J. Milošević

Angular correlations between charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV for transverse momentum ranges within 0.5 < $p_{\rm T}^{\rm assoc}$ < $p_{\rm T}^{\rm trig}$ < 4 GeV/$c$. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield obtained in low-multiplicity events is subtracted from the one in high-multiplicity events. The excess on the near-side is qualitatively similar to that recently reported by the CMS collaboration, while the excess on the away-side is reported for the first time. The two-ridge structure projected onto azimuthal angle is quantified with the second and third Fourier coefficients as well as by near-side and away-side yields and widths. The yields on the near side and on the away side are equal within the uncertainties for all studied event multiplicity and $p_{\rm T}$ bins, and the widths show no significant evolution with event multiplicity or $p_{\rm T}$. These findings suggest that the near-side ridge is accompanied by an essentially identical away-side ridge.

In this Letter, comprehensive results on π±, K±, KS0, p(p¯) and Λ(Λ¯) production at mid-rapidity (0<yCMS<0.5) in p–Pb collisions at sNN=5.02TeV, measured by the ALICE detector at the LHC, are reported. The transverse momentum distributions exhibit a hardening as a function of event multiplicity, which is stronger for heavier particles. This behavior is similar to what has been observed in pp and Pb–Pb collisions at the LHC. The measured pT distributions are compared to d–Au, Au–Au and Pb–Pb results at lower energy and with predictions based on QCD-inspired and hydrodynamic models.

Measurements of cross sections of inelastic and diffractive processes in proton–proton collisions at LHC energies were carried out with the ALICE detector. The fractions of diffractive processes in inelastic collisions were determined from a study of gaps in charged particle pseudorapidity distributions: for single diffraction (diffractive mass M X <200 GeV/c 2) $\sigma_{\mathrm{SD}}/\sigma_{\mathrm {INEL}} = 0.21 \pm 0.03, 0.20^{+0.07}_{-0.08}$ , and $0.20^{+0.04}_{-0.07}$ , respectively at centre-of-mass energies $\sqrt{s} = 0.9, 2.76\mbox{, and }7~\mbox{TeV}$ ; for double diffraction (for a pseudorapidity gap Δη>3) σ DD/σ INEL=0.11±0.03,0.12±0.05, and $0.12^{+0.05}_{-0.04}$ , respectively at $\sqrt{s} = 0.9, 2.76\mbox{, and }7~\mbox{TeV}$ . To measure the inelastic cross section, beam properties were determined with van der Meer scans, and, using a simulation of diffraction adjusted to data, the following values were obtained: $\sigma_{\mathrm{INEL}} = 62.8^{+2.4}_{-4.0} (\mathrm{model}) \pm1.2 (\mathrm{lumi})$ mb at $\sqrt{s} = 2.76\ \mbox{TeV}$ and $73.2^{+2.0}_{-4.6} (\mathrm{model}) \pm2.6 (\mathrm{lumi})~\mbox{mb}$ at $\sqrt{s} = 7\ \mbox{TeV}$ . The single- and double-diffractive cross sections were calculated combining relative rates of diffraction with inelastic cross sections. The results are compared to previous measurements at proton–antiproton and proton–proton colliders at lower energies, to measurements by other experiments at the LHC, and to theoretical models.

In this Letter we report the first results on $\pi^\pm$, K$^\pm$, p and $\mathrm {p\overline{p}}$ production at mid-rapidity ($\left|y\right|<0.5$) in central Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV, measured by the ALICE experiment at the LHC. The $p_{\rm T}$ distributions and yields are compared to previous results at $\sqrt{s_{\rm NN}}$ = 200 GeV and expectations from hydrodynamic and thermal models. The spectral shapes indicate a strong increase of the radial flow velocity with $\sqrt{s_{\rm NN}}$, which in hydrodynamic models is expected as a consequence of the increasing particle density. While the ${\rm K}/\pi$ ratio is in line with predictions from the thermal model, the ${\rm p}/\pi$ ratio is found to be lower by a factor of about 1.5. This deviation from thermal model expectations is still to be understood.

The production of (anti-)deuteron and (anti-)$^{3}\text{He}$ nuclei in Pb-Pb collisions at $\sqrt{{s}_{\mathrm{NN}}}=2.76$ TeV has been studied using the ALICE detector at the LHC. The spectra exhibit a significant hardening with increasing centrality. Combined blast-wave fits of several particles support the interpretation that this behavior is caused by an increase of radial flow. The integrated particle yields are discussed in the context of coalescence and thermal-statistical model expectations. The particle ratios, $^{3}\text{He}/d$ and $^{3}\text{He}/p$, in Pb-Pb collisions are found to be in agreement with a common chemical freeze-out temperature of ${T}_{\mathrm{chem}}\ensuremath{\approx}156$ MeV. These ratios do not vary with centrality which is in agreement with the thermal-statistical model. In a coalescence approach, it excludes models in which nucleus production is proportional to the particle multiplicity and favors those in which it is proportional to the particle density instead. In addition, the observation of 31 anti-tritons in Pb-Pb collisions is reported. For comparison, the deuteron spectrum in $pp$ collisions at $\sqrt{s}=7$ TeV is also presented. While the $p/\ensuremath{\pi}$ ratio is similar in $pp$ and Pb-Pb collisions, the $d/p$ ratio in $pp$ collisions is found to be lower by a factor of 2.2 than in Pb-Pb collisions.

Azimuthally anisotropic distributions of D0, D+, and D*+ mesons were studied in the central rapidity region (|y|<0.8) in Pb-Pb collisions at a center-of-mass energy sqrt[sNN]=2.76 TeV per nucleon-nucleon collision, with the ALICE detector at the LHC. The second Fourier coefficient v2 (commonly denoted elliptic flow) was measured in the centrality class 30%-50% as a function of the D meson transverse momentum pT, in the range 2-16 GeV/c. The measured v2 of D mesons is comparable in magnitude to that of light-flavor hadrons. It is positive in the range 2<pT<6 GeV/c with 5.7σ significance, based on the combination of statistical and systematic uncertainties.

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.

The inclusive J/$\psi$ production has been studied in Pn-Pb and pp collisions at the centre-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}}=5.02$ TeV, using the ALICE detector at the CERN LHC. The J/$\psi$ meson is reconstructed, in the centre-of-mass rapidity interval $2.5<y<4$ and in the transverse-momentum range $p_{\rm T}<12$ GeV/$c$, via its decay to a muon pair. In this Letter, we present results on the inclusive J/$\psi$ cross section in pp collisions at $\sqrt{s}=5.02$ TeV and on the nuclear modification factor $R_{\rm AA}$. The latter is presented as a function of the centrality of the collision and, for central collisions, as a function of the transverse momentum $p_{\rm T}$ of the J/$\psi$. The measured $R_{\rm AA}$ values indicate a suppression of the J/$\psi$ in nuclear collisions and are then compared to our previous results obtained in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV. The ratio of the $R_{\rm AA}$ values at the two energies is also computed and compared to calculations of statistical and dynamical models. The numerical value of the ratio for central events (0-10\% centrality) is $1.17 \pm 0.04 {\rm{(stat)}}\pm 0.20 {\rm{(syst)}}$. In central events, as a function of $p_{\rm T}$, a slight increase of $R_{\rm AA}$ with collision energy is visible in the region $2<p_{\rm T}<6$ GeV/$c$. Theoretical calculations provide a good description of the measurements, within uncertainties.

Differential cross sections of charged particles in inelastic pp collisions as a function of $p_{\rm T}$ have been measured at $\sqrt{s}=$ 0.9, 2.76 and 7 TeV at the LHC. The $p_{\rm T}$ spectra are compared to NLO-pQCD calculations. Though the differential cross section for an individual $\sqrt{s}$ cannot be described by NLO-pQCD, the relative increase of cross section with $\sqrt{s}$ is in agreement with NLO-pQCD. Based on these measurements and observations, procedures are discussed to construct pp reference spectra at $\sqrt{s} =$ 2.76 and 5.02 TeV up to $p_{\rm T}$ = 50 GeV/$c$ as required for the calculation of the nuclear modification factor in nucleus-nucleus and proton-nucleus collisions.

The production of K∗(892)0 and ϕ(1020) mesons in proton-proton (pp) and lead-lead (Pb-Pb) collisions at √sNN=2.76TeV has been analyzed using a high luminosity data sample accumulated in 2011 with the ALICE detector at the Large Hadron Collider (LHC). Transverse momentum (pT) spectra have been measured for K∗(892)0 and ϕ(1020) mesons via their hadronic decay channels for pT up to 20GeV/c. The measurements in pp collisions have been compared to model calculations and used to determine the nuclear modification factor and particle ratios. The K∗(892)0/K ratio exhibits significant reduction from pp to central Pb-Pb collisions, consistent with the suppression of the K∗(892)0 yield at low pT due to rescattering of its decay products in the hadronic phase. In central Pb-Pb collisions the pT dependent ϕ(1020)/π and K∗(892)0/π ratios show an enhancement over pp collisions for pT≈3GeV/c, consistent with previous observations of strong radial flow. At high pT, particle ratios in Pb-Pb collisions are similar to those measured in pp collisions. In central Pb-Pb collisions, the production of K∗(892)0 and ϕ(1020) mesons is suppressed for pT>8GeV/c. This suppression is similar to that of charged pions, kaons, and protons, indicating that the suppression does not depend on particle mass or flavor in the light quark sector.3 MoreReceived 17 February 2017DOI:https://doi.org/10.1103/PhysRevC.95.064606Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.©2017 CERN, for the ALICE CollaborationPhysics Subject Headings (PhySH)Research AreasParticle & resonance productionRelativistic heavy-ion collisionsNuclear Physics

We report on first measurements of low-mass electron-positron pairs in Pb-Au collisions at the CERN SPS beam energy of 40 AGeV. The observed pair yield integrated over the range of invariant masses 0.2<m</=1 GeV/c(2) is enhanced over the expectation from neutral meson decays by a factor of 5.9+/-1.5(stat)+/-1.2(syst data)+/-1.8(syst meson decays), somewhat larger than previously observed at the higher energy of 158 AGeV. The results are discussed with reference to model calculations based on pi(+)pi(-)-->e(+)e(-) annihilation with a modified rho propagator. They may be linked to chiral symmetry restoration and support the notion that the in-medium modifications of the rho are more driven by baryon density than by temperature.

Measurements of event-by-event fluctuations of the mean transverse momentum in Pb-Au collisions at 40, 80, and 158 A GeV/c are presented. A significant excess of mean p_T fluctuations at mid-rapidity is observed over the expectation from statistically independent particle emission. The results are somewhat smaller than recent measurements at RHIC. A possible non-monotonic behaviour of the mean p_T fluctuations as function of collision energy, which may have indicated that the system has passed the critical point of the QCD phase diagram in the range of mu_B under investigation, has not been observed. The centrality dependence of mean p_T fluctuations in Pb-Au is consistent with an extrapolation from pp collisions assuming that the non-statistical fluctuations scale with multiplicity. The results are compared to calculations by the RQMD and UrQMD event generators.

The ALICE Collaboration has measured the inclusive production of muons from heavy-flavor decays at forward rapidity, 2.5<y<4, in pp and Pb-Pb collisions at sqrt[s(NN)]=2.76 TeV. The p(t)-differential inclusive cross section of muons from heavy-flavor decays in pp collisions is compared to perturbative QCD calculations. The nuclear modification factor is studied as a function of p(t) 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(t)<10 GeV/c. The suppression shows no significant p(t) dependence.

We present a measurement of e+e− pair production in central PbAu collisions at 158AGeV/c. As reported earlier, a significant excess of the e+e− pair yield over the expectation from hadron decays is observed. The improved mass resolution of the present data set, recorded with the upgraded CERES experiment at the CERN-SPS, allows for a comparison of the data with different theoretical approaches. The data clearly favor a substantial in-medium broadening of the ρ spectral function over a density-dependent shift of the ρ pole mass. The in-medium broadening model implies that baryon induced interactions are the key mechanism to the observed modifications of the ρ meson at SPS energy.

The ALICE collaboration at the CERN Large Hadron Collider reports the first measurement of the inclusive differential jet cross section at mid-rapidity in pp collisions at $\sqrt{s} = 2.76$ TeV, with integrated luminosity of 13.6 nb$^{-1}$. Jets are measured over the transverse momentum range 20 to 125 GeV/c and are corrected to the particle level. Calculations based on Next-to-Leading Order perturbative QCD are in good agreement with the measurements. The ratio of inclusive jet cross sections for jet radii $R = 0.2$ and $R = 0.4$ is reported, and is also well reproduced by a Next-to-Leading Order perturbative QCD calculation when hadronization effects are included.

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.

A bstract The ALICE experiment at the LHC has studied J/ ψ production at mid-rapidity in pp collisions at $ \sqrt{s}=7 $ TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L int = 5 . 6 nb −1 . The fraction of J/ ψ from the decay of long-lived beauty hadrons was determined for J/ ψ candidates with transverse momentum p t &gt; 1 . 3 GeV/ c and rapidity | y | &lt; 0 . 9. The cross section for prompt J/ ψ mesons, i.e. directly produced J/ ψ and prompt decays of heavier charmonium states such as the ψ (2S) and χ c resonances, is σ prompt J/ ψ ( p t &gt; 1 . 3 GeV /c, | y | &lt; 0 . 9) = 8 . 3 ± 0 . 8 (stat . ) ± 1 . 1 (syst . ) $ _{-1.4}^{+1.5 } $ (syst . pol . ) μ b. The cross section for the production of b-hadrons decaying to J/ ψ with p t &gt; 1 . 3 GeV/ c and | y | &lt; 0 . 9 is $ {\sigma_{{{J \left/ {{\psi \leftarrow {{\mathrm{h}}_{\mathrm{B}}}}} \right.}}}} $ ( p t &gt; 1.3 GeV/ c , | y | &lt; 0.9) = 1.46 ± 0.38 (stat.) $ _{-0.32}^{+0.26 } $ (syst.) μ b. The results are compared to QCD model predictions. The shape of the p t and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the $ \mathrm{b}\overline{\mathrm{b}} $ pair total cross section and d σ/ d y at mid-rapidity.

We report the measurement of a new observable of jet quenching in central Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}}=2.76 $$ TeV, based on the semi-inclusive rate of charged jets recoiling from a high transverse momentum (high-p T) charged hadron trigger. Jets are measured using collinear-safe jet reconstruction with infrared cutoff for jet constituents of 0.15 GeV, for jet resolution parameters R = 0.2, 0.4 and 0.5. Underlying event background is corrected at the event-ensemble level, without imposing bias on the jet population. Recoil jet spectra are reported in the range 20 < p T,jet ch < 100 GeV. Reference distributions for pp collisions at $$ \sqrt{s}=2.76 $$ TeV are calculated using Monte Carlo and NLO pQCD methods, which are validated by comparing with measurements in pp collisions at $$ \sqrt{s}=7 $$ TeV. The recoil jet yield in central Pb-Pb collisions is found to be suppressed relative to that in pp collisions. No significant medium-induced broadening of the intra-jet energy profile is observed within 0.5 radians relative to the recoil jet axis. The angular distribution of the recoil jet yield relative to the trigger axis is found to be similar in central Pb-Pb and pp collisions, with no significant medium-induced acoplanarity observed. Large-angle jet deflection, which may provide a direct probe of the nature of the quasi-particles in hot QCD matter, is explored.

Prompt D meson and non-prompt J/$\psi$ yields are studied as a function of the multiplicity of charged particles produced in inelastic proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=7$ TeV. The results are reported as a ratio between yields in a given multiplicity interval normalised to the multiplicity-integrated ones (relative yields). They are shown as a function of the multiplicity of charged particles normalised to the average value for inelastic collisions (relative charged-particle multiplicity). D$^0$, D$^+$ and D$^{*+}$ mesons are measured in five $p_{\rm T}$ intervals from 1 to 20 GeV/$c$ and for $|y|<0.5$ via their hadronic decays. The D-meson relative yield is found to increase with increasing charged-particle multiplicity. For events with multiplicity six times higher than the average multiplicity of inelastic collisions, a yield enhancement of a factor about 15 relative to the multiplicity-integrated yield in inelastic collisions is observed. The yield enhancement is independent of transverse momentum within the uncertainties of the measurement. The D$^0$-meson relative yield is also measured as a function of the relative multiplicity at forward pseudorapidity. The non-prompt J/$\psi$, i.e. the B hadron, contribution to the inclusive J/$\psi$ production is measured in the di-electron decay channel at central rapidity. It is evaluated for $p_{\rm T}>1.3$ GeV/$c$ and $|y|<0.9$, and extrapolated to $p_{\rm T}>0$. The fraction of non-prompt J/$\psi$ in the inclusive J/$\psi$ yields shows no dependence on the charged-particle multiplicity at central rapidity. Charm and beauty hadron relative yields exhibit a similar increase with increasing charged-particle multiplicity. The measurements are compared to PYTHIA 8, EPOS 3 and percolation calculations.

For the first time the ALICE Collaboration has measured $D$-meson production down to zero transverse momentum at midrapidity in proton-proton collisions at the CERN Large Hadron Collider. This provides an important constraint on perturbative QCD calculations and the low-$x$ parton distribution functions. It will have implications for cosmic-ray and neutrino astrophysics as well as for modeling high-energy heavy-ion collisions.

A bstract The effect of event background fluctuations on charged particle jet reconstruction in Pb-Pb collisions at $ \sqrt {{{s_{\text{NN}}}}} = {2}{.76}\,{\text{TeV}} $ has been measured with the ALICE experiment. The main sources of non-statistical fluctuations are characterized based purely on experimental data with an unbiased method, as well as by using single high p t particles and simulated jets embedded into real Pb-Pb events and reconstructed with the anti- k t jet finder. The influence of a low transverse momentum cut-off on particles used in the jet reconstruction is quantified by varying the minimum track p t between 0.15 GeV/ c and 2 GeV/ c . For embedded jets reconstructed from charged particles with p t &gt; 0 . 15 GeV/ c , the uncertainty in the reconstructed jet transverse momentum due to the heavy-ion background is measured to be 11.3 GeV/ c (standard deviation) for the 10% most central Pb-Pb collisions, slightly larger than the value of 11.0 GeV/ c measured using the unbiased method. For a higher particle transverse momentum threshold of 2 GeV/ c , which will generate a stronger bias towards hard fragmentation in the jet finding process, the standard deviation of the fluctuations in the reconstructed jet transverse momentum is reduced to 4.8-5.0 GeV/ c for the 10% most central events. A non-Gaussian tail of the momentum uncertainty is observed and its impact on the reconstructed jet spectrum is evaluated for varying particle momentum thresholds, by folding the measured fluctuations with steeply falling spectra.

The directed flow of charged particles at midrapidity is measured in Pb-Pb collisions at √(s(NN))=2.76 TeV relative to the collision symmetry plane defined by the spectator nucleons. A negative slope of the rapidity-odd directed flow component with approximately 3 times smaller magnitude than found at the highest RHIC energy is observed. This suggests a smaller longitudinal tilt of the initial system and disfavors the strong fireball rotation predicted for the LHC energies. The rapidity-even directed flow component is measured for the first time with spectators and found to be independent of pseudorapidity with a sign change at transverse momenta p(T) between 1.2 and 1.7 GeV/c. Combined with the observation of a vanishing rapidity-even p(T) shift along the spectator deflection this is strong evidence for dipolelike initial density fluctuations in the overlap zone of the nuclei. Similar trends in the rapidity-even directed flow and the estimate from two-particle correlations at midrapidity, which is larger by about a factor of 40, indicate a weak correlation between fluctuating participant and spectator symmetry planes. These observations open new possibilities for investigation of the initial conditions in heavy-ion collisions with spectator nucleons.

The production cross section of electrons from semileptonic decays of beauty hadrons was measured at mid-rapidity (|y| &lt; 0.8) in the transverse momentum range $1 &lt; p_{\rm T} &lt; 8$ Gev/$c$ with the ALICE experiment at the CERN LHC in pp collisions at a center of mass energy $\sqrt{s} = 7$ TeV using an integrated luminosity of 2.2 nb$^{-1}$. Electrons from beauty hadron decays were selected based on the displacement of the decay vertex from the collision vertex. A perturbative QCD calculation agrees with the measurement within uncertainties. The data were extrapolated to the full phase space to determine the total cross section for the production of beauty quark-antiquark pairs.

Correlations induced by quantum statistics are sensitive to the spatiotemporal extent as well as dynamics of particle-emitting sources in heavy-ion collisions. In addition, such correlations can be used to search for the presence of a coherent component of pion production. Two- and three-pion correlations of same and mixed charge are measured at low relative momentum to estimate the coherent fraction of charged pions in Pb-Pb collisions at sNN=2.76 TeV at the CERN Large Hadron Collider with ALICE. The genuine three-pion quantum statistics correlation is found to be suppressed relative to the two-pion correlation based on the assumption of fully chaotic pion emission. The suppression is observed to decrease with triplet momentum. The observed suppression at low triplet momentum may correspond to a coherent fraction in charged-pion emission of 23%±8%.6 MoreReceived 1 November 2013Revised 29 January 2014DOI:https://doi.org/10.1103/PhysRevC.89.024911This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.©2014 CERN, for the Alice Collaboration

In high-energy heavy-ion collisions, the correlations between the emitted particles can be used as a probe to gain insight into the charge creation mechanisms. In this Letter, we report the first results of such studies using the electric charge balance function in the relative pseudorapidity ($\Delta\eta$) and azimuthal angle ($\Delta\varphi$) in Pb--Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV with the ALICE detector at the Large Hadron Collider. The width of the balance function decreases with growing centrality (i.e. for more central collisions) in both projections. This centrality dependence is not reproduced by HIJING, while AMPT, a model which incorporates strings and parton rescattering, exhibits qualitative agreement with the measured correlations in $\Delta\varphi$ but fails to describe the correlations in $\Delta\eta$. A thermal blast-wave model incorporating local charge conservation and tuned to describe the $p_{\rm T}$ spectra and v$_2$ measurements reported by ALICE, is used to fit the centrality dependence of the width of the balance function and to extract the average separation of balancing charges at freeze-out. The comparison of our results with measurements at lower energies reveals an ordering with $\sqrt{s_{\rm NN}}$: the balance functions become narrower with increasing energy for all centralities. This is consistent with the effect of larger radial flow at the LHC energies but also with the late stage creation scenario of balancing charges. However, the relative decrease of the balance function widths in $\Delta\eta$ and $\Delta\varphi$ with centrality from the highest SPS to the LHC energy exhibits only small differences. This observation cannot be interpreted solely within the framework where the majority of the charge is produced at a later stage in the evolution of the heavy--ion collision.

We report on measurements of a charge-dependent flow using a novel three-particle correlator with ALICE in Pb-Pb collisions at the LHC, and discuss the implications for observation of local parity violation and the Chiral Magnetic Wave (CMW) in heavy-ion collisions. Charge-dependent flow is reported for different collision centralities as a function of the event charge asymmetry. While our results are in qualitative agreement with expectations based on the CMW, the nonzero signal observed in higher harmonics correlations indicates a possible significant background contribution. We also present results on a differential correlator, where the flow of positive and negative charges is reported as a function of the mean charge of the particles and their pseudorapidity separation. We argue that this differential correlator is better suited to distinguish the differences in positive and negative charges expected due to the CMW and the background effects, such as local charge conservation coupled with strong radial and anisotropic flow.

We report the results of the femtoscopic analysis of pairs of identical pions measured in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. Femtoscopic radii are determined as a function of event multiplicity and pair momentum in three spatial dimensions. As in the pp collision system, the analysis is complicated by the presence of sizable background correlation structures in addition to the femtoscopic signal. The radii increase with event multiplicity and decrease with pair transverse momentum. When taken at comparable multiplicity, the radii measured in p-Pb collisions, at high multiplicity and low pair transverse momentum, are 10-20% higher than those observed in pp collisions but below those observed in A-A collisions. The results are compared to hydrodynamic predictions at large event multiplicity as well as discussed in the context of calculations based on gluon saturation.

We report the transverse energy $({E}_{\mathrm{T}})$ measured with ALICE at midrapidity in Pb-Pb collisions at $\sqrt{{s}_{\mathit{N}N}}=2.76$ TeV as a function of centrality. The transverse energy was measured using identified single-particle tracks. The measurement was cross checked using the electromagnetic calorimeters and the transverse momentum distributions of identified particles previously reported by ALICE. The results are compared to theoretical models as well as to results from other experiments. The mean ${E}_{\mathrm{T}}$ per unit pseudorapidity $(\ensuremath{\eta})$, $\ensuremath{\langle}d{E}_{\mathrm{T}}/d\ensuremath{\eta}\ensuremath{\rangle}$, in 0%--5% central collisions is $1737\ifmmode\pm\else\textpm\fi{}6(\mathrm{stat}.)\ifmmode\pm\else\textpm\fi{}97(\mathrm{sys}.)$ GeV. We find a similar centrality dependence of the shape of $\ensuremath{\langle}d{E}_{\mathrm{T}}/d\ensuremath{\eta}\ensuremath{\rangle}$ as a function of the number of participating nucleons to that seen at lower energies. The growth in $\ensuremath{\langle}d{E}_{\mathrm{T}}/d\ensuremath{\eta}\ensuremath{\rangle}$ at the LHC energies exceeds extrapolations of low-energy data. We observe a nearly linear scaling of $\ensuremath{\langle}d{E}_{\mathrm{T}}/d\ensuremath{\eta}\ensuremath{\rangle}$ with the number of quark participants. With the canonical assumption of a 1 fm/$c$ formation time, we estimate that the energy density in 0%--5% central Pb-Pb collisions at $\sqrt{{s}_{\mathit{N}N}}=2.76$ TeV is $12.3\ifmmode\pm\else\textpm\fi{}1.0\phantom{\rule{4pt}{0ex}}{\mathrm{GeV}/\mathrm{fm}}^{3}$ and that the energy density at the most central $80\phantom{\rule{4pt}{0ex}}{\text{fm}}^{2}$ of the collision is at least $21.5\ifmmode\pm\else\textpm\fi{}1.7\phantom{\rule{4pt}{0ex}}{\mathrm{GeV}/\mathrm{fm}}^{3}$. This is roughly 2.3 times that observed in 0%--5% central Au-Au collisions at $\sqrt{{s}_{\mathit{N}N}}=200$ GeV.

The production of J/ψ and ψ(2S) was studied 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 t ) in the dimuon decay channel. Inclusive J/ψ yields were extracted in different centrality classes and the centrality dependence of the average p t is presented. The J/ψ suppression, quantified with the nuclear modification factor (R AA), was measured as a function of centrality, transverse momentum and rapidity. Comparisons with similar measurements at lower collision energy and theoretical models indicate that the J/ψ 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 ψ(2S) suppression are provided via the ratio of ψ(2S) over J/ψ measured in pp and Pb-Pb collisions.

Results are presented of a two-pion interferometry (HBT) analysis in Pb+Au collisions at 40, 80, and 158 AGeV. A detailed study of the Bertsch-Pratt HBT radius parameters has been performed as function of the mean pair transverse momentum $k_t$ and in bins of the centrality of the collision. From these results we extract model dependent information about the space-time evolution of the reaction. An investigation of the effective volume of the pion emitting system provides an important tool to study the properties of thermal pion freeze-out.

Based on an evaluation of data on pion interferometry and on particle yields at midrapidity, we propose a universal condition for thermal freeze-out of pions in heavy-ion collisions. We show that freeze-out occurs when the mean free path of pions lambda(f) reaches a value of about 1 fm, which is much smaller than the spatial extent of the system at freeze-out. This critical mean free path is independent of the centrality of the collision and beam energy from the Alternating Gradient Synchrotron to the Relativistic Heavy Ion Collider.

Inclusive J/ψ production has been studied with the ALICE detector in p-Pb collisions at the nucleon-nucleon center of mass energy $ \sqrt{{{s_{\mathrm{NN}}}}} $ = 5.02 TeV at the CERN LHC. The measurement is performed in the center of mass rapidity domains 2.03 < y cms < 3.53 and −4.46 < y cms < −2.96, down to zero transverse momentum, studying the μ + μ − decay mode. In this paper, the J/ψ production cross section and the nuclear modification factor R pPb for the rapidities under study are presented. While at forward rapidity, corresponding to the proton direction, a suppression of the J/ψ yield with respect to binary-scaled pp collisions is observed, in the backward region no suppression is present. The ratio of the forward and backward yields is also measured differentially in rapidity and transverse momentum. Theoretical predictions based on nuclear shadowing, as well as on models including, in addition, a contribution from partonic energy loss, are in fair agreement with the experimental results.

The differential charged jet cross sections, jet fragmentation distributions, and jet shapes are measured in minimum bias proton-proton collisions at centre-of-mass energy $\sqrt{s}=7$ TeV using the ALICE detector at the LHC. Jets are reconstructed from charged particle momenta in the mid-rapidity region using the sequential recombination $k_{\rm T}$ and anti-$k_{\rm T}$ as well as the SISCone jet finding algorithms with several resolution parameters in the range $R=0.2$ to $0.6$. Differential jet production cross sections measured with the three jet finders are in agreement in the transverse momentum ($p_{\rm T}$) interval $20<p_{\rm T}^{\rm jet,ch}<100$ GeV/$c$. They are also consistent with prior measurements carried out at the LHC by the ATLAS collaboration. The jet charged particle multiplicity rises monotonically with increasing jet $p_{\rm T}$, in qualitative agreement with prior observations at lower energies. The transverse profiles of leading jets are investigated using radial momentum density distributions as well as distributions of the average radius containing 80% ($\langle R_{\rm 80} \rangle$) of the reconstructed jet $p_{\rm T}$. The fragmentation of leading jets with $R=0.4$ using scaled $p_{\rm T}$ spectra of the jet constituents is studied. The measurements are compared to model calculations from event generators (PYTHIA, PHOJET, HERWIG). The measured radial density distributions and $\langle R_{\rm 80} \rangle$ distributions are well described by the PYTHIA model (tune Perugia-2011). The fragmentation distributions are better described by HERWIG.

We report the first measurement at the LHC of coherent photoproduction of ρ 0 mesons in ultra-peripheral Pb-Pb collisions. The invariant mass and transverse momentum distributions for ρ 0 production are studied in the π + π − decay channel at mid-rapidity. The production cross section in the rapidity range |y| < 0.5 is found to be dσ/dy = 425 ± 10(stat.) − 50 + 42 (sys.) mb. Coherent ρ 0 production is studied with and without requirement of nuclear breakup, and the fractional yields for various breakup scenarios are presented. The results are compared with those from lower energies and with model predictions.

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.

Measurements of charged jet production as a function of centrality are presented for p-Pb collisions recorded at $\sqrt{s_{\rm NN}} = 5.02$ TeV with the ALICE detector. Centrality classes are determined via the energy deposit in neutron calorimeters at zero degree, close to the beam direction, to minimise dynamical biases of the selection. The corresponding number of participants or binary nucleon-nucleon collisions is determined based on the particle production in the Pb-going rapidity region. Jets have been reconstructed in the central rapidity region from charged particles with the anti-$k_{\rm T}$ algorithm for resolution parameters $R = 0.2$ and $R = 0.4$ in the transverse momentum range 20 to 120 GeV/$c$. The reconstructed jet momentum and yields have been corrected for detector effects and underlying-event background. In the five centrality bins considered, the charged jet production in p-Pb collisions is consistent with the production expected from binary scaling from pp collisions. The ratio of jet yields reconstructed with the two different resolution parameters is also independent of the centrality selection, demonstrating the absence of major modifications of the radial jet structure in the reported centrality classes.

Elliptic flow and two-particle azimuthal correlations of charged hadrons and high-p(T) pions (p(T)>1 GeV/c) have been measured close to midrapidity in 158A GeV/c Pb+Au collisions by the CERES experiment. Elliptic flow (v(2)) rises linearly with p(T) to a value of about 10% at 2 GeV/c. Beyond p(T) approximately 1.5 GeV/c, the slope decreases considerably, possibly indicating a saturation of v(2) at high p(T). Two-pion azimuthal anisotropies for p(T)>1.2 GeV/c exceed the elliptic flow values by about 60% in midcentral collisions. These nonflow contributions are attributed to nearside and back-to-back jetlike correlations, the latter exhibiting centrality dependent broadening.

The design, calibration, and performance of the first radial drift Time Projection Chamber (TPC) are presented. The TPC was built and installed at the CERES/NA45 experiment at the CERN SPS in the late nineties, with the objective to improve the momentum resolution of the spectrometer. The upgraded experiment took data twice, in 1999 and in 2000. After a detailed study of residual distortions a spatial resolution of 340 um in the azimuthal and 640 um in the radial direction was achieved, corresponding to a momentum resolution of Dp/p = sqrt{(1% * p/GeV)^2 + (2%)^2}.

Electrons from heavy-flavour hadron decays (charm and beauty) were measured with the ALICE detector in Pb-Pb collisions at a centre-of-mass of energy $\sqrt{s_{\rm NN}}=2.76$ TeV. The transverse momentum ($p_{\rm T}$) differential production yields at mid-rapidity were used to calculate the nuclear modification factor $R_{\rm AA}$ in the interval $3<p_{\rm T}< 18$ GeV/$c$. The $R_{\rm AA}$ shows a strong suppression compared to binary scaling of pp collisions at the same energy (up to a factor of 4) in the 10% most central Pb-Pb collisions. There is a centrality trend of suppression, and a weaker suppression (down to a factor of 2) in semi-peripheral (50-80%) collisions is observed. The suppression of electrons in this broad $p_{\rm T}$ interval indicates that both charm and beauty quarks lose energy when they traverse the hot medium formed in Pb-Pb collisions at LHC.

First experimental results are presented on event-by-event net-proton fluctuation measurements in Pb–Pb collisions at sNN=2.76 TeV, recorded by the ALICE detector at the CERN LHC. The ALICE detector is well suited for such studies due to its excellent particle identification capabilities and large acceptance, which is crucial for fluctuation analysis. The studies are focussed on second order cumulants, but the analysis technique used is more general and will be applied, in the near future, also to higher order cumulants.

We report on results of a measurement of meson production in central Pb-Au collisions at E(lab) = 158A GeV. For the first time in the history of high energy heavy-ion collisions, phi mesons were reconstructed both in the K+K- and the dilepton decay channels in the same experiment. This measurement yields rapidity densities near midrapidity, from the two decay channels, of 2.05 +/- 0.14(stat) +/- 0.25(syst) and 2.04 +/- 0.49(stat) +/- 0.32(syst), respectively. The shape of the measured transverse momentum spectrum is also in close agreement in both decay channels. The data rule out a possible enhancement of the phi yield in the leptonic over the hadronic decay channel of a factor 1.6 or larger at the 95% C.L. This rules out the discrepancy reported in the literature between measurements of the hadronic and dimuon decay channels by two different experiments.

The ALICE Collaboration has studied the inclusive production of the charmonium state $\psi(2S)$ in proton-lead (p-Pb) collisions at the nucleon-nucleon centre of mass energy $\sqrt{s_{NN}}$ = 5.02 TeV at the CERN LHC. The measurement was performed at forward ($2.03<y_{cms}<3.53$) and backward ($-4.46<y_{cms}<-2.96$) centre of mass rapidities, studying the decays into muon pairs. In this paper, we present the inclusive production cross sections $\sigma_{\psi(2S)}$, both integrated and as a function of the transverse momentum $p_{T}$, for the two $y_{cms}$ domains. The results are compared to those obtained for the 1S vector state (J/$\psi$), by showing the ratios between the production cross sections, as well as the double ratios $[\sigma_{\psi(2S)}/\sigma_{J/\psi}]_{pPb}/[\sigma_{\psi(2S)}/\sigma_{J/\psi}]_{pp}$ between p-Pb and proton-proton collisions. Finally, the nuclear modification factor for inclusive $\psi(2S)$ is evaluated and compared to the measurement of the same quantity for J/$\psi$ and to theoretical models including parton shadowing and coherent energy loss mechanisms. The results show a significantly larger suppression of the $\psi(2S)$ compared to that measured for J/$\psi$ and to models. These observations represent a clear indication for sizeable final state effects on $\psi(2S)$ production.

A measurement of dijet correlations in p–Pb collisions at sNN=5.02TeV with the ALICE detector is presented. Jets are reconstructed from charged particles measured in the central tracking detectors and neutral energy deposited in the electromagnetic calorimeter. The transverse momentum of the full jet (clustered from charged and neutral constituents) and charged jet (clustered from charged particles only) is corrected event-by-event for the contribution of the underlying event, while corrections for underlying event fluctuations and finite detector resolution are applied on an inclusive basis. A projection of the dijet transverse momentum, kTy=pT,jetch+nesin(Δφdijet) with Δφdijet the azimuthal angle between a full and charged jet and pT,jetch+ne the transverse momentum of the full jet, is used to study nuclear matter effects in p–Pb collisions. This observable is sensitive to the acoplanarity of dijet production and its potential modification in p–Pb collisions with respect to pp collisions. Measurements of the dijet kTy as a function of the transverse momentum of the full and recoil charged jet, and the event multiplicity are presented. No significant modification of kTy due to nuclear matter effects in p–Pb collisions with respect to the event multiplicity or a PYTHIA8 reference is observed.

The elliptic flow of electrons from heavy-flavour hadron decays at mid-rapidity (|y| < 0.7) is measured in Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}}=2.76 $$ TeV with ALICE at the LHC. The particle azimuthal distribution with respect to the reaction plane can be parametrized with a Fourier expansion, where the second coefficient (v 2) represents the elliptic flow. The v 2 coefficient of inclusive electrons is measured in three centrality classes (0–10%, 10–20% and 20–40%) with the event plane and the scalar product methods in the transverse momentum (p T) intervals 0.5–13 GeV/c and 0.5–8 GeV/c, respectively. After subtracting the background, mainly from photon conversions and Dalitz decays of neutral mesons, a positive v 2 of electrons from heavy-flavour hadron decays is observed in all centrality classes, with a maximum significance of 5.9σ in the interval 2 < p T < 2.5 GeV/c in semi-central collisions (20–40%). The value of v 2 decreases towards more central collisions at low and intermediate p T (0.5 < p T < 3 GeV/c). The v 2 of electrons from heavy-flavour hadron decays at mid-rapidity is found to be similar to the one of muons from heavy-flavour hadron decays at forward rapidity (2.5 < y < 4). The results are described within uncertainties by model calculations including substantial elastic interactions of heavy quarks with an expanding strongly-interacting medium.

The inclusive production of the $\psi$(2S) charmonium state was studied as a function of centrality in p-Pb collisions at the nucleon-nucleon center of mass energy $\sqrt{s_{\rm NN}}$ = 5.02 TeV at the CERN LHC. The measurement was performed with the ALICE detector in the center of mass rapidity ranges $-4.46<y_{\rm cms}<-2.96$ and $2.03<y_{\rm cms}<3.53$, down to zero transverse momentum, by reconstructing the $\psi$(2S) decay to a muon pair. The $\psi$(2S) production cross section $\sigma_{\psi(\rm 2S)}$ is presented as a function of the collision centrality, which is estimated through the energy deposited in forward rapidity calorimeters. The relative strength of nuclear effects on the $\psi$(2S) and on the corresponding 1S charmonium state J/$\psi$ is then studied by means of the double ratio of cross sections $[\sigma_{\psi(\rm 2S)}/\sigma_{\rm J/\psi}]_{\rm pPb}/[\sigma_{\psi(\rm 2S)}/\sigma_{\rm J/\psi}]_{\rm pp}$ between p-Pb and pp collisions, and by the values of the nuclear modification factors for the two charmonium states. The results show a large suppression of $\psi$(2S) production relative to the J/$\psi$ at backward (negative) rapidity, corresponding to the flight direction of the Pb-nucleus, while at forward (positive) rapidity the suppressions of the two states are comparable. Finally, comparisons to results from lower energy experiments and to available theoretical models are presented.

We present measurements of two-particle correlations with neutral pion trigger particles of transverse momenta 8<pTtrig<16GeV/c and associated charged particles of 0.5<pTassoc<10GeV/c versus the azimuthal angle difference Δφ at midrapidity in pp and central Pb–Pb collisions at sNN=2.76 TeV with ALICE. The new measurements exploit associated charged hadrons down to 0.5GeV/c, which significantly extends our previous measurement that only used charged hadrons above 3GeV/c. After subtracting the contributions of the flow background, v2 to v5, the per-trigger yields are extracted for |Δφ|<0.7 on the near and for |Δφ−π|<1.1 on the away side. The ratio of per-trigger yields in Pb–Pb to those in pp collisions, IAA, is measured on the near and away side for the 0–10% most central Pb–Pb collisions. On the away side, the per-trigger yields in Pb–Pb are strongly suppressed to the level of IAA≈0.6 for pTassoc>3GeV/c, while with decreasing momenta an enhancement develops reaching about 5 at low pTassoc. On the near side, an enhancement of IAA between 1.2 at the highest to 1.8 at the lowest pTassoc is observed. The data are compared to parton-energy-loss predictions of the JEWEL and AMPT event generators, as well as to a perturbative QCD calculation with medium-modified fragmentation functions. All calculations qualitatively describe the away-side suppression at high pTassoc. Only AMPT captures the enhancement at low pTassoc, both on the near and away side. However, it also underpredicts IAA above 5 GeV/c, in particular on the near-side.

We present results on transverse momentum correlations of charged particle pairs produced in PbAu collisions at 158A GeV/c at the Super Proton Synchrotron. The transverse momentum correlations have been studied as a function of collision centrality, angular separation of the particle pairs, transverse momentum and charge sign. We demonstrate that the results are in agreement with previous findings in scale-independent analyses at the same beam energy. Employing the two-particle momentum correlator 〈Δpt,i,Δpt,j〉 and the cumulative pt variable x(pt), we identify, using the scale-dependent approach presented in this paper, different sources contributing to the measured correlations, such as quantum and Coulomb correlations, elliptic flow and mini-jet fragmentation.

The aim of this work is to explore possible medium modifications to the substructure of inclusive charged jets in Pb-Pb relative to proton-proton collisions by measuring a set of jet shapes. The set of shapes includes the radial moment, g, and the momentum dispersion pTD. They provide complementary information on the fragmentation and can help to discriminate between two different scenarios: intra-jet broadening or collimation as a result of jet quenching. The shapes are measured in Pb–Pb collisions at sNN=2.76 TeV with a constituent cutoff of 0.15 GeV/c and jet resolution R=0.2. New techniques for background subtraction are applied and a two-dimensional unfolding is performed to correct the shapes to particle level. The corrected jet shapes for jet pT40≤pT,jet≤60 GeV/c are presented and discussed. The observed jet shape modifications suggest that the in-medium fragmentation is harder and more collimated than vacuum fragmentation as obtained by a PYTHIA calculation. The PYTHIA calculation is validated with proton-proton data at 7 TeV.

The Fourier harmonics, $v_2$ and $v_3$ of negative pions are measured at center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}$= 17.3 GeV around midrapidity by the CERES/NA45 experiment at the CERN SPS in 0--30% central PbAu collisions with a mean centrality of 5.5%. The analysis is performed in two centrality bins as a function of the transverse momentum $\mathrm{p_{\mathrm{T}}}$ from 0.05 GeV/$c$ to more than 2 GeV/$c$. This is the first measurement of the $v^{1/3}_{3}/v^{1/2}_{2}$ ratio as a function of transverse momentum at SPS energies. For $\mathrm{p_{\mathrm{T}}}$ above 0.5 GeV/$c$, the ratio is nearly flat in accordance with the hydrodynamic prediction and as previously observed by the ATLAS and ALICE experiments at the much higher LHC energies. The results are also compared with the SMASH-vHLLE hybrid model predictions.

We discuss the latest theoretical results on direct photon and dilepton production from relativistic heavy-ion collisions. While the dilepton spectra at low invariant mass show in-medium effects like collisional broadening of the vector meson spectral functions, the dilepton yield at high invariant masses (above 1.1 GeV) is dominated by QGP contributions for central heavy-ion collisions at relativistic energies. The present status of the photon v2 “puzzle” – a large elliptic flow v2 of the direct photons experimentally observed at RHIC and LHC energies – is also addressed. The role of hadronic and partonic sources for the photon spectra and v2 is considered as well as the possibility to subtract the QGP signal from the experimental observables.

ALICE (A Large Ion Collider Experiment) at the LHC contains a wide array of detector systems for measuring hadrons, leptons, and photons. ALICE is designed to carry out comprehensive measurements of high energy nucleus-nucleus collisions, in order to study QCD matter under extreme conditions and to study the phase transition between confined matter and the Quark-Gluon Plasma (QGP). Discussion of the full ALICE physics program can be found in [1, 2]. The interaction and energy loss of high energy partons in matter provides a sensitive tomographic probe of the medium generated in high energy nuclear collisions (“jet quenching”) [3–6]. Jet quenching measurements have played a key role at the Relativistic Heavy Ion Collider (RHIC) [7–10] and will be central to the study of nuclear collisions at the LHC. This Technical Design Report describes a large acceptance Electromagnetic Calorimeter (EMCal) that will be installed in the ALICE central detector. The EMCal enhances ALICE's capabilities for jet quenching measurements. The addition of the EMCal enables triggering on high energy jets, reduces significantly the measurement bias for jet quenching studies, improves jet energy resolution, and augments existing ALICE capabilities to measure high momentum photons and electrons. Combined with ALICE's excellent capabilities to track and identify particles from very low pt to high pt the EMCal enables an extensive study of jet quenching at the LHC.

The measurement of two-particle angular correlations is a powerful tool to study jet quenching in a p_{T} region inaccessible by direct jet identification. In these measurements pseudorapidity (Δη) and azimuthal (Δφ) differences are used to extract the shape of the near-side peak formed by particles associated with a higher p_{T} trigger particle (1<p_{T,trig}<8 GeV/c). A combined fit of the near-side peak and long-range correlations is applied to the data allowing the extraction of the centrality evolution of the peak shape in Pb-Pb collisions at sqrt[s_{NN}]=2.76 TeV. A significant broadening of the peak in the Δη direction at low p_{T} is found from peripheral to central collisions, which vanishes above 4 GeV/c, while in the Δφ direction the peak is almost independent of centrality. For the 10% most central collisions and 1<p_{T,assoc}<2 GeV/c, 1<p_{T,trig}<3 GeV/c a novel feature is observed: a depletion develops around the center of the peak. The results are compared to pp collisions at the same center of mass energy and ampt model simulations. The comparison to the investigated models suggests that the broadening and the development of the depletion is connected to the strength of radial and longitudinal flow.

The measurement of prompt D-meson production as a function of multiplicity in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV with the ALICE detector at the LHC is reported. D$^0$, D$^+$ and D$^{*+}$ mesons are reconstructed via their hadronic decay channels in the centre-of-mass rapidity range $-0.96< y_{\mathrm{cms}}<0.04$ and transverse momentum interval $1<p_{\rm T}<24$ GeV/$c$. The multiplicity dependence of D-meson production is examined by either comparing yields in p-Pb collisions in different event classes, selected based on the multiplicity of produced particles or zero-degree energy, with those in pp collisions, scaled by the number of binary nucleon-nucleon collisions (nuclear modification factor); as well as by evaluating the per-event yields in p-Pb collisions in different multiplicity intervals normalised to the multiplicity-integrated ones (relative yields). The nuclear modification factors for D$^0$, D$^+$ and D$^{*+}$ are consistent with one another. The D-meson nuclear modification factors as a function of the zero-degree energy are consistent with unity within uncertainties in the measured $p_{\rm T}$ regions and event classes. The relative D-meson yields, calculated in various $p_{\rm T}$ intervals, increase as a function of the charged-particle multiplicity. The results are compared with the equivalent pp measurements at $\sqrt{s}=7$ TeV as well as with EPOS~3 calculations.

Differential elliptic flow spectra v2(pT) of π−, KS0, p, Λ have been measured at sNN=17.3GeV around midrapidity by the CERN-CERES/NA45 experiment in mid-central Pb + Au collisions (10% of σgeo). The pT range extends from about 0.1 GeV/c (0.55 GeV/c for Λ) to more than 2 GeV/c. Protons below 0.4 GeV/c are directly identified by dE/dx. At higher pT, proton elliptic flow is derived as a constituent, besides π+ and K+, of the elliptic flow of positive pion candidates. This retrieval requires additional inputs: (i) of the particle composition, and (ii) of v2(pT) of positive pions. For (i), particle ratios obtained by NA49 are adapted to CERES conditions; for (ii), the measured v2(pT) of negative pions is substituted, assuming π+ and π− elliptic flow magnitudes to be sufficiently close. The v2(pT) spectra are compared to ideal-hydrodynamics calculations. In synopsis of the series π−–KS0–p–Λ, flow magnitudes are seen to fall with decreasing pT progressively even below hydro calculations with early kinetic freeze-out (Tf=160MeV) leaving not much time for hadronic evolution. The proton v2(pT) data show a downward swing towards low pT with excursions into negative v2 values. The pion-flow isospin asymmetry observed recently by STAR at RHIC, invalidating in principle our working assumption, is found in its impact on proton flow bracketed from above by the direct proton flow data, and not to alter any of our conclusions. Results are discussed in perspective of recent viscous hydrodynamics studies which focus on late hadronic stages.

The production of beauty hadrons was measured via semi-leptonic decays at mid-rapidity with the ALICE detector at the LHC in the transverse momentum interval 1<p T < 8 GeV/c in minimum-bias p-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}}=5.02 $$ TeV and in 1.3 < p T < 8 GeV/c in the 20% most central Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}}=2.76 $$ TeV. The pp reference spectra at $$ \sqrt{s_{\mathrm{NN}}}=5.02 $$ TeV and $$ \sqrt{s}=2.76 $$ TeV, needed for the calculation of the nuclear modification factors R pPb and R PbPb, were obtained by a pQCD-driven scaling of the cross section of electrons from beauty-hadron decays measured at $$ \sqrt{s}=7 $$ TeV. In the p T interval 3 < p T < 8 GeV/c, a suppression of the yield of electrons from beauty-hadron decays is observed in Pb-Pb compared to pp collisions. Towards lower p T, the R PbPb values increase with large systematic uncertainties. The R pPb is consistent with unity within systematic uncertainties and is well described by theoretical calculations that include cold nuclear matter effects in p-Pb collisions. The measured R pPb and these calculations indicate that cold nuclear matter effects are small at high transverse momentum also in Pb-Pb collisions. Therefore, the observed reduction of R PbPb below unity at high p T may be ascribed to an effect of the hot and dense medium formed in Pb-Pb collisions.

In two-particle angular correlation measurements, jets give rise to a near-side peak, formed by particles associated to a higher-${p}_{\mathrm{T}}$ trigger particle. Measurements of these correlations as a function of pseudorapidity ($\mathrm{\ensuremath{\Delta}}\ensuremath{\eta}$) and azimuthal ($\mathrm{\ensuremath{\Delta}}\ensuremath{\varphi}$) differences are used to extract the centrality and ${p}_{\mathrm{T}}$ dependence of the shape of the near-side peak in the ${p}_{\mathrm{T}}$ range $1&lt;{p}_{\mathrm{T}}&lt;8$ $\mathrm{GeV}/c$ in Pb-Pb and $\mathit{pp}$ collisions at $\sqrt{{s}_{NN}}$ = 2.76 TeV. A combined fit of the near-side peak and long-range correlations is applied to the data and the peak shape is quantified by the variance of the distributions. While the width of the peak in the $\mathrm{\ensuremath{\Delta}}\ensuremath{\varphi}$ direction is almost independent of centrality, a significant broadening in the $\mathrm{\ensuremath{\Delta}}\ensuremath{\eta}$ direction is found from peripheral to central collisions. This feature is prominent for the low-${p}_{\mathrm{T}}$ region and vanishes above $4 \mathrm{GeV}/c$. The widths measured in peripheral collisions are equal to those in $\mathit{pp}$ collisions in the $\mathrm{\ensuremath{\Delta}}\ensuremath{\varphi}$ direction and above $3 \mathrm{GeV}/c$ in the $\mathrm{\ensuremath{\Delta}}\ensuremath{\eta}$ direction. Furthermore, for the 10% most central collisions and $1&lt;{p}_{\mathrm{T},\mathrm{assoc}}&lt;$ $2 \mathrm{GeV}/c, 1&lt;{p}_{\mathrm{T},\mathrm{trig}}&lt;$ $3 \mathrm{GeV}/c$, a departure from a Gaussian shape is found: a depletion develops around the center of the peak. The results are compared to A Multi-Phase Transport (AMPT) model simulation as well as other theoretical calculations indicating that the broadening and the development of the depletion are connected to the strength of radial and longitudinal flow.

We present results of a two-pion correlation analysis performed with the $\mathrm{Pb}+\mathrm{Au}$ collision data collected by the upgraded CERES experiment in the fall of 2000. The analysis was done in bins of the reaction centrality and the pion azimuthal emission angle with respect to the reaction plane. The pion source, deduced from the data, is slightly elongated in the direction perpendicular to the reaction plane, similarly as was observed at the Brookhaven National Laboratory Alternating Gradient Synchrotron and Relativistic Heavy Ion Collider.

Results on event-by-event fluctuations of the mean transverse momentum and net charge in Pb-Au collisions, measured by the CERES Collaboration at CERN-SPS, are presented. We discuss the centrality and beam energy dependence and compare our data to cascade calculations.

The growth of La2NiO4+δ at the interface between La2O3 and NiO has been studied from 950 to 1450°C in argon, air and oxygen. The thickness, microstructure and composition of the formed La2NiO4+δ layers have been characterized by means of SEM, EDX, EBSD, EPMA and XRD. The growth rate follows parabolic kinetics. It has been concluded from the position of Pt markers that La2NiO4+δ grows predominantly by solid state diffusion of Ni2+, and the experimental results were accordingly fitted with Wagner's expressions for self-diffusion. Above 1100°C the diffusion coefficients follow Arrhenius-type temperature dependencies, with activation energies 243 ± 21 and 218 ± 21 kJ/mol evaluated for the conditions at the La2O3/La2NiO4+δ and NiO/La2NiO4+δ interfaces, respectively. Below 1100°C the diffusivity falls more steeply with decreasing temperature, and possible explanations are discussed. Compared to cation diffusion in perovskite-type oxides, Ni2+ diffusivity in La2NiO4+δ is in higher range.

The directed and elliptic flow of protons and negative pions in 4.2A GeV c-1 C + C collisions is studied using the Fourier analysis of azimuthal distributions. It is found that the protons exhibit pronounced directed flow, while the flow of pions is either non-existent or too weak to be detected experimentally. Also, it is found that in the entire rapidity interval the elliptic flow is very small if not zero. These results are confirmed by the quark-gluon-string model (QGSM) and the relativistic transport model (ART 1.0), except that these models predict a very weak antiflow of pions. The more detailed comparison with the QGSM suggests that the decay of resonances and rescattering of secondaries dominantly determine the proton and negative pion flow at this energy.

Results of a two-particle correlation analysis of high-pt charged particles in Pb–Au collisions at 158A GeV/c are presented. The data have been recorded by the CERES experiment at the CERN-SPS. The correlations are studied as function of transverse momentum, particle charge and collision centrality. We observe a jet-like structure in the vicinity of a high-pt trigger particle and a broad back-to-back distribution. The yields of associated particles per trigger show a strong dependence on the trigger/associate charge combination. A comparison to PYTHIA confirms the jet-like pattern at the near-side but suggests a strong modification at the away-side, implying significant energy transfer of the hard-scattered parton to the medium.

Recent LHC results on the appearance of sub-leading flow modes in PbPb collisions at 2.76~TeV, related to initial-state fluctuations, are analyzed and interpreted within the HYDJET++ model. Using the newly introduced Principal Component Analysis (PCA) method applied to two-particle azimuthal correlations extracted from the model calculations, the leading and the sub-leading flow modes are studied as a function of the transverse momentum ($p_{T}$) over a wide centrality range. The leading modes of the elliptic ($v^{(1)}_{2}$) and triangular ($v^{(1)}_{3}$) flow calculated within the HYDJET++ model reproduce rather well the $v_{2}\{2\}$ and $v_{3}\{2\}$ coefficients experimentally measured using the two-particle correlations. Within the $p_{T} \le $~3~GeV/c range where hydrodynamics dominates, the sub-leading flow effects are greatest at the highest $p_{T}$ of around 3~GeV/c. The sub-leading elliptic flow mode ($v^{(2)}_{2}$), which corresponds to $n = 2$ harmonic, has a small non-zero value and slowly increases from central to peripheral collisions, while the sub-leading triangular flow mode ($v^{(2)}_{3}$), which corresponds to $n = 3$ harmonic, is even smaller and does not depend on centrality. For $n = $~2, the relative magnitude of the effect measured with respect to the leading flow mode shows a shallow minimum for semi-central collisions and increases for very central and for peripheral collisions. For $n = $~3 case, there is no centrality dependence. The sub-leading flow mode results obtained from the HYDJET++ model are in a rather good agreement with the experimental measurements of the CMS Collaboration.

A Principle Component Analysis (PCA) of two-particle azimuthal correlations as a function of transverse momentum (pT) is presented in PbPb collisions at 2.76 TeV and high-multiplicity pPb collisions at 5.02 TeV. The data were recorded using the CMS detector at the LHC. It was shown that factorization breaking of two-particle azimuthal correlations can be attributed to the effect of initial-state fluctuations. Using a PCA approach, Fourier coefficients of observed two-particle azimuthal correlations as a function of both particles' pT are characterized into leading and sub-leading mode terms. The leading modes are essentially equivalent to anisotropy harmonics (vn) previously extracted from two-particle correlation methods as a function of pT. The sub-leading modes represent the largest sources of factorization breaking. In the context of hydrodynamic models, they are a direct consequence of initial-state fluctuations. The results are presented over a wide range of centrality and event multiplicity. The results are connected to the measurement of pT-dependent flow factorization breaking.

We present Λ and π elliptic flow measurements from Pb+Au collisions at the highest SPS energy. The data, collected by the CERES experiment which covers η = 2.05 , 2.70 with full azimuthal coverage and wide p T sensitivity up to 3.5 GeV/c, can be used to test hydrodynamical models and show sensitivity to the EoS. The value of v 2 as a function of centrality and p T is presented. Values of v 2 observed by STAR at RHIC are larger by about 1/3. Our measurements are compared to results from other SPS experiments and to hydrodynamical calculations. Huge statistics allows for a precise measurement of the differential pion elliptic flow.

Elliptic flow measurements as a function of p_T of charged (pi^+- and low-p_T protons) and strange (Lambda and K^0_S) particles from Pb+Au collisions at 158 AGeV/c are presented, together with measurements of phi and K^0_S meson production. A mass ordering effect was observed. Scaling to the number of constituent quarks and transverse rapidity y^fs_T scaling are presented. The results are compared with results from the NA49 and STAR experiments and with hydrodynamical calculations. For the first time in heavy-ion collisions, phi mesons were reconstructed in the same experiment both in the K^+K^- and in the e^+e^- decay channels. The obtained transverse mass distributions of phi mesons are compared with results from the NA49 and NA50 experiments. The yield and the inverse slope parameter of the K^0_S mesons were reconstructed from two independent analyses. Our results are compared with those from the NA49 and NA57 experiments.

Correlations between azimuthal anisotropy Fourier harmonics ${v}_{n}$ ($n=2,3,4$) are studied using the events from PbPb collisions at $\sqrt{{s}_{{}_{\mathrm{NN}}}}=2.76$ TeV generated by the $\text{HYDJET}++$ and multiphase transport (AMPT) models, and compared to the corresponding experimental results obtained by the ATLAS Collaboration. The Fourier harmonics ${v}_{n}$ are measured over a wide centrality range using the two-particle azimuthal correlation method. The slopes of the ${v}_{2}\text{\ensuremath{-}}{v}_{3}$ correlation from both models are in a good agreement with the ATLAS data. The $\text{HYDJET}++$ model predicts a stronger slope for the ${v}_{2}\text{\ensuremath{-}}{v}_{4}$ and ${v}_{3}\text{\ensuremath{-}}{v}_{4}$ correlations than the ones experimentally measured, while the results from the AMPT model are in a rather good agreement with the experimental results. In contrast to the $\text{HYDJET}++$ predictions, the AMPT model predicts a boomeranglike shape in the structure of the correlations as found in the experimental data.

Analytic formulas to calculate statistical uncertainties of $v_{n}\{2k\}$ harmonics extracted from the Q-cumulants are presented. The Q-cumulants are multivariate polynomial functions of the weighted means of $2m$-particle azimuthal correlations, $\llangle 2m \rrangle$. Variances and covariances of the $\llangle 2m \rrangle$ are included in the analytic formulas of the uncertainties that can be calculated simultaneously with the calculations of the $v_{n}\{2k\}$ harmonics. The calculations are performed using a simple toy model which roughly simulates elliptic flow azimuthal anisotropy with magnitudes around 0.05. The results are compared with the results obtained by the many data sub-sets, and by the bootstrapping method. The first one is a common way of estimation of the statistical uncertainties of the $v_{n}\{2k\}$ harmonics in a real experiment. In order to increase precision in the measurement of the $v_{n}\{2k\}$ harmonics, a large number of 15000 sub-sets and the same number of the re-sampling in the bootstrap method is used. A very good agreement in the comparison with the proposed way of the analytic calculation of the $v_{n}\{2k\}$ statistical uncertainties is found. Additionally, a recurrence equation for Q-cumulants calculation is also presented.

Abstract The method of Q -cumulants is a powerful tool for studying the fine details of azimuthal anisotropies in high energy nuclear collisions. This paper presents a new method, based on mathematical induction, to evaluate the analytical form of high-order Q -cumulants. The capability of this method is demonstrated via a toy model that uses the elliptic power distribution to simulate the anisotropic emission of particles, quantified in terms of Fourier flow harmonics <?CDATA $ {v_n} $?> . The method can help in studying the large amount of event statistics that can be collected in the future and allow measurements of the very high central moments of the <?CDATA $ {v_2} $?> distribution. This can, in turn, facilitate progress in understanding the initial geometry, the input to the hydrodynamic calculations of medium expansion in high energy nuclear collisions, and the constraints on it.

The collective anisotropic hydrodynamic behavior of charge hadrons is studied using the multiparticle correlation method.The elliptic anisotropy harmonic from different orders of multiparticle cumulants, v 2 {2k}, are measured up to the tenth order (k = 5) as functions of the collision centrality in lead-lead collisions at an energy of √ s NN = 5.02 TeV.The data were collected by the CMS experiment at the LHC, with an integrated luminosity of 0.58 nb -1 .A fine splittingis observed.The subtle differences in the higher-order cumulants allow for a precise determination of the underlying hydrodynamics.Based on these results, centrality-dependent moments for the fluctuation-driven event-by-event v 2 distribution are determined, including the skewness, the kurtosis and, for the first time, the superskewness.Assuming a hydrodynamic expansion of the produced medium, these moments probe the initial-state geometry in high-energy nucleus-nucleus collisions.

During the 1999 lead run, CERES has measured hadron and electron-pair production at 40 A GeV/c beam momentum with the spectrometer upgraded by the addition of a radial TPC. Here the analysis of Λ and will be presented.

Anisotropic flow of protons and negative pions in $4.2A\mathrm{GeV}/c$ $\mathrm{C}+\mathrm{Ta}$ collisions is studied using the Fourier analysis of azimuthal distributions. The protons exhibit pronounced directed flow. Directed flow of pions is positive in the entire rapidity interval and indicates that the pions are preferentially emitted in the reaction plane from the target to the projectile. The elliptic flow of protons and negative pions is close to zero. Comparison with the quark-gluon-string model and relativistic transport model show that they both yield a flow signature similar to the experimental data.

Differential triangular flow, v3(pT), of negative pions is measured at sNN=17.3GeV around midrapidity by the CERES/NA45 experiment at CERN in central PbAu collisions in the range 0–30% with a mean centrality of 5.5%. This is the first measurement as a function of transverse momentum of the triangular flow at SPS energies. The pT range extends from about 0.05 GeV/c to more than 2 GeV/c. The triangular flow magnitude, corrected for the HBT effects, is smaller by a factor of about 2 than the one measured by the PHENIX experiment at RHIC and the ALICE experiment at the LHC. Within the analyzed range of central collisions no significant centrality dependence is observed. The data are found to be well described by a viscous hydrodynamic calculation combined with an UrQMD cascade model for the late stages.

We apply color-spin and flavor-spin quark–quark interactions to the meson and baryon constituent quarks, and calculate constituent quark masses, as well as the coupling constants of these interactions. The main goal of this paper was to determine constituent quark masses from light and open bottom hadron masses, using the fitting method we have developed and clustering of hadron groups. We use color-spin Fermi–Breit (FB) and flavor-spin Glozman–Riska (GR) hyperfine interaction (HFI) to determine constituent quark masses (especially b quark mass). Another aim was to discern between the FB and GR HFI because our previous findings had indicated that both interactions were satisfactory. Our improved fitting procedure of constituent quark masses showed that on average color-spin (FB) HFI yields better fits. The method also shows the way how the constituent quark masses and the strength of the interaction constants appear in different hadron environments.

Recent results of the CERES experiment at the CERN SPS on low-mass electron pair analysis and ϕ→K+K− are discussed and compared to models.

Anisotropic flow measurements constrain the shear $(\eta/s)$ and bulk ($\zeta/s$) viscosity of the quark-gluon plasma created in heavy-ion collisions, as well as give insight into the initial state of such collisions and hadronization mechanisms. In these proceedings, elliptic ($v_2$) and higher harmonic ($v_3, v_4$) flow coefficients of $\pi^{\pm}$, $K^{\pm}$, p$(\overline{\rm{p}})$ and the $\phi$-meson,measured in Pb--Pb collisions at the highest-ever center-of-mass energy of $\sqrt{s_{\rm NN}}$ = 5.02 TeV, are presented.

In 1999 the CERES/NA45 ran at the CERN SPS with a beam energy of 40 GeV/nucleon. The data set comprises about 8.7 millions Pb-Au events with a trigger selection corresponding to approximately the most central 30% of the geometrical cross section. Results on low-mass electron pair analysis are presented. The upgrade of the experimental setup with the radial drift TPC has allowed to enhance hadron physics capabilities of the experiment. New results on hadron spectra (including Lambda) and flow are presented.

This paper presents the results of an attempt to measure the elliptic flow in the smallest collision system (pp) at the highest designed collision energy at the Large Hadron Collider (LHC) using the genuine collective correlation among a large number of particles. A huge non-flow effect introduced by a strong jet correlation in pp collisions makes the application of the standard event plane flow analysis non-feasible. Therefore, in order to measure a possible elliptic flow in pp collisions, the Lee?Yang zero method is used in HIJING-simulated events for the LHC top energy of TeV on which an additional subevent with elliptic flow is superimposed. The Lee?Yang zero method has been tested in two cases with different ratios between the numbers of particles generated in the two subevents. The applied method has successfully reproduced the shape of the differential ? and elliptic flow dependencies, and on average its magnitude taking into account all involved particles, albeit with huge fluctuations.

Results of two- and four-particle angular two-dimensional correlations in pPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV, collected with the CMS detector, are presented. In high-multiplicity pPb events a ridge-like structure at the near-side emerges in two-particle ??-?? correlation. It is compared to the ridge found in 2.76 TeV PbPb collisions. In both systems, the ridge yield rises, reaches a maximum at pT ? 1-3 GeV/c and then decreases at higher pt, and increases monotonically with multiplicity. The 2-nd order Fourier harmonic has qualitatively similar pT dependence, but with a moderate multiplicity dependence in both systems. The multiplicity dependence of the 3-rd Fourier harmonic is rather similar for pPb and PbPb collisions. Color glass condensate and hydrodynamic predictions are compared to the experimental results.

Differential elliptic flow of υ2(pT) for π−, Ks0, p and Λ is measured at centerof-mass energy of √sNN=17.3 GeV near the mid-rapidity region in rather central PbAu collisions collected by the CERES/NA45 experiment at CERN. The proton υ2(pT) is extracted from π+ sample and particle ratios measured by NA49 experiment adapted to CERES conditions. The proton υ2(pT) data show a downward swing towards low pT with excursions into negative υ2 values which was not observed earlier. The results are compared with corresponding measurements performed at NA49 and STAR experiments as well as with theoretical predictions from ideal relativistic hydrodynamics. The obtained results for baryons are below hydrodynamic predictions even at the kinetic freeze-out temperature of Tf=160 MeV which needs introducing of a viscous hydrodynamics at the late hadronic phase.

The single-particle anisotropy coefficients measured in PbPb collisions at √ sNN =2.76 TeV and highmultiplicity pPb collisions at √ sNN =5.02 TeV by the CMS collaboration are presented. These coefficients are obtained from two-particle ∆φ-∆η correlations. The observed correlations in ultra-central PbPb events are expected to be particularly sensitive to initial-state fluctuations. The breakdown of factorization of two-particle correlations into single-particle azimuthal anisotropies is observed in both colliding systems. This effect, recently predicted by hydrodynamics, is induced due to initial-state fluctuations which could produce a transverse momentum dependence of event-plane angle even if hydrodynamic flow is the only source of correlations. Presented at IWoC2014 International Workshop on Collectivity in Relativistic Heavy Ion Collisions 2014 Initial-state fluctuations and factorization breaking in Pb-Pb and p-Pb collisions at LHC energies Jovan Milosevic for the CMS Collaboration 1 University of Belgrade and Vinca Institute of Nuclear Sciences, Belgrade, Serbia e-mail: Jovan.Milosevic@cern.ch

The CMS collaboration measured second-order single-particle anisotropy, ν2, using 2-, 4-, 6- and 8-particle correlations as well as the Lee-Yang Zero method in pPb and PbPb collisions. This result shows that the correlations found in the small and highly asymmetric pPb collision system are long-range and have a many-particle origin. Deeper insight into the nature of these correlations is achieved by studying the factorization breaking effect which appears trough a pT-dependent event plane angle, caused by the initial-state fluctuations. The effect is largest for the most-central PbPb collisions (up to 20%), while it is on the level of few percent for peripheral PbPb and high-multiplicity pPb events. Hydrodynamics models which include a pT-dependent event plane angle semi-quantitatively describe the data and suggest that the effect is mainly determined by the initial-state conditions.

The yields of strange (${\rm K}^{0}_{S}$, $\Lambda$, $\bar{\Lambda}$) and multi-strange ($\Xi^{-}$, $\bar{\Xi}^{+}$, $\Omega^{-}$, $\bar{\Omega}^{+}$) hadrons are measured at midrapidity in proton-proton (pp) collisions at $\sqrt{s}$ = 7 TeV as a function of the charged-particle multiplicity density (${\rm d}N_{\rm ch}/{\rm d}\eta$).The production rate of strange particles increases faster than that of non-strange hadrons, leading to an enhancement of strange particles relative to pions, similar to that found in nucleus-nucleus collisions as well as in proton-nucleus collisions at the LHC. This is the first observation of an enhanced production of strange particles in high-multiplicity pp collisions. The magnitude of this strangeness enhancement increases with the event activity, quantified by ${\rm d}N_{\rm ch}/{\rm d}\eta$, and with hadron strangeness. It reaches almost a factor of two for the $\Omega$ at the highest multiplicity presented. No enhancement is observed for particles with no strange quark content, demonstrating that the observed effect is strangeness rather than mass related. The results are not reproduced by any of the Monte Carlo models commonly used at the LHC, suggesting that further developments are needed for a complete microscopic understanding of strangeness production and indicating the presence of a phenomenon novel in high-multiplicity pp collisions.

Twoand multi-particle angular correlations in pp, pPb and PbPb collisions at the LHC energies are presented as a function of centrality, charged-particle multiplicity and transverse momentum (pT ). The data were collected using the CMS detector. The Fourier coefficents in PbPb collisions are measured over an extended pT range up to 100 GeV/c. These vn measurements at high-pT are complementary to the RAA measurements. The elliptic flow of charged and strange particles and the triangular flow of charged particles in pp collisions is measured using the two-particle correlations. A clear mass ordering effect is observed for low-pT v2 values. For the first time, in 13 TeV pp collisions, the v2 is extracted from fourand six-particle correlations, and is comparable to the v2 from two-particle correlations. This supports the collective nature of the long-range correlations in high-multiplicity pp collisions. A Principle Component Analysis (PCA) of two-particle correlations as a function of pT is studied in PbPb collisions at 2.76 TeV and high-multiplicity pPb collisions at 5.02 TeV. The factorization breaking of two-particle correlations can be attributed to the effect of initial-state fluctuations (ISF). Using a PCA approach, Fourier harmonics Vn∆ are characterized through the leading and sub-leading mode terms. The leading modes are essentially equivalent to the two-particle vn harmonics. The sub-leading modes represent the largest sources of factorization breaking. In the context of hydrodynamic models, they are a direct consequence of the ISF. Presented at low x 2016 24th Low-x Meeting Heavy ion results from CMS J. Milosevic Vinca Institute of Nuclear Sciences M. Petrovica Alasa 12-14, Belgrade, Serbia September 16, 2016 Abstract Twoand multi-particle angular correlations in pp, pPb and PbPb collisions at the LHC energies are presented as a function of centrality, chargedparticle multiplicity and transverse momentum (pT ). The data were collected using the CMS detector. The Fourier coefficients in PbPb collisions are measured over an extended pT range up to 100 GeV/c. These vn measurements at high-pT are complementary to the RAA measurements. The v2{2} of charged and strange particles emitted in pp collisions is measured using the two-particle correlations. A mass ordering effect is observed for low-pT v2 values. For the first time, in 13 TeV pp collisions, the v2 is extracted from fourand six-particle correlations, and is comparable to the v2{2}. This supports the collective nature of the long-range correlations in high-multiplicity pp collisions. A Principle Component Analysis (PCA) of two-particle correlations as a function of pT is studied in PbPb collisions at 2.76 TeV and high-multiplicity pPb collisions at 5.02 TeV. The factorization breaking of two-particle correlations can be attributed to the effect of initial-state fluctuations (ISF). Using a PCA approach, Fourier harmonics Vn∆ are characterized through the leading and sub-leading mode terms. The leading modes are essentially equivalent to the vn{2}. The sub-leading modes represent the largest sources of factorization breaking. In the context of hydrodynamic models, they are a direct consequence of the ISF.Twoand multi-particle angular correlations in pp, pPb and PbPb collisions at the LHC energies are presented as a function of centrality, chargedparticle multiplicity and transverse momentum (pT ). The data were collected using the CMS detector. The Fourier coefficients in PbPb collisions are measured over an extended pT range up to 100 GeV/c. These vn measurements at high-pT are complementary to the RAA measurements. The v2{2} of charged and strange particles emitted in pp collisions is measured using the two-particle correlations. A mass ordering effect is observed for low-pT v2 values. For the first time, in 13 TeV pp collisions, the v2 is extracted from fourand six-particle correlations, and is comparable to the v2{2}. This supports the collective nature of the long-range correlations in high-multiplicity pp collisions. A Principle Component Analysis (PCA) of two-particle correlations as a function of pT is studied in PbPb collisions at 2.76 TeV and high-multiplicity pPb collisions at 5.02 TeV. The factorization breaking of two-particle correlations can be attributed to the effect of initial-state fluctuations (ISF). Using a PCA approach, Fourier harmonics Vn∆ are characterized through the leading and sub-leading mode terms. The leading modes are essentially equivalent to the vn{2}. The sub-leading modes represent the largest sources of factorization breaking. In the context of hydrodynamic models, they are a direct consequence of the ISF.

for the CMS Collaboration

The ATLAS experiment is measuring both pp and PbPb collisions at the largest energies available in laboratory delivered by the Large Hadron Collider.Tests of the Standard Model and searches for exotic phenomena require precise information on QCD processes, which are responsible for the background present in pp interactions.In the heavy ion collisions, the QCD processes are determining the properties of the quark-gluon plasma which is created in the conditions of the extreme energy density.In this contribution, selected recent pp results from the ATLAS experiment are presented, including studies of jet properties and correlations in the multiparticle production.The effects of strong interactions in the dense matter created in PbPb collisions observed as the jet suppression and the collective flow are discussed in more detail.

The recent CMS results on anisotropic particle emission will be presented.Consistency between the results obtained using four-, six and eigth-particle correlation as well as the Lee-Yang zero method reveals a multi-particle nature of the long-range correlations observed in pPb collisions.By correlating an identified strange hadron (K 0 S or Λ/ Λ) with a charged particle, at large relative pseudorapidity, the magnitude of the elliptic and triangular flow of strange particles from both pPb and PbPb collisions have been extracted.The results for K 0 S and Λ/ Λ scaled by the number of constituent quarks as a function of transverse kinetic energy per quark are in a mutual agreement (within 10) for both v 2 and v 3 over a wide range of particle transverse kinetic energy and event multiplicities.Due to the initialstate fluctuations, the event-plane angle depends on both, transverse momenta (p T ) and pseudorapidity (η), which consequently induce breaking of the factorization of the two-particle azimuthal anisotropy into a product of single-particle anisotropies.For p T , maximal effect of factorization breaking of about 20is observed in ultra-central PbPb collisions.For η, the effect is weakest for mid-central PbPb events and gets larger for more central or peripheral PbPb collisions as well as for high multiplicity pPb collisions.The experimental results are consistent with recent hydrodynamic predictions in which the factorization breakdown effect is incorporated.It is found that the effect is mainly sensitive to the initial-state conditions rather than the shear viscosity of the medium.

The v3 coefficient, obtained using the PbAu data from the CERES detector at the top SPS energy of √sNN = 17.3 GeV, is presented. The v2 is measured over a pT range up to 100 GeV/c in PbPb collisions collected with the CMS detector. The v2{2} of charged and strange particles emitted in pp collisions shows a mass ordering effect. The v2{4} and v2{6} are comparable to the v2{2}, and thus supports the collective nature of the long-range correlations in high-multiplicity pp collisions at 13 TeV. Principle Component Analysis (PCA) of two-particle harmonics (VnΔ) is studied in PbPb and high-multiplicity pPb collisions at the LHC. The factorization breaking of the VnΔ can be attributed to the effect of initial-state fluctuations. Using a PCA, the VnΔ are characterized through the leading and sub-leading modes. The leading modes are essentially equivalent to the vn{2}. The sub-leading modes represent the largest sources of factorization breaking.

Nonlinear response coefficients of higher-order anisotropy harmonics for charged particles are measured in PbPb collisions at 2.76 and 5.02 TeV as a function of transverse momentum and collision centrality. The nonlinear response coefficients are obtained from $v_{n}$ harmonics measured with respect to their own plane and the mixed harmonics. Additionally, at 5.02 TeV PbPb collisions, a significant negative skewness is observed by a fine splitting between $v_{2}\{4\}$ and $v_{2}\{6\}$ cumulants. The elliptic flow skewness is measured up to 60\% centrality. The results are compared with hydrodynamic models with different shear viscosity to entropy density ratios and initial conditions.

Mössbauer spectra of human liver ferritin and its pharmaceutical analogues Ferrum Lek and Maltofer® measured at various temperatures within the range of 295–83 K were fitted using five quadrupole doublets related to different 57Fe microenvironments in various layers/regions of the ferrihydrite and akaganéite iron cores. The observed anomalous temperature dependences of some Mössbauer parameters were considered as a result of low temperature structural rearrangements in different layers/regions in the iron core.

Nonlinear response coefficients of higher-order v n anisotropy harmonics for charged particles, as a function of transverse momentum (p T ) and collision centrality, are measured in PbPb collisions at √ s NN = 2.76 and 5.02 TeV.The nonlinear response coefficients are obtained using v n harmonics measured with respect to their own plane and the mixed harmonics.The results are compared with hydrodynamic models with different shear viscosity to entropy density ratios and initial conditions.Additionally, the v 2 and v 3 anisotropy harmonics of charged particles and prompt D 0 mesons are measured at |y| ≤ 1 as a function of p T and centrality in PbPb data at √ s NN = 5.02 TeV collected with the CMS detector.Prompt D 0 mesons, formed from the c quarks produced via initial hard scatterings, are separated up to a high extent from nonprompt D 0 mesons emerged from decays of b hadrons.The results indicate that the charm quarks interact strongly with the QGP medium.Comparisons between theoretical models and data provide new constraints on the interaction between charm quarks and the QGP medium.

Differential triangular flow, $v_3(p_T)$, of negative pions is measured at $\sqrt{s_{NN}}$= 17.3 GeV around midrapidity by the CERES/NA45 experiment at CERN in central PbAu collisions in the range 0-30\% with a mean centrality of 5.5\%. This is the first measurement as a function of transverse momentum of the triangular flow at SPS energies. The $p_T$ range extends from about 0.05 GeV/c to more than 2 GeV/c. The triangular flow magnitude, corrected for the HBT effects, is smaller by a factor of about 2 than the one measured by the PHENIX experiment at RHIC and the ALICE experiment at the LHC. Within the analyzed range of central collisions no significant centrality dependence is observed. The data are found to be well described by a viscous hydrodynamic calculation combined with an UrQMD cascade model for the late stages.