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We present the first measurement of the atomic mass dependence of central \Xi~- and \overline{\Xi}~+ production. It is measured using a sample of 22,459 \Xi~-'s and \overline{\Xi}~+'s produced in collisions between a 250 GeV \pi~- beam and targets of beryllium, aluminum, copper, and tungsten. The relative cross sections are fit to the two parameter function \sigma_0 A~\alpha, where A is the atomic mass. We measure \alpha = 0.924+-0.020+-0.025, for Feynman-x in the range -0.09 < x_F < 0.15.
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We report on the inclusive J/$\psi$ production cross section measured at the CERN Large Hadron Collider in proton-proton collisions at a centre-of-mass energy $\sqrt{s}~=~13$ TeV. The J/$\psi$ mesons are reconstructed in the $\rm e^{+} e^{-}$ decay channel and the measurements are performed at midrapidity ($|y|<0.9$) in the transverse-momentum interval $0< p_{\rm T} <40$ GeV/$c$, using a minimum bias data sample corresponding to an integrated luminosity $L_{\text{int}} = 32.2~\text{nb}^{-1}$ and an Electromagnetic Calorimeter triggered data sample with $L_{\text{int}} = 8.3~\mathrm{pb}^{-1}$. The $p_{\rm T}$-integrated J/$\psi$ production cross section at midrapidity, computed using the minimum bias data sample, is $\text{d}\sigma/\text{d}y|_{y=0} = 8.97\pm0.24~(\text{stat})\pm0.48~(\text{syst})\pm0.15~(\text{lumi})~\mu\text{b}$. An approximate logarithmic dependence with the collision energy is suggested by these results and available world data, in agreement with model predictions. The integrated and $p_{\rm T}$-differential measurements are compared with measurements in pp collisions at lower energies and with several recent phenomenological calculations based on the non-relativistic QCD and Color Evaporation models.
Inclusive J/psi cross section. The first systematic uncertainty is the combined systematic uncertainties excluding luminosity, the second is the luminosity
Inclusive J/psi cross section. The first systematic uncertainty is the combined systematic uncertainties excluding luminosity, the second is the luminosity
Inclusive J/psi cross section. The first systematic uncertainty is the combined systematic uncertainties excluding luminosity, the second is the luminosity
Understanding the production mechanism of light (anti)nuclei is one of the key challenges of nuclear physics and has important consequences for astrophysics, since it provides an input for indirect dark-matter searches in space. In this paper, the latest results about the production of light (anti)nuclei in pp collisions at $\sqrt{s} = 13$ TeV are presented, focusing on the comparison with the predictions of coalescence and thermal models. For the first time, the coalescence parameters $B_2$ for deuterons and $B_3$ for helions are compared with parameter-free theoretical predictions that are directly constrained by the femtoscopic measurement of the source radius in the same event class. A fair description of the data with a Gaussian wave function is observed for both deuteron and helion, supporting the coalescence mechanism for the production of light (anti)nuclei in pp collisions. This method paves the way for future investigations of the internal structure of more complex nuclear clusters, including the hypertriton.
(Anti)proton spectrum in HM V0M multiplicity class
(Anti)proton spectrum in HM I V0M multiplicity class
(Anti)proton spectrum in HM II V0M multiplicity class
The polarization of the $\Lambda$ and $\overline\Lambda$ hyperons along the beam ($z$) direction, $P_{\rm z}$, has been measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02TeV recorded with ALICE at the Large Hadron Collider (LHC). The main contribution to $P_{\rm z}$ comes from elliptic flow induced vorticity and can be characterized by the second Fourier sine coefficient $P_{\rm z,s2} = \langle P_{\rm z} \sin(2\varphi - 2 \Psi_{\rm 2}) \rangle$, where $\varphi$ is the hyperon azimuthal emission angle, and $\Psi_{\rm 2}$ is the elliptic flow plane angle. We report the measurement of $P_{\rm z,\,{\rm s2}}$ for different collision centralities, and in the 30-50% centrality interval as a function of the hyperon transverse momentum and rapidity. The $P_{\rm z,\,{\rm s2}}$ is positive similarly as measured by the STAR Collaboration in Au-Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV, with somewhat smaller amplitude in the semi-central collisions. This is the first experimental evidence of a non-zero hyperon $P_{\rm z}$ in Pb-Pb collisions at the LHC. The comparison of the measured $P_{\rm z,\,{\rm s2}}$ with the hydrodynamic model calculations shows sensitivity to the competing contributions from thermal and the recently found shear induced vorticity, as well as to whether the polarization is acquired at the quark-gluon plasma or the hadronic phase.
Invariant mass dependence of the $P_{z}$ for $\overline\Lambda$ in the 30-40% centrality class in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV.
The average $(\Lambda + \overline\Lambda)$ polarization along beam direction as function of centrality in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV.
The average $(\Lambda + \overline\Lambda)$ polarization along beam direction as function of hyperon transverse momentum ($p_{\mathrm{T}}$) for 30-50% centrality in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV.
The production of prompt $D^{0}$, $D^{+}_{\rm s}$, and $\Lambda_{\rm c}^{+}$ hadrons, and their ratios, $D^{+}_{\rm s}$/$D^{0}$ and $\Lambda_{\rm c}^{+}$/$D^{0}$, are measured in proton-proton collisions at $\sqrt{s}$ = 13 TeV at midrapidity ($|y| <0.5$) with the ALICE detector at the LHC. The measurements are performed as a function of the charm-hadron transverse momentum ($p_{\rm T}$) in intervals of charged-particle multiplicity, measured with two multiplicity estimators covering different pseudorapidity regions. While the strange to non-strange $D^{+}_{\rm s}$/$D^{0}$ ratio indicates no significant multiplicity dependence, the baryon-to-meson $p_{\rm T}$-differential $\Lambda_{\rm c}^{+}$/$D^{0}$ ratio shows a multiplicity-dependent enhancement, with a significance of 5.3$\sigma$ for $1< p_{\rm T} < 12$ GeV/$c$, comparing the highest multiplicity interval with respect to the lowest one. The measurements are compared with a theoretical model that explains the multiplicity dependence by a canonical treatment of quantum charges in the statistical hadronisation approach, and with predictions from event generators that implement colour reconnection mechanisms beyond the leading colour approximation to model the hadronisation process. The $\Lambda_{\rm c}^{+}$/$D^{0}$ ratios as a function of $p_{\rm T}$ present a similar shape and magnitude as the $\Lambda/K^{0}_{s}$ ratios in comparable multiplicity intervals, suggesting a potential common mechanism for light- and charm-hadron formation, with analogous multiplicity dependence. The $p_{\rm T}$-integrated ratios, extrapolated down to $p_{\rm T}$=0, do not show a significant dependence on multiplicity within the uncertainties.
Transverse-momentum spectra of $\mathrm{D^0}$ hadrons measured in pp collisions at $\sqrt{{s}} = 13$~TeV for different multiplicity classes selected with the $N_\mathrm{trkl}$ estimator at midrapidity.
Transverse-momentum spectra of $\mathrm{D_s^+}$ hadrons measured in pp collisions at $\sqrt{{s}} = 13$~TeV for different multiplicity classes selected with the $N_\mathrm{trkl}$ estimator at midrapidity.
Transverse-momentum spectra of $\mathrm{\Lambda_c^+}$ hadrons measured in pp collisions at $\sqrt{{s}} = 13$~TeV for different multiplicity classes selected with the $N_\mathrm{trkl}$ estimator at midrapidity.
The production of J/$\psi$ is measured at midrapidity ($|y|<0.9$) in proton-proton collisions at $\sqrt{s}$ = 5.02 and 13 TeV, through the dielectron decay channel, using the ALICE detector at the Large Hadron Collider. The data sets used for the analyses correspond to integrated luminosities of $\mathcal{L}_{\rm int}$ = 19.4 $\pm$ 0.4 nb$^{-1}$ and $\mathcal{L}_{\rm int}$ = 32.2 $\pm$ 0.5 nb$^{-1}$ at $\sqrt{s}$ = 5.02 and 13 TeV, respectively. The fraction of non-prompt J/$\psi$ mesons, i.e. those originating from the decay of beauty hadrons, is measured down to a transverse momentum $p_{\rm T}$ = 2 GeV/$c$ (1 GeV/$c$) at $\sqrt{s}$ = 5.02 TeV (13 TeV). The $p_{\rm T}$ and rapidity ($y$) differential cross sections, as well as the corresponding values integrated over $p_{\rm T}$ and $y$, are carried out separately for prompt and non-prompt J/$\psi$ mesons. The results are compared with measurements from other experiments and theoretical calculations based on quantum chromodynamics (QCD). The shapes of the $p_{\rm T}$ and $y$ distributions of beauty quarks predicted by state-of-the-art perturbative QCD models are used to extrapolate an estimate of the $\rm b\overline{b}$ pair cross section at midrapidity and in the total phase space. The total $\rm b\overline{b}$ cross sections are found to be $\sigma_{\rm b \overline{\rm b}} = 541 \pm 45 (\rm stat.) \pm 69 (\rm syst.)_{-12}^{+10} (\rm extr.)~{\rm \mu b}$ and $\sigma_{\rm b \overline{\rm b}}~=~218 \pm 37 (\rm stat.) \pm 31 (\rm syst.)_{-9.1}^{+8.2} (\rm extr.)~{\rm \mu b}$ at $\sqrt{s}$ = 13 and 5.02 TeV, respectively. The value obtained from the combination of ALICE and LHCb measurements in pp collisions at $\sqrt{s}$ = 13 TeV is also provided.
Non-prompt J/$\psi$ fraction as a function of transverse momentum in pp at 13 TeV
Non-prompt J/$\psi$ fraction as a function of transverse momentum in pp at 5.02 TeV
Non-prompt J/$\psi$ cross section as a function of transverse momentum in pp at 13 TeV
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 production of $\mathrm{K}^{*}(\mathrm{892})^{0}$ and $\mathrm{\phi(1020)}$ resonances has been measured in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 8.16 TeV using the ALICE detector. Resonances are reconstructed via their hadronic decay channels in the rapidity interval $-$0.5 $<$$y$$<$ 0 and the transverse momentum spectra are measured for various multiplicity classes up to $p_{\rm T}$ = 20 GeV/$c$ for $\mathrm{K}^{*}(\mathrm{892})^{0}$ and $p_{\rm T}$ = 16 GeV/$c$ for $\mathrm{\phi(1020)}$. The $p_{\rm T}$ -integrated yields and mean transverse momenta are reported and compared with previous results in pp, p-Pb and Pb-Pb collisions. The $x_{\mathrm{T}}$ scaling for $\mathrm{K}^{*}(\mathrm{892})^{0}$ and $\mathrm{\phi(1020)}$ resonance production is newly tested in p-Pb collisions and found to hold in the high-$p_{\rm T}$ region at LHC energies. The nuclear modification factors ($R_{\rm pPb}$) as a function of $p_{\rm T}$ for $\mathrm{K}^{*0}$ and $\mathrm{\phi}$ at $\sqrt{s_{NN}}$ = 8.16 TeV are presented along with the new $R_{\rm pPb}$ measurements of $\mathrm{K}^{*0}$, $\mathrm{\phi}$ , $\Xi$, and $\Omega$ at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. At intermediate $p_{\rm T}$ (2-8 GeV/$c$), $R_{\rm pPb}$ of $\Xi$, $\Omega$ show a Cronin-like enhancement, while $\mathrm{K}^{*0}$ and $\mathrm{\phi}$ show no or little nuclear modification. At high $p_{\rm T}$ ($>$ 8 GeV/$c$), the $R_{\rm pPb}$ values of all hadrons are consistent with unity within uncertainties. The $R_{\rm pPb}$ of $\mathrm{K}^{*}(\mathrm{892})^{0}$ and $\mathrm{\phi(1020)}$ at $\sqrt{s_{\rm NN}}$ = 8.16 and 5.02 TeV show no significant energy dependence.
$p_{\mathrm T}$-differential yield of $\frac{\mathrm{K^{*0}} + \overline{\mathrm{K^{*0}}}}{2}$ in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}~=~$8.16 TeV (NSD).
$p_{\mathrm T}$-differential yield of $\frac{\mathrm{K^{*0}} + \overline{\mathrm{K^{*0}}}}{2}$ in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}~=~$8.16 TeV (Multiplicity class 0-5%).
$p_{\mathrm T}$-differential yield of $\frac{\mathrm{K^{*0}} + \overline{\mathrm{K^{*0}}}}{2}$ in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}~=~$8.16 TeV (Multiplicity class 5-10%).
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
$p_\mathrm{T}$-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
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