The exclusive electroproduction of J/psi mesons, ep --> epJ/psi, has been studied with the ZEUS detector at HERA for virtualities of the exchanged photon in the ranges 0.15 < Q(2) < 0.8 GeV(2) and 2 < Q(2) < 100 GeV(2) using integrated luminosities of 69 and 83 pb(-1), respectively. The photonproton centre-of-mass energy was in the range 30 < W < 220 GeV and the squared four-momentum transfer at the proton vertex \t\ < 1 GeV(2). The cross sections and decay angular distributions are presented as functions of Q(2), W and t. The effective parameters of the pomeron trajectory are in agreement with those found in J/psi photoproduction. The spin-density matrix elements, calculated from the decay angular distributions, are consistent with the hypothesis of s-channel helicity conservation. The ratio of the longitudinal to transverse cross sections, sigma(L)/sigma(T), grows with Q(2), whilst no dependence on W or t is observed. The results are in agreement with perturbative QCD calculations and exhibit a strong sensitivity to the gluon distribution in the proton. (C) 2004 Elsevier B.V. All rights reserved. RI De Pasquale, Salvatore/B-9165-2008; Wing, Matthew/C-2169-2008; Doyle, Anthony/C-5889-2009; collins-tooth, christopher/A-9201-2012; Ferrando, James/A-9192-2012; Gladilin, Leonid/B-5226-2011

The exclusive electroproduction of J/psi mesons, ep --> epJ/psi, has been studied with the ZEUS detector at HERA for virtualities of the exchanged photon in the ranges 0.15 < Q(2) < 0.8 GeV(2) and 2 < Q(2) < 100 GeV(2) using integrated luminosities of 69 and 83 pb(-1), respectively. The photonproton centre-of-mass energy was in the range 30 < W < 220 GeV and the squared four-momentum transfer at the proton vertex \t\ < 1 GeV(2). The cross sections and decay angular distributions are presented as functions of Q(2), W and t. The effective parameters of the pomeron trajectory are in agreement with those found in J/psi photoproduction. The spin-density matrix elements, calculated from the decay angular distributions, are consistent with the hypothesis of s-channel helicity conservation. The ratio of the longitudinal to transverse cross sections, sigma(L)/sigma(T), grows with Q(2), whilst no dependence on W or t is observed. The results are in agreement with perturbative QCD calculations and exhibit a strong sensitivity to the gluon distribution in the proton. (C) 2004 Elsevier B.V. All rights reserved.

Exclusive electroproduction of J/psi mesons at HERA

SCHIOPPA, Marco;CAPUA, Marcella;MASTROBERARDINO, Anna;Schioppa M;TASSI, Enrico
2004-01-01

Abstract

The exclusive electroproduction of J/psi mesons, ep --> epJ/psi, has been studied with the ZEUS detector at HERA for virtualities of the exchanged photon in the ranges 0.15 < Q(2) < 0.8 GeV(2) and 2 < Q(2) < 100 GeV(2) using integrated luminosities of 69 and 83 pb(-1), respectively. The photonproton centre-of-mass energy was in the range 30 < W < 220 GeV and the squared four-momentum transfer at the proton vertex \t\ < 1 GeV(2). The cross sections and decay angular distributions are presented as functions of Q(2), W and t. The effective parameters of the pomeron trajectory are in agreement with those found in J/psi photoproduction. The spin-density matrix elements, calculated from the decay angular distributions, are consistent with the hypothesis of s-channel helicity conservation. The ratio of the longitudinal to transverse cross sections, sigma(L)/sigma(T), grows with Q(2), whilst no dependence on W or t is observed. The results are in agreement with perturbative QCD calculations and exhibit a strong sensitivity to the gluon distribution in the proton. (C) 2004 Elsevier B.V. All rights reserved.
2004
The exclusive electroproduction of J/psi mesons, ep --> epJ/psi, has been studied with the ZEUS detector at HERA for virtualities of the exchanged photon in the ranges 0.15 < Q(2) < 0.8 GeV(2) and 2 < Q(2) < 100 GeV(2) using integrated luminosities of 69 and 83 pb(-1), respectively. The photonproton centre-of-mass energy was in the range 30 < W < 220 GeV and the squared four-momentum transfer at the proton vertex \t\ < 1 GeV(2). The cross sections and decay angular distributions are presented as functions of Q(2), W and t. The effective parameters of the pomeron trajectory are in agreement with those found in J/psi photoproduction. The spin-density matrix elements, calculated from the decay angular distributions, are consistent with the hypothesis of s-channel helicity conservation. The ratio of the longitudinal to transverse cross sections, sigma(L)/sigma(T), grows with Q(2), whilst no dependence on W or t is observed. The results are in agreement with perturbative QCD calculations and exhibit a strong sensitivity to the gluon distribution in the proton. (C) 2004 Elsevier B.V. All rights reserved. RI De Pasquale, Salvatore/B-9165-2008; Wing, Matthew/C-2169-2008; Doyle, Anthony/C-5889-2009; collins-tooth, christopher/A-9201-2012; Ferrando, James/A-9192-2012; Gladilin, Leonid/B-5226-2011
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11770/127669
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