Determining the existence and nature of the quark-gluon plasma by Upsilon suppression at the LHC

Abstract

Minijet production in √ s = 5.5 TeV Pb+Pb collisions at the LHC is expected to produce a gluon-dominated plasma with large initial temperatures and energy densities. We discuss the implications of the high initial temperatures on the screening mass and on the relative suppression of members of the Υ family. We demonstrate that p T -dependence of the Υ ′ /Υ ratio is only expected if a quark-gluon plasma with significant energy density is present, and that the precise dependence of this ratio will strongly constrain the QGP models. We also propose that the p T spectra of the Υ resonances themselves will provide valuable information by comparing these spectra to that of the Z boson, which should not be influenced by plasma production.

Physics of ultra-relativistic nuclear collisions with heavy beams at LHC energy

“…Particularly interesting is the case of the three Υ resonances whose radii vary between 0.2 and 0.8 fm (for comparison, the radius of the J/Ψ meson is about 0.45 fm). The particular interest to study the suppression for the Υ family has been in detail discussed in [11].…”

Bottomonium production atsNN=200GeV andsNNGrandchamp1, Lumpkins2, Sun3 et al. 2006Phys. Rev. C9171100View full textAdd to dashboardCite

“…Earlier analyses of bottomonium in heavy-ion reactions have essentially focused on suppression mechanisms, using either the Debye-screening picture (combined with formation time effects) [19][20][21] or gluo-dissociation processes [22,23], g + ϒ → b +b [24]. In the present article we assess the role of backward reaction channels leading to bottomonium regeneration (secondary production) via bb coalescence throughout the QGP phase, as dictated by the principle of detailed balance.…”

The Muon Spectrometer of the ALICE experiment

“…Trigger rates for Pb+Pb collisions will be around 500 s −1 . Measurement of the ratio of Υ(2S)/Υ(1S) will provide a very powerful experimental observable to constraint the different models on quarkonia suppression in the QGP [ 22]. The measurement of J/ψ elliptic flow will also be possible.…”