Abstract
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 tonne-years and an unprecedentedly low background rate of between 1 and 30 keV, the data enable one of the most sensitive searches for solar axions, an enhanced neutrino magnetic moment using solar neutrinos, 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 significance, and a three-dimensional 90% confidence surface is reported for axion couplings to electrons, photons, and nucleons. This surface is inscribed in the cuboid defined by , , and , and excludes either or . The neutrino magnetic moment signal is similarly favored over background at , and a confidence interval of (90% C.L.) is reported. Both results are in strong tension with stellar constraints. The excess can also be explained by decays of tritium at significance with a corresponding tritium concentration in xenon of . Such a trace amount 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 decreased to and , respectively, if an unconstrained tritium component is included in the fitting. With respect to bosonic dark matter, the excess favors a monoenergetic peak at (68% C.L.) with a global ( local) significance over background. This analysis sets the most restrictive direct constraints to date on pseudoscalar and vector bosonic dark matter for most masses between 1 and . We also consider the possibility that may be present in the detector, yielding a 2.82 keV peak from electron capture. Contrary to tritium, the concentration can be tightly constrained and is found to be negligible.
8 More- Received 30 June 2020
- Accepted 16 September 2020
DOI:https://doi.org/10.1103/PhysRevD.102.072004
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Viewpoint
Dark Matter Detector Delivers Enigmatic Signal
Published 12 October 2020
Are the excess events detected by the XENON1T experiment a harbinger of new physics or a mundane background?
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