The ALICE Collaboration has studied the inclusive J/$\psi$ and
$\psi(\mathrm{2S})$ production in p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02
TeV, at the CERN LHC. The J/$\psi$ measurement is performed in the
$\mu^{+}\mu^{-}$ and in the $e^{+}e^{-}$ decay channels, down to zero
$p_{\mathrm{T}}$. The results are in fair agreement with theoretical
predictions. The $\psi(\mathrm{2S})$ measurement has also been performed. In
particular, a smaller $\psi(\mathrm{2S})$ nuclear modification factor, with
respect to the J$/\psi$ one, has been observed.Comment: arXiv admin note: substantial text overlap with arXiv:1410.176

Leoncino, Marco

English

arXiv

The ALICE Collaboration has studied the inclusive J/ψ and ψ(2S) production in p-Pb collisions at √sNN = 5.02TeV, at the CERN LHC. The J/ψ measurement is performed in the μ+μ−

and in the e+e− decay channels, down to zero pT. The results are in fair agreement with theoretical predictions. The ψ(2S) measurement has also been performed. In particular, a smaller ψ(2S) nuclear modification factor, with respect to the J/ψ one, has been observed

Leoncino, M.

Scientific Open-access Literature Archive and Repository

DOI 10.1393/ncc/i2015-15003-8Colloquia: IFAE 2014IL NUOVO CIMENTO 38 C (2015) 3J/ψ and ψ(2S) production in p-Pb collisions at√sNN = 5.02TeVwith ALICE at the LHCM. Leoncino for the ALICE CollaborationINFN and University, Torino, Italyreceived 7 January 2015Summary. — The ALICE Collaboration has studied the inclusive J/ψ and ψ(2S)production in p-Pb collisions at√sNN = 5.02TeV, at the CERN LHC. The J/ψmeasurement is performed in the μ+μ− and in the e+e− decay channels, downto zero pT. The results are in fair agreement with theoretical predictions. Theψ(2S) measurement has also been performed. In particular, a smaller ψ(2S) nuclearmodification factor, with respect to the J/ψ one, has been observed.PACS 25.75.-q – Relativistic heavy-ion collisions.PACS 12.38.Mh – Quark-gluon plasma.PACS 14.40.Pq – Heavy quarkonia.1. – IntroductionThe suppression of charmonia, bound states of c and c¯ quarks, is considered a cleansignature of Quark-Gluon Plasma (QGP) formation in heavy-ion collisions [1]. In addi-tion to the color screening mechanism, other effects may contribute to the charmoniumproduction in Pb-Pb collisions. In particular, one can expect a recombination of c andc¯ pairs from the medium (favoured by the large cc¯ multiplicity typical at the LHC ener-gies [2]). Furthermore, cold nuclear matter (CNM) effects, like shadowing [3,4] and initialstate parton energy loss [5], are expected to play a role. It is thus important to study theproduction of charmonia in proton-nucleus collisions in order to disentangle the suppres-sion contribution related to CNM from the one associated to the formation of a QGP.2. – The ALICE detector and the p-Pb runThe ALICE detector consists of a central barrel dedicated to particle tracking andidentification (in the range |η| < 0.9) and a forward spectrometer used for the detectionof muons (in the interval −4 < η < −2.5). More details about the experimental setupcan be found in [6]. The J/ψ resonance is detected both in the dielectron decay channel(using the central barrel detectors) and in the dimuon decay channel (using the forwardc© CERN on behalf of the ALICE CollaborationCreative Commons Attribution 4.0 License (http://creativecommons.org/licenses/by/4.0) 12 M. LEONCINO for the ALICE COLLABORATIONFig. 1. – Inclusive J/ψ nuclear modification factor as a function of rapidity. Open boxes areuncorrelated systematic uncertainties, filled area indicate partially correlated uncertainties andthe gray box at one the global uncertainty due to the TpPb. Theoretical models based onshadowing/energy loss [9-11] and CGC [12] are also shown.muon spectrometer), while, with the present statistics, the ψ(2S) can be studied only inthe dimuon decay channel. Due to the energy asymmetry of the LHC beams in p-Pbcollisions the nucleon-nucleon center-of-mass system is shifted by Δy = 0.465 in thedirection of the proton beam. Data have been collected in two beam configurations withinverted beam directions, resulting in the following rapidity coverages: −4.46 < ycms <−2.96 at backward rapidity, −1.37 < ycms < 0.46 at midrapidity and 2.03 < ycms < 3.53at forward rapidity.3. – ResultsThe nuclear effects on J/ψ production in p-Pb collisions are quantified by means of thenuclear modification factor, which is defined by: RpPb = YJ/ψ/〈TpPb〉 · σJ/ψpp , where YJ/ψis the efficiency corrected J/ψ yield, σJ/ψpp is the production cross section in pp collisionsin the same kinematical range at the same energy and TpPb is the nuclear thicknessfunction estimated through the Glauber model [7]. Since pp data at√s = 5.02TeV arenot available, the reference σJ/ψpp is obtained with an interpolation procedure [8]. Theresults are reported in fig. 1: at mid and forward rapidity, the inclusive J/ψ productionis suppressed with respect to that in pp collisions, whereas it is unchanged at backwardrapidity. Models containing shadowing and/or energy loss [9-11] are in agreement withALICE data (within uncertainties), while the CGC-based model [12] overestimates thesuppression.Since the Bjorken x-values in the Pb nucleus in p-Pb collisions at√sNN = 5.02TeVare similar to the ones in Pb-Pb collisions at√sNN = 2.76TeV and assuming a factoriza-tion of shadowing effects, an expectation for the RAA based on the RpA can be derived bycomparing RforwardpPb × RbackwardpPb with RPbPb (fig. 2). At low transverse momentum datasuggest a contribution from regeneration while, at higher transverse momenta, the sup-pression contribution starts to be dominant. The ψ(2S) analysis has been performed anal-ogously to the J/ψ one. In fig. 3 (left) the double ratio [ψ(2S)/J/ψ]pPb / [ψ(2S)/J/ψ]ppis shown as a function of rapidity and is compared with the PHENIX result in d-Au colli-sions at√sNN = 0.2TeV. ALICE results show a similar trend compared with PHENIXdata at midrapidity [13] indicating a suppression in the ψ(2S) production with respect toJ/ψ AND ψ(2S) PRODUCTION IN p-Pb COLLISIONS AT√SNN = 5.02TeV ETC. 3Fig. 2. – In the left plot the J/ψ RbackwardpPb × RforwardpPb is compared to the RforwardPbPb . In the rightplot the J/ψ is compared“RmidrapiditypPb”2with RmidrapidityPbPb .Fig. 3. – Left: the double ratio [ψ(2S)/J/ψ]pPb / [ψ(2S)/J/ψ]pp. PHENIX data at√sNN =0.2TeV at midrapidity is also shown. Right: the Rψ(2S)pPb compared to RJ/ψpPb.p-p collisions. This suppression is further investigated in fig. 3 (right) where the Rψ(2S)pPbis presented as a function of rapidity and is compared to RJ/ψpPb. The ψ(2S) is more sup-pressed with respect to the J/ψ. These results are compared to theoretical calculationsused for the J/ψ [9-11], which should hold for the ψ(2S). The available theoretical pre-dictions do not describe the ψ(2S) suppression, indicating that other mechanisms arerequired to explain it.REFERENCES[1] Matsui T. and Satz H., Phys. Lett. B, 178 (1986) 416.[2] Andronic A., Braun-Munzinger P. et al., J. Phys. G, 38 (2011) 124081.[3] de Florian D. and Sassot R., Phys. Rev. D, 69 (2004) 074028.[4] Hirai M., Kumano S. and Nagai T. H., Phys. Rev. C, 76 (2007) 065207.[5] Arleo F. and Peigne S., Phys. Rev. Lett., 109 (2012) 122301.[6] Aamodt K. et al. (ALICE Collaboration), JINST, 3 (2008) S08002.[7] ALICE Collaboration, Phys. Rev. Lett., 110 (2013) 082302.[8] ALICE and LHCb Collaborations, ALICE-PUBLIC-2013-002 LHCb-CONF-2013-013.[9] Albacete J. et al., Int. J. Mod. Phys. E, 22 (2013) 1330007.[10] Vogt R., private communications.[11] Arleo F. and Peigne S., JHEP, 03 (2013) 122.[12] Fujii H. and Watanabe K., Nucl. Phys. A, 915 (2013) 1.[13] Adare A. et al. (PHENIX Collaboration), Phys. Rev. Lett., 111 (2013) 202301.

J/ψ and ψ(2S) production in p-Pb collisions at √sNN = 5.02TeV with ALICE at the LHC

The ALICE Collaboration has studied the inclusive J/$\psi$ and $\psi(\mathrm{2S})$ production in p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV, at the CERN LHC. The J/$\psi$ measurement is performed in the $\mu^{+}\mu^{-}$ and in the $e^{+}e^{-}$ decay channels, down to zero $p_{\mathrm{T}}$. The results are in fair agreement with theoretical predictions. The $\psi(\mathrm{2S})$ measurement has also been performed. In particular, a smaller $\psi(\mathrm{2S})$ nuclear modification factor, with respect to the J$/\psi$ one, has been observed.The ALICE Collaboration has studied the inclusive J/ ψ and ψ (2S) production in p-Pb collisions at √ s NN =5 . 02TeV, at the CERN LHC. The J/ ψ measurement is performed in the μ + μ − and in the e + e − decay channels, down to zero p T . The results are in fair agreement with theoretical predictions. The ψ (2S) measurement has also been performed. In particular, a smaller ψ (2S) nuclear modification factor, with respect to the J /ψ one, has been observedThe ALICE Collaboration has studied the inclusive J/$\psi$ and $\psi(\mathrm{2S})$ production in p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV, at the CERN LHC. The J/$\psi$ measurement is performed in the $\mu^{+}\mu^{-}$ and in the $e^{+}e^{-}$ decay channels, down to zero $p_{\mathrm{T}}$. The results are in fair agreement with theoretical predictions. The $\psi(\mathrm{2S})$ measurement has also been performed. In particular, a smaller $\psi(\mathrm{2S})$ nuclear modification factor, with respect to the J$/\psi$ one, has been observed

J/ $\psi$ and $\psi$ (2S) production in p-Pb collisions at $\sqrt{s_{NN}}=\mathrm{5.02}$ TeV with ALICE at the LHC

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J/ψ\psiψ and ψ\psiψ(2S) production in p-Pb collisions at sNN=5.02\sqrt{s_{NN}}=\mathrm{5.02}sNN​​=5.02 TeV with ALICE at the LHC

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J/ $\psi$ and $\psi$ (2S) production in p-Pb collisions at $\sqrt{s_{NN}}=\mathrm{5.02}$ TeV with ALICE at the LHC