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.
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\(^2\)).
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.
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.
In 3D topological insulators achieving a genuine bulk-insulating state is an important research topic. Recently, the material system (Bi,Sb)\(_{2}\)(Te,Se)\(_{3}\) (BSTS) has been proposed as a ...topological insulator with high resistivity and a low carrier concentration (Ren \textit{et al.} \cite{Ren2011}). Here we present a study to further refine the bulk-insulating properties of BSTS. We have synthesized Bi\(_{2-x}\)Sb\({_x}\)Te\(_{3-y}\)Se\(_{y}\) single crystals with compositions around \(x = 0.5\) and \(y = 1.3\). Resistance and Hall effect measurements show high resistivity and record low bulk carrier density for the composition Bi\(_{1.46}\)Sb\(_{0.54}\)Te\(_{1.7}\)Se\(_{1.3}\). The analysis of the resistance measured for crystals with different thicknesses within a parallel resistor model shows that the surface contribution to the electrical transport amounts to 97% when the sample thickness is reduced to \(1 \mu\)m. The magnetoconductance of exfoliated BSTS nanoflakes shows 2D weak antilocalization with \(\alpha \simeq -1\) as expected for transport dominated by topological surface states.
We report on finding no correlation between the two strongest observed Solar
flares in September 2017 and the decay rates of $^{60}$Co, $^{44}$Ti and
$^{137}$Cs sources, which are continuously ...measured by two independent NaI(Tl)
detector setups. We test for variations in the number of observed counts with
respect to the number of expected counts over multiple periods with timescales
varying from 1 to 109 hours around the Solar flare. No excess or deficit
exceeds the 2$\sigma$ global significance. We set a conservative lower limit on
the decay rate deviation over an 84-hour period around the two correlated Solar
flares in September 2017 to $0.044\%$ with 2$\sigma$ confidence. A fractional
change of $~0.1\%$ in the decay rate of $^{54}$Mn over a period of 84 hours was
claimed with 7$\sigma$ significance during multiple Solar flares in December
2006. We exclude such an effect at 4.7$\sigma$ significance.
Xenon dual-phase time projection chambers designed to search for Weakly Interacting Massive Particles have so far shown a relative energy resolution which degrades with energy above \(\sim\)200 keV ...due to the saturation effects. This has limited their sensitivity in the search for rare events like the neutrinoless double-beta decay of \(^{136}\)Xe at its \(Q\)-value, \(Q_{\beta\beta}\simeq\) 2.46 MeV. For the XENON1T dual-phase time projection chamber, we demonstrate that the relative energy resolution at 1 \(\sigma/\mu\) is as low as (0.80\(\pm\)0.02) % in its one-ton fiducial mass, and for single-site interactions at \(Q_{\beta\beta}\). We also present a new signal correction method to rectify the saturation effects of the signal readout system, resulting in more accurate position reconstruction and indirectly improving the energy resolution. The very good result achieved in XENON1T opens up new windows for the xenon dual-phase dark matter detectors to simultaneously search for other rare events.
We report on finding no correlation between the two strongest observed Solar flares in September 2017 and the decay rates of \(^{60}\)Co, \(^{44}\)Ti and \(^{137}\)Cs sources, which are continuously ...measured by two independent NaI(Tl) detector setups. We test for variations in the number of observed counts with respect to the number of expected counts over multiple periods with timescales varying from 1 to 109 hours around the Solar flare. No excess or deficit exceeds the 2\(\sigma\) global significance. We set a conservative lower limit on the decay rate deviation over an 84-hour period around the two correlated Solar flares in September 2017 to \(0.044\%\) with 2\(\sigma\) confidence. A fractional change of \(~0.1\%\) in the decay rate of \(^{54}\)Mn over a period of 84 hours was claimed with 7\(\sigma\) significance during multiple Solar flares in December 2006. We exclude such an effect at 4.7\(\sigma\) significance.
The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to ...cover the available parameter space for Weakly Interacting Massive Particles (WIMPs), while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector.
