Evidence For Light-By-Light Scattering İn Ultraperipheral Pbpb Collisions At? Snn = 5.02 Tev

Yükleniyor...
Küçük Resim

Tarih

2019

Dergi Başlığı

Dergi ISSN

Cilt Başlığı

Yayıncı

The CMS Collaboration

Erişim Hakkı

Özet

Evidence for light-by-light (LbL) scattering, ?? ? ??, in ultraperipheral PbPb collisions at a nucleon-nucleon centerof- mass energy of 5.02 TeV is reported. LbL scattering processes are selected in events with just two photons produced, with transverse energy E? T > 2 GeV, pseudorapidity |??| < 2.4; and diphoton invariant mass m?? > 5 GeV, transverse momentum p?? T < 1 GeV, and acoplanarity (1 ? ????/?) < 0.01. After all selection criteria, 14 events are observed, compared to 11.1 ± 1.1 (theo) and 3.8 ± 1.3 (stat) events expected for signal and background processes respectively. The significance of the signal excess over the background-only hypothesis is 4.1?. The measured fiducial LbL scattering cross section, ?fid(?? ? ??) = 122 ± 46 (stat) ±29 (syst) ±4 (theo) nb is consistent with the standard model prediction

Açıklama

Anahtar Kelimeler

Light-by-light scattering, Heavy ions, Ultraperipheral collisions, CMS, LHC

Kaynak

WoS Q Değeri

Q3

Scopus Q Değeri

Q2

Cilt

Sayı

Künye

Nuclear Physics A 982 (2019) 791–794