We present measurements of the azimuthal dependence of charged jet production in central and semi-central $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as $v_{2}^{\mathrm{ch~jet}}$. Jet finding is performed employing the anti-$k_{\mathrm{T}}$ algorithm with a resolution parameter $R$ = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero $v_{2}^{\mathrm{ch~jet}}$ is observed in semi-central collisions (30-50\% centrality) for 20 $<$ $p_{\mathrm{T}}^{\rm ch~jet}$ $<$ 90 ${\mathrm{GeV}\kern-0.05em/\kern-0.02em c}$. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the $v_2$ of single charged particles at high $p_{\mathrm{T}}$. Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions.
Second-order harmonic coefficient $v_2^{ch~jet}$ as function a of $p_{T}^{ch~jet}$ for 0--5% collision centrality.
Second-order harmonic coefficient $v_2^{ch~jet}$ as function a of $p_{T}^{ch~jet}$ for 30--50% collision centrality.
Two-particle angular correlations between trigger particles in the forward pseudorapidity range ($2.5 < |\eta| < 4.0$) and associated particles in the central range ($|\eta| < 1.0$) are measured with the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV. The trigger particles are reconstructed using the muon spectrometer, and the associated particles by the central barrel tracking detectors. In high-multiplicity events, the double-ridge structure, previously discovered in two-particle angular correlations at midrapidity, is found to persist to the pseudorapidity ranges studied in this Letter. The second-order Fourier coefficients for muons in high-multiplicity events are extracted after jet-like correlations from low-multiplicity events have been subtracted. The coefficients are found to have a similar transverse momentum ($p_{\rm T}$) dependence in p-going (p-Pb) and Pb-going (Pb-p) configurations, with the Pb-going coefficients larger by about $16\pm6$%, rather independent of $p_{\rm T}$ within the uncertainties of the measurement. The data are compared with calculations using the AMPT model, which predicts a different $p_{\rm T}$ and $\eta$ dependence than observed in the data. The results are sensitive to the parent particle $v_2$ and composition of reconstructed muon tracks, where the contribution from heavy flavour decays are expected to dominate at $p_{\rm T}>2$ GeV/$c$.
$v_{2}^{\mu}\{\rm{2PC,sub}\}$ extracted from muon-track correlations.
$v_{2}^{\mu}\{\rm{2PC,sub}\}$ coefficients from muon-tracklet correlations in p-going direction.
$v_{2}^{\mu}\{\rm{2PC,sub}\}$ coefficients from muon-tracklet correlations in Pb-going direction.
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.
Azimuthally anisotropic distributions of D$^0$, D$^+$ and D$^{*+}$ mesons were studied in the central rapidity region ($|y|<0.8$) in Pb-Pb collisions at a centre-of-mass energy $\sqrt{s_{\rm NN}} = 2.76$ TeV per nucleon-nucleon collision, with the ALICE detector at the LHC. The second Fourier coefficient $v_2$ (commonly denoted elliptic flow) was measured in the centrality class 30-50% as a function of the D meson transverse momentum $p_{\rm T}$, in the range 2-16 GeV/$c$. The measured $v_2$ of D mesons is comparable in magnitude to that of light-flavour hadrons. It is positive in the range $2 < p_{\rm T} < 6$ GeV/$c$ with $5.7\sigma$ significance, based on the combination of statistical and systematic uncertainties.
v2 vs. pt for D0. The first systematic (sys) error is that from the data analysis and the second is from the B feed-down subtraction, as explained in the paper.
v2 vs. pt for D+. The first systematic (sys) error is that from the data analysis and the second is from the B feed-down subtraction, as explained in the paper.
v2 vs. pt for D*+. The first systematic (sys) error is that from the data analysis and the second is from the B feed-down subtraction, as explained in the paper.
We report on the first measurement of inclusive J/$\psi$ elliptic flow, $v_2$, in heavy-ion collisions at the LHC. The measurement is performed with the ALICE detector in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV in the rapidity range $2.5 < y < 4.0$. The dependence of the J/$\psi$ $v_2$ on the collision centrality and on the J/$\psi$ transverse momentum is studied in the range $0 < p_{\rm T} < 10$ GeV/$c$. For semi-central Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV, an indication of non-zero $v_2$ is observed with a maximum value of $v_2 = 0.116 \pm 0.046 {\rm (stat.)} \pm 0.029 {\rm (syst.)}$ for J/$\psi$ in the transverse momentum range $2 < p_{\rm T} < 4$ GeV/$c$. The elliptic flow measurement complements the previously reported ALICE results on the inclusive J/$\psi$ nuclear modification factor and favors the scenario of a significant fraction of J/$\psi$ production from charm quarks in a deconfined partonic phase.
Measurements of V2 for inclusive J/PSI production for semi-central (20%-40%) collisions as a function of transverse momentum.
Measurements of V2 for inclusive J/PSI production in the transverse momentum range 1.5-10 GeV/c as a function of the number of participating nucleons.
Measurements of the uncorrected mean transverse momentum for inclusive J/PSI production in the transverse momentum range 1.5-10 GeV/c as a function of the number of participating nucleons.
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