Search for exclusive or semi-exclusive γγ production and observation of exclusive and semi-exclusive e+e- production in pp collisions at √{s}=7 TeV
Abstract
A search for exclusive or semi-exclusive γγ production, pp → p(*) + γγ + 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}=7 TeV, 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 γγ or e+e- events are selected by requiring the presence of two photons or a positron and an electron, each with transverse energy E T > 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(*) + γγ + 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.[Figure not available: see fulltext.]
- Publication:
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Journal of High Energy Physics
- Pub Date:
- November 2012
- DOI:
- 10.1007/JHEP11(2012)080
- arXiv:
- arXiv:1209.1666
- Bibcode:
- 2012JHEP...11..080C
- Keywords:
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- Hadron-Hadron Scattering;
- High Energy Physics - Experiment
- E-Print:
- Replaced with published version. Added journal reference and DOI