Systematic studies of charge-dependent two- and three-particle correlations in Pb-Pb collisions at $\sqrt{\it{s}_\mathrm{{NN}}} = $ 2.76 and 5.02 TeV used to probe the Chiral Magnetic Effect (CME) are presented. These measurements are performed for charged particles in the pseudorapidity ($\eta$) and transverse momentum ($p_{\rm{T}}$) ranges $\left|\eta \right| < 0.8$ and $0.2 < p_{\mathrm{T}} < 5$ GeV/$c$. A significant charge-dependent signal that becomes more pronounced for peripheral collisions is reported for the CME-sensitive correlators $\gamma_{1,1} = \langle \cos (\varphi_{\alpha} +\varphi_{\beta} - 2\Psi_{2}) \rangle$ and $\gamma_{1,-3} = \langle \cos (\varphi_{\alpha} -3\varphi_{\beta} + 2\Psi_{2}) \rangle$. The results are used to estimate the contribution of background effects, associated with local charge conservation coupled to anisotropic flow modulations, to measurements of the CME. A blast-wave parametrisation that incorporates local charge conservation tuned to reproduce the centrality dependent background effects is not able to fully describe the measured $\gamma_{1,1}$. Finally, the charge and centrality dependence of mixed-harmonics three-particle correlations, of the form $\gamma_{1,2} = \langle \cos (\varphi_{\alpha} +2\varphi_{\beta} - 3\Psi_{3}) \rangle$, which are insensitive to the CME signal, verify again that background contributions dominate the measurement of $\gamma_{1,1}$.
2-particle integrated correlators
2-particle differential correlator versus pT difference
2-particle differential correlator versus average pT
The measurements of the (anti)deuterons elliptic flow ($v_2$) and the first measurements of triangular flow ($v_3$) in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon collisions $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV are presented. A mass ordering at low transverse momentum ($p_{\rm T}$) is observed when comparing these measurements with those of other identified hadrons, as expected from relativistic hydrodynamics. The measured (anti)deuterons $v_2$ lies between the predictions from the simple coalescence and blast-wave models, which provide a good description of the data only for more peripheral and for more central collisions, respectively. The mass number scaling, which is violated for $v_2$, is approximately valid for the (anti)deuterons $v_3$. The measured $v_2$ and $v_3$ are also compared with the predictions from a coalescence approach with phase-space distributions of nucleons generated by iEBE-VISHNU with AMPT initial conditions coupled with UrQMD, and from a dynamical model based on relativistic hydrodynamics coupled to the hadronic afterburner SMASH. The model predictions are consistent with the data within the uncertainties in mid-central collisions, while a deviation is observed in central centrality intervals.
v2 as a function of pT for Pb-Pb collisions at \sqrt{s_NN} = 5.02 TeV and centrality 0-5%.
v2 as a function of pT for Pb-Pb collisions at \sqrt{s_NN} = 5.02 TeV and centrality 5-10%.
v2 as a function of pT for Pb-Pb collisions at \sqrt{s_NN} = 5.02 TeV and centrality 10-20%.
The inclusive J/$\psi$ elliptic ($v_2$) and triangular ($v_3$) flow coefficients measured at forward rapidity (2.5 $
Inclusive J/$\psi$ $v_2$ as a function of $p_{T}$ in the centrality interval 0$-$10.0 %
Inclusive J/$\psi$ $v_2$ as a function of $p_{T}$ in the centrality interval 10$-$30 %
Inclusive J/$\psi$ $v_2$ as a function of $p_{T}$ in the centrality interval 30$-$50 %
We present the first study of charged-hadron production associated with jets originating from b quarks in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data sample used in this study was collected with the CMS detector at the CERN LHC and corresponds to an integrated luminosity of 27.4 pb$^{-1}$. To characterize the jet substructure, the differential jet shapes, defined as the normalized transverse momentum distribution of charged hadrons as a function of angular distance from the jet axis, are measured for b jets. In addition to the jet shapes, the per-jet yields of charged particles associated with b jets are also quantified, again as a function of the angular distance with respect to the jet axis. Extracted jet shape and particle yield distributions for b jets are compared with results for inclusive jets, as well as with the predictions from the PYTHIA and HERWIG++ event generators.
The charged particle yield distribution $Y(\Delta r)$ of inclusive jets with $p_T > 120$ GeV and $1< p^{\text{trk}}_T < 12$ GeV are presented as functions of $\Delta r$ for differential $p_{\text{T}}^{\text{trk}}$ bin.
The charged particle yield distribution $Y(\Delta r)$ of b jets with $p_T > 120$ GeV and $1< p^{\text{trk}}_T < 12$ GeV are presented as functions of $\Delta r$ for differential $p_{\text{T}}^{\text{trk}}$ bin.
Charged particle yield distributions $Y(\Delta r)$ of inclusive jets with $1 < p_{\text{T}}^{\text{trk}} < 12$ GeV are presented as functions of $\Delta r$.Inclusive jets with $p_T > 120$ GeV and charged particles with $1 < p^{\text{trk}}_{\text{T}} < 12$ GeV are used to construct the distributions as functions of $\Delta r$ differential $p_{\text{T}}^{\text{trk}}$ bins.
The first measurements of dielectron production at midrapidity ($|\eta_{c}|<0.8$) in proton-proton and proton-lead collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV at the LHC are presented. The dielectron cross section is measured with the ALICE detector as a function of the invariant mass $m_{\rm{ee}}$ and the pair transverse momentum $p_{\rm{T,ee}}$ in the ranges $m_{\rm{ee}}$ < 3.5 GeV/$c^{2}$ and $p_{\rm{T,ee}}$ < 8.0 GeV/$c^{2}$, in both collision systems. In proton-proton collisions, the charm and beauty cross sections are determined at midrapidity from a fit to the data with two different event generators. This complements the existing dielectron measurements performed at $\sqrt{s}$ = 7 and 13 TeV. The slope of the $\sqrt{s}$ dependence of the three measurements is described by FONLL calculations. The dielectron cross section measured in proton-lead collisions is in agreement, within the current precision, with the expected dielectron production without any nuclear matter effects for $\rm{e}^{+}\rm{e}^{-}$ pairs from open heavy-flavor hadron decays. For the first time at LHC energies, the dielectron production in proton-lead and proton-proton collisions are directly compared at the same $\sqrt{s_{\rm{NN}}}$ via the dielectron nuclear modification factor $R_{\rm{pPb}}$. The measurements are compared to model calculations including cold nuclear matter effects, or additional sources of dielectrons from thermal radiation.
Inclusive $e^+e^-$ cross section in pp collisions at $\sqrt{s}$ = 5.02 TeV as a function of $m_{\rm ee}$. Electrons are measured within $|\eta_{\rm e}| < 0.8$ and $p_{\rm T,e} > 0.2$ GeV/$c$.
Inclusive $e^+e^-$ cross section in p-Pb collisions at $\sqrt{s}$ = 5.02 TeV as a function of $m_{\rm ee}$. Electrons are measured within $|\eta_{\rm e}| < 0.8$ and $p_{\rm T,e} > 0.2$ GeV/$c$.
Inclusive $e^+e^-$ cross section in pp collisions at $\sqrt{s}$ = 5.02 TeV as a function of $p_{\rm T,ee}$ for $0.5 < m_{\rm ee} < 1.1$ GeV/$c$. Electrons are measured within $|\eta_{\rm e}| < 0.8$ and $p_{\rm T,e} > 0.2$ GeV/$c$.
The elliptic flow of electrons from beauty hadron decays at midrapidity ($|y|$$<$ 0.8) is measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with the ALICE detector at the LHC. The azimuthal distribution of the particles produced in the collisions can be parameterized with a Fourier expansion, in which the second harmonic coefficient represents the elliptic flow, $v_{\rm 2}$. The $v_{\rm 2}$ coefficient of electrons from beauty-hadron decays is measured for the first time in the transverse momentum ($p_{\rm{T}}$) range 1.3-6 GeV/$c$ in the centrality class 30-50%. The measurement of electrons from beauty-hadron decays exploits their larger mean proper decay length $c\tau \approx$ 500 $\mu$m compared to that of charm hadrons and most of the other background sources. The $v_{\rm 2}$ of electrons from beauty hadron decays at midrapidity is found to be positive with a significance of 3.75$\sigma$. The results provide insights on the degree of thermalization of beauty quarks in the medium. A model assuming full thermalization of beauty quarks is strongly disfavoured by the measurement at high $p_{\rm{T}}$, but is in agreement with the results at low $p_{\rm{T}}$. Transport models including substantial interactions of beauty quarks with an expanding strongly-interacting medium describe the measurement.
$v_{2}$ of electrons from beauty hadron decays as a function of $p_{\rm T}$ in the centrality range 30-50% for $\sqrt{s_{\rm NN}}=5.02 {\rm~TeV}$
In this Letter, we report the first measurement of the inelastic cross section for antideuteron-nucleus interactions at low particle momenta, covering a range of $0.3 \leq p < 4$ GeV/$c$. The measurement is carried out using p-Pb collisions at a center-of-mass energy per nucleon-nucleon pair of $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV, recorded with the ALICE detector at the CERN LHC and utilizing the detector material as an absorber for antideuterons and antiprotons. The extracted raw primary antiparticle-to-particle ratios are compared to the results from detailed ALICE simulations based on the GEANT4 toolkit for the propagation of antiparticles through the detector material. The analysis of the raw primary (anti)proton spectra serves as a benchmark for this study, since their hadronic interaction cross sections are well constrained experimentally. The first measurement of the inelastic cross section for antideuteron-nucleus interactions averaged over the ALICE detector material with atomic mass numbers $\langle A \rangle$ = 17.4 and 31.8 is obtained. The measured inelastic cross section points to a possible excess with respect to the Glauber model parameterization used in GEANT4 in the lowest momentum interval of $0.3 \leq p < 0.47$ GeV/$c$ up to a factor 2.1. This result is relevant for the understanding of antimatter propagation and the contributions to antinuclei production from cosmic ray interactions within the interstellar medium. In addition, the momentum range covered by this measurement is of particular importance to evaluate signal predictions for indirect dark-matter searches.
Raw primary antiproton-to-proton ratio as a function of the momentum p_primary.
Raw primary antiproton-to-proton ratio from Geant4-based MC simulations as a function of the momentum p_primary.
Raw primary antideuteron-to-deuteron ratio as a function of the momentum p_primary.
The elliptic and triangular flow coefficients $v_2$ and $v_3$ of prompt D$^{0}$, D$^{+}$, and D$^{*+}$ mesons were measured at midrapidity ($|y|<0.8$) in Pb-Pb collisions at the centre-of-mass energy per nucleon pair of $\sqrt{s_{NN}} = 5.02$ TeV with the ALICE detector at the LHC. The D mesons were reconstructed via their hadronic decays in the transverse momentum interval $1< p_{\rm T}<36$ GeV/$c$ in central (0-10%) and semi-central (30-50%) collisions. Compared to pions, protons, and J/$\psi$ mesons, the average D-meson $v_{n}$ harmonics are compatible within uncertainties with a mass hierarchy for $p_{\rm T} \lesssim 3$ GeV/$c$, and are similar to those of charged pions for higher $p_{\rm T}$. The coupling of the charm quark to the light quarks in the underlying medium is further investigated with the application of the event-shape engineering (ESE) technique to the D-meson $v_2$ and $p_{\rm T}$-differential yields. The D-meson $v_2$ is correlated with average bulk elliptic flow in both central and semi-central collisions. Within the current precision, the ratios of per-event D-meson yields in the ESE-selected and unbiased samples are found to be compatible with unity. All the measurements are found to be reasonably well described by theoretical calculations including the effects of charm-quark transport and the recombination of charm quarks with light quarks in a hydrodynamically expanding medium.
Average $v_2${SP} vs. $p_\mathrm{T}$ of prompt D$^0$, D$^+$, and D$^{*+}$ mesons in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV in the centrality class 0-10% in the rapidity interval $|y|<0.8$. The first (sys,data) error is the systematic uncertainty from all the other sources except for the B feed-down. The second (sys,FD) error is the systematic uncertainty from the B feed-down contribution.
Average $v_2${SP} vs. $p_\mathrm{T}$ of prompt D$^0$, D$^+$, and D$^{*+}$ mesons in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV in the centrality class 30-50% in the rapidity interval $|y|<0.8$. The first (sys,data) error is the systematic uncertainty from all the other sources except for the B feed-down. The second (sys,FD) error is the systematic uncertainty from the B feed-down contribution.
Average $v_3${SP} vs. $p_\mathrm{T}$ of prompt D$^0$, D$^+$, and D$^{*+}$ mesons in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV in the centrality class 0-10% in the rapidity interval $|y|<0.8$. The first (sys,data) error is the systematic uncertainty from all the other sources except for the B feed-down. The second (sys,FD) error is the systematic uncertainty from the B feed-down contribution.
Measurement of Z-boson production in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=8.16$ TeV and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV is reported. It is performed in the dimuon decay channel, through the detection of muons with pseudorapidity $-4 < \eta_{\mu} < -2.5$ and transverse momentum $p_{\rm T}^{\mu} > 20$ GeV/$c$ in the laboratory frame. The invariant yield and nuclear modification factor are measured for opposite-sign dimuons with invariant mass $60 < m^{\mu\mu} < 120$ GeV$c^2$ and rapidity $2.5 < y_{cms}^{\mu\mu} < 4$. They are presented as a function of rapidity and, for the Pb-Pb collisions, of centrality as well. The results are compared with theoretical calculations, both with and without nuclear modifications to the Parton Distribution Functions (PDFs). In p-Pb collisions the center-of-mass frame is boosted with respect to the laboratory frame, and the measurements cover the backward ($-4.46< y_{cms}^{\mu\mu}<-2.96$) and forward ($2.03< y_{cms}^{\mu\mu}<3.53$) rapidity regions. For the p-Pb collisions, the results are consistent within experimental and theoretical uncertainties with calculations that include both free-nucleon and nuclear-modified PDFs. For the Pb-Pb collisions, a $3.4\sigma$ deviation is seen in the integrated yield between the data and calculations based on the free-nucleon PDFs, while good agreement is found once nuclear modifications are considered.
Differential fiducial cross section in p-Pb
Integrated fiducial invariant yield in Pb-Pb
Rapidity differential fiducial invariant yield in Pb-Pb
The production of $\pi^{\pm}$, $\rm{K}^{\pm}$, $\rm{K}^{0}_{S}$, $\rm{K}^{*}(892)^{0}$, $\rm{p}$, $\phi(1020)$, $\Lambda$, $\Xi^{-}$, $\Omega^{-}$, and their antiparticles was measured in inelastic proton-proton (pp) collisions at a center-of-mass energy of $\sqrt{s}$ = 13 TeV at midrapidity ($|y|<0.5$) as a function of transverse momentum ($p_{\rm{T}}$) using the ALICE detector at the CERN LHC. Furthermore, the single-particle $p_{\rm{T}}$ distributions of $\rm{K}^{0}_{S}$, $\Lambda$, and $\overline{\Lambda}$ in inelastic pp collisions at $\sqrt{s}$ = 7 TeV are reported here for the first time. The $p_{\rm{T}}$ distributions are studied at midrapidity within the transverse momentum range $0\leq p_{\rm{T}}\leq20$ GeV/$c$, depending on the particle species. The $p_{\rm{T}}$ spectra, integrated yields, and particle yield ratios are discussed as a function of collision energy and compared with measurements at lower $\sqrt{s}$ and with results from various general-purpose QCD-inspired Monte Carlo models. A hardening of the spectra at high $p_{\rm{T}}$ with increasing collision energy is observed, which is similar for all particle species under study. The transverse mass and $x_{\rm{T}}\equiv2p_{\rm{T}}/\sqrt{s}$ scaling properties of hadron production are also studied. As the collision energy increases from $\sqrt{s}$ = 7 to 13 TeV, the yields of non- and single-strange hadrons normalized to the pion yields remain approximately constant as a function of $\sqrt{s}$, while ratios for multi-strange hadrons indicate enhancements. The $p_{\rm{T}}$-differential cross sections of $\pi^{\pm}$, $\rm{K}^{\pm}$ and $\rm{p}$ ($\overline{\rm{p}}$) are compared with next-to-leading order perturbative QCD calculations, which are found to overestimate the cross sections for $\pi^{\pm}$ and $\rm{p}$ ($\overline{\rm{p}}$) at high $p_{\rm{T}}$.
Transverse momentum spectrum of $\pi^{+} + \pi^{-}$ measured at midrapidity ($|y|<0.5$) in inelastic pp collisions at $\sqrt{s}$ = 13 TeV. The normalization uncertainty of $\pm2.6\%$ is excluded.
Transverse momentum spectrum of $K^{+} + K^{-}$ measured at midrapidity ($|y|<0.5$) in inelastic pp collisions at $\sqrt{s}$ = 13 TeV. The normalization uncertainty of $\pm2.6\%$ is excluded.
Transverse momentum spectrum of $K^{0}_{S}$ measured at midrapidity ($|y|<0.5$) in inelastic pp collisions at $\sqrt{s}$ = 13 TeV. The normalization uncertainty of $\pm2.6\%$ is excluded.
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