Abstract
The production of $\psi(2S)$ mesons is studied in dimuon final states using proton-lead collision data collected by the LHCb detector. The data sample corresponds to an integrated luminosity of $1.6~\mathrm{nb}^{-1}$. The nucleon-nucleon centre-of-mass energy of the proton-lead collisions is $\sqrt{s_{NN}}=5~\mathrm{TeV}$. The measurement is performed using $\psi(2S)$ mesons with transverse momentum less than $14~\mathrm{GeV}/c$ and rapidity $y$ in the ranges $1.5<y<4.0$ and $-5.0<y<-2.5$ in the nucleon-nucleon centre-of-mass system. The forward-backward production ratio and the nuclear modification factor are determined for $\psi(2S)$ mesons. Using the production cross-section results of $\psi(2S)$ and $J/\psi$ mesons from $b$-hadron decays, the $b\bar{b}$ cross-section in pPb collisions at $\sqrt{s_{NN}}=5~\mathrm{TeV}$ is obtained.
Highlights
Detector and datasetsThe LHCb detector [25, 26] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks
Rapidity of the produced particle, and sNN is the centre-of-mass energy of the protonnucleon system
One explanation for the fixed-target results is that the charmonium states produced at central rapidity spend more time in the medium than those at forward rapidities; the loosely bound ψ(2S) mesons are more suppressed than J/ψ mesons at central rapidity [22,23,24]
Summary
The LHCb detector [25, 26] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks. The online event selection is performed by a trigger, which 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. With the proton beam travelling in the direction from the vertex detector to the muon system and the lead beam circulating in the opposite direction, the LHCb spectrometer covers forward rapidities. Simulated samples based on pp collisions at s = 8 TeV are used to determine the acceptance and reconstruction efficiencies. The simulation samples are reweighted so that the track multiplicity distribution reproduces the experimental data of pPb collisions at √. The interaction of the generated particles with the detector, and its response, are implemented using the Geant toolkit [31, 32] as described in ref. [33]
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