J/psi production at the Tevatron and HERA: the effect of k_T smearing

Abstract

We study the effects of intrinsic transverse momentum smearing on J/psi production both at the Tevatron and at HERA. For the case of large-p_T J/psi production at the Tevatron, the effects due to k_T smearing are mild. On the other hand, inelastic J/psi photoproduction at HERA is very sensitive to the k_T smearing and, in fact, with a reasonable value of <k_T> it is possible to resolve the large-z discrepancy seen by comparing non-relativistic QCD (NRQCD) predictions with the HERA data. We conclude that, with the present kinematic cuts, photoproduction at HERA is not a good test of NRQCD.

Figures (2)

• Figure 1: The CDF data cdf for $Bd\sigma/dp_T$ (in nb/GeV) for $J/\psi$ production at 1.8 TeV with $-0.6 \le \eta \le 0.6$, compared to the model predictions with $\langle k_T \rangle =0,\ 0.7,\ 1.0$ GeV, respectively.
• Figure 2: The HERA data hera for $d\sigma/dz$ (in nb) for $J/\psi$ production at $\sqrt{s_{\gamma p}}=100$ GeV with $p_T>1$ GeV, compared with model predictions for three choices of the intrinsic transverse momentum distribution, namely $\langle k_T \rangle =0,\ 0.7,\ 1.0$ GeV.