This paper reports the cross section measurements for the process ep --> e J/ψ p for Q^2 < 4 GeV^2 at sqrt(s) = 296 GeV, based on an integrated luminosity of about 0.5 pb^(-1), using the ZEUS detector. The J/ψ was detected in its e+e- and μ+μ− decay modes. The photoproduction cross section was measured to be 52 (+7-12) ± 10 nb at an average γp centre of mass energy of 67 GeV and 71 (+13-20) ± 12 nb at 114 GeV. The significant rise of the cross section compared to lower energy measurements is not in agreement with VDM models, but can be described by QCD inspired models if a rise in the gluon momentum density at low x in the proton is assumed.
Measurement of the cross section for the reaction γp → J/ψ p with the ZEUS detector at HERA
ANZIVINO, Giuseppina
1995
Abstract
This paper reports the cross section measurements for the process ep --> e J/ψ p for Q^2 < 4 GeV^2 at sqrt(s) = 296 GeV, based on an integrated luminosity of about 0.5 pb^(-1), using the ZEUS detector. The J/ψ was detected in its e+e- and μ+μ− decay modes. The photoproduction cross section was measured to be 52 (+7-12) ± 10 nb at an average γp centre of mass energy of 67 GeV and 71 (+13-20) ± 12 nb at 114 GeV. The significant rise of the cross section compared to lower energy measurements is not in agreement with VDM models, but can be described by QCD inspired models if a rise in the gluon momentum density at low x in the proton is assumed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.