Abstract
The production of $J/\psi$ mesons with rapidity $1.5<y<4.0$ or $-5.0<y<-2.5$ and transverse momentum $p_\mathrm{T}<14 \mathrm{GeV}/c$ is studied with the LHCb detector in proton-lead collisions at a nucleon-nucleon centre-of-mass energy $\sqrt{s_{NN}}=5 \mathrm{TeV}$. The analysis is based on a data sample corresponding to an integrated luminosity of about $1.6 \mathrm{nb}^{-1}$. For the first time the nuclear modification factor and forward-backward production ratio are determined separately for prompt $J/\psi$ mesons and $J/\psi$ from $b$-hadron decays. Clear suppression of prompt $J/\psi$ production with respect to proton-proton collisions at large rapidity is observed, while the production of $J/\psi$ from $b$-hadron decays is less suppressed. These results show good agreement with available theoretical predictions. The measurement shows that cold nuclear matter effects are important for interpretations of the related quark-gluon plasma signatures in heavy-ion collisions.
Highlights
Detector and data setThe LHCb detector [14] is a single-arm forward spectrometer designed for the study of particles containing b or c quarks
J/ψ mesons are reconstructed using the dimuon decay mode
The calculation [5] based on parton energy loss with the EPS09 NLO nPDF agrees with the measurement of RFB for prompt J/ψ mesons
Summary
The LHCb detector [14] is a single-arm forward spectrometer designed for the study of particles containing b or c quarks. The VELO has the unique feature of being located very close to the beam line (about 8 mm) This allows excellent resolutions in reconstructing the position of the collision point, i.e., the primary vertex, and the vertex of the hadron decay, i.e., the. The trigger [17] consists of a hardware stage, based on information from the calorimeter and muon systems, followed by a software stage which applies a full event reconstruction. This analysis is based on a data sample acquired during the pPb run in early 2013, corresponding to an integrated luminosity of 1.1 nb−1 (0.5 nb−1) for forward (backward) collisions. The interactions of the generated particles with the detector and its response are implemented using the Geant toolkit [22, 23] as described in ref. [24]
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