Forward J/ψ production at high energy: Centrality dependence and mean transverse momentum

Abstract

Forward rapidity J/ψ meson production in proton-nucleus collisions can be an important constraint of descriptions of the small-x nuclear wavefunction. In an earlier work we studied this process using a dipole cross section satisfying the Balitsky-Kovchegov equation, fit to HERA inclusive data and consistently extrapolated to the nuclear case using a standard Woods-Saxon distribution. In this paper we present further calculations of these cross sections, studying the mean transverse momentum of the meson and the dependence on collision centrality. We also extend the calculation to backward rapidities using nuclear parton distribution functions. We show that the parametrization is overall rather consistent with the available experimental data. However, there is a tendency towards a too strong centrality dependence. This can be traced back to the rather small transverse area occupied by small-x gluons in the nucleon that is seen in the HERA data, compared to the total inelastic nucleon-nucleon cross section.

Isolated photon production in proton-nucleus collisions at forward rapidity

“…For particle production at forward rapidities and moderate transverse momenta, these high energy logarithms can be expected to dominate over the transverse momentum logarithms α s ln Q 2 resummed by the Dokshitzer-Gribov-Lipatov-AltarelliParisi (DGLAP) evolution. The leading order (LO) inclusive particle production calculations in the CGC framework have been shown to be in good agreement with a variety of RHIC and LHC data [18][19][20][21][22][23][24]. Recently, there has also been significant progress in developing the theory towards next-to-leading order (NLO) accuracy [25][26][27][28][29][30].…”

“…We note that our optical Glauber model, which uses a Woods-Saxon distribution to generalize the dipole-proton amplitude to the dipole-nucleus case [see Eq. (12)] may not be accurate with such a light nucleus (see also the related discussion in [24]). In particular, when we calculate the minimum bias cross sections, in the case of π 0 production approximately 80% of the cross section comes from regions where the saturation scale of the nucleus falls below that of the proton.…”

“…[22] and extended to nuclei using an optical Glauber procedure relying on standard nuclear geometry. The same dipole cross sections, without any additional parameters, have previously been used to calculate single inclusive particle production [22], forward J=Ψ production [23,24] and DrellYan cross sections [32] in proton-proton and proton-nucleus collisions. The range of processes addressed in these works demonstrates the universality and predictive power of the dilute-dense CGC framework, combining the dipole picture of DIS with the "hybrid" formalism for forward hadronic collisions.…”

Multigluon Correlations and Evidence of Saturation from Dijet Measurements at an Electron-Ion Collider

“…When applied to inclusive hadron, jet, vector meson and D meson production, this approach results in good agreement with LHC data[53][54][55][56][57] 4. The differential dΠ is defined as (2π) 2 |P |d|P ||∆|d|∆|dy 1 dy 2 .…”

Quarkonium Production at Collider Energies in Small-x Formalism

“…9 (left) shows the Q pA of forward J/ψ production at LHC as a function of N coll computed in the small-x formalism incorporated with the CEM and Eq. (26) [57]. The theoretical results strongly depend on the value of N coll in pA collision.…”