Bottomonium production atsNN=200GeV andsNN

Abstract

Properties of bottomonia (ϒ, χ b , and ϒ ) in the quark-gluon plasma (QGP) are investigated by assessing inelastic reaction rates and their interplay with open-bottom states (b quarks or B mesons) and color screening. The latter leads to vanishing quarkonium-binding energies at sufficiently high temperatures (close to the dissolution point), which, in particular, renders standard gluo-dissociation, g + ϒ → b +b, inefficient because of a substantial reduction in final-state phase space. This problem is overcome by invoking a "quasifree" destruction mechanism, g, q,q + ϒ → g, q,q + b +b, as previously introduced for charmonia. The pertinent reaction rates are implemented into a kinetic theory framework to evaluate the time evolution of bottomonia in heavy-ion reactions at the Relativistic Heavy Ion Collider and the CERN Large Hadron Collider within an expanding fireball model. Although bottom quarks are assumed to be exclusively produced in primordial nucleon-nucleon collisions, their thermal relaxation times in the QGP, which importantly figure into ϒ-formation rates, are estimated according to a recent Fokker-Planck treatment. Predictions for the centrality dependence of ϒ production are given for upcoming experiments at RHIC and LHC. At both energies, ϒ suppression turns out to be the prevalent effect.

Suppression of non-prompt J/ψ, prompt J/ψ, and $ \Upsilon $(1S) in PbPb collisions at $ \sqrt {{{s_{\text{NN}}}}} = 2.76 $ TeV

“…On the one hand, modifications to the parton distribution functions inside the nucleus (shadowing) and other cold-nuclear-matter effects can reduce the production of quarkonia without the presence of a QGP [9,10]. On the other hand, the large number of heavy quarks produced in heavyion collisions, in particular at the energies accessible by the Large Hadron Collider (LHC), could lead to an increased production of quarkonia via statistical recombination [11][12][13][14][15][16].…”

Dissociation of quarkonium in a complex potential

“…Earlier it was thought that a quarkonium state is dissociated when the Debye screening becomes so strong that it inhibits the formation of bound states but nowadays a quarkonium is dissociated at a lower temperature [16,35] even though its binding energy is nonvanishing, rather is overtaken by the Landau-damping induced thermal width [36], obtained from the imaginary part of the potential. Its consequences on heavy quarkonium spectral functions [35,37], perturbative thermal widths [36,38] quarkonia at finite velocity [39], in a T-matrix approach [40,41,42,43,44], and in stochastic real-time dynamics [45] have been studied. Recently the dynamical evolution of the plasma was combined with the real and imaginary parts of the binding energies to estimate the suppression of quarkonium [46] in RHIC and LHC energies.…”

Bottomonia suppression in relativistic heavy-ion collisions

“…Furthermore, the much smaller number of bottom quarks than charm quarks that is produced in heavy-ion collisions makes the contribution of regeneration from the QGP to Υ production also less important. Therefore, studying Υ production in heavy-ion collisions would provide a cleaner probe of the properties of QGP and also the in-medium properties of bottomonia [20,21]. Recently, the nuclear modification factor R AA of the sum of bottomonia Υ(1S), Υ(2S) and Υ(3S), defined by their yields relative to those from p+p collisions multiplied by the number of initial binary collisions, in Au+Au collisions at √ s N N = 200 GeV was measured by the STAR Collaboration at RHIC [22], while that of Υ(1S) [23] and the relative suppression of Υ(2S) and Υ(3S) to Υ(1S) [24] in Pb+Pb collisions at √ s N N = 2.76 TeV were measured by the CMS Collaboration at LHC.…”