Charmonia production from $b$-hadron decays at LHC with $k_T$-factorization: $J/\psi$, $\psi(2S)$ and $J/\psi + Z$

TL;DR

This paper models the production of $J/$ and $$S mesons from $b$-hadron decays at the LHC using $k_T$-factorization, matching experimental data and estimating double parton scattering effects.

Contribution

It introduces a $k_T$-factorization approach with CCFM-evolved gluon densities and NRQCD fragmentation functions for non-prompt charmonia production, aligning theory with recent LHC data.

Findings

Predictions agree well with CMS, ATLAS, LHCb data at various energies.

Double parton scattering contributions are small for $J/$ + Z production.

The approach effectively describes inclusive and associated charmonia production.

Abstract

We consider the production of $J/\psi$ and $\psi(2S)$ mesons originating from the decays of $b$-flavored hadrons at the LHC using the $k_T$-factorization approach. Our analysis covers both inclusive charmonia production and production of $J/\psi$ mesons in association with $Z$ bosons. We apply the transverse momentum dependent (or unintegrated) gluon density in a proton derived from Catani-Ciafaloni-Fiorani-Marchesini (CCFM) evolution equation and adopt fragmentation functions based on the non-relativistic QCD factorization to describe the inclusive $b$-hadron decays into the different charmonium states. Our predictions agree well with latest experimental data taken by the CMS, ATLAS and LHCb Collaborations at $\sqrt s = 7$, $8$ and $13$~TeV. The contributions from double parton scattering to the associated non-prompt $J/\psi + Z$ production are estimated and found to be small.