Study of J/$\psi$ meson production inside jets in pp collisions at $\sqrt{s} =$ 8 TeV

TL;DR

This paper investigates how prompt J/ψ mesons are produced within jets in proton-proton collisions at 8 TeV, comparing experimental data with theoretical models to test predictions of quantum chromodynamics.

Contribution

It introduces a new method to analyze prompt J/ψ production inside jets using the fragmenting jet function approach and tests nonrelativistic QCD predictions.

Findings

Most prompt J/ψ mesons with energy above 15 GeV are contained in central jets.

Data favor models where prompt J/ψ mesons are predicted to be unpolarized.

The technique provides a novel way to test QCD predictions for J/ψ production.

Abstract

A study of the production of prompt J/$\psi$ mesons contained in jets in proton-proton collisions at $\sqrt{s} =$ 8 TeV is presented. The analysis is based on data corresponding to an integrated luminosity of 19.1 fb$^{-1}$ collected with the CMS detector at the LHC. For events with at least one observed jet, the angular separation between the J/$\psi$ meson and the jet is used to test whether the J/$\psi$ meson is part of the jet. The analysis shows that most prompt J/$\psi$ mesons with energy above 15 GeV and rapidity $|y|<$ 1 are contained in jets with pseudorapidity $|\eta_{\text{jet}}|$ $<$ 1. The differential distributions of the probability to have a J/$\psi$ meson contained in a jet as a function of jet energy for a fixed J/$\psi$ energy fraction are compared to a theoretical model using the fragmenting jet function approach. The data agree best with fragmenting jet function calculations that use a long-distance matrix element parameter set in which prompt J/$\psi$ mesons are predicted to be unpolarized. This technique demonstrates a new way to test predictions for prompt J/$\psi$ production using nonrelativistic quantum chromodynamics.