Diffractive photoproduction of vector mesons, gammap --> VY, where Y is a proton-dissociative system, has been measured in e(+)p interactions with the ZEUS detector at HERA using an integrated luminosity of 25 pb(-1). The differential cross section, dsigma/dt, is presented for 1.2 < -t < 12 GeV(2), where t is the square of the four-momentum transferred to the vector meson. The data span the range in photon-proton centre-of-mass energy, W, from 80 GeV to 120 GeV. The t distributions are well fit by a power law, dsigma/dt proportional to (-t)(-n). The slope of the effective Pomeron trajectory, measured from the W dependence of the rho(0) and phi cross sections in bins of t, is consistent with zero. The ratios dsigma(gammap-->phiY)/dt to dsigma(gammap-->rho0Y)/dt and dsigma(gammap-->J/psiY)/dt to dsigma(gammap-->rho0Y)/dt increase with increasing -t. Decay- angle analyses for rho(0), phi and J/psi) mesons have been carried out. For the rho(0) and phi mesons, contributions from single and double helicity flip are observed. The results are compared to expectations of theoretical models.
Measurement of proton-dissociative diffractive photoproduction of vector mesons at large momentum transfer at HERA
CIRIO, Roberto;COSTA, Marco;MONACO, Vincenzo;PERONI, Cristiana;SACCHI, Roberto;SOLANO, Ada Maria;
2003-01-01
Abstract
Diffractive photoproduction of vector mesons, gammap --> VY, where Y is a proton-dissociative system, has been measured in e(+)p interactions with the ZEUS detector at HERA using an integrated luminosity of 25 pb(-1). The differential cross section, dsigma/dt, is presented for 1.2 < -t < 12 GeV(2), where t is the square of the four-momentum transferred to the vector meson. The data span the range in photon-proton centre-of-mass energy, W, from 80 GeV to 120 GeV. The t distributions are well fit by a power law, dsigma/dt proportional to (-t)(-n). The slope of the effective Pomeron trajectory, measured from the W dependence of the rho(0) and phi cross sections in bins of t, is consistent with zero. The ratios dsigma(gammap-->phiY)/dt to dsigma(gammap-->rho0Y)/dt and dsigma(gammap-->J/psiY)/dt to dsigma(gammap-->rho0Y)/dt increase with increasing -t. Decay- angle analyses for rho(0), phi and J/psi) mesons have been carried out. For the rho(0) and phi mesons, contributions from single and double helicity flip are observed. The results are compared to expectations of theoretical models.File | Dimensione | Formato | |
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