Inclusive $J/ψ$ and $Υ$ emissions from single-parton fragmentation in hybrid high-energy and collinear factorization

TL;DR

This work develops a hybrid high-energy and collinear factorization framework to study inclusive production of heavy quarkonia (J/ψ or Υ) with a light-flavor jet at high energy. Quarkonium fragmentation is modeled within NRQCD in a variable-flavor-number scheme, combining short-distance coefficients with LDME and DGLAP evolution, while the high-energy component is resummed via BFKL with NLO impact factors for the quarkonium and jet. Phenomenological predictions for ΔY- and φ-distributions are computed under CMS-like cuts using the ZCW19 fragmentation set, showing sizeable cross sections and partial stabilization of the NLA series, highlighting the regime where high-energy resummation is relevant. The study offers a path to probing quarkonium production mechanisms at high energies and to accessing the proton’s small-x structure through the unintegrated gluon density, with planned extensions to gluon-initiated fragmentation and other quarkonium channels.

Abstract

We present a novel study on the inclusive production of a heavy quarkonium ($J/ψ$ or $Υ$), in association with a light-flavored jet, as a test field of the high-energy QCD dynamics. The large transverse momenta at which the two final-state objects are detected permits us to perform an analysis in the spirit of the variable-flavor number scheme (VFNS), in which the cross section for the hadroproduction of a light parton is convoluted with a perturbative fragmentation function that describes the transition from a light quark to a heavy hadron. The quarkonium collinear fragmentation function is built as a product between a short-distance coefficient function, which encodes the resummation of DGLAP type logarithms, and a non-perturbative long-distance matrix element (LDME), calculated in the non-relativistic QCD (NRQCD) framework. Our theoretical setup is the hybrid high-energy and collinear factorization, where the standard collinear approach is supplemented by the resummation of leading and next-to-leading energy-type logarithms \emph{à la} BFKL. We propose this reaction as a suitable channel to probe the production mechanisms of quarkonia at high energies and large transverse momenta and to possibly unveil the transition region from the heavy-quark pair production mechanism to the single-parton fragmentation one.

Figures (2)

• Figure 1: $\Delta Y$-distribution in the $J/\psi$$+$ jet (left) and in the $J/\psi$$+$$J/\psi$ (right) channel, at $\sqrt{s} = 13$ TeV. Quarkonium fragmentation is described in terms of ZCW19 collinear FFs.
• Figure 2: In the left panel, $\Delta Y$-distribution in the $J/\psi$$+$ jet for $C_{\mu}=1,2,4,10,20,30$ at $13$ TeV. In the right panel, NLA predictions for the $\varphi$-distribution in the $J/\psi$$+$ jet channel, at $\sqrt{s} = 13$ TeV, and for three distinct values of $\Delta Y$. Quarkonium fragmentation is described in terms of ZCW19 collinear FFs.