Vector bosons in heavy-ion collisions at the LHC

Abstract

Vector bosons become accessible experimental probes in heavy-ion collisions at the LHC. The capabilities of the LHC experiments to perform their measurement are outlined. The focus is given to their utility to study the possible formation and properties of the Quark Gluon Plasma (QGP) in the most central heavy-ion collisions. Their own sensitivity (if any) to the QGP is discussed. Their interest as references to observe multiple QGP sensitive probes is justified.

Constraints for the nuclear parton distributions from Z and W ± production at the LHC

“…Therefore, it is relevant to check if already heavy boson production in PbPbcollisions would provide useful information about the nuclear effects in PDFs. In spite of the dense QCD-matter being created in PbPb-collisions, the leptons from the decays of heavy bosons should penetrate practically unaffected through this medium (for a short summary, see [29]) justifying the interpretation based on the pQCD parton model. First, in Figure 7, we plot the predicted absolute rapidity spectrum for Z and W ± bosons in Pb+Pb collisions.…”

Production ofZ0and ${W}^{+}{/W}^{-}$ in relativistic heavy-ion collisions at the LHC

“…Through the Drell-Yan (DY) mechanism [11], the gauge boson production with final state lepton pair provides an interesting insight on perturbative quantum chromodynamics (pQCD) for both hadronic and nuclear collisions. It's also noteworthy that in the heavy-ion collisions (HIC), the electro-weak boson production is hardly affected by the evolution of the extremely hot and dense QCD matter, since the boson (decayed lepton pair) mean-free-path in the QCD matter is much longer than the size of the QCD medium [12][13][14]. Therefore, the production of massive gauge boson is insensitive to the possible final-state interactions and provides a good probe of the initial-state cold nuclear matter (CNM) effects in high-energy nuclear collisions [12][13][14][15][16][17][18][19].…”

Study ofZBoson Production in PbPb Collisions atsNN=2.76 TeV

“…At the Relativistic Heavy Ion Collider (RHIC), direct photons play the reference role [1], although their measurement is complicated by copious background from 0 and other decays, and by the existence of a parton fragmentation component which is potentially modified by the medium [2]. At the Large Hadron Collider (LHC) energies, a new and cleaner reference becomes available: the Z boson, decaying into leptons [3,4].…”

“…Their leptonic decays are of particular interest since leptons lose negligible energy in the produced medium regardless of its nature (partonic or hadronic) and properties [4]. Dileptons from Z bosons can thus serve as a reference to the processes expected to be heavily modified in the QGP, such as quarkonia production, or the production of an opposite-side jet in Z þ jet processes [3,11].…”