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Evidence for Higgs boson decays to a low-mass dilepton system and a photon in pp collisions at s=13 TeV with the ATLAS detector

  • Author(s): Aad, G;
  • Abbott, B;
  • Abbott, DC;
  • Abed Abud, A;
  • Abeling, K;
  • Abhayasinghe, DK;
  • Abidi, SH;
  • AbouZeid, OS;
  • Abraham, NL;
  • Abramowicz, H;
  • Abreu, H;
  • Abulaiti, Y;
  • Abusleme Hoffman, AC;
  • Acharya, BS;
  • Achkar, B;
  • Adam, L;
  • Adam Bourdarios, C;
  • Adamczyk, L;
  • Adamek, L;
  • Adelman, J;
  • Adiguzel, A;
  • Adorni, S;
  • Adye, T;
  • Affolder, AA;
  • Afik, Y;
  • Agapopoulou, C;
  • Agaras, MN;
  • Aggarwal, A;
  • Agheorghiesei, C;
  • Aguilar-Saavedra, JA;
  • Ahmad, A;
  • Ahmadov, F;
  • Ahmed, WS;
  • Ai, X;
  • Aielli, G;
  • Akatsuka, S;
  • Akbiyik, M;
  • Åkesson, TPA;
  • Akilli, E;
  • Akimov, AV;
  • Al Khoury, K;
  • Alberghi, GL;
  • Albert, J;
  • Alconada Verzini, MJ;
  • Alderweireldt, S;
  • Aleksa, M;
  • Aleksandrov, IN;
  • Alexa, C;
  • Alexopoulos, T;
  • Alfonsi, A;
  • Alfonsi, F;
  • Alhroob, M;
  • Ali, B;
  • Ali, S;
  • Aliev, M;
  • Alimonti, G;
  • Allaire, C;
  • Allbrooke, BMM;
  • Allport, PP;
  • Aloisio, A;
  • Alonso, F;
  • Alpigiani, C;
  • Alunno Camelia, E;
  • Alvarez Estevez, M;
  • Alviggi, MG;
  • Amaral Coutinho, Y;
  • Ambler, A;
  • Ambroz, L;
  • Amelung, C;
  • Amidei, D;
  • Amor Dos Santos, SP;
  • Amoroso, S;
  • Amrouche, CS;
  • Anastopoulos, C;
  • Andari, N;
  • Andeen, T;
  • Anders, JK;
  • Andrean, SY;
  • Andreazza, A;
  • Andrei, V;
  • Angelidakis, S;
  • Angerami, A;
  • Anisenkov, AV;
  • Annovi, A;
  • Antel, C;
  • Anthony, MT;
  • Antipov, E;
  • Antonelli, M;
  • Antrim, DJA;
  • Anulli, F;
  • Aoki, M;
  • Aparisi Pozo, JA;
  • Aparo, MA;
  • Aperio Bella, L;
  • Aranzabal, N;
  • Araujo Ferraz, V;
  • Arcangeletti, C;
  • Arce, ATH;
  • Arena, E;
  • Arguin, JF
  • et al.
Abstract

A search for the Higgs boson decaying into a photon and a pair of electrons or muons with an invariant mass mℓℓ<30 GeV is presented. The analysis is performed using 139 fb−1 of proton–proton collision data, produced by the LHC at a centre-of-mass energy of 13 TeV and collected by the ATLAS experiment. Evidence for the H→ℓℓγ process is found with a significance of 3.2 over the background-only hypothesis, compared to an expected significance of 2.1 for the Standard Model prediction. The best-fit value of the signal-strength parameter, defined as the ratio of the observed signal yield to the one expected in the Standard Model, is μ=1.5±0.5. The Higgs boson production cross-section times the H→ℓℓγ branching ratio for mℓℓ<30 GeV is determined to be 8.7−2.7+2.8 fb.

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