Abstract
A study of the production of prompt J/ψ mesons contained in jets in proton-proton collisions at s=8TeV 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/ψ meson and the jet is used to test whether the J/ψ meson is part of the jet. The analysis shows that most prompt J/ψ mesons having energy above 15 GeV and rapidity |y|<1 are contained in jets with pseudorapidity |ηjet|<1. The differential distributions of the probability to have a J/ψ meson contained in a jet as a function of jet energy for a fixed J/ψ 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/ψ mesons are predicted to be unpolarized. This technique demonstrates a new way to test predictions for prompt J/ψ production using nonrelativistic quantum chromodynamics.
Highlights
The mechanism for producing J/ψ mesons as bound states of charm quark pairs in hadronic collisions has been under intensive experimental and theoretical study since the 1974 discovery of the J/ψ meson in proton-nucleon collisions [1] and in e+e− annihilations [2]
The analysis described in this Letter combines the experimental measurement of J/ψ mesons contained in jets with a theoretical approach based on the fragmenting jet function (FJF) model [13]
The first analysis has been presented comparing data for prompt J/ψ mesons produced as constituents of central gluonic jets with a theoretical analysis based on the fragmenting jet function (FJF) approach
Summary
The mechanism for producing J/ψ mesons as bound states of charm quark pairs (cc) in hadronic collisions has been under intensive experimental and theoretical study since the 1974 discovery of the J/ψ meson in proton-nucleon collisions [1] and in e+e− annihilations [2]. The NRQCD model includes both colorsinglet and color-octet amplitudes for the cc system that produces the J/ψ meson. It proved to be capable of explaining the cross section data, using phenomenological parameters called long-distance matrix elements (LDMEs) that are adjusted to describe J/ψ meson production data. The analysis described in this Letter combines the experimental measurement of J/ψ mesons contained in jets with a theoretical approach based on the fragmenting jet function (FJF) model [13]. It is the first experimental study of prompt J/ψ mesons contained in jets produced in the gluondominated central rapidity region, where the FJF theory for gluonic jet fragmentation applies
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