We present a measurement of azimuthal correlations between inclusive J/$\psi$ and charged hadrons in p-Pb collisions recorded with the ALICE detector at the CERN LHC. The J/$\psi$ are reconstructed at forward (p-going, 2.03 $<$ y $<$ 3.53) and backward (Pb-going, $-$4.46 $<$ y $<$ $-$2.96) rapidity via their $\mu^+\mu^-$ decay channel, while the charged hadrons are reconstructed at mid-rapidity ($|\eta|$ $<$ 1.8). The correlations are expressed in terms of associated charged-hadron yields per J/$\psi$ trigger. A rapidity gap of at least 1.5 units is required between the trigger J/$\psi$ and the associated charged hadrons. Possible correlations due to collective effects are assessed by subtracting the associated per-trigger yields in the low-multiplicity collisions from those in the high-multiplicity collisions. After the subtraction, we observe a strong indication of remaining symmetric structures at $\Delta\varphi$ $\approx$ 0 and $\Delta\varphi$ $\approx$ $\pi$, similar to those previously found in two-particle correlations at middle and forward rapidity. The corresponding second-order Fourier coefficient ($v_2$) in the transverse momentum interval between 3 and 6 GeV/$c$ is found to be positive with a significance of about 5$\sigma$. The obtained results are similar to the J/$\psi$ $v_2$ coefficients measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV, suggesting a common mechanism at the origin of the J/$\psi$ $v_2$.
$v_2^{J/\psi}${2,sub} in bins of $p_T^{J/\psi}$ for p-Pb collisions in proton-going direction at $\sqrt{s_{NN}}$ = 5.02 TeV. The quoted global systematic uncertainties correspond to the combined statistical and systematic uncertainties of the measured $v_2^{tracklet}$ coefficient. The results are obtained by subtracting associated per-trigger yields in low-multiplicity (40-100% V0M) collisions from the yields in high-multiplicity (0-20% V0M) collisions.
$v_2^{J/\psi}${2,sub} in bins of $p_T^{J/\psi}$ for p-Pb collisions in Pb-going direction at $\sqrt{s_{NN}}$ = 5.02 TeV. The quoted global systematic uncertainties correspond to the combined statistical and systematic uncertainties of the measured $v_2^{tracklet}$ coefficient. The results are obtained by subtracting associated per-trigger yields in low-multiplicity (40-100% V0M) collisions from the yields in high-multiplicity (0-20% V0M) collisions.
$v_2^{J/\psi}${2,sub} in bins of $p_T^{J/\psi}$ for p-Pb collisions in proton-going direction at $\sqrt{s_{NN}}$ = 8.16 TeV. The quoted global systematic uncertainties correspond to the combined statistical and systematic uncertainties of the measured $v_2^{tracklet}$ coefficient. The results are obtained by subtracting associated per-trigger yields in low-multiplicity (40-100% V0M) collisions from the yields in high-multiplicity (0-20% V0M) collisions.
We report a precise measurement of the J/$\psi$ elliptic flow in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV with the ALICE detector at the LHC. The J/$\psi$ mesons are reconstructed at mid-rapidity ($|y| < 0.9$) in the dielectron decay channel and at forward rapidity ($2.5
Transverse momentum dependence of inclusive J/$\psi$ $v_2$ at $\sqrt{s_{\rm NN}}=5.02$ TeV for the 20-40% centrality class (forward rapidity). The first uncertainty (stat) is statistical, the second (sys,uncorrel) is the uncorrelated systematic, while the third one (sys,correl) is a $p_{\rm T}$-correlated systematic uncertainty.
Transverse momentum dependence of inclusive J/$\psi$ $v_2$ at $\sqrt{s_{\rm NN}}=5.02$ TeV for the 20-40% centrality class (mid-rapidity). The first uncertainty (stat) is statistical, the second (sys,uncorrel) is the uncorrelated systematic, while the third one (sys,correl) is a $p_{\rm T}$-correlated systematic uncertainty.
Transverse momentum dependence of inclusive J/$\psi$ $v_2$ at $\sqrt{s_{\rm NN}}=5.02$ TeV for the 5-20% centrality class (forward rapidity). The first uncertainty (stat) is statistical, the second (sys,uncorrel) is the uncorrelated systematic, while the third one (sys,correl) is a $p_{\rm T}$-correlated systematic uncertainty.
In ultrarelativistic heavy-ion collisions, the event-by-event variation of the elliptic flow $v_2$ reflects fluctuations in the shape of the initial state of the system. This allows to select events with the same centrality but different initial geometry. This selection technique, Event Shape Engineering, has been used in the analysis of charge-dependent two- and three-particle correlations in Pb-Pb collisions at $\sqrt{s_{_{\rm NN}}} =2.76$ TeV. The two-particle correlator $\langle \cos(\varphi_\alpha - \varphi_\beta) \rangle$, calculated for different combinations of charges $\alpha$ and $\beta$, is almost independent of $v_2$ (for a given centrality), while the three-particle correlator $\langle \cos(\varphi_\alpha + \varphi_\beta - 2\Psi_2) \rangle$ scales almost linearly both with the event $v_2$ and charged-particle pseudorapidity density. The charge dependence of the three-particle correlator is often interpreted as evidence for the Chiral Magnetic Effect (CME), a parity violating effect of the strong interaction. However, its measured dependence on $v_2$ points to a large non-CME contribution to the correlator. Comparing the results with Monte Carlo calculations including a magnetic field due to the spectators, the upper limit of the CME signal contribution to the three-particle correlator in the 10-50% centrality interval is found to be 26-33% at 95% confidence level.
$v_2\{EP\}$ with $|\Delta\eta| > 2.0$ as a function of centrality for unbiased events in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV.
$v_2\{EP\}$ with $|\Delta\eta| > 2.0$ as a function of centrality for shape selected events (0-10% $q_2$) in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV.
$v_2\{EP\}$ with $|\Delta\eta| > 2.0$ as a function of centrality for shape selected events (10-20% $q_2$) in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV.
The modification of the production of $J/\psi$, $\psi(\mathrm{2S})$, and $\mit{\Upsilon}(n\mathrm{S})$ ($n = 1, 2, 3$) in $p$+Pb collisions with respect to their production in $pp$ collisions has been studied. The $p$+Pb and $pp$ datasets used in this paper correspond to integrated luminosities of $28$ $\mathrm{nb}^{-1}$ and $25$ $\mathrm{pb}^{-1}$ respectively, collected in 2013 and 2015 by the ATLAS detector at the LHC, both at a centre-of-mass energy per nucleon pair of 5.02 TeV. The quarkonium states are reconstructed in the dimuon decay channel. The yields of $J/\psi$ and $\psi(\mathrm{2S})$ are separated into prompt and non-prompt sources. The measured quarkonium differential cross sections are presented as a function of rapidity and transverse momentum, as is the nuclear modification factor, $R_{p\mathrm{Pb}}$ for $J/\psi$ and $\mit{\Upsilon}(\mathrm{1S})$. No significant modification of the $J/\psi$ production is observed while $\mit{\Upsilon}(\mathrm{1S})$ production is found to be suppressed at low transverse momentum in $p$+Pb collisions relative to $pp$ collisions. The production of excited charmonium and bottomonium states is found to be suppressed relative to that of the ground states in central $p$+Pb collisions.
Summary of results for cross-section of non-prompt J/psi decaying to a muon pair in pp collisions at 5.02 TeV in nb/GeV. Uncertainties are statistical and systematic, respectively.
Summary of results for cross-section of non-prompt psi(2S) decaying to a muon pair in pp collisions at 5.02 TeV in nb/GeV. Uncertainties are statistical and systematic, respectively.
Summary of results for cross-section of prompt J/psi decaying to a muon pair in pp collisions at 5.02 TeV in nb/GeV. Uncertainties are statistical and systematic, respectively.
We present the results of three-dimensional femtoscopic analyses for charged and neutral kaons recorded by ALICE in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV. Femtoscopy is used to measure the space-time characteristics of particle production from the effects of quantum statistics and final-state interactions in two-particle correlations. Kaon femtoscopy is an important supplement to that of pions because it allows one to distinguish between different model scenarios working equally well for pions. In particular, we compare the measured 3D kaon radii with a purely hydrodynamical calculation and a model where the hydrodynamic phase is followed by a hadronic rescattering stage. The former predicts an approximate transverse mass ($m_{\mathrm{T}}$) scaling of source radii obtained from pion and kaon correlations. This $m_{\mathrm{T}}$ scaling appears to be broken in our data, which indicates the importance of the hadronic rescattering phase at LHC energies. A $k_{\mathrm{T}}$ scaling of pion and kaon source radii is observed instead. The time of maximal emission of the system is estimated using the three-dimensional femtoscopic analysis for kaons. The measured emission time is larger than that of pions. Our observation is well supported by the hydrokinetic model predictions.
Out projection of raw 3D LCMS K+- K+- correlation function for 0.2 < kT < 0.4 GeV/c bin.
Side projection of raw 3D LCMS K+- K+- correlation function for 0.2 < kT < 0.4 GeV/c bin
Long projection of raw 3D LCMS K+- K+- correlation function for 0.2 < kT < 0.4 GeV/c bin
The correlations between event-by-event fluctuations of anisotropic flow harmonic amplitudes have been measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV with the ALICE detector at the LHC. The results are reported in terms of multiparticle correlation observables dubbed Symmetric Cumulants. These observables are robust against biases originating from nonflow effects. The centrality dependence of correlations between the higher order harmonics (the quadrangular $v_4$ and pentagonal $v_5$ flow) and the lower order harmonics (the elliptic $v_2$ and triangular $v_3$ flow) is presented. The transverse momentum dependence of correlations between $v_3$ and $v_2$ and between $v_4$ and $v_2$ is also reported. The results are compared to calculations from viscous hydrodynamics and A Multi-Phase Transport ({AMPT}) model calculations. The comparisons to viscous hydrodynamic models demonstrate that the different order harmonic correlations respond differently to the initial conditions and the temperature dependence of the ratio of shear viscosity to entropy density ($\eta/s$). A small average value of $\eta/s$ is favored independent of the specific choice of initial conditions in the models. The calculations with the AMPT initial conditions yield results closest to the measurements. Correlations between the magnitudes of $v_2$, $v_3$ and $v_4$ show moderate $p_{\rm T}$ dependence in mid-central collisions. Together with existing measurements of individual flow harmonics, the presented results provide further constraints on the initial conditions and the transport properties of the system produced in heavy-ion collisions.
Centrality dependence of observables SC(5,2) in Pb-Pb collisions at 2.76 TeV.
Centrality dependence of observables SC(5,3) in Pb-Pb collisions at 2.76 TeV.
Centrality dependence of observables SC(4,3) in Pb-Pb collisions at 2.76 TeV.
An invariant differential cross section measurement of inclusive $\pi^{0}$ and $\eta$ meson production at mid-rapidity in pp collisions at $\sqrt{s}=8$ TeV was carried out by the ALICE experiment at the LHC. The spectra of $\pi^{0}$ and $\eta$ mesons were measured in transverse momentum ranges of $0.3
Invariant differential cross section of $\pi^0$ produced in inelastic pp collisions at center of mass energy 8 TeV, the uncertainty of $\sigma_{MB}$ of 2.6% is not included in the systematic error.
Invariant differential cross section of $\eta$ produced in inelastic pp collisions at center of mass energy 8 TeV, the uncertainty of $\sigma_{MB}$ of 2.6% is not included in the systematic error.
Integrated yields of $\pi^{0}$ mesons produced in inelastic pp collisions at center of mass energies of 2.76 and 8 TeV. The uncertainty of $\sigma_{MB}$ of $^{+3.9\%}_{-6.4\%}(model)\pm2.0(lumi)$% for $\sqrt{s}=2.76$ TeV and $\pm2.3$% for 8 TeV is not included in the systematic error.
We present the charged-particle multiplicity distributions over a wide pseudorapidity range ($-3.4<\eta<5.0$) for pp collisions at $\sqrt{s}=$ 0.9, 7, and 8 TeV at the LHC. Results are based on information from the Silicon Pixel Detector and the Forward Multiplicity Detector of ALICE, extending the pseudorapidity coverage of the earlier publications and the high-multiplicity reach. The measurements are compared to results from the CMS experiment and to PYTHIA, PHOJET and EPOS LHC event generators, as well as IP-Glasma calculations.
Multiplicity distribution in the pseudorapidity region -2.0 to 2.0 for NSD collisions at a centre-of-mass energy of 900 GeV.
Multiplicity distribution in the pseudorapidity region -2.4 to 2.4 for NSD collisions at a centre-of-mass energy of 900 GeV.
Multiplicity distribution in the pseudorapidity region -3.0 to 3.0 for NSD collisions at a centre-of-mass energy of 900 GeV.
The transverse momentum ($p_{\rm T}$) spectra and elliptic flow coefficient ($v_2$) of deuterons and anti-deuterons at mid-rapidity ($|y|<0.5$) are measured with the ALICE detector at the LHC in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV. The measurement of the $p_{\rm T}$ spectra of (anti-)deuterons is done up to 8 GeV/$c$ in 0-10% centrality class and up to GeV/$c$ in 10-20% and 20-40% centrality classes. The $v_2$ is measured in the $0.8
Deuteron $p_{\mathrm T}$ spectra for $p_{\mathrm T} > $ 4.4 GeV/$c$. Low $p_{\mathrm T}$ points can be found here 'http://hepdata.cedar.ac.uk/view/ins1380491'
$\overline{\mathrm d}/ d $ vs $p_{\mathrm T}$ for $p_{\mathrm T} > $ 4.4 GeV/$c$. Low $p_{\mathrm T}$ points can be found here 'http://hepdata.cedar.ac.uk/view/ins1380491'
v2 of anti-deuterons and deuterons vs $p_{\mathrm T}$ for different centrality intervals
The measurement of azimuthal correlations of charged particles is presented for Pb-Pb collisions at $\sqrt{s_{\rm NN}}=$ 2.76 TeV and p-Pb collisions at $\sqrt{s_{\rm NN}}=$ 5.02 TeV with the ALICE detector at the CERN Large Hadron Collider. These correlations are measured for the second, third and fourth order flow vector in the pseudorapidity region $|\eta|<0.8$ as a function of centrality and transverse momentum $p_{\rm T}$ using two observables, to search for evidence of $p_{\rm T}$-dependent flow vector fluctuations. For Pb-Pb collisions at 2.76 TeV, the measurements indicate that $p_{\rm T}$-dependent fluctuations are only present for the second order flow vector. Similar results have been found for p-Pb collisions at 5.02 TeV. These measurements are compared to hydrodynamic model calculations with event-by-event geometry fluctuations in the initial state to constrain the initial conditions and transport properties of the matter created in Pb-Pb and p-Pb collisions.
$v_2\{2\}$ with $|\eta| > 0.0$ for centrality class 0-5\% in Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV.
$v_2\{2\}$ with $|\eta| > 0.0$ for centrality class 5-10\% in Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV.
$v_2\{2\}$ with $|\eta| > 0.0$ for centrality class 10-20\% in Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV.
Forum