Associated non-prompt $J/\psi + \mu$ and $J/\psi + J/\psi$ production at LHC as a test for TMD gluon density

TL;DR

This paper studies associated production of $J/$ mesons with muons and double $J/$ at the LHC to test the validity of TMD gluon densities, using a $k_T$-factorization approach and comparing with experimental data.

Contribution

It introduces a novel analysis of associated $J/$ and muon production and double $J/$ production at the LHC to test TMD gluon densities with new theoretical and phenomenological methods.

Findings

Predictions agree with ATLAS and LHCb data at 8 TeV.

Parton shower effects and double parton scattering are significant.

TMD gluon densities can be effectively tested with these processes.

Abstract

We consider the associated production of $J/\psi$ mesons and muons originating from the $b$-flavored hadron decays and non-prompt double $J/\psi$ production at the LHC using the $k_T$-factorization approach. To describe the inclusive $b$-hadron decays into the different charmonium states we apply fragmentation approach and adopt fragmentation functions based on the non-relativistic QCD factorization. The transverse momentum dependent (TMD) gluon densities in a proton are determined using the Catani-Ciafaloni-Fiorani-Marchesini equation and Kimber-Martin-Ryskin prescription. We investigate the effects coming from parton showers, estimate the double parton scattering contribution and compare our predictions with the first experimental data taken by the ATLAS and LHCb Collaborations at $\sqrt s = 8$~TeV. These data can serve as an additional test for TMD gluon density function in a proton.