We report on a search for nuclear recoil signals from solar ^{8}B neutrinos elastically scattering off xenon nuclei in XENON1T data, lowering the energy threshold from 2.6 to 1.6 keV. We develop a ...variety of novel techniques to limit the resulting increase in backgrounds near the threshold. No significant ^{8}B neutrinolike excess is found in an exposure of 0.6 t×y. For the first time, we use the nondetection of solar neutrinos to constrain the light yield from 1-2 keV nuclear recoils in liquid xenon, as well as nonstandard neutrino-quark interactions. Finally, we improve upon world-leading constraints on dark matter-nucleus interactions for dark matter masses between 3 and 11 GeV c^{-2} by as much as an order of magnitude.
The selection of low-radioactive construction materials is of the utmost importance for rare-event searches and thus critical to the XENONnT experiment. Results of an extensive radioassay program are ...reported, in which material samples have been screened with gamma-ray spectroscopy, mass spectrometry, and \(^{222}\)Rn emanation measurements. Furthermore, the cleanliness procedures applied to remove or mitigate surface contamination of detector materials are described. Screening results, used as inputs for a XENONnT Monte Carlo simulation, predict a reduction of materials background (\(\sim\)17%) with respect to its predecessor XENON1T. Through radon emanation measurements, the expected \(^{222}\)Rn activity concentration in XENONnT is determined to be 4.2\(\,(^{+0.5}_{-0.7})\,\mu\)Bq/kg, a factor three lower with respect to XENON1T. This radon concentration will be further suppressed by means of the novel radon distillation system.
A novel online distillation technique was developed for the XENON1T dark matter experiment to reduce intrinsic background components more volatile than xenon, such as krypton or argon, while the ...detector was operating. The method is based on a continuous purification of the gaseous volume of the detector system using the XENON1T cryogenic distillation column. A krypton-in-xenon concentration of \((360 \pm 60)\) ppq was achieved. It is the lowest concentration measured in the fiducial volume of an operating dark matter detector to date. A model was developed and fit to the data to describe the krypton evolution in the liquid and gas volumes of the detector system for several operation modes over the time span of 550 days, including the commissioning and science runs of XENON1T. The online distillation was also successfully applied to remove Ar-37 after its injection for a low energy calibration in XENON1T. This makes the usage of Ar-37 as a regular calibration source possible in the future. The online distillation can be applied to next-generation experiments to remove krypton prior to, or during, any science run. The model developed here allows further optimization of the distillation strategy for future large scale detectors.
We report the results of a search for the inelastic scattering of weakly interacting massive particles (WIMPs) in the XENON1T dark matter experiment. Scattering off \(^{129}\)Xe is the most sensitive ...probe of inelastic WIMP interactions, with a signature of a 39.6 keV de-excitation photon detected simultaneously with the nuclear recoil. Using an exposure of 0.89 tonne-years, we find no evidence of inelastic WIMP scattering with a significance of more than 2\(\sigma\). A profile-likelihood ratio analysis is used to set upper limits on the cross-section of WIMP-nucleus interactions. We exclude new parameter space for WIMPs heavier than 100 GeV/c\({}^2\), with the strongest upper limit of \(3.3 \times 10^{-39}\) cm\({}^2\) for 130 GeV/c\({}^2\) WIMPs at 90\% confidence level.
We detail the sensitivity of the liquid xenon (LXe) DARWIN observatory to solar neutrinos via elastic electron scattering. We find that DARWIN will have the potential to measure the fluxes of five ...solar neutrino components: \(pp\), \(^7\)Be, \(^{13}\)N, \(^{15}\)O and \(pep\). The precision of the \(^{13}\)N, \(^{15}\)O and \(pep\) components is hindered by the double-beta decay of \(^{136}\)Xe and, thus, would benefit from a depleted target. A high-statistics observation of \(pp\) neutrinos would allow us to infer the values of the weak mixing angle, \(\sin^2\theta_w\), and the electron-type neutrino survival probability, \(P_e\), in the electron recoil energy region from a few keV up to 200 keV for the first time, with relative precision of 5% and 4%, respectively, at an exposure of 300 ty. An observation of \(pp\) and \(^7\)Be neutrinos would constrain the neutrino-inferred solar luminosity down to 0.2%. A combination of all flux measurements would distinguish between the high (GS98) and low metallicity (AGS09) solar models with 2.1-2.5\(\sigma\) significance, independent of external measurements from other experiments or a measurement of \(^8\)B neutrinos through coherent elastic neutrino-nucleus scattering in DARWIN. Finally, we demonstrate that with a depleted target DARWIN may be sensitive to the neutrino capture process of \(^{131}\)Xe.
Phys. Rev. Lett. 126, 091301 (2021) We report on a search for nuclear recoil signals from solar $^8$B neutrinos
elastically scattering off xenon nuclei in XENON1T data, lowering the energy
threshold ...from 2.6 keV to 1.6 keV. We develop a variety of novel techniques to
limit the resulting increase in backgrounds near the threshold. No significant
$^8$B neutrino-like excess is found in an exposure of 0.6 t $\times$ y. For the
first time, we use the non-detection of solar neutrinos to constrain the light
yield from 1-2 keV nuclear recoils in liquid xenon, as well as non-standard
neutrino-quark interactions. Finally, we improve upon world-leading constraints
on dark matter-nucleus interactions for dark matter masses between 3 GeV/c$^2$
and 11 GeV/c$^2$ by as much as an order of magnitude.
The selection of low-radioactive construction materials is of utmost importance for the success of low-energy rare event search experiments. Besides radioactive contaminants in the bulk, the ...emanation of radioactive radon atoms from material surfaces attains increasing relevance in the effort to further reduce the background of such experiments. In this work, we present the \(^{222}\)Rn emanation measurements performed for the XENON1T dark matter experiment. Together with the bulk impurity screening campaign, the results enabled us to select the radio-purest construction materials, targeting a \(^{222}\)Rn activity concentration of 10 \(\mu\)Bq/kg in 3.2 t of xenon. The knowledge of the distribution of the \(^{222}\)Rn sources allowed us to selectively eliminate critical components in the course of the experiment. The predictions from the emanation measurements were compared to data of the \(^{222}\)Rn activity concentration in XENON1T. The final \(^{222}\)Rn activity concentration of (4.5 \(\pm\) 0.1) \(\mu\)Bq/kg in the target of XENON1T is the lowest ever achieved in a xenon dark matter experiment.
XENONnT is a dark matter direct detection experiment, utilizing 5.9 t of instrumented liquid xenon, located at the INFN Laboratori Nazionali del Gran Sasso. In this work, we predict the experimental ...background and project the sensitivity of XENONnT to the detection of weakly interacting massive particles (WIMPs). The expected average differential background rate in the energy region of interest, corresponding to (1, 13) keV and (4, 50) keV for electronic and nuclear recoils, amounts to \(12.3 \pm 0.6\) (keV t y)\(^{-1}\) and \((2.2\pm 0.5)\times 10^{-3}\) (keV t y)\(^{-1}\), respectively, in a 4 t fiducial mass. We compute unified confidence intervals using the profile construction method, in order to ensure proper coverage. With the exposure goal of 20 t\(\,\)y, the expected sensitivity to spin-independent WIMP-nucleon interactions reaches a cross-section of \(1.4\times10^{-48}\) cm\(^2\) for a 50 GeV/c\(^2\) mass WIMP at 90% confidence level, more than one order of magnitude beyond the current best limit, set by XENON1T. In addition, we show that for a 50 GeV/c\(^2\) WIMP with cross-sections above \(2.6\times10^{-48}\) cm\(^2\) (\(5.0\times10^{-48}\) cm\(^2\)) the median XENONnT discovery significance exceeds 3\(\sigma\) (5\(\sigma\)). The expected sensitivity to the spin-dependent WIMP coupling to neutrons (protons) reaches \(2.2\times10^{-43}\) cm\(^2\) (\(6.0\times10^{-42}\) cm\(^2\)).
We report results from searches for new physics with low-energy electronic recoil data recorded with the XENON1T detector. With an exposure of 0.65 t-y and an unprecedentedly low background rate of ...\(76\pm2\) events/(t y keV) between 1 and 30 keV, the data enables sensitive searches for solar axions, an enhanced neutrino magnetic moment, and bosonic dark matter. An excess over known backgrounds is observed at low energies and most prominent between 2 and 3 keV. The solar axion model has a 3.4\(\sigma\) significance, and a 3D 90% confidence surface is reported for axion couplings to electrons, photons, and nucleons. This surface is inscribed in the cuboid defined by \(g_{ae}<3.8 \times 10^{-12}\), \(g_{ae}g_{an}^{eff}<4.8\times 10^{-18}\), and \(g_{ae}g_{a\gamma}<7.7\times10^{-22} GeV^{-1}\), and excludes either \(g_{ae}=0\) or \(g_{ae}g_{a\gamma}=g_{ae}g_{an}^{eff}=0\). The neutrino magnetic moment signal is similarly favored over background at 3.2\(\sigma\) and a confidence interval of \(\mu_{\nu} \in (1.4,2.9)\times10^{-11}\mu_B\) (90% C.L.) is reported. Both results are in strong tension with stellar constraints. The excess can also be explained by \(\beta\) decays of tritium at 3.2\(\sigma\) with a trace amount that can neither be confirmed nor excluded with current knowledge of its production and reduction mechanisms. The significances of the solar axion and neutrino magnetic moment hypotheses are reduced to 2.0\(\sigma\) and 0.9\(\sigma\), respectively, if an unconstrained tritium component is included in the fitting. With respect to bosonic dark matter, the excess favors a monoenergetic peak at (\(2.3\pm0.2\)) keV (68% C.L.) with a 3.0\(\sigma\) global (4.0\(\sigma\) local) significance. We also consider the possibility that \(^{37}\)Ar may be present in the detector and yield a 2.82 keV peak. Contrary to tritium, the \(^{37}\)Ar concentration can be tightly constrained and is found to be negligible.
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