Studies of gluon TMDs and their evolution using quarkonium-pair production at the LHC

Abstract

J/ψ-or Υ -pair production at the LHC are promising processes to study the gluon transverse momentum distributions (TMDs) which remain very poorly known. In this article, we improve on previous results by including the TMD evolution in the computation of the observables such as the pair-transverse-momentum spectrum and asymmetries arising from the linear polarization of gluons inside unpolarized protons. We show that the azimuthal asymmetries generated by the gluon polarization are reduced compared to the tree level case but are still of measurable size (in the 5%-10% range). Such asymmetries should be measurable in the available data sets of J/ψ pairs and in the future data sets of the high-luminosity LHC for Υ pairs. arXiv:1909.05769v1 [hep-ph]

J/ψ meson production in SIDIS: matching high and low transverse momentum

“…First of all, since its discovery in 1974, the J/ψ meson, a charm-anticharm quarkonium bound state with odd charge parity, has always attracted a lot of attention as a probe of the perturbative and nonperturbative aspects of quantum chromodynamics (QCD) and their interplay. Moreover, J/ψ production in both ep [12][13][14][15] and pp collisions [12,[16][17][18][19] has been proposed lately as a tool to access gluon TMDs. Similar studies have also been carried out within the so-called generalized parton model approach [20][21][22][23][24][25][26][27].…”

Studying the gluon TMDs with J/ψ- and Upsilon- pair production at the LHC

“…We reported on the formalism used to estimate the size of the related asymmetries, including TMD evolution in the computations. The full analysis can be found in [17]. We note that more efforts are needed to obtain rigorous factorisation theorems along the lines of [29].…”

“…This allowed to perform a first fit of the width of a Gaussian-modelled TMD using the normalised transverse-momentum-spectrum of di-J/ψ production at LHCb hinting at the presence of QCD evolution effects [16]. More observables could be extracted from data already acquired and to come and this motivates us advancing the theory description of such processes by including TMD QCD evolution as we report on here along the lines of [17].…”

The cos 2ϕ azimuthal asymmetry in ρ0 meson production in ultraperipheral heavy ion collisions

“…It was shown in refs. [30,[33][34][35][36][37][38][39][40][41][42] that the linear polarization of photons/gluons can be probed through the azimuthal asymmetries in two particles correlations. For instance, the QED calculations [31,32] predict a sizable cos 4φ azimuthal asymmetry for pure electromagnetic dilepton production in heavy ion collisions.…”