The production cross section of inclusive J/$\psi$ pairs in pp collisions at a centre-of-mass energy $\sqrt{s} = 13$ TeV is measured with ALICE. The measurement is performed for J/$\psi$ in the rapidity interval $2.5 < y < 4.0$ and for transverse momentum $p_{\rm T} > 0$. The production cross section of inclusive J/$\psi$ pairs is reported to be $10.3 \pm 2.3 {\rm (stat.)} \pm 1.3 {\rm (syst.)}$ nb in this kinematic interval. The contribution from non-prompt J/$\psi$ (i.e. originated from beauty-hadron decays) to the inclusive sample is evaluated. The results are discussed and compared with data.
Inclusive JPSI pair cross section in $2.5 < y < 4.0$.
The measurements of the inclusive J/$\psi$ yield at midrapidity ($\left | y \right | < 0.9$) and forward rapidity (2.5 $< y <$ 4) in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ALICE detector at the LHC are reported. The inclusive J/$\psi$ production yields and nuclear modification factors, $R_{\rm AA}$, are measured as a function of the collision centrality, J/$\psi$ transverse momentum ($p_{\rm T}$), and rapidity. The J/$\psi$ average transverse momentum and squared transverse momentum ($\langle p_{\mathrm{T}}\rangle$ and $\langle p_{\mathrm{T}}^{\mathrm{2}}\rangle$) are evaluated as a function of the centrality at midrapidity. Compared to the previous ALICE publications, here the entire Pb$-$Pb collisions dataset collected during the LHC Run 2 is used, which improves the precision of the measurements and extends the $p_{\rm T}$ coverage. The $p_{\rm T}$-integrated $R_{\rm AA}$ shows a hint of an increasing trend towards unity from semicentral to central collisions at midrapidity, while it is flat at forward rapidity. The $p_{\rm T}$-differential $R_{\rm AA}$ shows a strong suppression at high $p_{\rm T}$ with less suppression at low $p_{\rm T}$ where it reaches a larger value at midrapidity compared to forward rapidity. The ratio of the $p_{\rm T}$-integrated yields of J/$\psi$ to those of D$^{0}$ mesons is reported for the first time for the central and semicentral event classes at midrapidity. Model calculations implementing charmonium production via the coalescence of charm quarks and antiquarks during the fireball evolution (transport models) or in a statistical approach with thermal weights are in good agreement with the data at low $p_{\rm T}$. At higher $p_{\rm T}$, the data are well described by transport models and a model based on energy loss in the strongly-interacting medium produced in nuclear collisions at the LHC.
Inclusive J$/psi$ invariant yield as a function of pT in Pb-Pb collisions at $\sqrt{{s}_{NN}}$ = 5.02 TeV for 0-10% centrality interval and |y|< 0.9. The given systematic uncertainties are the total systematic ones and are mostly considered as fully correlated over pT.;
Inclusive J$/psi$ invariant yield as a function of pT in Pb-Pb collisions at $\sqrt{{s}_{NN}}$ = 5.02 TeV for 30-50% centrality interval and |y|< 0.9. The given systematic uncertainties are the total systematic ones and are mostly considered as fully correlated over pT.;
Inclusive J$/psi$ invariant yield as a function of pT in Pb-Pb collisions at $\sqrt{{s}_{NN}}$ = 5.02 TeV for 0-20% centrality interval and 2.5 < y < 4. The given systematic uncertainties are the total systematic ones. It contains the correlated uncertainties over pT which amount to 1.69%. ;
The correlations between different moments of two flow amplitudes, extracted with the recently developed asymmetric cumulants, are measured in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV recorded by the ALICE detector at the CERN Large Hadron Collider. The magnitudes of the measured observables show a dependence on the different moments as well as on the collision centrality, indicating the presence of non-linear response in all even moments up to the eighth. Furthermore, the higher-order asymmetric cumulants show different signatures than the symmetric and lower-order asymmetric cumulants. Comparisons with state-of-the-art event generators using two different parametrizations obtained from Bayesian optimization show differences between data and simulations in many of the studied observables, indicating a need for further tuning of the models behind those event generators. These results provide new and independent constraints on the initial conditions and transport properties of the system created in heavy-ion collisions.
Centrality dependence of ${\rm SC}(2,3)$ in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV.
Centrality dependence of ${\rm AC}_{2,1}(2,3)$ in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV.
Centrality dependence of ${\rm AC}_{1,2}(2,3)$ in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV.
The azimuthal ($\Delta\varphi$) correlation distributions between heavy-flavor decay electrons and associated charged particles are measured in pp and p$-$Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.02$ TeV. Results are reported for electrons with transverse momentum $4<p_{\rm T}<16$ GeV/$c$ and pseudorapidity $|\eta|<0.6$. The associated charged particles are selected with transverse momentum $1<p_{\rm T}<7$ GeV/$c$, and relative pseudorapidity separation with the leading electron $|\Delta\eta| < 1$. The correlation measurements are performed to study and characterize the fragmentation and hadronization of heavy quarks. The correlation structures are fitted with a constant and two von Mises functions to obtain the baseline and the near- and away-side peaks, respectively. The results from p$-$Pb collisions are compared with those from pp collisions to study the effects of cold nuclear matter. In the measured trigger electron and associated particle kinematic regions, the two collision systems give consistent results. The $\Delta\varphi$ distribution and the peak observables in pp and p$-$Pb collisions are compared with calculations from various Monte Carlo event generators.
$\Delta\varphi$ distribution between heavy-flavor decay electrons and associated charged particles for $4 < p_{\rm T}^{\rm e} < 12$ ${\rm GeV}/c$ and $1 < p_{\rm T}^{\rm assoc} < 7$ ${\rm GeV}/c$ in pp collisions at $\sqrt{s_{\rm{NN}}} = 5.02$ TeV. The publication shows $\Delta\varphi$ distribution only for the ranges $1 < p_{\rm T}^{\rm assoc} < 2$, $2 < p_{\rm T}^{\rm assoc} < 3$, and $5 < p_{\rm T}^{\rm assoc} < 7$ ${\rm GeV}/c$.
$\Delta\varphi$ distribution between heavy-flavor decay electrons and associated charged particles for $4 < p_{\rm T}^{\rm e} < 12$ ${\rm GeV}/c$ and $1 < p_{\rm T}^{\rm assoc} < 7$ ${\rm GeV}/c$ in p$\textendash$Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.02$ TeV. The publication shows $\Delta\varphi$ distribution only for the ranges $1 < p_{\rm T}^{\rm assoc} < 2$, $2 < p_{\rm T}^{\rm assoc} < 3$, and $5 < p_{\rm T}^{\rm assoc} < 7$ ${\rm GeV}/c$.
Baseline of $\Delta\varphi$ distribution between heavy-flavor decay electrons and associated charged particles for $4 < p_{\rm T}^{\rm e} < 12$ ${\rm GeV}/c$ in pp and p$\textendash$Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.02$ TeV. The publication shows $\Delta\varphi$ distribution only for the ranges $1 < p_{\rm T}^{\rm assoc} < 2$, $2 < p_{\rm T}^{\rm assoc} < 3$, and $5 < p_{\rm T}^{\rm assoc} < 7$ ${\rm GeV}/c$.
A study of multiplicity and pseudorapidity distributions of inclusive photons measured in pp and p$-$Pb collisions at a center-of-mass energy per nucleon$-$nucleon collision of $\sqrt{s_{\rm NN}} = 5.02$ TeV using the ALICE detector in the forward pseudorapidity region $2.3 < \eta_{\rm lab} < 3.9$ is presented. Measurements in p$-$Pb collisions are reported for two beam configurations in which the directions of the proton and lead ion beam were reversed. The pseudorapidity distributions in p$-$Pb collisions are obtained for seven centrality classes which are defined based on different event activity estimators, i.e., the charged-particle multiplicity measured at midrapidity as well as the energy deposited in a calorimeter at beam rapidity. The inclusive photon multiplicity distributions for both pp and p$-$Pb collisions are described by double negative binomial distributions. The pseudorapidity distributions of inclusive photons are compared to those of charged particles at midrapidity in \pp collisions and for different centrality classes in p$-$Pb collisions. The results are compared to predictions from various Monte Carlo event generators. None of the generators considered in this paper reproduces the inclusive photon multiplicity distributions in the reported multiplicity range. The pseudorapidity distributions are, however, better described by the same generators.
Inclusive photon multiplicity distribution measured within $2.3<\eta_{\rm lab}<3.9$ in pp collisions at $\sqrt{s} = 5020~\mathrm{GeV}$.
Inclusive photon multiplicity distribution measured within $2.3<\eta_{\rm lab}<3.9$ in p-Pb collisions at $\sqrt{s_\mathrm{NN}} = 5020~\mathrm{GeV}$.
Inclusive photon multiplicity distribution measured within $2.3<\eta_{\rm lab}<3.9$ in Pb-p collisions at $\sqrt{s_\mathrm{NN}} = 5020~\mathrm{GeV}$.
A new, more precise measurement of the $\Lambda$ hyperon lifetime is performed using a large data sample of Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV with ALICE. The $\Lambda$ and $\overline{\Lambda}$ hyperons are reconstructed at midrapidity using their two-body weak decay channel $\Lambda \rightarrow \mathrm{p} + \pi^{-}$ and $\overline{\Lambda} \rightarrow \overline{\mathrm{p}} + \pi^{+}$. The measured value of the $\Lambda$ lifetime is $\tau_{\Lambda} = [261.07 \pm 0.37 \ ( \rm stat.) \pm 0.72 \ (\rm syst.) ]\ \rm ps$. The relative difference between the lifetime of $\Lambda$ and $\overline{\Lambda}$, which represents an important test of CPT invariance in the strangeness sector, is also measured. The obtained value $(\tau_{\Lambda}-\tau_{\overline{\Lambda}})/\tau_{\Lambda} = 0.0013 \pm 0.0028 \ (\mathrm{stat.}) \pm 0.0021 \ (\mathrm{syst.})$ is consistent with zero within the uncertainties. Both measurements of the $\Lambda$ hyperon lifetime and of the relative difference between $\tau_{\Lambda}$ and $\tau_{\overline{\Lambda}}$ are in agreement with the corresponding world averages of the Particle Data Group and about a factor of three more precise.
Lproper spectrum of Lambda and exponential fit for the lifetime extraction. Only statistical uncertainties are shown for each data point and for the mean lifetime extracted from the exponential fit.
Lproper spectrum of Antilambda and exponential fit for the lifetime extraction. Only statistical uncertainties are shown for each data point and for the mean lifetime extracted from the exponential fit.
Lproper spectrum of Lambda and Antilambda and exponential fit for the lifetime extraction. Only statistical uncertainties are shown for each data point and for the mean lifetime extracted from the exponential fit.
The ALICE Collaboration reports a differential measurement of inclusive jet suppression using pp and Pb$-$Pb collision data at a center-of-mass energy per nucleon-nucleon collision $\sqrt{s_{\rm NN}} = 5.02$ TeV. Charged-particle jets are reconstructed using the anti-$k_{\rm T}$ algorithm with resolution parameters $R =$ 0.2, 0.3, 0.4, 0.5, and 0.6 in pp collisions and $R =$ 0.2, 0.4, 0.6 in central (0$-$10%), semi-central (30$-$50%), and peripheral (60$-$80%) Pb$-$Pb collisions. A novel approach based on machine learning is employed to mitigate the influence of jet background. This enables measurements of inclusive jet suppression in new regions of phase space, including down to the lowest jet $p_{\rm T} \geq 40$ GeV/$c$ at $R = 0.6$ in central Pb$-$Pb collisions. This is an important step for discriminating different models of jet quenching in the quark-gluon plasma. The transverse momentum spectra, nuclear modification factors, derived cross section, and nuclear modification factor ratios for different jet resolution parameters of charged-particle jets are presented and compared to model predictions. A mild dependence of the nuclear modification factor ratios on collision centrality and resolution parameter is observed. The results are compared to a variety of jet-quenching models with varying levels of agreement.
delta pT distributions for ML and AB methods in central collisions with R = 0.4.
Summary of standard deviation of delta pT distributions for ML and AB methods in central and semi-central collisions as a function of the jet resolution parameter.
Raa toy distributions for charged jets as a function of jet pT for fractional in cone, fractional out of cone, and medium response toy modifications.
The fractions of non-prompt (i.e. originating from beauty-hadron decays) D$^0$ and D$^+$ mesons with respect to the inclusive yield are measured as a function of the charged-particle multiplicity in proton$-$proton collisions at a centre-of-mass energy of $\sqrt{s} = 13$ TeV with the ALICE detector at the LHC. The results are reported in intervals of transverse momentum ($p_{\rm T}$) and integrated in the range $1 < p_{\rm T} < 24$ GeV/$c$. The fraction of non-prompt D$^0$ and D$^+$ mesons is found to increase slightly as a function of $p_{\rm T}$ in all the measured multiplicity intervals, while no significant dependence on the charged-particle multiplicity is observed. In order to investigate the production and hadronisation mechanisms of charm and beauty quarks, the results are compared to PYTHIA 8 as well as EPOS 3 and EPOS 4 Monte Carlo simulations, and to calculations based on the colour glass condensate including three-pomeron fusion.
A newly developed observable for correlations between symmetry planes, which characterize the direction of the anisotropic emission of produced particles, is measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV with ALICE. This so-called Gaussian Estimator allows for the first time the study of these quantities without the influence of correlations between different flow amplitudes. The centrality dependence of various correlations between two, three and four symmetry planes is presented. The ordering of magnitude between these symmetry plane correlations is discussed and the results of the Gaussian Estimator are compared with measurements of previously used estimators. The results utilizing the new estimator lead to significantly smaller correlations than reported by studies using the Scalar Product method. Furthermore, the obtained symmetry plane correlations are compared to state-of-the-art hydrodynamic model calculations for the evolution of heavy-ion collisions. While the model predictions provide a qualitative description of the data, quantitative agreement is not always observed, particularly for correlators with significant non-linear response of the medium to initial state anisotropies of the collision system. As these results provide unique and independent information, their usage in future Bayesian analysis can further constrain our knowledge on the properties of the QCD matter produced in ultrarelativistic heavy-ion collisions.
Centrality dependence of $\langle \cos[4(\Psi_{4}-\Psi_{2})]\rangle_{\mathrm{GE}}$ in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV.
Centrality dependence of $\langle \cos[6(\Psi_{6}-\Psi_{3})]\rangle_{\mathrm{GE}}$ in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV.
Centrality dependence of $\langle \cos[6(\Psi_{2}-\Psi_{3})]\rangle_{\mathrm{GE}}$ in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV.
Recent measurements of charm-baryon production in hadronic collisions have questioned the universality of charm-quark fragmentation across different collision systems. In this work the fragmentation of charm quarks into charm baryons is probed, by presenting the first measurement of the longitudinal jet momentum fraction carried by $\Lambda_{\rm c}^{+}$ baryons, $z^{\mathrm{ch}}_\mathrm{||}$, in hadronic collisions. The results are obtained in proton-proton (pp) collisions at $\sqrt{s}=13$ TeV at the LHC, with $\Lambda_{\rm c}^{+}$ baryons and charged (track-based) jets reconstructed in the transverse momentum intervals of $3 \leq p_{\rm T}^{\Lambda_{\rm c}^{+}} < 15$ GeV/$c$ and $7 \leq p_{\rm T}^{\rm jet\;ch} < 15$ GeV/$c$, respectively. The $z^{\mathrm{ch}}_\mathrm{||}$ distribution is compared to a measurement of ${\rm D}^0$-tagged charged jets in pp collisions as well as to PYTHIA 8 simulations. The data hints that the fragmentation of charm quarks into charm baryons is softer with respect to charm mesons, in the measured kinematic interval, as predicted by hadronisation models which include colour correlations beyond leading-colour in the string formation.
$z_{\parallel}^{\rm{ch}}$ for $\Lambda_{\rm{c}}^{+}$-tagged jets and D$^{0}$-tagged jets in the $p_{\rm{T}}^{\rm{jet\text{ }ch}}$: 7-15 GeV/$c$ interval.
$z_{\parallel}^{\rm{ch}}$ ratio of $\Lambda_{\rm{c}}^{+}$-tagged jets and D$^{0}$-tagged jets in the $p_{\rm{T}}^{\rm{jet\text{ }ch}}$: 7-15 GeV/$c$ interval.
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