This Letter describes the observation of the light-by-light scattering process, γγ→γγ, in Pb+Pb collisions at √sNN=5.02  TeV. The analysis is conducted using a data sample corresponding to an integrated luminosity of 1.73  nb−1, collected in November 2018 by the ATLAS experiment at the LHC. Light-by-light scattering candidates are selected in events with two photons produced exclusively, each with transverse energy EγT>3  GeV and pseudorapidity |ηγ|<2.4, diphoton invariant mass above 6 GeV, and small diphoton transverse momentum and acoplanarity. After applying all selection criteria, 59 candidate events are observed for a background expectation of 12±3 events. The observed excess of events over the expected background has a significance of 8.2 standard deviations. The measured fiducial cross section is 78±13(stat)±7(syst)±3(lumi)  nb.

Observation of Light-by-Light Scattering in Ultraperipheral Pb+Pb Collisions with the ATLAS Detector

De Castro , S.;Fabbri , L.;Gabrielli , A.;Rinaldi , L.;Semprini Cesari , N.;Sioli , M.;Villa , M.;Zoccoli , A.;Bellagamba , L.;Boscherini , D.;Bruni , A.;D’Amen , G.;Giacobbe , B.;Polini , A.;Sbarra , C.;Franchini , M.;Mengarelli , A.;Romano , M.;Valentinetti , S.;Alberghi , G. L.;Biondi , S.;Fabbri , F.;Lasagni Manghi , F;Massa , L.;Ucchielli , G.;Vittori , C.;Alfonsi , F:;Cabras , G.;Giangiacomi , N.;
2019

Abstract

This Letter describes the observation of the light-by-light scattering process, γγ→γγ, in Pb+Pb collisions at √sNN=5.02  TeV. The analysis is conducted using a data sample corresponding to an integrated luminosity of 1.73  nb−1, collected in November 2018 by the ATLAS experiment at the LHC. Light-by-light scattering candidates are selected in events with two photons produced exclusively, each with transverse energy EγT>3  GeV and pseudorapidity |ηγ|<2.4, diphoton invariant mass above 6 GeV, and small diphoton transverse momentum and acoplanarity. After applying all selection criteria, 59 candidate events are observed for a background expectation of 12±3 events. The observed excess of events over the expected background has a significance of 8.2 standard deviations. The measured fiducial cross section is 78±13(stat)±7(syst)±3(lumi)  nb.
2019
De Castro , S. ; Fabbri , L. ; Gabrielli , A. ; Rinaldi , L. ; Semprini Cesari , N. ; Sioli , M. ; Villa , M. ; Zoccoli , A. ; Bellagamba , L. ; Boscherini , D. ; Bruni , A. ; Bruni , G. ; D’Amen , G. ; Giacobbe , B. ; Polini , A. ; Sbarra , C. ; Sidoti , A. ; Spighi , R. ; Franchini , M. ; Mengarelli , A. ; Romano , M. ; Valentinetti , S. ; Alberghi , G. L. ; Biondi , S. ; Fabbri , F. ; Lasagni Manghi , F; Massa , L. ; Ucchielli , G. ; Vittori , C. ; Alfonsi , F: ; Cabras , G. ; Cervelli , A. ; Giangiacomi , N. ; Negrini , M. ; ATLAS collaboration
File in questo prodotto:
File Dimensione Formato  
PhysRevLett.123.pdf

accesso aperto

Tipo: Versione (PDF) editoriale
Licenza: Licenza per Accesso Aperto. Creative Commons Attribuzione (CCBY)
Dimensione 431.75 kB
Formato Adobe PDF
431.75 kB Adobe PDF Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/717989
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 114
  • ???jsp.display-item.citation.isi??? 88
social impact