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%. ;
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
The production of K$^{*}(892)^{0}$ and $\phi(1020)$ mesons in proton-proton (pp) and lead-lead (Pb-Pb) collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV has been measured using the ALICE detector at the Large Hadron Collider (LHC). The transverse momentum ($p_{\mathrm{T}}$) distributions of K$^{*}(892)^{0}$ and $\phi(1020)$ mesons have been measured at midrapidity $(|y|<0.5)$ up to $p_{\mathrm{T}} = 20$ GeV$/c$ in inelastic pp collisions and for several Pb-Pb collision centralities. The collision centrality and collision energy dependence of the average transverse momenta agree with the radial flow scenario observed with stable hadrons, showing that the effect is stronger for more central collisions and higher collision energies. The $\mathrm{K^{*0}/K}$ ratio is found to be suppressed in Pb-Pb collisions relative to pp collisions: this indicates a loss of the measured K$^{*}(892)^{0}$ signal due to rescattering of its decay products in the hadronic phase. In contrast, for the longer-lived $\phi(1020)$ mesons, no such suppression is observed. The nuclear modification factors ($R_{\rm AA}$) of K$^{*}(892)^{0}$ and $\phi(1020)$ mesons are calculated using pp reference spectra at the same collision energy. In central Pb-Pb collisions for $p_{\rm T} > 8$ GeV$/c$, the $R_{\rm AA}$ values of K$^{*}(892)^{0}$ and $\phi(1020)$ are below unity and observed to be similar to those of pions, kaons, and (anti)protons. The $R_{\rm AA}$ values at high $p_{\mathrm T}$ ($>$~8 GeV$/c$) for K$^{*}(892)^{0}$ and $\phi(1020)$ mesons are in agreement within uncertainties for $\sqrt{s_\mathrm{NN}} = 5.02$ and 2.76 TeV.
$p_{T}$-dependent nuclear modification factor of $\rm{K}^{*0}$ (average of particle and anti-particle) meson measured in 0-10% centrality class for Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV.
$p_{T}$-dependent nuclear modification factor of $\rm{K}^{*0}$ (average of particle and anti-particle) meson measured in 10-20% centrality class for Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV.
$p_{T}$-dependent nuclear modification factor of $\rm{K}^{*0}$ (average of particle and anti-particle) meson measured in 20-30% centrality class for Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV.
Recent $p_{\rm T}$-integrated cross section measurements of the ground-state charm mesons and baryons, D$^{\rm 0}$, D$^+$, D$_{\rm s}^{+}$, $\Lambda_{\rm c}^{+}$, and $\Xi_{\rm c}^0$, are used to evaluate the charm fragmentation fractions and production cross section per unit of rapidity at midrapidity ($|y|<0.5$), in pp collisions at $\sqrt{s} = 5.02$ TeV at the LHC. The latter is ${\rm d} \sigma^{\rm c \overline{c}}/{\rm d} y|_{|y| < 0.5}$ =1165 $\pm 44(\rm{stat})^{+134}_{-101}(\rm{syst})$$\mu b$. These measurements were obtained for the first time in hadronic collisions at the LHC including the charm baryon states, recently measured by ALICE at midrapidity. The charm fragmentation fractions differ significantly from the values measured in e$^+$e$^-$ and ep collisions, providing evidence of the dependence of the parton-to-hadron fragmentation fractions on the collision system, indicating that the assumption of their universality is not supported by the measured cross sections. An increase of a factor of about 3.3 for the fragmentation fraction for the $\Lambda_{\rm c}^{+}$ with a significance of $5\,\sigma$ between the values obtained in pp collisions and those obtained in e$^+$e$^-$ (ep) collisions is reported. The fragmentation fraction for the $\Xi_{\rm c}^0$ was obtained for the first time in any collision system. The measured fragmentation fractions were used to update the $\rm c \overline{c}$ cross sections per unit of rapidity at $|y|<0.5$ at $\sqrt{s} = 2.76$ and 7 TeV, which are about 40% higher than the previously published results. The data were compared with perturbative-QCD calculations and lie at the upper edge of the theoretical bands.
Ratio of prompt open-charm hadrons H$_\mathrm{c}$ and inclusive $\mathrm{J}/\psi$ mesons over D$^0$-meson production cross section in pp collisions at $\sqrt{s} = 5.02$ TeV.
Fragmentation fractions of charm quark to open-charm hadrons $f(\mathrm{c \rightarrow H_c})$ in pp collisions at $\sqrt{s} = 5.02$ TeV.
Production cross section of charm-anticharm quark pairs per unity of rapidity at midrapidity $\mathrm{d}\sigma^{\mathrm{c\overline{c}}}/\mathrm{d}y|_{|y| < 0.5}$ in pp collisions at $\sqrt{s} = 2.76$, $5.02$, and $7$ TeV.
The transverse momentum ($p_{\rm T}$) differential cross section of the charm-strange baryon $\Xi^0_{\rm c}$ is measured at midrapidity ($|y|<$ 0.5) via its semileptonic decay into ${\rm e^{+}}\Xi^{-}\nu_{\rm e}$ in pp collisions at $\sqrt{s}$ = 5.02 TeV with the ALICE detector at the LHC. The ratio of the $p_{\rm T}$-differential $\Xi^0_{\rm c}$-baryon and ${\rm D^0}$-meson production cross sections is also reported. The measurements are compared with simulations with different tunes of the PYTHIA 8 event generator, with predictions from a statistical hadronisation model (SHM) with a largely augmented set of charm-baryon states beyond the current lists of the Particle Data Group, and with models including hadronisation via quark coalescence. The $p_{\rm T}$-integrated cross section of prompt $\Xi^0_{\rm c}$-baryon production at midrapidity is also reported, which is used to calculate the baryon-to-meson ratio $\Xi^0_{\rm c}/{\rm D^0} = 0.20 \pm 0.04~{\rm (stat.)} ^{+0.08}_{-0.07}~{\rm (syst.)}$. These results provide an additional indication of a modification of the charm fragmentation from $\rm e^+e^-$ and $\rm e^{-}p$ collisions to pp collisions.
$p_{\rm T}-$differential production cross section of prompt $\Xi^{0}_{\rm c}$ baryons in pp collisions at $\sqrt{s} =$ 5.02 TeV for $|y| < 0.5$.
$p_{\rm T}-$differential production cross section of inclusive $\Xi^{0}_{\rm c}$ baryons in pp collisions at $\sqrt{s} =$ 7 TeV for $|y| < 0.5$. The cross section result now is divided by the BR, which was not applied in the previous paper and HEPData.
$\Xi^0_{\rm c}$/${\rm D^0}$ ratio measured in pp collisions at $\sqrt{s}$ = 5.02 TeV for $|y| < 0.5$. The uncertainty of the BR of ${\rm D^0}$ and $\Xi^0_{\rm c}$ are written separately
In quantum scattering processes between two particles, aspects characterizing the strong and Coulomb forces can be observed in kinematic distributions of the particle pairs. The sensitivity to the interaction potential reaches a maximum at low relative momentum and vanishing distance between the two particles. Ultrarelativistic heavy-ion collisions at the LHC provide an abundant source of many hadron species and can be employed as a measurement method of scattering parameters that is complementary to scattering experiments. This study confirms that momentum correlations of particles produced in Pb-Pb collisions at the LHC provide an accurate measurement of kaon-proton scattering parameters at low relative momentum, allowing precise access to the $ {K}^{-} p\rightarrow {K}^{-} p$ process. This work also validates the femtoscopic measurement in ultrarelativistic heavy-ion collisions as an alternative to scattering experiments and a complementary tool to the study of exotic atoms with comparable precision. In this work, the first femtoscopic measurement of momentum correlations of ${K}^{-} p\ ({K}^{+}\overline{p})$ and ${K}^{+}p ({K}^{-}\overline{p})$ pairs in Pb-Pb collisions at centre-of-mass energy per nucleon pair of $\sqrt{s_{\rm NN}} = 5.02$ TeV registered by the ALICE experiment is reported. The components of the ${K}^{-} p$ complex scattering length are extracted and found to be $\Re f_0=-0.91\pm~{0.03}$(stat)$^{+0.17}_{-0.03}$(syst) and $\Im f_0 = 0.92\pm~{0.05}$(stat)$^{+0.12}_{-0.33}$(syst). The results are compared with chiral effective field theory predictions as well as with existing data from dedicated scattering and exotic kaonic atom experiments.
K p (opposite charge) correlation function for centrality 0-5% from Pb-Pb collisions at 5020 GeV
K p (same charge) correlation function for centrality 0-5% from Pb-Pb collisions at 5020 GeV
K p (opposite charge) correlation function for centrality 5-10% from Pb-Pb collisions at 5020 GeV
This Letter presents the first experimental evidence of the attractive strong interaction between a proton and a $\phi$ meson. The result is obtained from two-particle correlations of combined p-$\phi \oplus \overline{\rm {p}}$-$\phi$ pairs measured in high-multiplicity pp collisions at $\sqrt{s}~=~13$ TeV by the ALICE collaboration. The spin-averaged scattering length and effective range of the p-$\phi$ interaction are extracted from the fully corrected correlation function employing the Lednický-Lyuboshits approach. In particular, the imaginary part of the scattering length vanishes within uncertainties, indicating that inelastic processes do not play a prominent role for the p-$\phi$ interaction. These data demonstrate that the interaction is dominated by elastic p-$\phi$ scattering. Furthermore, an analysis employing phenomenological Gaussian- and Yukawa-type potentials is conducted. Under the assumption of the latter, the N-$\phi$ coupling constant is found to be $g_{\rm{N}-\phi} = 0.14\pm 0.03\,(\mathrm{stat.})\pm 0.02\,(\mathrm{syst.})$. This work provides valuable experimental input to accomplish a self-consistent description of the N-$\phi$ interaction, which is particularly relevant for the more fundamental studies on partial restoration of chiral symmetry in nuclear medium.
Measured $\mathrm{p}-\phi$ $\oplus$ $\overline{\mathrm{p}}-\phi$ correlation function.
Genuine $\mathrm{p}-\phi$ $\oplus$ $\overline{\mathrm{p}}-\phi$ correlation function.
The first results on K$^{*}$(892)$^{\mathrm{\pm}}$ resonance production in inelastic pp collisions at LHC energies of $\sqrt{s} = 5.02$, 8, and 13 TeV are presented. The K$^{*}$(892)$^{\mathrm{\pm}}$ has been reconstructed via its hadronic decay channel K$^{*}$(892)$^{\mathrm{\pm}}$$\rightarrow$$\mathrm {K^0_S}$$~+~\pi^{\pm}$ with the ALICE detector. Measurements of transverse momentum distributions, $p_{\mathrm{T}}$-integrated yields, and mean transverse momenta for charged K$^{*}$(892) are found to be consistent with previous ALICE measurements for neutral K$^{*}$(892) within uncertainties. For $p_{\mathrm{T}} > 1$ GeV/$c$ the K$^{*}$(892)$^{\mathrm{\pm}}$ transverse momentum spectra become harder with increasing centre-of-mass energy from 5.02 to 13 TeV, similar to what previously observed for charged kaons and pions. For $p_{\mathrm{T}} < 1$ GeV/$c$ the K$^{*}$(892)$^{\mathrm{\pm}}$ yield does not evolve significantly and the abundance of K$^{*}$(892)$^{\mathrm{\pm}}$ relative to K is rather independent of the collision energy. The transverse momentum spectra, measured for K$^{*}$(892)$^{\mathrm{\pm}}$ at midrapidity in the interval $0 < p_{\mathrm{T}} < 15$ GeV/$c$, are not well described by predictions of different versions of PYTHIA 6, PYTHIA 8 and EPOS-LHC event generators. These generators reproduce the measured $p_{\mathrm{T}}$-integrated K$^{*\mathrm{\pm}}$/K ratios and describe well the momentum dependence for $p_{\mathrm{T}} < 2$ GeV/$c$.
The p$_{T}$ distribution of K*(892)$^{\pm}$ in inelastic pp collisions at $\sqrt{s} = 13$ TeV. The data were collected in 2015 with an integrated luminosity of 0.92 nb$^{-1}$.
The p$_{T}$ distribution of K*(892)$^{\pm}$ in inelastic pp collisions at $\sqrt{s} = 8$ TeV. The data were collected in 2012 with an integrated luminosity of 1.25 nb$^{-1}$.
The p$_{T}$ distribution of K*(892)$^{\pm}$ in inelastic pp collisions at $\sqrt{s} = 5$ TeV. The data were collected in 2015 with an integrated luminosity of 2.12 nb$^{-1}$.
The production of $\Lambda$ baryons and ${\rm K}^{0}_{\rm S}$ mesons (${\rm V}^{0}$ particles) was measured in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV and pp collisions at $\sqrt{s} = 7$ TeV with ALICE at the LHC. The production of these strange particles is studied separately for particles associated with hard scatterings and the underlying event to shed light on the baryon-to-meson ratio enhancement observed at intermediate transverse momentum ($p_{\rm T}$) in high multiplicity pp and p-Pb collisions. Hard scatterings are selected on an event-by-event basis with jets reconstructed with the anti-$k_{\rm T}$ algorithm using charged particles. The production of strange particles associated with jets $p_{\rm T,\;jet}^{\rm ch}>10$ and $p_{\rm T,\;jet}^{\rm ch}>20$ GeV/$c$ in p-Pb collisions, and with jet $p_{\rm T,\;jet}^{\rm ch}>10$ GeV/$c$ in pp collisions is reported as a function of $p_{\rm T}$. Its dependence on angular distance from the jet axis, $R({\rm V}^{0},\;{\rm jet})$, for jets with $p_{\rm T,\;jet}^{\rm ch}>10$ GeV/$c$ in p-Pb collisions is reported as well. The $p_{\rm T}$-differential production spectra of strange particles associated with jets are found to be harder compared to that in the underlying event and both differ from the inclusive measurements. In events containing a jet, the density of the ${\rm V}^{0}$ particles in the underlying event is found to be larger than the density in the minimum bias events. The $\Lambda/{\rm K}^{0}_{\rm S}$ ratio associated with jets in p-Pb collisions is consistent with the ratio in pp collisions and follows the expectation of jets fragmenting in vacuum. On the other hand, this ratio within jets is consistently lower than the one obtained in the underlying event and it does not show the characteristic enhancement of baryons at intermediate $p_{\rm T}$ often referred to as "baryon anomaly" in the inclusive measurements.
$p_{\rm T}$-differential density of inclusive ${\rm V}^{0}$ particles in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV.
$p_{\rm T}$-differential density of ${\rm V}^{0}$ particles in underlying events (perp. cone) in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV.
$p_{\rm T}$-differential densities of ${\rm V}^{0}$ particles selected with $R({\rm V}^{0},{\rm jet}) < 0.4$ and that produced in jets in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV.
The $p_{\rm T}$-differential cross sections of prompt charm-strange baryons $Ξ^0_{\rm c}$ and $Ξ^+_{\rm c}$ were measured at midrapidity ($|y| < 0.5$) in proton-proton (pp) collisions at a centre-of-mass energy $\sqrt{s}=$~13~TeV with the ALICE detector at the LHC. The $Ξ^0_{\rm c}$ baryon was reconstructed via both the semileptonic decay ($Ξ^{-}{\rm e^{+}}ν_{\rm e}$) and the hadronic decay ($Ξ^{-}{\rm π^{+}}$) channels. The $Ξ^+_{\rm c}$ baryon was reconstructed via the hadronic decay ($Ξ^{-}π^{+}π^{+}$) channel. The branching-fraction ratio $\rm {\rm BR}(Ξ_c^0\rightarrow~ Ξ^-e^+ν_e)/\rm {\rm BR}(Ξ_c^0\rightarrow Ξ^{-}π^+)=$ 0.95 $\pm$ 0.15 (stat) $\pm$ 0.16 (syst) was consistent with the Belle's result within 1$σ$. The transverse momentum ($p_{\rm T}$) dependence of the $Ξ^0_{\rm c}$- and $Ξ^+_{\rm c}$-baryon production relative to the ${\rm D^0}$-meson and to the $Σ^{0,+,++}_{\rm c}$- and $Λ^+_{\rm c}$-baryon production are reported. The baryon-to-meson ratio increases towards low $p_{\rm T}$ up to a value of approximately 0.3. The measurements are compared with various models that take different hadronisation mechanisms into consideration. The results provide stringent constraints to these theoretical calculations and additional evidence that different processes are involved in charm hadronisation in electron-positron ($\rm e^+e^-$) and hadronic collisions.
Cross section of prompt $\rm \Xi_c^0$ baryon as a function of $p_{\rm T}$ in pp collisions at $\sqrt{s}=13$ TeV for $|y|<0.5$.
Cross section of prompt $\rm \Xi_c^0$ baryon as a function of $p_{\rm T}$ in pp collisions at $\sqrt{s}=13$ TeV for $|y|<0.5$.
Cross section of prompt $\rm \Xi_c^0$ baryon as a function of $p_{\rm T}$ in pp collisions at $\sqrt{s}=13$ TeV for $|y|<0.5$.
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