The production of non-prompt ${\rm D}^{0}$ mesons from beauty-hadron decays was measured at midrapidity ($\left| y \right| < 0.5$) in Pb-Pb collisions at a nucleon-nucleon center-of-mass energy of $\sqrt{s_{\rm NN}}=5.02~\mathrm{TeV}$ with the ALICE experiment at the LHC. Their nuclear modification factor ($R_{\rm AA}$), measured for the first time down to $p_{\rm T}=1~\mathrm{GeV}/c$ in the $0-10$% and $30-50$% centrality classes, indicates a significant suppression, up to a factor of about three, for $p_{\rm T} > 5~\mathrm{GeV}/c$ in the $0-10$% central Pb-Pb collisions. The data are described by models that include both collisional and radiative processes in the calculation of beauty-quark energy loss in the quark-gluon plasma, and quark recombination in addition to fragmentation as a hadronisation mechanism. The ratio of the non-prompt to prompt ${\rm D}^{0}$-meson $R_{\rm AA}$ is larger than unity for $p_{\rm T} > 4~\mathrm{GeV}/c$ in the $0-10$% central Pb-Pb collisions, as predicted by models in which beauty quarks lose less energy than charm quarks in the quark-gluon plasma because of their larger mass.
Transverse-momentum-differential production yields of non-prompt $\rm D^0$ in central (0-10%) and mid-central (30-50%) Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV.
The nuclear modification factor of non-prompt $\rm D^0$ as a function of transverse momentum in central (0-10%) and mid-central (30-50%) Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV.
The non-prompt to prompt $\rm D^0$-meson nuclear modification factor ratio as a function of transverse momentum in central (0-10%) Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV.
The $B_\mathrm{c}^+$ meson is observed for the first time in heavy ion collisions. Data from the CMS detector are used to study the production of the $B_\mathrm{c}^+$ meson in lead-lead (PbPb) and proton-proton (pp) collisions at a center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}} =$ 5.02 TeV, via the $B_\mathrm{c}^+ \to (J/\psi\to\mu^+\mu^-)\mu^+\nu_\mu$ decay. The $B_\mathrm{c}^+$ nuclear modification factor, derived from the PbPb-to-pp ratio of production cross sections, is measured in two bins of the trimuon transverse momentum and of the PbPb collision centrality. The B$_\mathrm{c}^+$ meson is shown to be less suppressed than quarkonia and most of the open heavy-flavor mesons, suggesting that effects of the hot and dense nuclear matter created in heavy ion collisions contribute to its production. This measurement sets forth a promising new probe of the interplay of suppression and enhancement mechanisms in the production of heavy-flavor mesons in the quark-gluon plasma.
The $B_c$ meson production (pp-equivalent) cross-section times branching fraction of the $B_c\rightarrow (J/\psi \rightarrow \mu\mu) \mu \nu_{\mu}$ decay in pp and PbPb collisions. The used kinematic variables correspond to those of the trimuon final state. The two $p_T$ bins correspond to different rapidity ranges. The total uncertainty is decomposed in an uncertainty from the fit and one representing all other sources. The markers of the $p_T^{\mu\mu\mu}$ bins are placed according to the Lafferty-Wyatt prescription.
The $B_c$ meson nuclear modification factor in PbPb collisions, in $p_T^{\mu\mu\mu}$ bins corresponding to different trimuon rapidity ranges. The total uncertainty is decomposed in a bin-to-bin-uncorrelated uncertainty and one fully correlated along the two bins. The markers of the $p_T^{\mu\mu\mu}$ bins are placed at the average of the Lafferty-Wyatt prescriptions applied to the pp and PbPb spectra.
The $B_c$ meson nuclear modification factor in PbPb collisions, in centrality bins, integrated over the studied kinematic range. The cut on the trimuon rapidity depends on the trimuon $p_T$. The total uncertainty is decomposed in a bin-to-bin-uncorrelated uncertainty and one fully correlated along the two bins. The centrality bin markers are placed at the minimum bias average number of participants $N_{part}$.
The production of J/$\psi$ is measured as a function of charged-particle multiplicity at forward rapidity in proton$-$proton (pp) collisions at center-of-mass energies $\sqrt{s} =$ 5.02 and 13 TeV. The J/$\psi$ mesons are reconstructed via their decay into dimuons in the rapidity interval (2.5 $< y <$ 4.0), whereas the charged-particle multiplicity density (${\rm d}N_{\rm{ch}}/{\rm d}\eta$) is measured at midrapidity $(|\eta| < 1)$. The production rate as a function of multiplicity is reported as the ratio of the yield in a given multiplicity interval to the multiplicity-integrated one. This observable shows a linear increase with charged-particle multiplicity normalized to the corresponding average value for inelastic events (${{\rm d}N_{\rm ch}/{\rm d}\eta}/{\langle {\rm d}N_{\rm ch}/{\rm d}\eta \rangle}$), at both the colliding energies. Measurements are compared with available ALICE results at midrapidity and theoretical model calculations. First measurement of the mean transverse momentum ($\langle p_{\mathrm{T}}\rangle$) of J/$\psi$ in pp collisions exhibits an increasing trend as a function of ${{\rm d}N_{\rm ch}/{\rm d}\eta}/{\langle {\rm d}N_{\rm ch}/{\rm d}\eta \rangle}$ showing a saturation towards high charged-particle multiplicities.
The study of the production of nuclei and antinuclei in pp collisions has proven to be a powerful tool to investigate the formation mechanism of loosely bound states in high-energy hadronic collisions. In this paper, the production of protons, deuterons and $^3$He and their charge conjugates at midrapidity is studied as a function of the charged-particle multiplicity in inelastic pp collisions at $\sqrt{s}=5.02$ TeV using the ALICE detector. Within the uncertainties, the yields of nuclei in pp collisions at $\sqrt{s}=5.02$ TeV are compatible with those in pp collisions at different energies and to those in p-Pb collisions when compared at similar multiplicities. The measurements are compared with the expectations of coalescence and Statistical Hadronisation Models. The results suggest a common formation mechanism behind the production of light nuclei in hadronic interactions and confirm that they do not depend on the collision energy but on the number of produced particles.
(Anti)proton spectrum in V0M multiplicity class I
(Anti)proton spectrum in V0M multiplicity class II
(Anti)proton spectrum in V0M multiplicity class III
The cross sections for inclusive and Mueller-Navelet dijet production are measured as a function of the rapidity separation between the jets in proton-proton collisions at $\sqrt{s} =$ 2.76 TeV for jets with transverse momentum $p_\mathrm{T}$$\gt$ 35 GeV and rapidity $\vert y\vert$$\lt$ 4.7. Various dijet production cross section ratios are also measured. A veto on additional jets with $p_\mathrm{T}$$\gt$ 20 GeV is introduced to improve the sensitivity to the effects of the Balitsky-Fadin-Kuraev-Lipatov (BFKL) evolution. The measurement is compared with the predictions of various Monte Carlo models based on leading-order and next-to-leading-order calculations including the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi leading-logarithm (LL) parton shower as well as the LL BFKL resummation.
Summary of the systematic uncertainties on the cross section dσincl/d∆y.
Summary of the systematic uncertainties on the cross section dσMN/d∆y.
Summary of the systematic uncertainties on the ratio Rincl.
Angular correlations of heavy-flavour and charged particles in high-energy proton-proton collisions are sensitive to the production mechanisms of heavy quarks and to their fragmentation as well as hadronisation processes. The measurement of the azimuthal-correlation function of prompt D mesons with charged particles in proton-proton collisions at a centre-of-mass energy of $\sqrt{s} = 13$ TeV with the ALICE detector is reported, considering D$^{0}$, D$^{+}$, and D$^{*+}$ mesons in the transverse-momentum interval $3 < p_{\rm T} < 36$ GeV/$c$ at midrapidity ($|y| < 0.5$), and charged particles with $p_{\rm T} > 0.3$ GeV/$c$ and pseudorapidity $|\eta| < 0.8$. This measurement has an improved precision and provides an extended transverse-momentum coverage compared to previous ALICE measurements at lower energies. The study is also performed as a function of the charged-particle multiplicity, showing no modifications of the correlation function with multiplicity within uncertainties. The properties and the transverse-momentum evolution of the near- and away-side correlation peaks are studied and compared with predictions from various Monte Carlo event generators. Among those considered, PYTHIA8 and POWHEG+PYTHIA8 provide the best description of the measured observables. The obtained results can provide guidance on tuning the generators.
Comparison of the azimuthal-correlation distributions of D mesons (average of D$^{0}$, D$^{+}$, and D$^{*+}$) with $3 < p_{\rm T} < 5$ GeV/$c$ and charged particles with $0.3 < p_{\rm T} < 1$ GeV/$c$, in pp collisions at $\sqrt{s} = $5, 7, and 13 TeV, after baseline subtraction. Rapidity range for the D mesons is $|y^{\rm D}_{\rm cms}| < 0.5$. Correlations are integrated for $|\Delta\eta|=|\eta_{\rm ch}-\eta_{\rm D}| < 1$. The azimuthal-correlation distributions are reported in the range $0 < \Delta\varphi < \pi$.
Comparison of the azimuthal-correlation distributions of D mesons (average of D$^{0}$, D$^{+}$, and D$^{*+}$) with $8 < p_{\rm T} < 16$ GeV/$c$ and charged particles with $0.3 < p_{\rm T} < 1$ GeV/$c$, in pp collisions at $\sqrt{s} = $5, 7, and 13 TeV, after baseline subtraction. Rapidity range for the D mesons is $|y^{\rm D}_{\rm cms}| < 0.5$. Correlations are integrated for $|\Delta\eta|=|\eta_{\rm ch}-\eta_{\rm D}| < 1$. The azimuthal-correlation distributions are reported in the range $0 < \Delta\varphi < \pi$.
Comparison of the azimuthal-correlation distributions of D mesons (average of D$^{0}$, D$^{+}$, and D$^{*+}$) with $16 < p_{\rm T} < 24$ GeV/$c$ and charged particles with $0.3 < p_{\rm T} < 1$ GeV/$c$, in pp collisions at $\sqrt{s} = $5, 7, and 13 TeV, after baseline subtraction. Rapidity range for the D mesons is $|y^{\rm D}_{\rm cms}| < 0.5$. Correlations are integrated for $|\Delta\eta|=|\eta_{\rm ch}-\eta_{\rm D}| < 1$. The azimuthal-correlation distributions are reported in the range $0 < \Delta\varphi < \pi$.
The production yield and angular anisotropy of prompt ${D_s^+}$ mesons were measured as a function of transverse momentum ($p_{ T}$) in Pb-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{ NN}} = 5.02$ TeV collected with the ALICE detector at the LHC. ${D_s^+}$ mesons and their charge conjugates were reconstructed at midrapidity ($|y|<0.5$) from their hadronic decay channel ${D_s^+ \to \phi \pi^+}$, with ${\phi \to K^-K^+}$, in the $p_{ T}$ intervals $2<p_{ T}<50$ GeV/$c$ and $2<p_{ T}<36$ GeV/$c$ for the 0-10% and 30-50% centrality intervals. For $p_{ T}>10$ GeV/$c$, the measured ${D_s^+}$-meson nuclear modification factor $R_{ AA}$ is consistent with the one of non-strange D mesons within uncertainties, while at lower $p_{ T}$ a hint for a ${D_s^+}$-meson $R_{ AA}$ larger than that of non-strange D mesons is seen. The enhanced production of ${D_s^+}$ relative to non-strange D mesons is also studied by comparing the $p_{ T}$-dependent ${D_s^+/D^0}$ production yield ratios in Pb-Pb and in pp collisions. The ratio measured in Pb-Pb collisions is found to be on average higher than that in pp collisions in the interval $2<p_{ T} <8$ GeV/$c$ with a significance of 2.3$\sigma$ and 2.4$\sigma$ for the 0-10% and 30-50% centrality intervals. The azimuthal anisotropy coefficient $v_2$ of prompt ${D_s^+}$ mesons was measured in Pb-Pb collisions in the 30-50% centrality interval and is found to be compatible with that of non-strange D mesons. The main features of the measured $R_{ AA}$, ${D_s^+/D^0}$ ratio, and $v_2$ as a function of $p_{ T}$ are described by theoretical calculations of charm-quark transport in a hydrodynamically expanding quark-gluon plasma including hadronisation via charm-quark recombination with light quarks from the medium. The $p_{ T}$-integrated production yield of ${D_s^+}$ mesons is compatible with the prediction of the statistical hadronisation model.
$p_\mathrm{T}$-differential production yield of prompt $\mathrm{D_s^+}$ mesons in the 0-10% centrality class in Pb-Pb collisions at $\sqrt{{s_\mathrm{NN}}}=5.02~\mathrm{{TeV}}$ in the rapidity interval $|y|<0.5$. Branching ratio of $\mathrm{D_s^+\to \phi\pi^+\to K^-K^+\pi^+}$: 0.0224
$p_\mathrm{T}$-differential production yield of prompt $\mathrm{D_s^+}$ mesons in the 0-10% centrality class in Pb-Pb collisions at $\sqrt{{s_\mathrm{NN}}}=5.02~\mathrm{{TeV}}$ in the rapidity interval $|y|<0.5$. Branching ratio of $\mathrm{D_s^+\to \phi\pi^+\to K^-K^+\pi^+}$: 0.0224
$p_\mathrm{T}$-differential production yield of prompt $\mathrm{D_s^+}$ mesons in the 30-50% centrality class in Pb-Pb collisions at $\sqrt{{s_\mathrm{NN}}}=5.02~\mathrm{{TeV}}$ in the rapidity interval $|y|<0.5$. Branching ratio of $\mathrm{D_s^+\to \phi\pi^+\to K^-K^+\pi^+}$: 0.0224
The production of prompt D$^{0}$, D$^{+}$, and D$^{*+}$ mesons was measured at midrapidity (|y|< 0.5) in Pb-Pb collisions at the centre-of-mass energy per nucleon-nucleon pair $\sqrt{s_{\rm NN}}$ = 5.02 TeV with the ALICE detector at the LHC. The D mesons were reconstructed via their hadronic decay channels and their production yields were measured in central (0-10%) and semicentral (30-50%) collisions. The measurement was performed up to a transverse momentum ($p_{\rm T}$) of 36 or 50 GeV/$c$ depending on the D meson species and the centrality interval. For the first time in Pb-Pb collisions at the LHC, the yield of D$^0$ mesons was measured down to $p_{\rm T}$ = 0, which allowed a model-independent determination of the $p_{\rm T}$-integrated yield per unit of rapidity (d$N$/d$y$). A maximum suppression by a factor 5 and 2.5 was observed with the nuclear modification factor ($R_{\rm AA}$) of prompt D mesons at $p_{\rm T}$ = 6-8 GeV/$c$ for the 0-10% and 30-50% centrality classes, respectively. The D-meson $R_{\rm AA}$ is compared with that of charged pions, charged hadrons, and J/$\psi$ mesons as well as with theoretical predictions. The analysis of the agreement between the measured $R_{\rm AA}$, elliptic ($v_2$) and triangular ($v_3$) flow, and the model predictions allowed us to constrain the charm spatial diffusion coefficient $D_s$. Furthermore the comparison of $R_{\rm AA}$ and $v_2$ with different implementations of the same models provides an important insight into the role of radiative energy loss as well as charm quark recombination in the hadronisation mechanisms.
Transverse momentum distributions d$N$/(d$y$d$p_{\mathrm{T}}$) of prompt D$^{0}$ (left) meson in the 0-10% (crosses) centrality classes in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV in |y|<0.5. The uncertainties on the BRs are quoted separately and the horizontal bars represent bin widths. Branching ratio of D$^0$ --> K$\pi$ = 0.0395
Transverse momentum distributions d$N$/(d$y$d$p_{\mathrm{T}}$) of prompt D$^{0}$ (left) meson in the 30-50% (diamonds) centrality classes in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV in |y|<0.5. The uncertainties on the BRs are quoted separately and the horizontal bars represent bin widths. The points in the figure of the paper are scaled for visibility by a factor 10$^{-1}$. Branching ratio of D$^0$ --> K$\pi$ = 0.0395
Transverse momentum distributions d$N$/(d$y$d$p_{\mathrm{T}}$) of prompt D$^{+}$ (middle) meson in the 0-10% (crosses) centrality classes in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV in |y|<0.5. The uncertainties on the BRs are quoted separately and the horizontal bars represent bin widths. Branching ratio of D$^+$ --> K$\pi\pi$ = 0.0938
A measurement of the inclusive b-jet production cross section is presented in pp and p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV, using data collected with the ALICE detector at the LHC. The jets were reconstructed in the central rapidity region $|\eta|<0.5$ from charged particles using the anti-$k_{\rm T}$ algorithm with resolution parameter $R=0.4$. Identification of b jets exploits the long lifetime of b hadrons, using the properties of secondary vertices and impact parameter distributions. The $p_{\rm T}$-differential inclusive production cross section of b jets, as well as the corresponding inclusive b-jet fraction, are reported for pp and p-Pb collisions in the jet transverse momentum range $10 \le p_{\text{T, ch jet}} \le 100$ GeV/$c$, together with the nuclear modification factor, $R_{\rm pPb}^{\text{b-jet}}$. The analysis thus extends the lower $p_{\rm T}$ limit of b-jet measurements at the LHC. The nuclear modification factor is found to be consistent with unity, indicating that the production of b jets in p-Pb at $\sqrt{s_{\rm NN}} = 5.02$ TeV is not affected by cold nuclear matter effects within the current precision. The measurements are well reproduced by POWHEG NLO pQCD calculations with PYTHIA fragmentation.
Fig. 11 left: The $p_\mathrm{T}$ differential production cross section of charged-particle anti-$k_{T}$ $R=0.4$ b jets in pp collisions at $\sqrt{s}~=~5.02$ TeV using the SV method.
Fig. 11 left: The $p_\mathrm{T}$ differential production cross section of charged-particle anti-$k_{T}$ $R=0.4$ b jets in pp collisions at $\sqrt{s}~=~5.02$ TeV using the IP method.
Fig. 11 right: The $p_\mathrm{T}$ differential production cross section of charged-particle anti-$k_{T}$ $R=0.4$ b jets in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}~=~5.02$ TeV using the SV method.
This article reports on the inclusive production cross section of several quarkonium states, $\mathrm{J}/\psi$, $\psi {\rm (2S)}$, $\Upsilon\rm(1S)$, $\Upsilon\rm(2S)$, and $\Upsilon\rm(3S)$, measured with the ALICE detector at the LHC, in pp collisions at $\sqrt{s} = 5.02$ TeV. The analysis is performed in the dimuon decay channel at forward rapidity ($2.5 < y < 4$). The integrated cross sections and transverse-momentum ($p_{\rm T}$) and rapidity ($y$) differential cross sections for $\mathrm{J}/\psi$, $\psi {\rm (2S)}$, $\Upsilon\rm(1S)$, and the $\psi {\rm (2S)}$-to-$\mathrm{J}/\psi$ cross section ratios are presented. The integrated cross sections, assuming unpolarized quarkonia, are: $\sigma_{\mathrm{J}/\psi}$($p_{\rm T}<20$ GeV/c) = 5.88 $\pm$ 0.03 $\pm$ 0.34 $\mu$b, $\sigma_{\psi {\rm (2S)}}$($p_{\rm T}<12$ GeV/c) = 0.87 $\pm$ 0.06 $\pm$ 0.10 $\mu$b, $\sigma_{\Upsilon\rm(1S)}$($p_{\rm T}<15$ GeV/c) = 45.5 $\pm$ 3.9 $\pm$ 3.5 nb, $\sigma_{\Upsilon\rm(2S)}$($p_{\rm T}<15$ GeV/c) = 22.4 $\pm$ 3.2 $\pm$ 2.7 nb, and $\sigma_{\Upsilon\rm(3S)}$($p_{\rm T}<15$ GeV/c) = 4.9 $\pm$ 2.2 $\pm$ 1.0 nb, where the first (second) uncertainty is the statistical (systematic) one. For the first time, the cross sections of the three $\Upsilon$ states, as well as the $\psi {\rm (2S)}$ one as a function of $p_{\rm T}$ and $y$, are measured at $\sqrt{s} = 5.02$ TeV at forward rapidity. These measurements also significantly extend the $\mathrm{J}/\psi$$p_{\rm T}$ reach and supersede previously published results. A comparison with ALICE measurements in pp collisions at $\sqrt{s} = 2.76$, 7, 8, and 13 TeV is presented and the energy dependence of quarkonium production cross sections is discussed. Finally, the results are compared with the predictions from several production models.
Differential production cross sections of J/$\psi$ as a function of $p_{\rm T}$.
Differential production cross sections of J/$\psi$ as a function of rapidity.
Rapidity Differential production cross sections of J/$\psi$ in the range 0.3 $\leq$ p$_{\rm T}$ < 2 GeV/c