Invariant yields of neutral pions at midrapidity in the transverse momentum range $0.6 < p_{T} < 12 GeV/c$ measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV are presented for six centrality classes. The pp reference spectrum was measured in the range $0.4 < p_{T} < 10 GeV/c$ at the same center-of-mass energy. The nuclear modification factor, $R_{\rm AA}$, shows a suppression of neutral pions in central Pb-Pb collisions by a factor of up to about $8-10$ for $5 \lesssim p_{T} \lesssim 7 GeV/c$. The presented measurements are compared with results at lower center-of-mass energies and with theoretical calculations.
Invariant differential yields of PI0 produced in inelastic pp collisions at center-of-mass energy 2.76 TeV.
Invariant differential cross section of PI0 produced in inelastic pp collisions at center-of-mass energy 2.76 TeV, the uncertainty of \sigma_{inel} of 3.9% is not included in the systematic error.
Invariant differential yields of PI0 produced in 0-5% central inelastic PbPb collisions at center-of-mass energy per nucleon 2.76 TeV.
The nuclear modification factor, $R_{\rm AA}$, of the prompt charmed mesons ${\rm D^0}$, ${\rm D^+}$ and ${\rm D^{*+}}$, and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at a centre-of-mass energy $\sqrt{s_{\rm NN}} = 2.76$ TeV in two transverse momentum intervals, $5<p_{\rm T}<8$ GeV/$c$ and $8<p_{\rm T}<16$ GeV/$c$, and in six collision centrality classes. The $R_{\rm AA}$ shows a maximum suppression of a factor of 5-6 in the 10% most central collisions. The suppression and its centrality dependence are compatible within uncertainties with those of charged pions. A comparison with the $R_{\rm AA}$ of non-prompt ${\rm J}/\psi$ from B meson decays, measured by the CMS Collaboration, hints at a larger suppression of D mesons in the most central collisions.
${\rm D^+}$ meson $R_{\rm AA}$ in $5 < p_{\rm T} < 8$ GeV/c.
${\rm D^+}$ meson $R_{\rm AA}$ in $8 < p_{\rm T} < 16$ GeV/c.
${\rm D^{*+}}$ meson $R_{\rm AA}$ in $5 < p_{\rm T} < 8$ GeV/c.
The ALICE experiment has measured the inclusive J/$\psi$ production in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}} } = 2.76$ TeV down to zero transverse momentum in the rapidity range $2.5 < y < 4$. A suppression of the inclusive J/$\psi$ yield in Pb-Pb is observed with respect to the one measured in pp collisions scaled by the number of binary nucleon-nucleon collisions. The nuclear modification factor, integrated over the 0-80% most central collisions, is $0.545 \pm 0.032 \rm{(stat.)} \pm 0.083 \rm{(syst.)}$ and does not exhibit a significant dependence on the collision centrality. These features appear significantly different from measurements at lower collision energies. Models including J/$\psi$ production from charm quarks in a deconfined partonic phase can describe our data.
Jpsi Nuclear Modification Factor (Raa) measured in Pb-Pb collisions at sqrt(sNN) = 2.76 TeV in 2.5 < y < 4 and pt > 0 GeV/c, as a function of - the average number of participating nucleons (<Npart>), - the average number of participating nucleons (<Npart,w>) weigthed by the average number of binary collisions, - the mid-rapidity charged-particle density measured at pseudo-rapidity eta = 0 dNch,w/deta|eta=0 weigthed by the average number of binary collisions.
Centrality integrated (0%-80%) inclusive Jpsi Nuclear Modification Factor (Raa) measured in Pb-Pb collisions at sqrt(sNN) = 2.76 TeV as a function of rapidity for two transverse momentum ranges.
The ALICE Collaboration has measured the inclusive production of muons from heavy flavour decays at forward rapidity, 2.5 < y < 4, in pp and Pb-Pb collisions at $\sqrt {s_{NN}}$ = 2.76 TeV. The $p_{\rm T}$-differential inclusive cross section of muons from heavy flavour decays in pp collisions is compared to perturbative QCD calculations. The nuclear modification factor is studied as a function of pt and collision centrality. A weak suppression is measured in peripheral collisions. In the most central collisions, a suppression of a factor of about 3-4 is observed in 6 < $p_{\rm T}$ < 10 GeV/$c$. The suppression shows no significant $p_{\rm T}$ dependence.
Transverse momentum differential inclusive cross section of muons from heavy-flavour decays in the rapidity range 2.5-4.
RAA of muons from heavy-flavour decays in the rapidity range 2.5-4 as a function of PT in the 0-10% and 40-80% centrality classes. The second (sys) error is the separate normalization error for each class.
RAA of muons from heavy-flavour decays as a function of the mean number of participating nucleons, NPART, in the rapidity range 2.5-4.0 and PT 6-10 GeV. The first (sys) error is the correlated systematic error and the second is the uncorrelated systematic error.
The inclusive transverse momentum ($p_{\rm T}$) distributions of primary charged particles are measured in the pseudo-rapidity range $|\eta|<0.8$ as a function of event centrality in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}=2.76$ TeV with ALICE at the LHC. The data are presented in the $p_{\rm T}$ range $0.15<p_{\rm T}<50$ GeV/$c$ for nine centrality intervals from 70-80% to 0-5%. The Pb-Pb spectra are presented in terms of the nuclear modification factor $R_{\rm{AA}}$ using a pp reference spectrum measured at the same collision energy. We observe that the suppression of high-$p_{\rm T}$ particles strongly depends on event centrality. In central collisions (0-5%) the yield is most suppressed with $R_{\rm{AA}}\approx0.13$ at $p_{\rm T}=6$-7 GeV/$c$. Above $p_{\rm T}=7$ GeV/$c$, there is a significant rise in the nuclear modification factor, which reaches $R_{\rm{AA}} \approx0.4$ for $p_{\rm T}>30$ GeV/$c$. In peripheral collisions (70-80%), the suppression is weaker with $R_{\rm{AA}} \approx 0.7$ almost independently of $p_{\rm T}$. The measured nuclear modification factors are compared to other measurements and model calculations.
Normalized differential primary charged particle yield in the centrality interval 0-5%.
Normalized differential primary charged particle yield in the centrality interval 5-10%.
Normalized differential primary charged particle yield in the centrality interval 10-20%.
Inclusive transverse momentum spectra of primary charged particles in Pb-Pb collisions at $\sqrt{s_{_{\rm NN}}}$ = 2.76 TeV have been measured by the ALICE Collaboration at the LHC. The data are presented for central and peripheral collisions, corresponding to 0-5% and 70-80% of the hadronic Pb-Pb cross section. The measured charged particle spectra in $|\eta|<0.8$ and $0.3 < p_T < 20$ GeV/$c$ are compared to the expectation in pp collisions at the same $\sqrt{s_{\rm NN}}$, scaled by the number of underlying nucleon-nucleon collisions. The comparison is expressed in terms of the nuclear modification factor $R_{\rm AA}$. The result indicates only weak medium effects ($R_{\rm AA} \approx $ 0.7) in peripheral collisions. In central collisions, $R_{\rm AA}$ reaches a minimum of about 0.14 at $p_{\rm T}=6$-7GeV/$c$ and increases significantly at larger $p_{\rm T}$. The measured suppression of high-$p_{\rm T}$ particles is stronger than that observed at lower collision energies, indicating that a very dense medium is formed in central Pb-Pb collisions at the LHC.
PT distributions of primary charged particles at mid-rapidity in central and peripheral PB-PB collisions.
PT distributions of primary charged particles at mid-rapidity in central and peripheral PB-PB collisions estimated from scaled PP data as described in the text of the paper.
Measurments of RAA, the nuclear modification factor (rate of PB-PB to P P cross section) in the central region.
The production of the prompt charmed mesons $D^0$, $D^+$ and $D^{*+}$ relative to the reaction plane was measured in Pb-Pb collisions at a centre-of-mass energy per nucleon-nucleon collision of $\sqrt{s_{\rm NN}} = 2.76$ TeV with the ALICE detector at the LHC. D mesons were reconstructed via their hadronic decays at central rapidity in the transverse momentum ($p_{\rm T}$) interval of 2-16 GeV/$c$. The azimuthal anisotropy is quantified in terms of the second coefficient $v_2$ in a Fourier expansion of the D meson azimuthal distribution, and in terms of the nuclear modification factor $R_{\rm AA}$, measured in the direction of the reaction plane and orthogonal to it. The $v_2$ coefficient was measured with three different methods and in three centrality classes in the interval 0-50%. A positive $v_2$ is observed in mid-central collisions (30-50% centrality class), with an mean value of $0.204_{-0.036}^{+0.099}$ (tot.unc.) in the interval $2 < p_{\rm T} < 6$ GeV/$c$, which decreases towards more central collisions (10-30% and 0-10% classes). The positive $v_2$ is also reflected in the nuclear modification factor, which shows a stronger suppression in the direction orthogonal to the reaction plane for mid-central collisions. The measurements are compared to theoretical calculations of charm quark transport and energy loss in high-density strongly-interacting matter at high temperature. The models that include substantial elastic interactions with an expanding medium provide a good description of the observed anisotropy. However, they are challenged to simultaneously describe the strong suppression of high-$p_{\rm T}$ yield of D mesons in central collisions and their azimuthal anisotropy in non-central collisions.
Prompt D^0 meson v2 as a function of pT for centrality 0-10%. The first systematic uncertainty is from the data and the second from the B feed-down.
Prompt D^0 meson v2 as a function of pT for centrality 10-30%. The first systematic uncertainty is from the data and the second from the B feed-down.
Prompt D^0 meson v2 as a function of pT for centrality 30-50%. The first systematic uncertainty is from the data and the second from the B feed-down.
The inclusive $J/\psi$ nuclear modification factor $R_{\rm AA}$ in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$=2.76 TeV has been measured by ALICE as a function of centrality in the e$^+$e$^-$ decay channel at mid-rapidity $|y|<0.8$ and as a function of centrality, transverse momentum and rapidity in the $\mu^{+}\mu^{-}$ decay channel at forward-rapidity $2.5<y<4$.The $J/\psi$ yields measured in Pb-Pb are suppressed compared to those in pp collisions scaled by the number of binary collisions. The $R_{\rm AA}$ integrated over a centrality range corresponding to 90% of the inelastic Pb-Pb cross section is $0.72\pm0.06$ (stat.) $\pm0.10$ (syst.) at mid-rapidity and $0.57 \pm 0.01$ (stat.) $\pm0.09$ (syst.) at forward-rapidity. At low transverse momentum, significantly larger values of $R_{\rm AA}$ are measured at forward-rapidity compared to measurements at lower energy. These features suggest that a contribution to the $J/\psi$ yield originates from charm quarks (re)combination in the deconfined partonic medium.
Inclusive Jpsi Nuclear Modification Factor (Raa) measured in Lead-Lead collisions at sqrt(sNN) = 2.76 TeV in 2.5 < y < 4 and 0 < pt < 8 GeV/c, as a function of the average number of participating nucleons (<Npart>). Data have been collected in 2011 and the integrated luminosity is ~ 70 inverse microbarn.
Inclusive Jpsi Nuclear Modification Factor (Raa) measured in Lead-Lead collisions at sqrt(sNN) = 2.76 TeV in |y| < 0.8 and pt > 0 GeV/c, as a function of the average number of participating nucleons (<Npart>). Data have been collected in 2010 and 2011 and the integrated luminosity is ~ 28 inverse microbarn.
Inclusive Jpsi Nuclear Modification Factor (Raa) measured in Lead-Lead collisions at sqrt(sNN) = 2.76 TeV as a function of transverse momentum in 2.5 < y < 4 for the centrality range 0%-90%. Data have been collected in 2011 and the integrated luminosity is ~ 70 inverse microbarn.
We report on the production of inclusive $\Upsilon$(1S) and $\Upsilon$(2S) in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV at the LHC. The measurement is performed with the ALICE detector at backward ($-4.46< y_{{\rm cms}}<-2.96$) and forward ($2.03< y_{{\rm cms}}<3.53$) rapidity down to zero transverse momentum. The production cross sections of the $\Upsilon$(1S) and $\Upsilon$(2S) are presented, as well as the nuclear modification factor and the ratio of the forward to backward yields of $\Upsilon$(1S). A suppression of the inclusive $\Upsilon$(1S) yield in p-Pb collisions with respect to the yield from pp collisions scaled by the number of binary nucleon-nucleon collisions is observed at forward rapidity but not at backward rapidity. The results are compared to theoretical model calculations including nuclear shadowing or partonic energy loss effects.
Inclusive UPSI(1S) production cross section as a function of rapidity in p-Pb collisions at sqrt(s_NN) = 5.02 TeV. The data was collected in 2013 with two beam configurations, p-Pb and Pb-p with integrated luminosities of 5.0 nb-1 and 5.8 nb-1, respectively.
Inclusive UPSI(1S) production cross section as a function of rapidity in p-Pb collisions at sqrt(s_NN) = 5.02 TeV. The data was collected in 2013 with two beam configurations, p-Pb and Pb-p with integrated luminosities of 5.0 nb-1 and 5.8 nb-1, respectively.
Inclusive UPSI(2S) production cross section as a function of rapidity in p-Pb collisions at sqrt(s_NN) = 5.02 TeV. The data was collected in 2013 with two beam configurations, p-Pb and Pb-p with integrated luminosities of 5.0 nb-1 and 5.8 nb-1, respectively.
The production of J/$\psi$ and $\psi(2S)$ was measured with the ALICE detector in Pb-Pb collisions at the LHC. The measurement was performed at forward rapidity ($2.5 < y < 4 $) down to zero transverse momentum ($p_{\rm T}$) in the dimuon decay channel. Inclusive J/$\psi$ yields were extracted in different centrality classes and the centrality dependence of the average $p_{\rm T}$ is presented. The J/$\psi$ suppression, quantified with the nuclear modification factor ($R_{\rm AA}$), was studied as a function of centrality, transverse momentum and rapidity. Comparisons with similar measurements at lower collision energy and theoretical models indicate that the J/$\psi$ production is the result of an interplay between color screening and recombination mechanisms in a deconfined partonic medium, or at its hadronization. Results on the $\psi(2S)$ suppression are provided via the ratio of $\psi(2S)$ over J/$\psi$ measured in pp and Pb-Pb collisions.
Values of $\langle p_{\rm T}\rangle$ and $\langle p^2_{\rm T}\rangle$ of inclusive J/$\psi$ measured in $0<p_{\rm T}<8$ GeV/$c$ and $2.5<y<4$. Statistical and systematic uncertainties are also reported.
Inclusive J/$\psi$ yields in $p_{\rm T}$ intervals for the 0-20%, 20-40% and 40-90% most central Pb-Pb collisions. The rapidity range is $2.5<y<4$. Statistical and systematic uncertainties are also reported. A global systematic uncertainty of 4% affects all the values. A 2%, 1% and 2% systematic uncertainty, independent of $p_{\rm T}$, affects the centrality classes 0-20%, 20-40% and 40-90%, respectively.
Inclusive J/$\psi$ $R_{\rm AA}$ and Pb-Pb yields as a function of centrality, $p_{\rm T}<8$ GeV/$c$ and $2.5<y<4.0$. Statistical and systematic uncertainties are also reported. A global systematic uncertainty of 15% (12%) affects all the $R_{\rm AA}$ (yields) values.