The multi-strange baryon yields in Pb--Pb collisions have been shown to exhibit an enhancement relative to pp reactions. In this work, $\Xi$ and $\Omega$ production rates have been measured with the ALICE experiment as a function of transverse momentum, ${p_{\rm T}}$, in p-Pb collisions at a centre-of-mass energy of ${\sqrt{s_{\rm NN}}}$ = 5.02 TeV. The results cover the kinematic ranges 0.6 GeV/$c<{p_{\rm T}} <$7.2 GeV/$c$ and 0.8 GeV/$c<{p_{\rm T}}<$ 5 GeV/$c$, for $\Xi$ and $\Omega$ respectively, in the common rapidity interval -0.5 $<{y_{\rm CMS}}<$ 0. Multi-strange baryons have been identified by reconstructing their weak decays into charged particles. The ${p_{\rm T}}$ spectra are analysed as a function of event charged-particle multiplicity, which in p-Pb collisions ranges over one order of magnitude and lies between those observed in pp and Pb-Pb collisions. The measured ${p_{\rm T}}$ distributions are compared to the expectations from a Blast-Wave model. The parameters which describe the production of lighter hadron species also describe the hyperon spectra in high multiplicity p-Pb. The yield of hyperons relative to charged pions is studied and compared with results from pp and Pb-Pb collisions. A statistical model is employed, which describes the change in the ratios with volume using a canonical suppression mechanism, in which the small volume causes a species-dependent relative reduction of hadron production. The calculations, in which the magnitude of the effect depends on the strangeness content, show good qualitative agreement with the data.
Xi pt spectrum in 0-5% multiplicity class.
Xi pt spectrum in 5-10% multiplicity class.
Xi pt spectrum in 10-20% multiplicity class.
A measurement of the multi-strange $\Xi^-$ and $\Omega^-$ baryons and their antiparticles by the ALICE experiment at the CERN Large Hadron Collider (LHC) is presented for inelastic proton-proton collisions at centre of mass energy of 7 TeV. The transverse momentum ($p_{\rm T}$) distributions were studied at mid-rapidity (|y| < 0.5) in the range of 0.6 < $p_{\rm T}$ < 8.5 GeV/$c$ for $\Xi^-$ and $\Xi^+$ baryons, and in the range of 0.8 < $p_{\rm T}$ < 5 GeV/$c$ for $\Omega^-$ and $\Omega^+$. Baryons and antibaryons were measured as separate particles and we find that the baryon to antibaryon ratio of both particle species is consistent with unity over the entire range of the measurement. The statistical precision of the current LHC data has allowed us to measure a difference between the mean $p_{\rm T}$ of $\Xi^-$ ($\Xi^+$) and $\Omega^-$ ($\Omega^+$). Particle yields, mean $p_{\rm T}$, and the spectra in the intermediate $p_{\rm T}$ range are not well described by the PYTHIA Perugia 2011 tune Monte Carlo event generator, which has been tuned to reproduce the early LHC data. The discrepancy is largest for $\Omega^-$ ($\Omega^+$). This PYTHIA tune approaches the $p_{\rm T}$ spectra of $\Xi^-$ and $\Xi^+$ baryons below $p_{\rm T}$ < 0.85 GeV/$c$ and describes the $\Xi^-$ and $\Xi^+$ spectra above $p_{\rm T}$ > 6.0 GeV/$c$. We also illustrate the difference between the experimental data and model by comparing the corresponding ratios of ($\Omega^{-}+\Omega^+)/(\Xi^-+\Xi^+)$ as a function of transverse mass.
pT differential yield for OMEGA- and OMEGABAR+ production in P-P collisions in the rapidity range -5 to 0.5. Note: there is no division by (2.pi.pT) included in the ordinate values.
pT differential yield for XI- and XIBAR+ production in P-P collisions in the rapidity range -5 to 0.5. Note: there is no division by (2.pi.pT) included in the ordinate values.
Ratio of (OMEGA-+OMEGABAR+) to (XI-+XIBAR+) production as a function of MT-M0. Note: the binning in (mT-m0) is the consequence of the pT binning of the Omega spectra.
The production of charged pions, kaons and (anti)protons has been measured at mid-rapidity ($-0.5 y 0$) in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV using the ALICE detector at the LHC. Exploiting particle identification capabilities at high transverse momentum ($p_{\rm T}$), the previously published $p_{\rm T}$ spectra have been extended to include measurements up to 20 GeV/$c$ for seven event multiplicity classes. The $p_{\rm T}$ spectra for pp collisions at $\sqrt{s}=7$ TeV, needed to interpolate a pp reference spectrum, have also been extended up to 20 GeV/$c$ to measure the nuclear modification factor ($R_{\rm pPb}$) in non-single diffractive p-Pb collisions. At intermediate transverse momentum ($2 p_{\rm T} 10$\,GeV/$c$) the proton-to-pion ratio increases with multiplicity in p-Pb collisions, a similar effect is not present in the kaon-to-pion ratio. The $p_{\rm T}$ dependent structure of such increase is qualitatively similar to those observed in pp and heavy-ion collisions. At high $p_{\rm T}$ ($>10$ GeV/$c$), the particle ratios are consistent with those reported for pp and Pb-Pb collisions at the LHC energies. At intermediate $p_{\rm T}$ the (anti)proton $R_{\rm pPb}$ shows a Cronin-like enhancement, while pions and kaons show little or no nuclear modification. At high $p_{\rm T}$ the charged pion, kaon and (anti)proton $R_{\rm pPb}$ are consistent with unity within statistical and systematic uncertainties.
pT-differential invariant yield of charged pions in p-Pb collisions with centre-of-mass energy/nucleon=5.02 TeV, measured for different V0A multiplicity classes. The first uncertainty is statistical, the second one is the total systematic uncertainty, while the third one is the uncorrelated systematic uncertainty which is multiplicity dependent.
pT-differential invariant yield of charged pions in p-Pb collisions with centre-of-mass energy/nucleon=5.02 TeV, measured for NSD events. The first uncertainty is statistical, the second one is the total systematic uncertainty, while the third one is the uncorrelated systematic uncertainty which is multiplicity dependent.
pT-differential invariant yield of charged kaons in p-Pb collisions with centre-of-mass energy/nucleon=5.02 TeV, measured for different V0A multiplicity classes. The first uncertainty is statistical, the second one is the total systematic uncertainty, while the third one is the uncorrelated systematic uncertainty which is multiplicity dependent.
The transverse momentum ($p_{\rm{T}}$) differential yields of (anti-)$^3$He and (anti-)$^3$H measured in p-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV with ALICE at the Large Hadron Collider (LHC) are presented. The ratios of the $p_{\rm{T}}$-integrated yields of (anti-)$^3$He and (anti-)$^3$H to the proton yields are reported, as well as the $p_{\rm{T}}$ dependence of the coalescence parameters $B_3$ for (anti-)$^3$He and (anti-)$^3$H. For (anti-)$^3$He, the results obtained in four classes of the mean charged-particle multiplicity density are also discussed. These results are compared to predictions from a canonical statistical hadronization model and coalescence approaches. An upper limit on the total yield of $^4\bar{\mathrm{He}}$ is determined.
Transverse momentum spectra of (anti-)$^3\mathrm{He}$ measured in $\mathrm{INEL}>0$ p--Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$
Transverse momentum spectra of (anti-)$^3\mathrm{H}$ measured in $\mathrm{INEL}>0$ p--Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$
$^3\overline{\mathrm{He}} /\,^3\mathrm{He}$ ratio in $\mathrm{INEL}>0$ p--Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$
The pseudorapidity ($\eta$) and transverse-momentum ($p_{\rm T}$) distributions of charged particles produced in proton-proton collisions are measured at the centre-of-mass energy $\sqrt{s}$ = 13 TeV. The pseudorapidity distribution in $|\eta|<$ 1.8 is reported for inelastic events and for events with at least one charged particle in $|\eta|<$ 1. The pseudorapidity density of charged particles produced in the pseudorapidity region $|\eta|<$ 0.5 is 5.31 $\pm$ 0.18 and 6.46 $\pm$ 0.19 for the two event classes, respectively. The transverse-momentum distribution of charged particles is measured in the range 0.15 $<$ $p_{\rm T}$ $<$ 20 GeV/c and $|\eta|<$ 0.8 for events with at least one charged particle in $|\eta|<$ 1. The correlation between transverse momentum and particle multiplicity is also investigated by studying the evolution of the spectra with event multiplicity. The results are compared with calculations from PYTHIA and EPOS Monte Carlo generators.
Average pseudorapidity density of charged particles as a function of eta produced in pp collisions at sqrt(s) = 13 TeV. The results are shown in the normalisation classes INEL and INEL>0. The uncertainties are the quadratic sum of statistical and systematic contributions.
Invariant charged-particle yield as a function of pT normalised to INEL>0 events.
Ratio of transverse-momentum spectra in INEL>0 events at $\sqrt{s}$ = 13 and 7 TeV.
The transverse momentum ($p_{\mathrm T}$) distribution of primary charged particles is measured in minimum bias (non-single-diffractive) p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ALICE detector at the LHC. The $p_{\mathrm T}$ spectra measured near central rapidity in the range $0.5<p_{\mathrm T}<20$ GeV/$c$ exhibit a weak pseudorapidity dependence. The nuclear modification factor $R_{\mathrm{pPb}}$ is consistent with unity for $p_{\mathrm T}$ above 2 GeV/$c$. This measurement indicates that the strong suppression of hadron production at high $p_{\mathrm T}$ observed in Pb-Pb collisions at the LHC is not due to an initial-state effect. The measurement is compared to theoretical calculations.
Normalized differential primary charged particle yield.
pp INEL cross section scaled by nuclear overlap.
Nuclear Modification Factor R_pPb in the central region.
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