Chatrchyan, S. and Apresyan, A. and Bornheim, A. and Chen, Y. and Di Marco, E. and Duarte, J. and Gataullin, M. and Ma, Y. and Mott, A. and Newman, H. B. and Rogan, C. and Timciuc, V. and Traczyk, P. and Veverka, J. and Wilkinson, R. and Yang, Y. and Zhu, R. Y. and Dias, F. A. and Spiropulu, M. (2012) 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. Journal of High Energy Physics, 2012 (11). Art. No. 80. ISSN 1126-6708. http://resolver.caltech.edu/CaltechAUTHORS:20130208-130630898
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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.
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| Additional Information: | © 2012 CERN for the benefit of the CMS collaboration. Received: September 8, 2012. Accepted: October 24, 2012. Published: November 15, 2012. This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited. We congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC machine. We thank the technical and administrative staff at CERN and other CMS institutes, and acknowledge support from BMWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); MoER, SF0690030s09 and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); MSI (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MON, RosAtom, RAS and RFBR (Russia); MSTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); ThEP, IPST and NECTEC (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United Kingdom); DOE and NSF (USA). Individuals have received support from the Marie-Curie programme and the European Research Council (European Union); the Leventis Foundation; the A. P. Sloan Foundation; the Alexander von Humboldt Foundation; the Austrian Science Fund (FWF); the Belgian Federal Science Policy Office; the Fonds pour la Formation à la Recherche dans l'Industrie et dans l'Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); the Ministry of Education, Youth and Sports (MEYS) of Czech Republic; the Council of Science and Industrial Research, India; the Compagnia di San Paolo (Torino); and the HOMING PLUS programme of Foundation for Polish Science, coffinanced from European Union, Regional Development Fund. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Subject Keywords: | Hadron-Hadron Scattering | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Official Citation: | 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 S. Chatrchyan, V. Khachatryan, A. M. Sirunyan… | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Deposited By: | Ruth Sustaita | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Deposited On: | 08 Feb 2013 22:10 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Last Modified: | 29 Aug 2014 14:27 |
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