A search for exclusive or semi-exclusive gamma gamma production, pp -> p(()*()) + gamma gamma + 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 root 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 gamma gamma 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 vertical bar eta vertical bar < 2.5, and no other particles in the region vertical bar eta vertical bar < 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(()*()) + gamma gamma + 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. RI tosi, mia/J-5777-2012; Della Ricca, Giuseppe/B-6826-2013; Kadastik, Mario/B-7559-2008; Mundim, Luiz/A-1291-2012; De La Cruz Burelo, Eduard/B-9802-2013; Bagliesi, Giuseppe/C-2230-2013; Petrushanko, Sergey/D-6880-2012; Santaolalla, Javier/C-3094-2013; Alves, Gilvan/C-4007-2013; Azzi, Patrizia/H-5404-2012; Tinoco Mendes, Andre David/D-4314-2011; Novaes, Sergio/D-3532-2012; Wulz, Claudia-Elisabeth/H-5657-2011; Fruhwirth, Rudolf/H-2529-2012; de Jesus Damiao, Dilson/G-6218-2012; Rolandi, Luigi (Gigi)/E-8563-2013; Flix, Josep/G-5414-2012; Montanari, Alessandro/J-2420-2012; Raidal, Martti/F-4436-2012; Tomei, Thiago/E-7091-2012; Zalewski, Piotr/H-7335-2013 OI Della Ricca, Giuseppe/0000-0003-2831-6982; Mundim, Luiz/0000-0001-9964-7805; De La Cruz Burelo, Eduard/0000-0002-7469-6974; Tinoco Mendes, Andre David/0000-0001-5854-7699; Novaes, Sergio/0000-0003-0471-8549; de Jesus Damiao, Dilson/0000-0002-3769-1680; Rolandi, Luigi (Gigi)/0000-0002-0635-274X;
Search for exclusive or semi-exclusive gamma gamma production and observation of exclusive and semi-exclusive e(+)e(-) production in pp collisions at root s=7 TeV
ABBRESCIA, Marcello;CALABRIA, CESARE;COLALEO, ANNA;LUSITO, LETIZIA;MARANGELLI, Bartolomeo;MY, Salvatore;NUZZO, Salvatore Vitale;PACIFICO, NICOLA;POMPILI, ALEXIS;SELVAGGI, Giovanna;SINGH, GURPREET;Venditti, Rosamaria;
2012-01-01
Abstract
A search for exclusive or semi-exclusive gamma gamma production, pp -> p(()*()) + gamma gamma + 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 root 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 gamma gamma 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 vertical bar eta vertical bar < 2.5, and no other particles in the region vertical bar eta vertical bar < 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(()*()) + gamma gamma + 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. RI tosi, mia/J-5777-2012; Della Ricca, Giuseppe/B-6826-2013; Kadastik, Mario/B-7559-2008; Mundim, Luiz/A-1291-2012; De La Cruz Burelo, Eduard/B-9802-2013; Bagliesi, Giuseppe/C-2230-2013; Petrushanko, Sergey/D-6880-2012; Santaolalla, Javier/C-3094-2013; Alves, Gilvan/C-4007-2013; Azzi, Patrizia/H-5404-2012; Tinoco Mendes, Andre David/D-4314-2011; Novaes, Sergio/D-3532-2012; Wulz, Claudia-Elisabeth/H-5657-2011; Fruhwirth, Rudolf/H-2529-2012; de Jesus Damiao, Dilson/G-6218-2012; Rolandi, Luigi (Gigi)/E-8563-2013; Flix, Josep/G-5414-2012; Montanari, Alessandro/J-2420-2012; Raidal, Martti/F-4436-2012; Tomei, Thiago/E-7091-2012; Zalewski, Piotr/H-7335-2013 OI Della Ricca, Giuseppe/0000-0003-2831-6982; Mundim, Luiz/0000-0001-9964-7805; De La Cruz Burelo, Eduard/0000-0002-7469-6974; Tinoco Mendes, Andre David/0000-0001-5854-7699; Novaes, Sergio/0000-0003-0471-8549; de Jesus Damiao, Dilson/0000-0002-3769-1680; Rolandi, Luigi (Gigi)/0000-0002-0635-274X;I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
