowly decreases with decreasing energy, from 0.144 ± 0.009 at 15 keV down to 0.088 +0.014 −0.015 at 3 keV.

Liquid noble gas detectors for low energy particle physics

“…Most experimental measurements of the scintillation efficiency for nuclear recoils to date were carried out with different setups but using the same method -elastic scattering of mono-energetic ∼MeV neutrons off a LXe target [61,123,124,125,126,127,128]. The scattered neutrons are detected at a fixed angle, thus allowing the energy transferred to Xe atoms to be determined kinematically.…”

“…Figure 12. Energy-dependent relative scintillation yield for nuclear recoils in liquid xenon; data from monoenergetic neutron beam measurements are labelled by the following markers: ( ) [61]; (•) [127]; ( ) [126]; ( ) [123]; ( ) [124]; (•) [128]; ( ) [125]. Indirect measurements from Monte Carlo: ( ) [66]; the two lines are the indirect measurements obtained from the first and second runs of ZEPLIN-III, with 68% CL bands shown in green (\\\) and blue (///), respectively [67].…”

Measurement of the ionization yield of nuclear recoils in liquid argon using a two-phase detector with electroluminescence gap

“…Such a calibration is usually performed by measuring the ionization yield and scintillation efficiency of nuclear recoils, using neutron elastic scattering off nuclei. While for liquid Xe there are ample experimental data on such yields [2][3][4], little is known about the ionization yield in liquid Ar.…”

Using effective operators to understand CoGeNT and CDMS-Si signals

“…It is possible that a non-Maxwell-Boltzmann velocity distribution [9] or non-trivial particle physics (for example, exothermic or isospin-violating dark matter [10][11][12][13]) could alleviate this tension. The response of xenon to low-energy recoils is also a matter of some debate [14][15][16][17][18][19], and could result in a significant reduction of sensitivity from the xenon-based experiments. Additionally, though the prospective signals from DAMA/LIBRA, CDMS-Si, and CoGeNT are usually interpreted in terms of spin-independent interactions between dark matter and the target nuclei, a spin-dependent interpretation is not firmly ruled out [20].…”