Particle-yield modification in jet-like azimuthal dihadron correlations in Pb-Pb collisions at sNN\sqrt{s_{NN}} = 2.76 TeV

The yield of charged particles associated with high-pT trigger particles (8 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

Suppression of high transverse momentum D mesons in central Pb--Pb collisions at sNN=2.76\sqrt{s_{NN}}=2.76 TeV

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 $p_t$-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

Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at s\sqrt{s}=0.9, 2.76 and 7 TeV

Measurements of the sphericity of primary charged particles in minimum bias proton--proton collisions at $\sqrt{s}$.0.9, 2.76 and 7 TeV with the ALICE detector at the LHC are presented. The observable is linearized to be collinear safe and is measured in the plane perpendicular to the beam direction using primary charged tracks with $p_{\rm T}\geq0.5$ GeV/c in $|\eta|\leq0.8$. The mean sphericity as a function of the charged particle multiplicity at mid-rapidity $N_{\rm ch}$ is reported for events with different $p_{\rm T}$ scales ("soft" and "hard") defined by the transverse momentum of the leading particle. In addition, the mean charged particle transverse momentum versus multiplicity is presented for the different event classes, and the sphericity distributions in bins of multiplicity are presented. The data are compared with calculations of standard Monte Carlo event generators. The transverse sphericity is found to grow with multiplicity at all collision energies, with a steeper rise at low $N_{\rm ch}$. whereas the event generators show the opposite tendency. The combined study of the sphericity and the mean $p_{\rm T}$ with multiplicity indicates that most of the tested event generators produce events with higher multiplicity by generating more back-to-back jets resulting in decreased sphericity (and isotropy). The PYTHIA6 generator with tune PERUGIA-2011 exhibits a noticeable improvement in describing the data, compared to the other tested generators

Suppression of high transverse momentum D mesons in central Pb--Pb collisions at sNN=2.76\sqrt{s_{NN}}=2.76 TeV

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 $p_t$-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.publishedVersio

Production of K∗(892)0K*(892)^0 and ϕ\phi(1020) in pp collisions at s\sqrt{s} =7 TeV

The production of K*(892)\).0\) and $\phi$.1020) in pp collisions at $\sqrt{s}$.7 TeV was measured by the ALICE experiment at the LHC. The yields and the transverse momentum spectra $d^2 N/dydp_T$ at midrapidity |y|<0.5 in the range 0 < $p_T$ < 6 GeV/c for K*(892)\).0\) and 0.4 < $p_T$ < 6 GeV/c for $\phi$.1020) are reported and compared to model predictions. Using the yield of pions, kaons, and Omega baryons measured previously by ALICE at $\sqrt{s}$.7 TeV, the ratios $K^*/K^-, \phi/K^*, \phi/K^-, \phi/\pi^-$. and $\Omega + anti-\Omega)/\phi$ are presented. The values of the $K^*/K^-, \phi/K^*$ and $\phi/K^-$ ratios are similar to those found at lower centre-of-mass energies. In contrast, the $\phi/\pi^-$ ratio, which has been observed to increase with energy, seems to saturate above 200 GeV. The $\Omega + anti-\Omega)/\phi$ ratio in the $p_T$ range 1-5 GeV/c is found to be in good agreement with the prediction of the HIJING/\).\bar{B}\) v2.0 model with a strong colour field.publishedVersio

Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at sNN\sqrt{s_{NN}}=2.76 TeV

The elliptic, $v_2$, triangular, $v_3$, and quadrangular, $v_4$, azimuthal anisotropic flow coefficients are measured for unidentified charged particles, pions, and (anti-)protons in Pb–Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV with the ALICE detector at the Large Hadron Collider. Results obtained with the event plane and four-particle cumulant methods are reported for the pseudo-rapidity range |$\eta$|8 GeV/c. The small $p_T$ dependence of the difference between elliptic flow results obtained from the event plane and four-particle cumulant methods suggests a common origin of flow fluctuations up to $p_T$ =8 GeV/c. The magnitude of the (anti-)proton elliptic and triangular flow is larger than that of pions out to at least $p_T$ =8 GeV/c indicating that the particle type dependence persists out to high $p_T$

Production of K∗(892)0K*(892)^0 and ϕ\phi(1020) in pp collisions at s\sqrt{s} =7 TeV

The production of K*(892)\).0\) and $\phi$.1020) in pp collisions at $\sqrt{s}$.7 TeV was measured by the ALICE experiment at the LHC. The yields and the transverse momentum spectra $d^2 N/dydp_T$ at midrapidity |y|<0.5 in the range 0 < $p_T$ < 6 GeV/c for K*(892)\).0\) and 0.4 < $p_T$ < 6 GeV/c for $\phi$.1020) are reported and compared to model predictions. Using the yield of pions, kaons, and Omega baryons measured previously by ALICE at $\sqrt{s}$.7 TeV, the ratios $K^*/K^-, \phi/K^*, \phi/K^-, \phi/\pi^-$. and $\Omega + anti-\Omega)/\phi$ are presented. The values of the $K^*/K^-, \phi/K^*$ and $\phi/K^-$ ratios are similar to those found at lower centre-of-mass energies. In contrast, the $\phi/\pi^-$ ratio, which has been observed to increase with energy, seems to saturate above 200 GeV. The $\Omega + anti-\Omega)/\phi$ ratio in the $p_T$ range 1-5 GeV/c is found to be in good agreement with the prediction of the HIJING/\).\bar{B}\) v2.0 model with a strong colour field

Suppression of high transverse momentum D mesons in central Pb-Pb collisions at root s(NN)=2.76 TeV

The production of the prompt charm mesons D0, D+, D*+, and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at the LHC, at a centre-of-mass energy sNN−−−√=2.76TeVsNN=2.76TeV per nucleon-nucleon collision. The pt-differential production yields in the range 2 < pt < 16 GeV/c at central rapidity, |y| < 0.5, were used to calculate the nuclear modification factor RAA with respect to a proton-proton reference obtained from the cross section measured at s√=7TeVs=7TeV and scaled to s√=2.76TeVs=2.76TeV . For the three meson species, RAA 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