The yields of the K*(892)$^{0}$ and $\Phi$(1020) resonances are measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV through their hadronic decays using the ALICE detector. The measurements are performed in multiple centrality intervals at mid-rapidity (|$y$|<0.5) in the transverse-momentum ranges 0.3 < $p_{\rm T}$ < 5 GeV/$c$ for the K*(892)$^{0}$ and 0.5 < $p_{\rm T}$ < 5 GeV/$c$ for the $\Phi$(1020). The yields of K*(892)$^{0}$ are suppressed in central Pb-Pb collisions with respect to pp and peripheral Pb-Pb collisions (perhaps due to rescattering of its decay products in the hadronic medium), while the longer lived $\Phi$(1020) meson is not suppressed. These particles are also used as probes to study the mechanisms of particle production. The shape of the $p_{\rm T}$ distribution of the $\Phi$(1020) meson, but not its yield, is reproduced fairly well by hydrodynamic models for central Pb-Pb collisions. In central Pb-Pb collisions at low and intermediate $p_{\rm T}$, the p/$\Phi$(1020) ratio is flat in $p_{\rm T}$, while the p/$\pi$ and $\Phi$(1020)/$\pi$ ratios show a pronounced increase and have similar shapes to each other. These results indicate that the shapes of the $p_{\rm T}$ distributions of these particles in central Pb-Pb collisions are determined predominantly by the particle masses and radial flow. Finally, $\Phi$(1020) production in Pb-Pb collisions is enhanced, with respect to the yield in pp collisions and the yield of charged pions, by an amount similar to the $\Lambda$ and $\Xi$.
Transverse-momentum distributions of (K*(892)0 + anti-K*(892)0)/2 in Pb-Pb collisions at sqrt(sNN)=2.76 TeV, centrality 0.0-20.0%.
Transverse-momentum distributions of (K*(892)0 + anti-K*(892)0)/2 in Pb-Pb collisions at sqrt(sNN)=2.76 TeV, centrality 20.0-40.0%.
Transverse-momentum distributions of (K*(892)0 + anti-K*(892)0)/2 in Pb-Pb collisions at sqrt(sNN)=2.76 TeV, centrality 40.0-60.0%.
The measurement of primary $\pi^{\pm}$, K$^{\pm}$, p and $\overline{p}$ production at mid-rapidity ($|y| <$ 0.5) in proton-proton collisions at $\sqrt{s} = 7$ TeV performed with ALICE (A Large Ion Collider Experiment) at the Large Hadron Collider (LHC) is reported. Particle identification is performed using the specific ionization energy loss and time-of-flight information, the ring-imaging Cherenkov technique and the kink-topology identification of weak decays of charged kaons. Transverse momentum spectra are measured from 0.1 up to 3 GeV/$c$ for pions, from 0.2 up to 6 GeV/$c$ for kaons and from 0.3 up to 6 GeV/$c$ for protons. The measured spectra and particle ratios are compared with QCD-inspired models, tuned to reproduce also the earlier measurements performed at the LHC. Furthermore, the integrated particle yields and ratios as well as the average transverse momenta are compared with results at lower collision energies.
Combined transverse momentum spectra of PI, K and P, sum of particles and antiparticles, measured at mid-rapidity in pp collisions at SQRT(S) = 7 TeV normalized to the number of inelastic collisions. Statistical and systematic uncertainties are reported. The uncertainty due to the normalization to inelastic collisions (+7-4 %) is not included.
Kaon/Pion ratio in pp collisions at SQRT(S) = 7 TeV.
Proton/Pion ratio in pp collisions at SQRT(S) = 7 TeV.
The transverse momentum ($p_{\mathrm T}$) distribution of primary charged particles is measured at midrapidity in minimum-bias p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ALICE detector at the LHC in the range $0.15<p_{\mathrm T}<50$ GeV/$c$. The spectra are compared to the expectation based on binary collision scaling of particle production in pp collisions, leading to a nuclear modification factor consistent with unity for $p_{\mathrm T}$ larger than 2 GeV/$c$, with a weak indication of a Cronin-like enhancement for $p_{\rm T}$ around 4 GeV/$c$. The measurement is compared to theoretical calculations and to data in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV.
Transverse momentum distributions of charged particles in minimum-bias (NSD) p-Pb collisions for different pseudorapidity ranges.
The histogram represents the reference spectrum (cross section scaled by the nuclear overlap function, T(pPb)) in inelastic pp collisions, determined in |eta(cms)| < 0.8.
The ratio of spectra in p-Pb at backward pseudorapidities to that at |eta(cms)| < 0.3.
Transverse momentum spectra of $\pi^{\pm}$, $\rm K^{\pm}$ and p($\bar{\rm p}$) up to $p_{\rm T}$ = 20 GeV/$c$ at mid-rapidity in pp and Pb-Pb collisions at $\sqrt{s_{\rm NN}}=$ 2.76 TeV have been measured using the ALICE detector at the Large Hadron Collider. The proton-to-pion and the kaon-to-pion ratios both show a distinct peak at $p_{\rm T} \approx 3 GeV/c$ in central Pb-Pb collisions. Below the peak, $p_{\rm T}$ < 3 GeV/$c$, both ratios are in good agreement with hydrodynamical calculations, suggesting that the peak itself is dominantly the result of radial flow rather than anomalous hadronization processes. For $p_{\rm T}$ > 10 GeV/$c$ particle ratios in pp and Pb-Pb collisions are in agreement and the nuclear modification factors for $\pi^{\pm}$, $\rm K^{\pm}$ and $\rm p$($\bar{\rm p}$) indicate that, within the systematic and statistical uncertainties, the suppression is the same. This suggests that the chemical composition of leading particles from jets in the medium is similar to that of vacuum jets.
Invariant yields of identified pions in central and peripheral Pb-Pb collisions, together with the unscaled pp reference yields.
Invariant yields of identified kaons in central and peripheral Pb-Pb collisions, together with the unscaled pp reference yields.
Invariant yields of identified protons in central and peripheral Pb-Pb collisions, together with the unscaled pp reference yields.
This note describes the details of the analysis of charged-particle pseudorapidity densities and multiplicity distributions measured by the ALICE detector in pp collisions at $\sqrt{s}$ = 0.9 and 7 TeV in specific phase space regions. The primary goal of the analysis is to provide reference measurements for Monte Carlo tuning. The pseudorapidity range |h| < 0.8 is considered and a lower $p_T$ cut is applied, at 0.15, 0.5 GeV/c and at 1 GeV/c. The choice of such phase space regions to measure the charged-particle multiplicity allows a direct comparison with the analogous results obtained by other LHC collaborations, namely ATLAS and CMS. The class of events considered are those having at least one charged particle in the kinematical ranges just described. In the note, the analysis procedure is presented, together with the corrections applied to the data, and the systematic uncertainty evaluation. The comparison of the results with different Monte Carlo generators is also shown.
dNch/deta versus eta obtained at sqrt(s) = 0.9 and 7 TeV with pT > 0.15 GeV.
dNch/deta versus eta obtained at sqrt(s) = 0.9 and 7 TeV with pT > 0.50 GeV.
dNch/deta versus eta obtained at sqrt(s) = 0.9 and 7 TeV with pT > 1.00 GeV.
The production of ${\rm\Xi}^-$ and ${\rm\Omega}^-$ baryons and their anti-particles in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV has been measured using the ALICE detector. The transverse momentum spectra at mid-rapidity ($|y| < 0.5$) for charged $\rm\Xi$ and $\rm\Omega$ hyperons have been studied in the range $0.6 < p_{\rm T} < 8.0$ GeV/$c$ and $1.2 < p_{\rm T} < 7.0$ GeV/$c$, respectively, and in several centrality intervals (from the most central 0-10% to the most peripheral 60-80% collisions). These spectra have been compared with the predictions of recent hydrodynamic models. In particular, the Krak${\'o}$w and EPOS models give a satisfactory description of the data, with the latter covering a wider $p_{\rm T}$ range. Mid-rapidity yields, integrated over $p_{\rm T}$, have been determined. The hyperon-to-pion ratios are similar to those at RHIC: they rise smoothly with centrality up to $\langle N_{\rm part}\rangle$~150 and saturate thereafter. The enhancements (yields per participant nucleon relative to pp collisions) increase both with the strangeness content of the baryon and with centrality, but are less pronounced than at lower energies.
pT-differential production yields for Xi- and XiBar+ baryons with centrality 0-10%.
pT-differential production yields for Xi- and XiBar+ baryons with centrality 10-20%.
pT-differential production yields for Xi- and XiBar+ baryons with centrality 20-40%.
The charged-particle pseudorapidity density measured over 4 units of pseudorapidity in non-single-diffractive (NSD) p-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}} = 5.02$ TeV is presented. The average value at midrapidity is measured to be $16.81 \pm 0.71$ (syst.), which corresponds to $2.14 \pm 0.17$ (syst.) per participating nucleon. This is 16% lower than in NSD pp collisions interpolated to the same collision energy, and 84% higher than in d-Au collisions at $\sqrt{s_{\rm NN}} = 0.2$ TeV. The measured pseudorapidity density in p-Pb collisions is compared to model predictions, and provides new constraints on the description of particle production in high-energy nuclear collisions.
The pseudorapidity density of charged particles in the lab. frame.
The ALICE measurement of K$^0_{\rm S}$ and $\rm\Lambda$ production at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV is presented. The transverse momentum ($p_{\rm T}$) spectra are shown for several collision centrality intervals and in the $p_{\rm T}$ range from 0.4 GeV/$c$ (0.6 GeV/$c$ for $\rm\Lambda$) to 12 GeV/$c$. The $p_{\rm T}$ dependence of the $\rm \Lambda$/K$^0_{\rm S}$ ratios exhibits maxima in the vicinity of 3 GeV/$c$, and the positions of the maxima shift towards higher $p_{\rm T}$ with increasing collision centrality. The magnitude of these maxima increases by almost a factor of three between most peripheral and most central Pb-Pb collisions. This baryon excess at intermediate $p_{\rm T}$ is not observed in pp interactions at sqrt(s) = 0.9 TeV and at sqrt(s) = 7 TeV. Qualitatively, the baryon enhancement in heavy-ion collisions is expected from radial flow. However, the measured $p_{\rm T}$ spectra above 2 GeV/$c$ progressively decouple from hydrodynamical-model calculations. For higher values of $p_{\rm T}$, models that incorporate the influence of the medium on the fragmentation and hadronization processes describe qualitatively the $p_{\rm T}$ dependence of the $\rm\Lambda$/K$^0_{\rm S}$ ratio.
pT spectra of K0Short in the rapidity range -0.5<y<0.5 in the centrality interval 0.0-5.0%.
pT spectra of K0Short in the rapidity range -0.5<y<0.5 in the centrality interval 5.0-10.0%.
pT spectra of K0Short in the rapidity range -0.5<y<0.5 in the centrality interval 10.0-20.0%.
The production of K$^{*}$(892)$^{0}$ and $\phi$(1020) mesons has been measured in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV. K$^{*0}$ and $\phi$ are reconstructed via their decay into charged hadrons with the ALICE detector in the rapidity range $-0.5 < y <0$. The transverse momentum spectra, measured as a function of the multiplicity, have p$_{\mathrm{T}}$ range from 0 to 15 GeV/$c$ for K$^{*0}$ and from 0.3 to 21 GeV/$c$ for $\phi$. Integrated yields, mean transverse momenta and particle ratios are reported and compared with results in pp collisions at $\sqrt{s}$ = 7 TeV and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV. In Pb-Pb and p-Pb collisions, K$^{*0}$ and $\phi$ probe the hadronic phase of the system and contribute to the study of particle formation mechanisms by comparison with other identified hadrons. For this purpose, the mean transverse momenta and the differential proton-to-$\phi$ ratio are discussed as a function of the multiplicity of the event. The short-lived K$^{*0}$ is measured to investigate re-scattering effects, believed to be related to the size of the system and to the lifetime of the hadronic phase.
Average charged particle pseudo-rapidity density, $\langle\mathrm{d}N_{\rm ch}/\mathrm{d}\eta_{\mathrm{lab}}\rangle$, measured at mid-rapidity in visible cross section event classes and average number of colliding nucleons, $\langle\mathrm{N_{coll}}\rangle$. Multiplicity classes are defined using the V0A estimator; values for $\langle\mathrm{d}N_{\rm ch}/\mathrm{d}\eta_{\mathrm{lab}}\rangle$ are corrected for vertexing and trigger efficiency. Since statistical uncertainties are negligible, only total systematic uncertainties are reported.
$p_{\rm T}$-differential yield of (K$^{*0}$ + $\overline{K^{*0}}$)/2 in p-Pb collisions with centre-of-mass energy/nucleon=5.02 TeV (NSD). Additional systematic error: +- 3.1% (normalization).
$p_{\rm T}$-differential yield of (K$^{*0}$ + $\overline{K^{*0}}$)/2 in p-Pb collisions with centre-of-mass energy/nucleon=5.02 TeV (0-20% multiplicity class).
The production of the hypertriton nuclei $^{3}_{\Lambda}\mathrm H$ and $^{3}_{\bar{\Lambda}} \overline{\mathrm H}$ has been measured for the first time in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV with the ALICE experiment at LHC energies. The total yield, d$N$/d$y$ $\times \mathrm{B.R.}_{\left( ^{3}_{\Lambda}\mathrm H \rightarrow ^{3}\mathrm{He},\pi^{-} \right)} = \left( 3.86 \pm 0.77 (\mathrm{stat.}) \pm 0.68 (\mathrm{syst.})\right) \times 10^{-5}$ in the 0-10% most central collisions, is consistent with the predictions from a statistical thermal model using the same temperature as for the light hadrons. The coalescence parameter $B_3$ shows a dependence on the transverse momentum, similar to the $B_2$ of deuterons and the $B_3$ of $^{3}\mathrm{He}$ nuclei. The ratio of yields $S_3$ = $^{3}_{\Lambda}\mathrm H$/($^{3}\mathrm{He}$ $\times \Lambda/\mathrm{p}$) was measured to be $S_3$ = 0.60 $\pm$ 0.13 (stat.) $\pm$ 0.21 (syst.) in 0-10% centrality events; this value is compared to different theoretical models. The measured $S_3$ is fully compatible with thermal model predictions. The measured $^{3}_{\Lambda}\mathrm H$ lifetime, $ \tau = 181^{+54}_{-39} (\mathrm{stat.}) \pm 33 (\mathrm{syst.})\ \mathrm{ps}$ is compatible within 1$\sigma$ with the world average value.
(Hypertriton + Anti-Hypertriton)dN/d(ct) distribution.
Hypertriton and Anti-hypertriton $p_{\rm T}$ spectra x B.R.
$B_2$ as a function of $p_{\rm T}$/A for Hypertriton.
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