Multi-strange Baryon Production Research Articles

Centrality dependence of multistrange baryon production in high-energy heavy-ion collisions

We consider the experimental data on the production of strange \Lambda^{\prime}Λ′s, and multistrange baryons (\XiΞ, \OmegaΩ), and antibaryons, on nuclear targets, at the energy region from SPS up to LHC, in the framework of the Quark-Gluon String Model. One remarkable result of this analysis is the significant dependence on the centrality of the collision of the experimental \overline{\Xi}^+/\overline{\Lambda}Ξ¯+/Λ¯ and \overline{\Omega}^+/\overline{\Lambda}Ω¯+/Λ¯ ratios in heavy-ion collisions, at SPS energies.

Performance of the MPD Detector for the Study of Multi-strange Baryon Production in Heavy-ion Collisions at the Nuclotron-based Ion Collider Facility (NICA)

Presented are selected results of the Multi-Purpose Detector (MPD) for reconstruction of  and -baryons and K0-mesons in a Monte Carlo simulation of heavy-ion collisions at the Nuclotron-based Ion Collider fAcility (NICA). The results were obtained from the full MPD simulation and reconstruction chain, and include yields, spectra, and anisotropy coefficients from the centrality selected Au+Au collisions.

Multiplicity dependence of strangeness and hadronic resonance production in pp and p-Pb collisions with ALICE at the LHC

One of the key results of the LHC Run 1 was the observation of an enhanced production of strange particles in high multiplicity pp and p–Pb collisions at sNN=7 and 5.02 TeV, respectively. The strangeness enhancement is investigated by measuring the evolution with multiplicity of single-strange and multi-strange baryon production relative to non-strange particles. A smooth increase of strange particle yields relative to the non-strange ones with event multiplicity has been observed in such systems. We report the latest results on multiplicity dependence of strange and multi-strange hadron production in pp collisions at s=13TeV with ALICE. We also presented recent measurements of mesonic and baryonic resonances in small collision systems like pp and p–Pb at sNN=13 and 8.16 TeV, respectively. The multiplicity dependent studies in pp and p-Pb collisions have been used to investigate how the hadronic scattering processes affect measured resonance yields and to better understand the interplay between canonical suppression and strangeness enhancement. The measurement of the ϕ(1020) meson as a function of multiplicity provides crucial constraints in this context.

Multi-strange baryon production in pp, p–Pb and Pb–Pb collisions measured with ALICE

Transverse momentum spectra and yields of charged Ξ and Ω at mid-rapidity in pp, p-Pb and Pb-Pb collisions at the LHC have been measured by the ALICE Collaboration. These baryons are identified by reconstruction of their weak decay topology, in modes with only charged decay products, using the excellent tracking and particle identification capabilities of the detector. The recent measurements of the multi-strange baryon production relative to non-strange particles in p-Pb collisions are presented: this would help to understand the change in relative strangeness production from pp collisions to Pb-Pb collisions. Results on the nuclear modification factors for the charged Ξ and Ω particles, compared with those for other light particles, are also reported.

Multi-strange baryon production in pp, p–Pb and Pb–Pb collisions measured with ALICE at the LHC

Multi-strange baryons are of particular interest in the understanding of particle production mechanisms, as their high strangeness content makes them susceptible to changes in the hadrochemistry of the colliding systems. In ALICE, these hyperons are reconstructed via the detection of their weak decay products, which are identified through their measured ionisation losses and momenta in the Time Projection Chamber. The production rates of charged $\Xi$ and $\Omega$ baryons in proton-proton (pp), proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions are reported as a function of $p_{\mathrm{T}}$. A direct comparison in the hyperon-to-pion ratios between the three collision systems is made as a function of event charged-particle multiplicity. The recently measured production rates in p-Pb interactions reveal an enhancement with increasing event multiplicity, consistent with a hierarchy dependent on the strangeness content of the hyperons. These results are discussed in the context of chemical equilibrium predictions, taking into account the extracted temperature parameter from a thermal model fit to the hadron yields in Pb-Pb data.

Multi-strange baryon production in Pb-Pb and pp collisions at = 2.76 TeV with the ALICE experiment at the LHC

The production of Ξ− and Ω− baryons and their anti-particles in Pb-Pb and pp collisions at = 2.76 TeV has been measured by the ALICE collaboration. The transverse momentum spectra at mid-rapidity (|y| < 0.5) in pp and in Pb-Pb collisions for five centrality intervals have been compared with model predictions. Hyperon yields and spectra in Pb-Pb collisions, normalized to the corresponding measurements in pp at the same centre-of-mass energy, allow the study of the strangeness enhancement and the nuclear modification factor as a function of the transverse momentum (pT) and collision centrality.

Multi-strange baryon production in pp, p–Pb and Pb–Pb collisions measured with ALICE

The production of {\Xi}$^{-}$ and {\Omega}$^{-}$ baryons and their anti-particles in pp, p-Pb and Pb-Pb collisions has been measured by the ALICE Collaboration. These hyperons are reconstructed via the detection of their charged weak-decay products, which are identified through their measured ionisation losses and momenta in the ALICE Time Projection Chamber. Comparing the production yields in Pb-Pb and pp collisions, a strangeness enhancement has been measured and found to increase with the centrality of the collision and with the strangeness content of the baryon; moreover, in the comparison with similar measurements at lower energies, it decreases as the centre-of-mass energy increases, following the trend already observed moving from SPS to RHIC. Recent measurement of cascade and {\Omega} in p-Pb interactions are compared with results in Pb-Pb and pp collisions and with predictions from thermal models, based on a grand canonical approach. The nuclear modification factors for the charged {\Xi} and {\Omega}, compared to the ones for the lighter particles, are also presented.

Multi-strange baryon production at mid-rapidity in Pb–Pb collisions at [formula omitted

The production of Ξ− and Ω− baryons and their anti-particles in Pb–Pb collisions at sNN=2.76 TeV has been measured using the ALICE detector. The transverse momentum spectra at mid-rapidity (|y|<0.5) for charged Ξ and Ω hyperons have been studied in the range 0.6<pT<8.0 GeV/c and 1.2<pT<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 Kraków and EPOS models give a satisfactory description of the data, with the latter covering a wider pT range. Mid-rapidity yields, integrated over pT, have been determined. The hyperon-to-pion ratios are similar to those at RHIC: they rise smoothly with centrality up to 〈Npart〉∼150 and saturate thereafter. The enhancements (yields per participant nucleon relative to those in pp collisions) increase both with the strangeness content of the baryon and with centrality, but are less pronounced than at lower energies.

Multi-strange baryon production in pp collisions at [formula omitted] with ALICE

A measurement of the multi-strange Ξ− and Ω− baryons and their antiparticles by the ALICE experiment at the CERN Large Hadron Collider (LHC) is presented for inelastic proton–proton collisions at a centre-of-mass energy of 7 TeV. The transverse momentum (pT) distributions were studied at mid-rapidity (|y|<0.5) in the range of 0.6<pT<8.5 GeV/c for Ξ− and Ξ¯+ baryons, and in the range of 0.8<pT<5 GeV/c for Ω− and Ω¯+. 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 data has allowed us to measure a difference between the mean pT of Ξ− (Ξ¯+) and Ω− (Ω¯+). Particle yields, mean pT, and the spectra in the intermediate pT 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 Ω− (Ω¯+). This PYTHIA tune approaches the pT spectra of Ξ− and Ξ¯+ baryons below pT<0.85 GeV/c and describes the Ξ− and Ξ¯+ spectra above pT>6.0 GeV/c. We also illustrate the difference between the experimental data and model by comparing the corresponding ratios of (Ω−+Ω¯+)/(Ξ−+Ξ¯+) as a function of transverse mass.

Multi-strange baryon production in Au+Au collisions at top RHIC energy as a probe of bulk properties

We report STAR preliminary results on multi-strange baryon production in Au+Au collisions at at RHIC. Its implication for the formation of a new state of matter is discussed. The system size dependence on the production of strange baryons is investigated to study the onset of strange quark equilibration in the medium. The nuclear modification factor of Λ, Ξ and Ω is also presented. Its suppression at pT > 3 GeV/c supports the formation of a dense interacting medium at RHIC. The spectra of multi-strange baryons reveal that within a hydro-inspired model, they may decouple earlier than lighter particles and that their flow may be mostly developed at a partonic level. This idea is emphasized by the measurement of the v2 of and whose behaviour is close to the baryon elliptic flow in the intermediate pT region where a constituent quark scaling of v2 is observed.

Investigating multi-strange baryon production in Au+Au collisions at GeV and its excitation function in high-energy heavy-ion collisions

We present here preliminary results on multi-strange baryon (Ξ and Ω) production in Au+Au collisions at the collision energy of GeV as measured with the STAR detector at RHIC. Two different methods have been used on the data for selecting these particles: the ‘classical’ method and a linear discriminant analysis (LDA). We discuss the observed dynamical and chemical properties with respect to beam energy from SPS to top RHIC energies.

Multistrange baryon production in Au-Au collisions at sqrt[s(NN)]=130 GeV.

The transverse mass spectra and midrapidity yields for Xis and Omegas are presented. For the 10% most central collisions, the (-)Xi(+)/h(-) ratio increases from the Super Proton Synchrotron to the Relativistic Heavy Ion Collider energies while the Xi(-)/h(-) stays approximately constant. A hydrodynamically inspired model fit to the Xi spectra, which assumes a thermalized source, seems to indicate that these multistrange particles experience a significant transverse flow effect, but are emitted when the system is hotter and the flow is smaller than values obtained from a combined fit to pi, K, p, and Lambdas.

Multi-strange baryon production in Au+Au collisions near threshold

The centrality dependence of Ξ− and Λ production in Au+Au interactions at Elab=6 AGeV is studied within a microscopic transport approach. In line with recent data, a slight enhancement of the Ξ−/(Λ+Σ0) ratio toward central collisions is found. It is demonstrated that the observed production of multiple strange baryons can be traced back to multi-step meson–baryon interactions in the late stages of the collisions. Therefore, the present analysis supports an interpretation of the observed Ξ abundance in terms of hadronic rescattering.

Multistrange baryon production in relativistic heavy ion collisions

Using a multiphase transport model, we study the production of multistrange (anti)baryons from the hadronic matter formed in relativistic heavy ion collisions. The mechanism we introduce is the strangeness-exchange reactions between antikaons and hyperons for strange particle production and between kaons and antihyperons for strange antiparticle production. We find that these reactions contribute significantly to the production of multistrange baryons and antibaryons in heavy ion collisions at SPS energies, which has been found to be appreciably enhanced. We have also made predictions for multistrange baryon and antibaryon production in heavy ion collisions at RHIC and found a similar enhancement. The (anti)particle mass dependence of inverse slope parameters extracted from their transverse mass spectra in the transport model exhibit similar trend as in the available experimental data at both SPS and RHIC energies.

Mid-rapidity multi-strange baryon production at √sNN = 130 GeV

We report preliminary results on production of multi-strange Ξ− and their anti-particles, +, at mid-rapidity in √sNN = 130 GeV Au + Au collisions from the STAR experiment. An exponential fit to the Ξ− transverse mass spectrum for the 14% most central collisions results in an inverse slope parameter T = 346 ± 7 MeV, an invariant yield dN/dy = 3.07 ± 0.13 (stat) and a non-identical particle ratio Ξ−/Λ = 0.244 ± 0.011. The multi-strange baryon production with respect to negative hadrons is found to be Ξ−/h− = 0.0122 ± 0.0006.

Multiphase transport model for heavy ion collisions at RHIC

Using a multiphase transport model (AMPT) with both partonic and hadronic interactions, we study the multiplicity and transverse momentum distributions of charged particles such as pions, kaons and protons in central Au+Au collisions at RHIC energies. Effects due to nuclear shadowing and jet quenching on these observables are also studied. We further show preliminary results on the production of multistrange baryons from the strangeness-exchange reactions during the hadronic stage of heavy ion collisions.

Multistrange baryon production in heavy-ion reactions at the SPS

Multistrange baryon production in heavy-ion reactions at the SPS

A microscopic picture of strangeness production at theSPS

The microscopic origin of the strangeness enhancements observed in PbPbcollisions at the SPS is studied by testing the effects of threemechanisms. First, the junction processes found in the HIJING/BB eventgenerator are reviewed showing that they can account for only part of theobserved hyperon enhancements. Second, the efficient final state chemicalchanging processes (e.g. Λ + K↔Ξ + π) areincluded by adding the General Cascade Program (GCP) to HIJING/BB. Whilethese processes are shown to further enhance multistrange baryonproduction, HIJING/BB+GCP is still unable to fully describe either thelarge hyperon yields or the increasing K+/π+ ratio. Finally, theaddition of transient field fluctuations or ropes to HIJING/BB+GCP isshown to be needed to account for the large hyperon yields and for thebehaviour of the K+/π+ ratio.

Enhancement of strange and multi-strange baryons and anti-baryons in SW interactions at 200 GeV/ c

Strange and multistrange baryon production is expected to be enhanced in heavy ion interactions if a phase transition from hadronic matter to a Quark-Gluon Plasma takes place. The production yields of Λs, Λ s, Ξ −s, and Ξ + s relative to the production of negative particles are presented for sulphur-tungsten interactions at 200 GeV/ c per nucleon. These production yields are compared to those produced in proton-tungsten interactions and the enhancements of strange and multistrange baryons and antibaryons are presented.

Experiment NA57 at the CERN SPS

Experiment NA57 studies the production of strange and multi-strange baryons and antibaryons in ultrarelativistic nucleus-nucleus collisions at the SPS. The principal aim of NA57 is to investigate the existence of an onset for the strangeness enhancement effect at the variation of the energy and centrality (i.e. number of participants) of the nucleus-nucleus collisions. The experiment was successfully installed and commissioned in 1997.