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Excess electronic recoil events in XENON1T

E. Aprile 1 J. Aalbers 2 F. Agostini 3, 4 M. Alfonsi 5 L. Althueser 6 F.D. Amaro 7 V.C. Antochi 2 E. Angelino 8, 9 J.R. Angevaare 10, 11 F. Arneodo 12 D. Barge 2 L. Baudis 13 B. Bauermeister 2 L. Bellagamba 4 M.L. Benabderrahmane 12 T. Berger 14 A. Brown 13 E. Brown 14 S. Bruenner 11 G. Bruno 12 R. Budnik 15 C. Capelli 13 J.M.R. Cardoso 7 D. Cichon 16 B. Cimmino 17 M. Clark 18 D. Coderre 19 A.P. Colijn 11 J. Conrad 2 Jean-Pierre Cussonneau 20 M.P. Decowski 11 A. Depoian 18 P. Di Gangi 4 A. Di Giovanni 12 R. Di Stefano 17 S. Diglio 20 A. Elykov 19 G. Eurin 16 A.D. Ferella 21 W. Fulgione 8 P. Gaemers 11 R. Gaior 22 M. Galloway 13 F. Gao 1 L. Grandi 23 C. Hasterok 17 C. Hils 5 K. Hiraide 24 L. Hoetzsch 16 J. Howlett 1 M. Iacovacci 17 Y. Itow 25 F. Joerg 16 N. Kato 24 S. Kazama 25 M. Kobayashi 1 G. Koltman 15 A. Kopec 18 H. Landsman 15 R.F. Lang 18 L. Levinson 15 Q. Lin 1 S. Lindemann 19 M. Lindner 16 F. Lombardi 7 J. Long 23 J.A.M. Lopes 7 E. López Fune 22 C. Macolino 26 J. Mahlstedt 2 A. Mancuso 4 L. Manenti 12 A. Manfredini 13 F. Marignetti 17 T. Marrodán Undagoitia 16 K. Martens 24 J. Masbou 20 D. Masson 19 S. Mastroianni 17 M. Messina K. Miuchi 27 K. Mizukoshi 27 A. Molinario K. Morå 1, 2 S. Moriyama 24 Y. Mosbacher 15 M. Murra 6 J. Naganoma K. Ni 28 U. Oberlack 5 K. Odgers 14 J. Palacio 20, 16 B. Pelssers 2 R. Peres 13 J. Pienaar 29 V. Pizzella 16 G. Plante 1 J. Qin 18 H. Qiu 15 D. Ramírez García 19 S. Reichard 13 A. Rocchetti 19 N. Rupp 16 J.M.F. dos Santos 7 G. Sartorelli 4 N. Šarčević 19 M. Scheibelhut 5 J. Schreiner 16 D. Schulte 6 M. Schumann 19 L. Scotto Lavina 22 M. Selvi 4 F. Semeria 4 P. Shagin 30 E. Shockley 29 M. Silva 7 H. Simgen 16 A. Takeda 25 C. Therreau 20 D. Thers 20 F. Toschi 19 G. Trinchero 9 C. Tunnell 30 M. Vargas 6 G. Volta 13 H. Wang 31 Y. Wei 28 C. Weinheimer 6 M. Weiss 15 D. Wenz 5 C. Wittweg 6 Z. Xu 1 M. Yamashita 25 J. Ye 28 G. Zavattini 4 Y. Zhang 1 T. Zhu 1 J.P. Zopounidis 22 Xavier Mougeot 32
32 LNHB - Laboratoire National Henri Becquerel
DM2I - Département Métrologie Instrumentation & Information : DRT/LIST/DM2I
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 76±2stat  events/(tonne×year×keV) 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 3.4σ 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 gae<3.8×10-12, gaeganeff<4.8×10-18, and gaegaγ<7.7×10-22  GeV-1, and excludes either gae=0 or gaegaγ=gaeganeff=0. The neutrino magnetic moment signal is similarly favored over background at 3.2σ, and a confidence interval of μν∈(1.4,2.9)×10-11  μB (90% C.L.) is reported. Both results are in strong tension with stellar constraints. The excess can also be explained by β decays of tritium at 3.2σ significance with a corresponding tritium concentration in xenon of (6.2±2.0)×10-25  mol/mol. 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 2.0σ and 0.9σ, 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±0.2)  keV (68% C.L.) with a 3.0σ global (4.0σ 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 210  keV/c2. We also consider the possibility that Ar37 may be present in the detector, yielding a 2.82 keV peak from electron capture. Contrary to tritium, the Ar37 concentration can be tightly constrained and is found to be negligible.
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Submitted on : Tuesday, December 8, 2020 - 6:57:04 PM
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E. Aprile, J. Aalbers, F. Agostini, M. Alfonsi, L. Althueser, et al.. Excess electronic recoil events in XENON1T. Physical Review D, American Physical Society, 2020, 102 (7), pp.072004. ⟨10.1103/PhysRevD.102.072004⟩. ⟨hal-03047288⟩

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