Abstract
Proton-ion collisions are probed in the forward acceptance by the LHCb detector in a unique kinematic range, complementary to the other LHC experiments. The production of J/ψ and decaying into two muons is studied in proton-lead collisions at a proton-nucleon centre-of-mass energy . The results are based on a data sample corresponding to an integrated luminosity of 1.6 nb-1. The nuclear modification factor and the forward-backward production ratio are determined for J/ψ and (1S) mesons. Significant suppression of prompt J/ψ production is observed with respect to the production in pp collisions at large rapidity, while the suppression of J/ψ from b-hadron decays is less pronounced. The nuclear modification factor for (1S) mesons in the forward region is found to be similar to those for J/ψ from b-hadron decays. First observation of Z bosons in proton-lead collisions at a proton-nucleon centre-of-mass energy is also reported.
Highlights
In ultra-relativistic heavy-ion collisions, the production of heavy quarkonia or electroweak bosons is expected to be suppressed with respect to proton-proton collisions, if a quark-gluon plasma, QGP, is created [1]
The two data samples correspond to two different beam configurations, with the proton beam into the direction of LHCb, referred to as forward
The number of prompt J/ψ and J/ψ from b candidates are determined by a combined fit to the dimuon invariant mass and pseudo-proper time distributions
Summary
In ultra-relativistic heavy-ion collisions, the production of heavy quarkonia or electroweak bosons is expected to be suppressed with respect to proton-proton (pp) collisions, if a quark-gluon plasma, QGP, is created [1]. The LHCb detector [5] collected two data samples correspond√ing to 1.6 nb−1 of proton-lead collisions at a centre-of-mass energy per proton-nucleon pair of sNN = 5 TeV.
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