C Blume

Publications (184)261.88 Total impact

• Article: Transverse Momentum Distribution and Nuclear Modification Factor of Charged Particles in p+Pb Collisions at sqrt[s_{NN}]=5.02 TeV.

  B Abelev, J Adam, D Adamová, A M Adare, M M Aggarwal, G Aglieri Rinella, M Agnello, A G Agocs, A Agostinelli, Z Ahammed, [......], D Zhou, X Zhu, J Zhu, H Zhu, A Zichichi, A Zimmermann, G Zinovjev, Y Zoccarato, M Zynovyev, M Zyzak
  [show abstract] [hide abstract]
  ABSTRACT: The transverse momentum (p_{T}) distribution of primary charged particles is measured in minimum bias (non-single-diffractive) p+Pb collisions at sqrt[s_{NN}]=5.02 TeV with the ALICE detector at the LHC. The p_{T} spectra measured near central rapidity in the range 0.5<p_{T}<20 GeV/c exhibit a weak pseudorapidity dependence. The nuclear modification factor R_{pPb} is consistent with unity for p_{T} above 2 GeV/c. This measurement indicates that the strong suppression of hadron production at high p_{T} observed in Pb+Pb collisions at the LHC is not due to an initial-state effect. The measurement is compared to theoretical calculations.
  Physical Review Letters 02/2013; 110(8):082302. · 7.37 Impact Factor
• Source

  Available from: Varlen Grabski

  Dataset: ALICE LHC 1748-0221 3 08 S08002

  ALICE Collaboration, K. Aamodt, A. Abrahantes Quintana, R. Achenbach, S. Acounis, D. Adamová, C. Adler, M. Aggarwal, F. Agnese, G. Aglieri Rinella, [......], F. Borotto, V. Borshchov, Y. Bortoli, O. Borysov, S. Bose, L. Bosisio, M. Botje, S. Böttger, G. Bourdaud, O. Bourrion
• Source

  Available from: Varlen Grabski

  Article: Pseudorapidity Density of Charged Particles in p+Pb Collisions at sqrt[s_{NN}]=5.02 TeV.

  B Abelev, J Adam, D Adamová, A M Adare, M M Aggarwal, G Aglieri Rinella, M Agnello, A G Agocs, A Agostinelli, Z Ahammed, [......], Y Zhou, J Zhu, H Zhu, X Zhu, A Zichichi, A Zimmermann, G Zinovjev, Y Zoccarato, M Zynovyev, M Zyzak
  [show abstract] [hide abstract]
  ABSTRACT: The charged-particle pseudorapidity density measured over four units of pseudorapidity in nonsingle-diffractive p+Pb collisions at a center-of-mass energy per nucleon pair sqrt[s_{NN}]=5.02 TeV is presented. The average value at midrapidity is measured to be 16.81±0.71 (syst), which corresponds to 2.14±0.17 (syst) per participating nucleon, calculated with the Glauber model. This is 16% lower than in nonsingle-diffractive pp collisions interpolated to the same collision energy and 84% higher than in d+Au collisions at sqrt[s_{NN}]=0.2 TeV. The measured pseudorapidity density in p+Pb collisions is compared to model predictions and provides new constraints on the description of particle production in high-energy nuclear collisions.
  Physical Review Letters 01/2013; 110(3):032301. · 7.37 Impact Factor
• Article: Charge separation relative to the reaction plane in Pb-Pb collisions at sqrt[s_{NN}]=2.76 TeV.

  B Abelev, J Adam, D Adamová, A M Adare, M M Aggarwal, G Aglieri Rinella, A G Agocs, A Agostinelli, S Aguilar Salazar, Z Ahammed, [......], D Zhou, F Zhou, J Zhu, X Zhu, A Zichichi, A Zimmermann, G Zinovjev, Y Zoccarato, M Zynovyev, M Zyzak
  [show abstract] [hide abstract]
  ABSTRACT: Measurements of charge-dependent azimuthal correlations with the ALICE detector at the LHC are reported for Pb-Pb collisions at sqrt[s_{NN}]=2.76 TeV. Two- and three-particle charge-dependent azimuthal correlations in the pseudorapidity range |η|<0.8 are presented as a function of the collision centrality, particle separation in pseudorapidity, and transverse momentum. A clear signal compatible with a charge-dependent separation relative to the reaction plane is observed, which shows little or no collision energy dependence when compared to measurements at RHIC energies. This provides a new insight for understanding the nature of the charge-dependent azimuthal correlations observed at RHIC and LHC energies.
  Physical Review Letters 01/2013; 110(1):012301. · 7.37 Impact Factor
• Article: Measurement of the Cross Section for Electromagnetic Dissociation with Neutron Emission in Pb-Pb Collisions at sqrt[s_{NN}]=2.76 TeV.

  B Abelev, J Adam, D Adamová, A M Adare, M M Aggarwal, G Aglieri Rinella, A G Agocs, A Agostinelli, S Aguilar Salazar, Z Ahammed, [......], D Zhou, F Zhou, Y Zhou, J Zhu, X Zhu, A Zichichi, A Zimmermann, G Zinovjev, Y Zoccarato, M Zynovyev
  [show abstract] [hide abstract]
  ABSTRACT: The first measurement of neutron emission in electromagnetic dissociation of ^{208}Pb nuclei at the LHC is presented. The measurement is performed using the neutron zero degree calorimeters of the ALICE experiment, which detect neutral particles close to beam rapidity. The measured cross sections of single and mutual electromagnetic dissociation of Pb nuclei at sqrt[s_{NN}]=2.76 TeV with neutron emission are σ_{singleEMD}=187.4±0.2(stat)_{-11.2}^{+13.2}(syst) b and σ_{mutualEMD}=5.7±0.1(stat)±0.4(syst) b, respectively. The experimental results are compared to the predictions from a relativistic electromagnetic dissociation model.
  Physical Review Letters 12/2012; 109(25):252302. · 7.37 Impact Factor
• Source

  Available from: C. Oppedisano

  Article: Pion, Kaon, and Proton Production in Central Pb-Pb Collisions at sqrt[s_{NN}]=2.76 TeV.

  B Abelev, J Adam, D Adamová, A M Adare, M M Aggarwal, G Aglieri Rinella, A G Agocs, A Agostinelli, S Aguilar Salazar, Z Ahammed, [......], Y Zhou, F Zhou, J Zhu, X Zhu, A Zichichi, A Zimmermann, G Zinovjev, Y Zoccarato, M Zynovyev, M Zyzak
  [show abstract] [hide abstract]
  ABSTRACT: In this Letter we report the first results on π^{±}, K^{±}, p, and p[over ¯] production at midrapidity (|y|<0.5) in central Pb-Pb collisions at sqrt[s_{NN}]=2.76 TeV, measured by the ALICE experiment at the LHC. The p_{T} distributions and yields are compared to previous results at sqrt[s_{NN}]=200 GeV and expectations from hydrodynamic and thermal models. The spectral shapes indicate a strong increase of the radial flow velocity with sqrt[s_{NN}], which in hydrodynamic models is expected as a consequence of the increasing particle density. While the K/π ratio is in line with predictions from the thermal model, the p/π ratio is found to be lower by a factor of about 1.5. This deviation from thermal model expectations is still to be understood.
  Physical Review Letters 12/2012; 109(25):252301. · 7.37 Impact Factor
• Article: Critical fluctuations of the proton density in A+A collisions at $158A$ GeV

  T. Anticic, B. Baatar, D. Barna, J. Bartke, J. Beck, L. Betev, H. Białkowska, C. Blume, M. Bogusz, B. Boimska, [......], D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranić, Z. Włodarczyk, A. Wojtaszek-Szwarć, N. G. Antoniou, N. Davis, F. K. Diakonos
  [show abstract] [hide abstract]
  ABSTRACT: Studies of QCD suggest the existence of a critical point in the phase diagram of strongly interacting matter. Close to this point, according to recent theoretical investigations, the net-proton density carries the critical fluctuations of the chiral order parameter. Using intermittency analysis in the transverse momentum phase space of protons produced around midrapidity in the 12.5% most central C+C, Si+Si and Pb+Pb collisions at the maximum SPS energy of 158$A$ GeV we find evidence of power-law fluctuations for the Si+Si and Pb+Pb data. The fitted power-law exponent approaches the value expected for critical fluctuations. This suggests that the freeze-out states of these two systems are located in the phase diagram in the neighbourhood of the chiral critical point.
  08/2012;
• Article: System-size and centrality dependence of charged kaon and pion production in nucleus-nucleus collisions at 40A GeV and158A GeV beam energy

  T. Anticic, B. Baatar, D. Barna, J. Bartke, H. Beck, L. Betev, H. Bialkowska, C. Blume, M. Bogusz, B. Boimska, [......], T. Susa, M. Szuba, M. Utvic, D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranic, Z. Wlodarczyk, A. Wojtaszek-Szwarc
  [show abstract] [hide abstract]
  ABSTRACT: Measurements of charged pion and kaon production are presented in centrality selected Pb+Pb collisions at 40A GeV and 158A GeV beam energy as well as in semi-central C+C and Si+Si interactions at 40A GeV. Transverse mass spectra, rapidity spectra and total yields are determined as a function of centrality. The system-size and centrality dependence of relative strangeness production in nucleus-nucleus collisions at 40A GeV and 158A GeV beam energy are derived from the data presented here and published data for C+C and Si+Si collisions at 158A GeV beam energy. At both energies a steep increase with centrality is observed for small systems followed by a weak rise or even saturation for higher centralities. This behavior is compared to calculations using transport models (UrQMD and HSD), a percolation model and the core-corona approach.
  07/2012;
• Source

  Available from: Varlen Grabski

  Article: J/ψ production as a function of charged particle multiplicity in pp collisions at s =7 TeV

  ALICE Collaboration, B. Abelev, J. Adam, D. Adamová, A. M. Adare, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, A. Agostinelli, S. Aguilar Salazar, [......], X. Zhang, Y. Zhou, D. Zhou, F. Zhou, X. Zhu, A. Zichichi, A. Zimmermann, G. Zinovjev, Y. Zoccarato, M. Zynovyev
  [show abstract] [hide abstract]
  ABSTRACT: The ALICE Collaboration reports the measurement of the relative J/ψ yield as a function of charged particle pseudorapidity density dNch/dη in pp collisions at s=7 TeV at the LHC. J/ψ particles are detected for pt>0, in the rapidity interval |y|<0.9 via decay into e+e-, and in the interval 2.5<y<4.0 via decay into μ+μ- pairs. An approximately linear increase of the J/ψ yields normalized to their event average (dN/dy)/<dN/dy> with (dNch/dη)/<dNch/dη> is observed in both rapidity ranges, where dNch/dη is measured within |η|<1 and pt>0. In the highest multiplicity interval with <dNch/dη(bin)>=24.1, corresponding to four times the minimum bias multiplicity density, an enhancement relative to the minimum bias J/ψ yield by a factor of about 5 at 2.5<y<4 (8 at |y|<0.9) is observed.
  Physics Letters B 05/2012; 712:165-175. · 3.95 Impact Factor
• Article: Search for deconfinement in NA49 at the CERN SPS

  Peter Seyboth, Collaboration, S. V. Afanasiev, T. Anticic, D. Barna, J. Bartke, R. A. Barton, L. Betev, H. Bialkowska, A. Billmeier, [......], D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranic, S. Wenig, A. Wetzler, I. KYoo, J. Zaranek, J. Zimanyi
  [show abstract] [hide abstract]
  ABSTRACT: Experiment NA49 at the CERN SPS uses a large acceptance detector for a systematic study of particle yields and correlations in nucleus-nucleus, nucleon-nucleus and nucleon-nucleon collisions. Preliminary results for Pb+Pb collisions at 40, 80 and 158 A⋅GeV beam energy shown and compared to measurements at lower and higher energies.
  Pramana 04/2012; 60(4):725-737. · 0.57 Impact Factor
• Source

  Available from: Varlen Grabski

  Article: First proton–proton collisions at the LHC as observed with the ALICE detector: measurement of the charged-particle pseudorapidity density at GeV

  The ALICE Collaboration, K. Aamodt, N. Abel, U. Abeysekara, A. Abrahantes Quintana, A. Acero, D. Adamová, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, [......], X. Zhang, D. Zhou, S. Zhou, J. Zhu, A. Zichichi, A. Zinchenko, G. Zinovjev, M. Zinovjev, Y. Zoccarato, V. Zycháček
  [show abstract] [hide abstract]
  ABSTRACT: On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), two counter-rotating proton bunches were circulated for the first time concurrently in the machine, at the LHC injection energy of 450GeV per beam. Although the proton intensity was very low, with only one pilot bunch per beam, and no systematic attempt was made to optimize the collision optics, all LHC experiments reported a number of collision candidates. In the ALICE experiment, the collision region was centred very well in both the longitudinal and transverse directions and 284 events were recorded in coincidence with the two passing proton bunches. The events were immediately reconstructed and analyzed both online and offline. We have used these events to measure the pseudorapidity density of charged primary particles in the central region. In the range |η|<0.5, we obtain dN ch/dη=3.10±0.13(stat.)±0.22(syst.) for all inelastic interactions, and dN ch/dη=3.51±0.15(stat.)±0.25(syst.) for non-single diffractive interactions. These results are consistent with previous measurements in proton–antiproton interactions at the same centre-of-mass energy at the CERN Sp [`(p)]\overline{\mathrm{p}} S collider. They also illustrate the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase.
  European Physical Journal C 04/2012; 65(1):111-125. · 3.63 Impact Factor
• Source

  Available from: Daniel Felea

  Article: Production of pions, kaons and protons in pp collisions at with ALICE at the LHC

  The ALICE Collaboration, K. Aamodt, N. Abel, U. Abeysekara, A. Abrahantes Quintana, A. Abramyan, D. Adamová, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, [......], X. Zhang, D. Zhou, S. Zhou, J. Zhu, A. Zichichi, A. Zinchenko, G. Zinovjev, Y. Zoccarato, V. Zycháček, M. Zynovyev
  [show abstract] [hide abstract]
  ABSTRACT: The production of π +, π −, K+, K−, p, and [`(p)]\overline{\mathrm{p}} at mid-rapidity has been measured in proton-proton collisions at Ös = 900GeV\sqrt{s} = 900~\mathrm{GeV} with the ALICE detector. Particle identification is performed using the specific energy loss in the inner tracking silicon detector and the time projection chamber. In addition, time-of-flight information is used to identify hadrons at higher momenta. Finally, the distinctive kink topology of the weak decay of charged kaons is used for an alternative measurement of the kaon transverse momentum (p t) spectra. Since these various particle identification tools give the best separation capabilities over different momentum ranges, the results are combined to extract spectra from p t=100MeV/c to 2.5 GeV/c. The measured spectra are further compared with QCD-inspired models which yield a poor description. The total yields and the mean p t are compared with previous measurements, and the trends as a function of collision energy are discussed.
  European Physical Journal C 04/2012; 71(6):1-22. · 3.63 Impact Factor
• Source

  Available from: Vladimir Peskov

  Article: Strange particle production in proton–proton collisions at with ALICE at the LHC

  K. Aamodt, A. Abrahantes Quintana, D. Adamová, A. M. Adare, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, S. Aguilar Salazar, Z. Ahammed, N. Ahmad, [......], P. Zelnicek, A. Zenin, I. Zgura, M. Zhalov, X. Zhang, D. Zhou, A. Zichichi, G. Zinovjev, Y. Zoccarato, M. Zynovyev
  [show abstract] [hide abstract]
  ABSTRACT: The production of mesons containing strange quarks ($\mbox {$\mbox {, φ) and both singly and doubly strange baryons ($\mbox {$\mbox {, $\mbox {$\mbox {, and $\mbox {$\mbox {) are measured at mid-rapidity in pp collisions at _boxclose_boxclose_boxclose\sqrt{s}=0.9TeV{\rm TeV} with the ALICE experiment at the LHC. The results are obtained from the analysis of about 250k minimum bias events recorded in 2009. Measurements of yields (dN/dy) and transverse momentum spectra at mid-rapidity for inelastic pp collisions are presented. For mesons, we report yields (〈dN/dy〉) of 0.184±0.002(stat.)±0.006(syst.) for $\mbox {$\mbox { and 0.021±0.004(stat.)±0.003(syst.) forφ. For baryons, we find 〈dN/dy〉=0.048±0.001(stat.)±0.004(syst.) for $\mbox {$\mbox {, 0.047±0.002(stat.)±0.005(syst.) for $\mbox {$\mbox { and 0.0101±0.0020(stat.)±0.0009(syst.) for $\mbox {$\mbox {. The results are also compared with predictions for identified particle spectra from QCD-inspired models and provide a baseline for comparisons with both future pp measurements at higher energies and heavy-ion collisions.
  European Physical Journal C 04/2012; 71(3):1-24. · 3.63 Impact Factor
• Source

  Available from: Mikhail Ippolitov

  Article: Multiplicity distributions and charged-neutral fluctuations

  Tapan K Nayak, MM Aggarwal, A Agnihotri, Z Ahammed, ALS Angelis, V Antonenko, V Arefiev, V Astakhov, V Avdeitchikov, TC Awes, [......], GJV Nieuwenhuizen, A Vinogradov, YP Viyogi, A Vodopianov, S Vörös, MA Vos, B Wyslouch, K Yagi, Y Yokota, GR Young
  [show abstract] [hide abstract]
  ABSTRACT: Results from the multiplicity distributions of inclusive photons and charged particles, scaling of particle multiplicities, event-by-event multiplicity fluctuations, and charged-neutral fluctuations in 158A GeV Pb+Pb collisions are presented and discussed. A scaling of charged particle multiplicity as N part 1.07±0.05 and photos as N part 1.12±0.03 have been observed, indicating violation of naive wounded nucleon model. The analysis of localized charged-neutral fluctuation indicates a model-independent demonstration of non-statistical fluctuations in both charged particles and photons in limited azimuthal regions. However, no correlated charged-neutral fluctuations are observed.
  Pramana 04/2012; 57(2):285-300. · 0.57 Impact Factor
• Source

  Available from: Varlen Grabski

  Article: Charged-particle multiplicity measurement in proton–proton collisions at and 2.36 TeV with ALICE at LHC

  The ALICE Collaboration, K. Aamodt, N. Abel, U. Abeysekara, A. Abrahantes Quintana, A. Abramyan, D. Adamová, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, [......], X. Zhang, D. Zhou, S. Zhou, J. Zhu, A. Zichichi, A. Zinchenko, G. Zinovjev, Y. Zoccarato, V. Zycháček, M. Zynovyev
  [show abstract] [hide abstract]
  ABSTRACT: Charged-particle production was studied in proton–proton collisions collected at the LHC with the ALICE detector at centre-of-mass energies 0.9TeV and 2.36TeV in the pseudorapidity range |η|<1.4. In the central region (|η|<0.5), at 0.9TeV, we measure charged-particle pseudorapidity density dNch/dh = 3.02±0.01(stat.)+0.08-0.05(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=3.02\pm 0.01(\mathit{stat.})^{+0.08}_{-0.05}(\mathit{syst.}) for inelastic interactions, and dNch/dh = 3.58±0.01(stat.)+0.12-0.12(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=3.58\pm0.01(\mathit{stat.})^{+0.12}_{-0.12}(\mathit{syst.}) for non-single-diffractive interactions. At 2.36TeV, we find dNch/dh = 3.77±0.01(stat.)+0.25-0.12(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=3.77\pm0.01(\mathit{stat.})^{+0.25}_{-0.12}(\mathit{syst.}) for inelastic, and dNch/dh = 4.43±0.01(stat.)+0.17-0.12(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=4.43\pm0.01(\mathit{stat.})^{+0.17}_{-0.12}(\mathit{syst.}) for non-single-diffractive collisions. The relative increase in charged-particle multiplicity from the lower to higher energy is 24.7%±0.5%(stat.)+5.7-2.8%(syst.)24.7\%\pm0.5\%(\mathit{stat.})^{+5.7}_{-2.8}\%(\mathit{syst.}) for inelastic and 23.7%±0.5%(stat.)+4.6-1.1%(syst.)23.7\%\pm0.5\%(\mathit{stat.})^{+4.6}_{-1.1}\%(\mathit{syst.}) for non-single-diffractive interactions. This increase is consistent with that reported by the CMS collaboration for non-single-diffractive events and larger than that found by a number of commonly used models. The multiplicity distribution was measured in different pseudorapidity intervals and studied in terms of KNO variables at both energies. The results are compared to proton–antiproton data and to model predictions.
  European Physical Journal C 04/2012; 68(1):89-108. · 3.63 Impact Factor
• Article: Antideuteron and deuteron production in midcentral Pb+Pb collisions at 158A GeV

  T. Anticic, B. Baatar, D. Barna, J. Bartke, H. Beck, L. Betev, H. Białkowska, C. Blume, M. Bogusz, B. Boimska, [......], T. Susa, M. Szuba, M. Utvić, D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranić, Z. Włodarczyk, A. Wojtaszek-Szwarć
  [show abstract] [hide abstract]
  ABSTRACT: Production of deuterons and antideuterons was studied by the NA49 experiment in the 23.5% most central Pb+Pb collisions at the top CERN Super Proton Synchroton (SPS) energy of √sNN=17.3 GeV. Invariant yields for d̅ and d were measured as a function of centrality in the center-of-mass rapidity range −1.2<y<−0.6. Results for d̅ (d) together with previously published p̅ (p) measurements are discussed in the context of the coalescence model. The coalescence parameters B2 were deduced as a function of transverse momentum pt and collision centrality.
  Phys. Rev. C. 04/2012; 85(4).
• Article: Inclusive J/psi production in pp collisions at sqrt(s) = 2.76 TeV

  ALICE Collaboration, B. Abelev, J. Adam, D. Adamova, A. M. Adare, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, A. Agostinelli, S. Aguilar Salazar, [......], X. Zhang, D. Zhou, Y. Zhou, F. Zhou, X. Zhu, A. Zichichi, A. Zimmermann, G. Zinovjev, Y. Zoccarato, M. Zynovyev
  [show abstract] [hide abstract]
  ABSTRACT: The ALICE Collaboration has measured inclusive J/psi production in pp collisions at a center of mass energy sqrt(s)=2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges |y|<0.9 and 2.5<y<4 and have been obtained by measuring the electron and muon pair decay channels, respectively. The integrated luminosities for the two channels are L^e_int=1.1 nb^-1 and L^mu_int=19.9 nb^-1, and the corresponding signal statistics are N_J/psi^e+e-=59 +/- 14 and N_J/psi^mu+mu-=1364 +/- 53. We present dsigma_J/psi/dy for the two rapidity regions under study and, for the forward-y range, d^2sigma_J/psi/dydp_t in the transverse momentum domain 0<p_t<8 GeV/c. The results are compared with previously published results at sqrt(s)=7 TeV and with theoretical calculations.
  03/2012;
• Article: Suppression of high transverse momentum D mesons in central Pb--Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV

  ALICE Collaboration, B. Abelev, J. Adam, D. Adamová, A. M. Adare, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, A. Agostinelli, S. Aguilar Salazar, [......], D. Zhou, F. Zhou, Y. Zhou, X. Zhu, J. Zhu, A. Zichichi, A. Zimmermann, G. Zinovjev, Y. Zoccarato, M. Zynovyev
  [show abstract] [hide abstract]
  ABSTRACT: The production of the prompt charm mesons $D^0$, $D^+$, $D^{*+}$, and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at the LHC, at a centre-of-mass energy $\sqrt{s_{NN}}=2.76$ TeV per nucleon--nucleon collision. The $\pt$-differential production yields in the range $2<p_t<16$ GeV/c at central rapidity, $|y|<0.5$, were used to calculate the nuclear modification factor $R_{AA}$ with respect to a proton-proton reference obtained from the cross section measured at $\sqrt{s}=7$ TeV and scaled to $\sqrt{s}=2.76$ TeV. For the three meson species, $R_{AA}$ shows a suppression by a factor 3-4, for transverse momenta larger than 5 GeV/c in the 20% most central collisions. The suppression is reduced for peripheral collisions.
  03/2012;
• Article: Particle-yield modification in jetlike azimuthal dihadron correlations in Pb-Pb collisions at √s(NN)=2.76 TeV.

  K Aamodt, B Abelev, A Abrahantes Quintana, D Adamová, A M Adare, M M Aggarwal, G Aglieri Rinella, A G Agocs, A Agostinelli, S Aguilar Salazar, [......], X Zhang, D Zhou, F Zhou, Y Zhou, X Zhu, A Zichichi, A Zimmermann, G Zinovjev, Y Zoccarato, M Zynovyev
  [show abstract] [hide abstract]
  ABSTRACT: The yield of charged particles associated with high-p(t) trigger particles (8<p(t)<15 GeV/c) is measured with the ALICE detector in Pb-Pb collisions at √s(NN)=2.76 TeV relative to proton-proton collisions at the same energy. The conditional per-trigger yields are extracted from the narrow jetlike correlation peaks in azimuthal dihadron correlations. In the 5% most central collisions, we observe that the yield of associated charged particles with transverse momenta p(t)>3 GeV/c on the away side drops to about 60% of that observed in pp collisions, while on the near side a moderate enhancement of 20%-30% is found.
  Physical Review Letters 03/2012; 108(9):092301. · 7.37 Impact Factor
• Article: J/ψ polarization in pp collisions at √s=7 TeV.

  B Abelev, A Abrahantes Quintana, D Adamová, A M Adare, M M Aggarwal, G Aglieri Rinella, A G Agocs, A Agostinelli, S Aguilar Salazar, Z Ahammed, [......], X Zhang, F Zhou, D Zhou, Y Zhou, X Zhu, A Zichichi, A Zimmermann, G Zinovjev, Y Zoccarato, M Zynovyev
  [show abstract] [hide abstract]
  ABSTRACT: The ALICE Collaboration has studied J/ψ production in pp collisions at √s=7 TeV at the LHC through its muon pair decay. The polar and azimuthal angle distributions of the decay muons were measured, and results on the J/ψ polarization parameters λ(θ) and λ(φ) were obtained. The study was performed in the kinematic region 2.5<y<4, 2<p(t)<8 GeV/c, in the helicity and Collins-Soper reference frames. In both frames, the polarization parameters are compatible with zero, within uncertainties.
  Physical Review Letters 02/2012; 108(8):082001. · 7.37 Impact Factor