Search for Light Dark Matter Interactions Enhanced by the Migdal Effect or Bremsstrahlung in XENON1T.

E Aprile ,C Hils ,J P Cussonneau ,J Naganoma ,G Plante ,P A Breur ,J Pienaar ,Stefan Lindemann ,A Fieguth ,D Barge ,J Ye ,L Baudis ,S Kazama ,K Miller ,C Therreau ,S Reichard ,A Gallo Rosso ,H Qiu ,F Arneodo ,A Kish ,Y Zhang ,D Coderre ,P Gaemers ,L Althueser ,Q Lin ,J Conrad ,S Mastroianni ,M P Decowski ,M L Benabderrahmane ,F Toschi ,E López Fune ,P Di Gangi ,N Rupp ,D Thers ,L Scotto Lavina ,M Selvi ,F Lombardi ,J A M Lopes ,E Angelino ,M Murra ,L Grandi ,D Wenz ,N Upole ,F D Amaro ,E Brown ,P De Perio ,T Marrodán Undagoitia ,J Schreiner ,Benedikt Riedel ,T Zhu ,Z Greene ,M Manenti ,M Lindner ,N Šarčević ,M Garbini ,V C Antochi ,C Capelli ,K Morå ,C Macolino ,S Diglio ,L J Levinson ,A Kopec ,A Elykov ,F Gao ,T Berger ,G Volta ,J Fei ,M Scheibelhut ,F Agostini ,A Manfredini ,W Fulgione ,A D Ferella ,A Rocchetti ,G Trinchero ,K Ni ,M Iacovacci ,A Molinario ,S Bruenner ,J Qin ,C Tunnell ,G Eurin ,C Hasterok ,J Howlett ,Y Wei ,R F Lang ,Miguel Silva ,V Pizzella ,B Pelssers ,M Messina ,H Simgen ,J Wulf ,D Cichon ,O Wack ,J Mahlstedt ,U Oberlack ,L Bellagamba ,M Schümann ,K Odgers ,R Itay ,Y Mosbacher ,J Palacio ,Fabrizio Marignetti ,H Landsman ,R Peres ,C Weinheimer ,B Bauermeister ,D Schulte ,F Joerg ,M Vargas ,A Di Giovanni ,A P Colijn ,P Shagin ,A Depoian ,R Podviianiuk ,G Sartorelli ,Masaaki Kobayashi ,C Wittweg ,M Alfonsi ,S M Schindler ,G Koltman ,A Brown ,D Ramírez García ,K Micheneau ,J M R Cardoso ,H Wang ,R Budnik ,G Bruno ,M Galloway ,J Masbou ,J Aalbers ,E Shockley ,J M F Dos Santos ,E Hogenbirk ,J P Zopounidis

doi:10.1103/physrevlett.123.241803

Abstract

Direct dark matter detection experiments based on a liquid xenon target are leading the search for dark matter particles with masses above ∼5 GeV/c^{2}, but have limited sensitivity to lighter masses because of the small momentum transfer in dark matter-nucleus elastic scattering. However, there is an irreducible contribution from inelastic processes accompanying the elastic scattering, which leads to the excitation and ionization of the recoiling atom (the Migdal effect) or the emission of a bremsstrahlung photon. In this Letter, we report on a probe of low-mass dark matter with masses down to about 85 MeV/c^{2} by looking for electronic recoils induced by the Migdal effect and bremsstrahlung using data from the XENON1T experiment. Besides the approach of detecting both scintillation and ionization signals, we exploit an approach that uses ionization signals only, which allows for a lower detection threshold. This analysis significantly enhances the sensitivity of XENON1T to light dark matter previously beyond its reach.

Highlights

There is an irreducible contribution from inelastic processes accompanying the elastic scattering, which leads to the excitation and ionization of the recoiling atom or the emission of a bremsstrahlung photon
In this Letter, we report on a probe of low-mass dark matter with masses down to about 85 MeV=c2 by looking for electronic recoils induced by the Migdal effect and bremsstrahlung using data from the XENON1T experiment
The most promising DM candidate is the so-called weakly interacting massive particle (WIMP) [4], which explains the current abundance of dark matter as a thermal relic of the big bang [5]

Summary

Published by the American Physical Society

The effective exposure, which is defined as exposure times detection efficiency, and its uncertainty as a function of deposited ER energy for the S1-S2 data are shown, with the signal spectra from MIGD and BREM induced by 0.1 and 1 GeV=c2 DM masses overlaid. The reduction of available information in the S2-only data implies less background discrimination, the increased detection efficiency in the < 1 keV ER energy region, shown, enables a more sensitive search for LDMnucleus interactions through MIGD and BREM. The interpretation of such S2-only data is based on the uncorrected S2 signal, combining both signals from top and bottom PMT arrays.

Number of electrons

Findings

BREM MIGD