Search for exclusive or semi-exclusive γ γ production and observation of exclusive and semi-exclusive e+e- production in pp collisions at √ s = 7 TeV


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Chatrchyan S., Khachatryan V., Sirunyan A., Tumasyan A., Adam W., Bergauer T., ...Daha Fazla

Journal of High Energy Physics, cilt.2012, sa.11, 2012 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 2012 Sayı: 11
  • Basım Tarihi: 2012
  • Doi Numarası: 10.1007/jhep11(2012)080
  • Dergi Adı: Journal of High Energy Physics
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Anahtar Kelimeler: Hadron-Hadron Scattering
  • Yıldız Teknik Üniversitesi Adresli: Evet

Özet

A search for exclusive or semi-exclusive production, pp → p(*) +γ γ+p(*) (where p* stands for a diffractively- dissociated proton), and the observation of exclusive and semi-exclusive e +e- production, pp → p(*) + e+e - + p(*), in proton-proton collisions at √s = 7TeV, are presented. The analysis is based on a data sample corresponding to an integrated luminosity of 36 pb-1 recorded by the CMS experiment at the LHC at low instantaneous luminosities. Candidate γ γor e+e - events are selected by requiring the presence of two photons or a positron and an electron, each with transverse energy ET > 5.5 GeV and pseudorapidity |η| < 2.5, and no other particles in the region |η| < 5.2. No exclusive or semi-exclusive diphoton candidates are found in the data. An upper limit on the cross section for the reaction pp → p(*) +γ γ+ p(*), within the above kinematic selections, is set at 1.18 pb at 95% confidence level. Seventeen exclusive or semi-exclusive dielectron candidates are observed, with an estimated background of 0.85 ± 0.28 (stat.) events, in agreement with the QED-based prediction of 16.3 ± 1.3 (syst.) events. © SISSA 2012.