We report on a search for nuclear recoil signals from solar B-8 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 B-8 neutrinolike excess is found in an exposure of 0.6 t x 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.
This paper details the first application of a software tagging algorithm to reduce radon-induced backgrounds in liquid noble element time projection chambers, such as XENON1T and XENONnT. The ...convection velocity field in XENON1T was mapped out using Rn 222 and Po 218 events, and the rms convection speed was measured to be 0.30 ± 0.01 cm / s . Given this velocity field, Pb 214 background events can be tagged when they are followed by Bi 214 and Po 214 decays, or preceded by Po 218 decays. This was achieved by evolving a point cloud in the direction of a measured convection velocity field, and searching for Bi 214 and Po 214 decays or Po 218 decays within a volume defined by the point cloud. In XENON1T, this tagging system achieved a Pb 214 background reduction of 6.2 − 0.9 + 0.4 % with an exposure loss of 1.8 ± 0.2 % , despite the timescales of convection being smaller than the relevant decay times. We show that the performance can be improved in XENONnT, and that the performance of such a software-tagging approach can be expected to be further improved in a diffusion-limited scenario. Finally, a similar method might be useful to tag the cosmogenic Xe 137 background, which is relevant to the search for neutrinoless double-beta decay. Published by the American Physical Society 2024
In this work, we expand on the XENON1T nuclear recoil searches to study the individual signals of dark matter interactions from operators up to dimension eight in a chiral effective field theory ...(ChEFT) and a model of inelastic dark matter (iDM). We analyze data from two science runs of the XENON1T detector totaling 1 t × yr exposure. For these analyses, we extended the region of interest from 4.9 , 40.9 keV NR to 4.9 , 54.4 keV NR to enhance our sensitivity for signals that peak at nonzero energies. We show that the data are consistent with the background-only hypothesis, with a small background overfluctuation observed peaking between 20 and 50 keV NR , resulting in a maximum local discovery significance of 1.7 σ for the Vector ⊗ Vector strange ChEFT channel for a dark matter particle of 70 GeV / c 2 and 1.8 σ for an iDM particle of 50 GeV / c 2 with a mass splitting of 100 keV / c 2 . For each model, we report 90% confidence level upper limits. We also report upper limits on three benchmark models of dark matter interaction using ChEFT where we investigate the effect of isospin-breaking interactions. We observe rate-driven cancellations in regions of the isospin-breaking couplings, leading to up to 6 orders of magnitude weaker upper limits with respect to the isospin-conserving case. Published by the American Physical Society 2024
Abstract
A low-energy electronic recoil calibration of XENON1T, a dual-phase xenon time projection chamber, with an internal
$^{37}$$
37
Ar source was performed. This calibration source features a ...35-day half-life and provides two mono-energetic lines at 2.82 keV and 0.27 keV. The photon yield and electron yield at 2.82 keV are measured to be (
$$32.3\,\pm \,0.3$$
32.3
±
0.3
) photons/keV and (
$$40.6\,\pm \,0.5$$
40.6
±
0.5
) electrons/keV, respectively, in agreement with other measurements and with NEST predictions. The electron yield at 0.27 keV is also measured and it is (
$$68.0^{+6.3}_{-3.7}$$
68
.
0
-
3.7
+
6.3
) electrons/keV. The
$^{37}$$
37
Ar calibration confirms that the detector is well-understood in the energy region close to the detection threshold, with the 2.82 keV line reconstructed at (
$$2.83\,\pm \,0.02$$
2.83
±
0.02
) keV, which further validates the model used to interpret the low-energy electronic recoil excess previously reported by XENON1T. The ability to efficiently remove argon with cryogenic distillation after the calibration proves that
$^{37}$$
37
Ar can be considered as a regular calibration source for multi-tonne xenon detectors.
A low-energy electronic recoil calibration of XENON1T, a dual-phase xenon time projection chamber, with an internal 37Ar source was performed. This calibration source features a 35-day half-life and ...provides two mono-energetic lines at 2.82 keV and 0.27 keV. The photon yield and electron yield at 2.82 keV are measured to be (32.3±0.3) photons/keV and (40.6±0.5) electrons/keV, respectively, in agreement with other measurements and with NEST predictions. The electron yield at 0.27 keV is also measured and it is (68.0+6.3−3.7) electrons/keV. The 37Ar calibration confirms that the detector is well-understood in the energy region close to the detection threshold, with the 2.82 keV line reconstructed at (2.83±0.02) keV, which further validates the model used to interpret the low-energy electronic recoil excess previously reported by XENON1T. The ability to efficiently remove argon with cryogenic distillation after the calibration proves that 37Ar can be considered as a regular calibration source for multi-tonne xenon detectors.
We present results on the search for two-neutrino double-electron capture (2 ν ECEC) of 124 Xe and neutrinoless double- β decay (0 νββ ) of 136 Xe in XENON1T. We consider captures from the K shell up ...to the N shell in the 2 ν ECEC signal model and measure a total half-life of T 2 ν ECEC 1/2 =(1.1±0.2 stat ±0.1 sys )×10 22 yr with a 0.87 kg yr isotope exposure. The statistical significance of the signal is 7.0 σ . We use XENON1T data with 36.16 kg yr of 136 Xe exposure to search for 0 νββ . We find no evidence of a signal and set a lower limit on the half-life of T 0 νββ 1/2 >1.2×10 24 yr at 90%CL. This is the best result from a dark matter detector without an enriched target to date. We also report projections on the sensitivity of XENONnT to 0 νββ . Assuming a 275 kg yr 136 Xe exposure, the expected sensitivity is T 0 νββ 1/2 >2.1×10 25 yr at 90%CL, corresponding to an effective Majorana mass range of ⟨ mββ ⟩<(0.19–0.59)eV/c 2 .
Abstract Background There are only limited data on sofosbuvir-based treatment regimens in hepatitis C virus (HCV) genotype 4-infected patients. Aims To evaluate safety and efficacy of ...sofosbuvir-based triple-therapy in HCV genotype 4 infection. Methods All HCV genotype 4-infected patients who started sofosbuvir-based triple-therapy at our two centres between January and June 2014 were prospectively included ( N = 24) and compared to genotype 4 patients treated with peginterferon/ribavirin between January 2001 and December 2012 ( N = 63). Results The demographics in the sofosbuvir group and the controls were comparable (males 87.5% and 82.5%; mean age 46.7 ± 9.0 years and 42.0 ± 9.8 years, respectively). Sustained virological response was achieved in 83.3% in the sofosbuvir group and in 47.6% of controls ( P = 0.003). Fatigue ( P = 0.007), flu-like ( P = 0.015), gastrointestinal ( P < 0.001), dermatologic ( P < 0.001) and psychiatric symptoms ( P = 0.022) were more common in the control group. Conclusions In our real-life cohort, sofosbuvir-based triple therapy confirmed its high efficacy and safety for chronic genotype 4 hepatitis C.
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