Phenomenological interpolation of the inclusive J/psi cross section to proton-proton collisions at 2.76 TeV and 5.5 TeV

TL;DR

The paper develops a phenomenological framework to interpolate inclusive J/psi cross sections in pp collisions to LHC energies of 2.76 and 5.5 TeV. It combines mid-rapidity energy evolution using a functional form and pQCD-based (FONLL) and LO CEM models with rapidity-shape and universal z_t scaling for pt distributions, producing predictions and uncertainty estimates. The interpolated results agree with ALICE measurements at 2.76 TeV within uncertainties, providing a validated pp reference for heavy-ion and proton-nucleus analyses at the LHC. The work offers a structured procedure and comparative cross-checks across data-driven and theory-driven approaches, enabling robust R_AA and R_pA interpretations.

Abstract

We present a study of the inclusive J/psi cross section at 2.76 TeV and 5.5 TeV. The energy dependence of the cross section, rapidity and transverse momentum distributions are evaluated phenomenologically. Their knowledge is crucial as a reference for the interpretation of A-A and p-A J/psi results at the LHC. Our approach is the following: first, we estimate the energy evolution of the pt-integrated J/psi cross section at mid-rapidity; then, we evaluate the rapidity dependence; finally, we study the transverse momentum distribution trend. Whenever possible, both theory driven (based on pQCD predictions) and functional form (data driven fits) calculations are discussed. Our predictions are compared with the recently obtained results by the ALICE collaboration in pp collisions at 2.76 TeV.

Figures (12)

• Figure 1: Energy dependence of inclusive J/$\psi$ production cross section at mid-rapidity as fitted by a power-law function: $BR_{ll} \times {\rm d} \sigma_{\mathrm{pp}}/{\rm d} y|_{y=0}(\sqrt{s}) = A \times \left(\sqrt{s/s_0}\right)^b$ where $A=124\pm9$ nb, $b=0.60\pm0.06$ and $\sqrt{s_0}=1$ TeV.
• Figure 2: Energy dependence of inclusive J/$\psi$ production cross section as fitted by Eq. \ref{['eq:crsecFONLL']} using charm and beauty FONLL calculations with their central parameterization.
• Figure 3: Energy dependence of inclusive J/$\psi$ production cross section as fitted by Eq. \ref{['eq:crsecCEM']}, with the J/$\psi$ LO CEM and the beauty FONLL calculations, and the CTEQ6 parton distribution functions.
• Figure 4: Inclusive J/$\psi$ rapidity distribution at $\sqrt{s}=200$ GeV PHENIX07 as fitted using the LO CEM and the FONLL calculations. The measurement uncertainties are obtained by summing in quadrature the PHENIX systematic and statistical uncertainties.
• Figure 5: Inclusive J/$\psi$ rapidity distribution at $\sqrt{s}=7$ TeV ALICEjpsi10CMSjpsi10LHCbjpsi10 as fitted using the LO CEM and the FONLL calculations. The data uncertainties are obtained by summing in quadrature the measurement systematic and statistical uncertainties.