Heavy Flavour Hadro-Production from Fixed-Target to Collider Energies

TL;DR

This article surveys open charm and beauty hadro-production data from fixed-target and collider experiments, updating charm BR evolution and contrasting measurements with LO pQCD using modern PDFs. It uses Pythia to compute production cross-sections, single-meson spectra, and pair correlations, while exploring the roles of nuclear effects and fragmentation models. The study highlights how charm and beauty yields influence J/ψ production through feed-down and dilepton backgrounds, and provides energy-dependent predictions for SPS and RHIC energies. The findings underscore the viability of LO+PDF frameworks with appropriate K-factors and fragmentation parameters, while stressing the need for improved constraints on nuclear gluon densities and direct beauty measurements in heavy-ion environments.

Abstract

We review the hadro-production data presently available on open charm and beauty absolute production cross-sections, collected by experiments at CERN, DESY and Fermilab. The published charm production cross-section values are updated, in particular for the "time evolution" of the branching ratios. These measurements are compared to LO pQCD calculations, as a function of the collision energy, using recent parametrisations of the parton distribution functions. We then estimate, including nuclear effects of the parton densities, the charm and beauty production cross-sections relevant for measurements at SPS and RHIC energies, in proton-proton, proton-nucleus and nucleus-nucleus collisions. The calculations are also compared with measurements of single D and B kinematical distributions, and DDbar pair correlations. We finish with two brief comments, concerning the importance of beauty production as a feed-down source of J/psi production, and open charm measurements performed using leptonic decays.

Figures (34)

• Figure 1: Heavy flavour production mechanisms at leading order.
• Figure 2: Valence quark ($\rm u_v$, $\rm d_v$), sea quark ($\rm u_s$, $\rm d_s$) and gluon (g) distributions inside a proton, evaluated at $Q^2$ values relevant for charm and beauty production.
• Figure 4: Three different sets of NLO pion PDFS (left) and comparison of pion and proton LO PDFs (right).
• Figure 5: Relative contribution of gluon fusion to the total ${\rm c}\bar{\rm c}$ production cross-section, as a function of $\sqrt{s}$, in pp (left and middle) and $\pi^-$p (right) collisions.
• Figure 7: Nuclear modifications of the PDFs, for the Pb nucleus, according to the EKS 98 eks weight functions.