Updated measurements of exclusive J/psi and psi(2S) production cross-sections in pp collisions at root s=7 TeV

The differential cross-section as a function of rapidity has been measured for the exclusive production of J/psi and psi(2S) mesons in proton-proton collisions at root s = 7 TeV, using data collected by the LHCb experiment, corresponding to an integrated luminosity of 930 pb(-1). The cross-sections times branching fractions to two muons having pseudorapidities between 2.0 and 4.5 are measured to be sigma (pp -> J/psi -> mu+mu-)(2.0 < eta(mu +/-) < 4.5) = 291 +/- 7 +/- 19 pb, sigma (pp ->psi(2S)->mu+mu-)(2.0 < eta(mu +/-) < 4.5) = 6.5 +/- 0.9 +/- 0.4 pb, where the first uncertainty is statistical and the second is systematic. The measurements agree with next-to-leading order QCD predictions as well as with models that include saturation effects.

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https://infoscience.epfl.ch/record/198872?ln=fr

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Measurement of J/psi production in pp collisions at sqrt(s)=7 TeV

Vladislav Balagura, Christophe Bauer, Aurelio Bay, Marc-Olivier Bettler, Frédéric Blanc, Joël Bressieux, Peter Clarke, Victor Coco, Géraldine Conti, Greig Alan Cowan, Michel De Cian, Hans Dijkstra, Frédéric Guillaume Dupertuis, Vincent Fave, Christoph Frei, Neal Gauvin, Guido Haefeli, Plamen Hristov Hopchev, Pierre Jaton, Anne Keune, Mathias Oleg Knecht, Yiming Li, Johan Luisier, Andreas Alexander Maier, Raluca Anca Muresan, Tatsuya Nakada, Matthew Needham, Niko Neufeld, Cédric Potterat, Albert Puig Navarro, Barinjaka Rakotomiaramanana, Gerhard Raven, Julien Rouvinet, Christophe Salzmann, Olivier Schneider, Frédéric Teubert, Mark Tobin, Minh Tâm Tran, Jian Wang, Yi Zhang, Lei Zhang

The production of J/psi mesons in proton-proton collisions at root s = 7 TeV is studied with the LHCb detector at the LHC. The differential cross-section for prompt J/psi production is measured as a function of the J/psi transverse momentum p(T) and rapidity y in the fiducial region p(T) is an element of [0; 14] GeV/c and y is an element of [2.0; 4.5]. The differential cross-section and fraction of J/psi from b-hadron decays are also measured in the same p(T) and y ranges. The analysis is based on a data sample corresponding to an integrated luminosity of 5.2 pb(-1). The measured cross-sections integrated over the fiducial region are 10.52 +/- 0.04 +/- 1.40(-2.20)(+1.64) mu b for prompt J/psi production and 1.14 +/- 0.01 +/- 0.16 mu b for J/psi from b-hadron decays, where the first uncertainty is statistical and the second systematic. The prompt J/psi production cross-section is obtained assuming no J/psi polarisation and the third error indicates the acceptance uncertainty due to this assumption.

2011

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Observation of J/psi-pair production in pp collisions at root s=7 TeV

Vladislav Balagura, Christophe Bauer, Aurelio Bay, Marc-Olivier Bettler, Frédéric Blanc, Joël Bressieux, Peter Clarke, Victor Coco, Géraldine Conti, Greig Alan Cowan, Michel De Cian, Hans Dijkstra, Frédéric Guillaume Dupertuis, Vincent Fave, Christoph Frei, Neal Gauvin, Luis Alberto Granado Cardoso, Guido Haefeli, Plamen Hristov Hopchev, Pierre Jaton, Anne Keune, Mathias Oleg Knecht, Johan Luisier, Raluca Anca Muresan, Tatsuya Nakada, Matthew Needham, Niko Neufeld, Cédric Potterat, Jessica Prisciandaro, Albert Puig Navarro, Barinjaka Rakotomiaramanana, Gerhard Raven, Julien Rouvinet, Christophe Salzmann, Olivier Schneider, Frédéric Teubert, Mark Tobin, Minh Tâm Tran, Jian Wang, Yi Zhang, Lei Zhang

The production of J/psi pairs in proton-proton collisions at a centre-of-mass energy of 7 TeV has been observed using an integrated luminosity of 37.5 pb(-1) collected with the LHCb detector. The production cross-section for pairs with both J/psi in the rapidity range 2 < y(J/psi) < 4.5 and transverse momentum p(T)(J/psi) < 10 GeV/c is

2012

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Precision luminosity measurements at LHCb

Liupan An, Aurelio Bay, Marc-Olivier Bettler, Frédéric Blanc, Joël Bressieux, Peter Clarke, Victor Coco, Greig Alan Cowan, Adam Davis, Michel De Cian, Hans Dijkstra, Mirco Dorigo, Frédéric Guillaume Dupertuis, Paolo Durante, Christoph Frei, Sebastiana Gianì, Guido Haefeli, Xiaoxue Han, Pierre Jaton, Chitsanu Khurewathanakul, Ilya Komarov, Yiming Li, Alessandro Mapelli, Pietro Marino, Maurizio Martinelli, Bastien Luca Muster, Tatsuya Nakada, Matthew Needham, Niko Neufeld, Luca Pescatore, Cédric Potterat, Jessica Prisciandaro, Barinjaka Rakotomiaramanana, Gerhard Raven, Federico Leo Redi, Julien Rouvinet, Olivier Schneider, Maxime Schubiger, Liang Sun, Frédéric Teubert, Mark Tobin, Minh Tâm Tran, Maria Vieites Diaz, Jian Wang, Jean Wicht, Zhirui Xu, Yi Zhang, Lei Zhang

Measuring cross-sections at the LHC requires the luminosity to be determined accurately at each centre-of-mass energy root s. In this paper results are reported from the luminosity calibrations carried out at the LHC interaction point 8 with the LHCb detector for root s = 2.76, 7 and 8TeV (proton-proton collisions) and for root s(NN) = 5TeV (proton-lead collisions). Both the "van der Meer scan" and "beam-gas imaging" luminosity calibration methods were employed. It is observed that the beam density profile cannot always be described by a function that is factorizable in the two transverse coordinates. The introduction of a two-dimensional description of the beams improves significantly the consistency of the results. For proton-proton interactions at root s = 8TeV a relative precision of the luminosity calibration of 1.47% is obtained using van der Meer scans and 1.43% using beam-gas imaging, resulting in a combined precision of 1.12%. Applying the calibration to the full data set determines the luminosity with a precision of 1.16%. This represents the most precise luminosity measurement achieved so far at a bunched-beam hadron collider.

Institute of Physics2014

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