Design and performance of the field cage for the XENONnT experiment

The precision in reconstructing events detected in a dual-phase time projection chamber depends on an homogeneous and well understood electric field within the liquid target. In the XENONnT TPC the field homogeneity is achieved through a double-array field cage, consisting of two nested arrays of field shaping rings connected by an easily accessible resistor chain. Rather than being connected to the gate electrode, the topmost field shaping ring is independently biased, adding a degree of freedom to tune the electric field during operation. Two-dimensional finite element simulations were used to optimize the field cage, as well as its operation. Simulation results were compared to 83mKr calibration data. This comparison indicates an accumulation of charge on the panels of the TPC which is constant over time, as no evolution of the reconstructed position distribution of events is observed. The simulated electric field was then used to correct the charge signal for the field dependence of the charge yield. This correction resolves the inconsistent measurement of the drift electron lifetime when using different calibrations sources and different field cage tuning voltages

Solar neutrino detection sensitivity in DARWIN via electron scattering

We detail the sensitivity of the proposed liquid xenon 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, $$^7$$ 7 Be, $$^{13}$$ 13 N, $$^{15}$$ 15 O and pep. The precision of the $$^{13}$$ 13 N, $$^{15}$$ 15 O and pep components is hindered by the double-beta decay of $$^{136}$$ 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 electroweak mixing angle, $$\sin ^2\theta _w$$ sin 2 θ w , and the electron-type neutrino survival probability, $$P_{ee}$$ P ee , 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, with 10 live years of data and a 30 tonne fiducial volume. An observation of pp and $$^7$$ 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 $$\sigma$$ σ significance, independent of external measurements from other experiments or a measurement of $$^8$$ 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 $$^{131}$$ 131 Xe.DARWIN Collaboration (ukupan broj autora: 166

An approximate likelihood for nuclear recoil searches with XENON1T data

The XENON collaboration has published stringent limits on specific dark matter – nucleon recoil spectra from dark matter recoiling on the liquid xenon detector target. In this paper, we present an approximate likelihood for the XENON1T 1 t-year nuclear recoil search applicable to any nuclear recoil spectrum. Alongside this paper, we publish data and code to compute upper limits using the method we present. The approximate likelihood is constructed in bins of reconstructed energy, profiled along the signal expectation in each bin. This approach can be used to compute an approximate likelihood and therefore most statistical results for any nuclear recoil spectrum. Computing approximate results with this method is approximately three orders of magnitude faster than the likelihood used in the original publications of XENON1T, where limits were set for specific families of recoil spectra. Using this same method, we include toy Monte Carlo simulation-derived binwise likelihoods for the upcoming XENONnT experiment that can similarly be used to assess the sensitivity to arbitrary nuclear recoil signatures in its eventual 20 t-year exposure

Emission of single and few electrons in XENON1T and limits on light dark matter

Delayed single- and few-electron emissions plague dual-phase time projection chambers, limiting their potential to search for light-mass dark matter. This paper examines the origins of these events in the XENON1T experiment. Characterization of the intensity of delayed electron backgrounds shows that the resulting emissions are correlated, in time and position, with high-energy events and can effectively be vetoed. In this work we extend previous S2-only analyses down to a single electron. From this analysis, after removing the correlated backgrounds, we observe rates <30 events/(electron×kg×day) in the region of interest spanning 1 to 5 electrons. We derive 90% confidence upper limits for dark matter-electron scattering, first direct limits on the electric dipole, magnetic dipole, and anapole interactions, and bosonic dark matter models, where we exclude new parameter space for dark photons and solar dark photons

Low-energy Calibration of XENON1T with an Internal 37^{37}Ar Source

A low-energy electronic recoil calibration of XENON1T, a dual-phase xenontime projection chamber, with an internal $^{37}$Ar source was performed. Thiscalibration source features a 35-day half-life and provides two mono-energeticlines at 2.82 keV and 0.27 keV. The photon yield and electron yield at 2.82 keVare measured to be (32.3$\pm$0.3) photons/keV and (40.6$\pm$0.5) electrons/keV,respectively, in agreement with other measurements and with NEST predictions.The electron yield at 0.27 keV is also measured and it is(68.0$^{+6.3}_{-3.7}$) electrons/keV. The $^{37}$Ar calibration confirms thatthe detector is well-understood in the energy region close to the detectionthreshold, with the 2.82 keV line reconstructed at (2.83$\pm$0.02) keV, whichfurther validates the model used to interpret the low-energy electronic recoilexcess previously reported by XENON1T. The ability to efficiently remove argonwith cryogenic distillation after the calibration proves that $^{37}$Ar can beconsidered as a regular calibration source for multi-tonne xenon detectors.<br

Search for Coherent Elastic Scattering of Solar ⁸B Neutrinos in the XENON1T Dark Matter Experiment

We report on a search for nuclear recoil signals from solar 8B 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 8B 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

Effective Field Theory and Inelastic Dark Matter Results from XENON1T

In this work, we expand on the XENON1T nuclear recoil searches to study theindividual signals of dark matter interactions from operators up todimension-eight in a Chiral Effective Field Theory (ChEFT) and a model ofinelastic dark matter (iDM). We analyze data from two science runs of theXENON1T detector totaling 1\,tonne$\times$year exposure. For these analyses, weextended the region of interest from [4.9, 40.9]$\,$keV$_{\text{NR}}$ to [4.9,54.4]$\,$keV$_{\text{NR}}$ to enhance our sensitivity for signals that peak atnonzero energies. We show that the data is consistent with the background-onlyhypothesis, with a small background over-fluctuation observed peaking between20 and 50$\,$keV$_{\text{NR}}$, resulting in a maximum local discoverysignificance of 1.7\,$\sigma$ for the Vector$\otimes$Vector$_{\text{strange}}$($VV_s$) ChEFT channel for a dark matter particle of 70$\,$GeV/c$^2$, and$1.8\,\sigma$ for an iDM particle of 50$\,$GeV/c$^2$ with a mass splitting of100$\,$keV/c$^2$. For each model, we report 90\,\% confidence level (CL) upperlimits. We also report upper limits on three benchmark models of dark matterinteraction using ChEFT where we investigate the effect of isospin-breakinginteractions. We observe rate-driven cancellations in regions of theisospin-breaking couplings, leading to up to 6 orders of magnitude weaker upperlimits with respect to the isospin-conserving case.<br