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## ‣ Multi-strange baryon production in pp collisions at root s=7 TeV with ALICE

Abelev, B.; Adam, J.; Adamova, D.; Adare, A. M.; Aggarwal, M. M.; Rinella, G. Aglieri; Agocs, A. G.; Agostinelli, A.; Aguilar Salazar, S.; Ahammed, Z.; Ahmad, N.; Masoodi, A. Ahmad; Ahn, S. U.; Akindinov, A.; Aleksandrov, D.; Alessandro, B.; Alfaro Molina
Fonte: ELSEVIER SCIENCE BV; AMSTERDAM Publicador: ELSEVIER SCIENCE BV; AMSTERDAM
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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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 a centre-of-mass energy of 7 TeV. The transverse momentum (p(T)) distributions were studied at mid-rapidity (vertical bar y vertical bar < 0.5) in the range of 0.6 < p(T) < 8.5 GeV/c Xi(-) for and Xi(+) baryons, and in the range of 0.8 < P-T < 5 GeV/c for Omega(-) and<(Omega)over bar>(+). 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 p(T) of Xi(-) ((Xi) over bar)(+) and Omega(-) ((Omega) over bar (+)). Particle yields, mean pi, and the spectra in the intermediate pi 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) over bar (+)). This PYTHIA tune approaches the pi spectra of Xi(-) and Xi(+) baryons below p(T) <0.85 GeV/c and describes the Xi(-) and Xi(+) spectra above p(T) > 6.0 GeV/c. We also illustrate the difference between the experimental data and model by comparing the corresponding ratios of (Omega(-) +(Omega) over bar (+))/(Xi(-) + Xi(+)) as a function of transverse mass. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.

## ‣ Multi-strange baryon production in pp collisions at root s=7 TeV with ALICE

Abelev, B.; Adam, J.; Adamova, D.; Adare, A. M.; Aggarwal, M. M.; Rinella, G. Aglieri; Agocs, A. G.; Agostinelli, A.; Aguilar Salazar, S.; Ahammed, Z.; Ahmad, N.; Masoodi, A. Ahmad; Ahn, S. U.; Akindinov, A.; Aleksandrov, D.; Alessandro, B.; Alfaro Molina
Fonte: Elsevier; Amsterdam Publicador: Elsevier; Amsterdam
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
79.468013%
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 a centre-of-mass energy of 7 TeV. The transverse momentum (p(T)) distributions were studied at mid-rapidity (vertical bar y vertical bar < 0.5) in the range of 0.6 < p(T) < 8.5 GeV/c Xi(-) for and Xi(+) baryons, and in the range of 0.8 < P-T < 5 GeV/c for Omega(-) and<(Omega)over bar>(+). 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 p(T) of Xi(-) ((Xi) over bar)(+) and Omega(-) ((Omega) over bar (+)). Particle yields, mean pi, and the spectra in the intermediate pi 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) over bar (+)). This PYTHIA tune approaches the pi spectra of Xi(-) and Xi(+) baryons below p(T) <0.85 GeV/c and describes the Xi(-) and Xi(+) spectra above p(T) > 6.0 GeV/c. We also illustrate the difference between the experimental data and model by comparing the corresponding ratios of (Omega(-) +(Omega) over bar (+))/(Xi(-) + Xi(+)) as a function of transverse mass. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

## ‣ The elliptic flow of multi-strange hadrons in $\sqrt{s_{NN}}$ = 200 GeV Au + Au collisions at STAR

Shi, Shusu; Collaboration, for the STAR
Tipo: Artigo de Revista Científica
Publicado em 15/01/2011 Português
Relevância na Pesquisa
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The measurement of the elliptic flow, $v_{2}$, provides a powerful tool for studying the properties of hot and dense medium created in high-energy nuclear collisions. We present the measurement of $v_{2}$ of multi-strange hadrons ($\phi$, $\Xi$ and $\Omega$) in $\sqrt{s_{NN}}$= 200 GeV Au + Au collisions at STAR. In minimum-bias Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV, a significant amount of elliptic flow, almost identical to other mesons and baryons, is observed for multi-strange hadrons. Experimental observations of $p_{T}$ dependence of $v_{2}$ of identified particles at RHIC support partonic collectivity. We also discuss the possible breaking of mass ordering of the $\phi$ mesons in the low $p_{T}$ region.; Comment: 4 pages, 3 figures. The proceedings of the sixth International Conference on Physics and Astrophysics of Quark Gluon Plasma

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

Zeeb, Gebhard; Reiter, Manuel; Bleicher, Marcus
Tipo: Artigo de Revista Científica
Publicado em 04/12/2003 Português
Relevância na Pesquisa
48.33121%
The centrality dependence of Xi^- and Lambda production in Au+Au interactions at E_lab=6 AGeV is studied within a microscopic transport approach. In line with recent data, a slight enhancement of the Xi^-/(Lambda+Sigma^0) 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 Xi abundance in terms of hadronic re-scattering.; Comment: 5 pages, 6 figures

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

Domenico Colella for the ALICE Collaboration
Tipo: Artigo de Revista Científica
Publicado em 08/12/2014 Português
Relevância na Pesquisa
48.530625%
Transverse momentum spectra and yields of charged $\Xi$ and $\Omega$ 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 $\Xi$ and $\Omega$ particles, compared with those for other light particles, are also reported.; Comment: 4 pages, 3 figures, Proceedings of the Hot Quarks 2014 conference, 21-28 September 2014, Las Negras - Cabo de Gata Natural Park (Spain)

## ‣ Multi-strange particle measurements in 7 TeV proton-proton and 2.76 TeV PbPb collisions with the ALICE experiment at the LHC

Chinellato, D. D.; Collaboration, for the ALICE
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
48.65755%
The production of charged multi-strange particles is studied with the ALICE experiment at the CERN LHC. Measurements of the central rapidity yields of $\Xi^-$ and $\Omega^-$ baryons, as well as their antiparticles, are presented as a function of transverse momentum ($p_\mathrm{t}$) for inelastic pp collisions at $\sqrt{s}=7$ TeV and compared to existing measurements performed at the same and/or at lower energies. The results are also compared to predictions from two different tunes of the PYTHIA event generator. We find that data significantly exceed the production rates from those models. Finally, we present the status of the multi-strange particle production studies in Pb-Pb at $\sqrt{s_{NN}}=2.76$ TeV performed as a function of collision centrality.; Comment: 4 pages, 3 figures. Submitted to the Proceedings of QM2011

## ‣ Elliptic flow of multi-strange baryons Xi and Omega in Au+Au collisions at sqrt(s_NN)=200 GeV

Castillo, Javier; collaboration, for the STAR
Tipo: Artigo de Revista Científica
Publicado em 15/03/2004 Português
Relevância na Pesquisa
68.72378%
The first measurement of the elliptic transverse flow for multi-strange baryons Xi and Omega in high energy heavy ion collisions is presented, which may indicate the presence of partonic collectivity. A hydrodynamically inspired model fit to the transverse momentum spectra and elliptic flow of Xi- and AntiXi+ indicates that these particles might be emitted from the system at a high temperature (~150 MeV) with significant radial transverse flow and that the emitting system is spatially asymmetric.; Comment: Contribution to the Quark Matter 2004 proceedings, 5 pages, 4 figures

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

Alexandre, Didier; Collaboration, for the ALICE
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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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.

## ‣ Strange anti-baryons - QGP versus HG

Rafelski, Johann; Letessier, Jean; Tounsi, Ahmed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
38.68088%
We study quark-gluon plasma (QGP) and hadronic gas (HG) models of the central fireball presumed to be the source of abundantly produced strange (anti-)baryons in S -> W collisions at 200 GeV A. We consider how multi-strange (anti-)baryon multiplicities depend on strangeness conservation and compare the HG and QGP fireball scenarios. We argue that the total particle multiplicity emerging from the central rapidity region as well as the variation of production rates with changes in the beam energy allows to distinguish between the two reaction scenarios.; Comment: 10 pages, LaTeX, 4 postscript figures, Published in Dallas HEP (1992) 983-990

## ‣ Strange and Multi-Strange Particle Production in ALICE

Chinellato, D. D.; Collaboration, for the ALICE
Tipo: Artigo de Revista Científica
Publicado em 30/11/2012 Português
Relevância na Pesquisa
48.65334%
The production of strange and multi-strange hadrons in proton-proton (pp) and lead-lead (Pb-Pb) collisions is studied with the ALICE experiment at the CERN LHC. These particles are reconstructed via their weak decay topologies, exploiting the tracking and particle identification capabilities of ALICE. Measurements of central rapidity yields of $\Lambda$, $\Xi^{-}$ and $\Omega^{-}$ baryons, their antiparticles and ${\mathrm K}^{0}_{S}$ mesons are presented as a function of transverse momentum for Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV. They are compared to those observed in pp collisions as well as to results from lower energy nucleus-nucleus measurements.; Comment: 4 pages, 3 figures, Hot Quarks 2012 Proceedings

## ‣ Enhanced strange baryon production in Au+Au collisions compared to p+p at sqrts = 200 GeV

STAR Collaboration; Abelev, B. I.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
49.152393%
We report on the observed differences in production rates of strange and multi-strange baryons in Au+Au collisions at sqrts = 200 GeV compared to pp interactions at the same energy. The strange baryon yields in Au+Au collisions, then scaled down by the number of participating nucleons, are enhanced relative to those measured in pp reactions. The enhancement observed increases with the strangeness content of the baryon, and increases for all strange baryons with collision centrality. The enhancement is qualitatively similar to that observed at lower collision energy sqrts =17.3 GeV. The previous observations are for the bulk production, while at intermediate pT, 1 < pT< 4 GeV/c, the strange baryons even exceed binary scaling from pp yields.; Comment: 7 pages, 4 figures. Printed in PRC

## ‣ Strangeness enhancement at the hadronic chemical freeze-out

Sagun, V. V.; Oliinychenko, D. R.; Bugaev, K. A.; Cleymans, J.; Ivanytskyi, A. I.; Mishustin, I. N.; Nikonov, E. G.
Tipo: Artigo de Revista Científica
Publicado em 25/03/2014 Português
Relevância na Pesquisa
38.92319%
The chemical freeze-out of hadrons created in the high energy nuclear collisions is studied within the realistic version of the hadron resonance gas model. The chemical non-equilibrium of strange particles is accounted via the usual $\gamma_{s}$ factor which gives us an opportunity to perform a high quality fit with $\chi^2/dof \simeq 63.5/55 \simeq 1.15$ of the hadronic multiplicity ratios measured from the low AGS to the highest RHIC energies. In contrast to previous findings, at low energies we observe the strangeness enhancement instead of a suppression. In addition, the performed $\gamma_{s}$ fit allows us to achieve the highest quality of the Strangeness Horn description with $\chi^2/dof=3.3/14$. For the first time the top point of the Strangeness Horn is perfectly reproduced, which makes our theoretical horn as sharp as an experimental one. However, the $\gamma_{s}$ fit approach does not sizably improve the description of the multi-strange baryons and antibaryons. Therefore, an apparent deviation of multi-strange baryons and antibaryons from chemical equilibrium requires further explanation.; Comment: 7 pages, 12 figures

## ‣ Time Dependence of Chemical Freeze-out in Relativistic Heavy Ion Collisions

Bellwied, R.; Caines, H.; Humanic, T. J.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
39.009226%
We investigate chemical and thermal freeze-out time dependencies for strange particle production for CERN SPS heavy ion collisions in the framework of a dynamical hadronic transport code. We show that the Lambda yield changes considerably after hadronization in the case of Pb+Pb collisions, whereas for smaller system sizes (e.g. S+S) the direct particle production dominates over production from inelastic rescattering. Chemical freeze-out times for strange baryons in Pb+Pb are smaller than for non-strange baryons, but they are still sufficiently long for hadronic rescattering to contribute significantly to the final Lambda yield. Based on inelastic and elastic cross section estimates we expect the trend of shorter freeze-out times (chemical and kinetic), and thus less particle production after hadronization, to continue for multi-strange baryons.; Comment: 10 pages, 7 postscript figures

## ‣ Production of multi-strange baryons in 7 TeV proton-proton collisions with ALICE

Maire, Antonin
Tipo: Artigo de Revista Científica
Publicado em 09/12/2011 Português
Relevância na Pesquisa
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In the perspective of comparisons between proton-proton and heavy-ion physics, understanding the production mechanisms (soft and hard) in pp that lead to strange particles is of importance. Measurements of charged multi-strange (anti-)baryons (Omega and Xi) are presented for pp collisions at sqrt(s) = 7 TeV. This report is based on results obtained by ALICE (A Large Ion Collider Experiment) from the 2010 data-taking. Taking advantage of the characteristic cascade-decay topology, the identification of Xi-, anti-Xi+, Omega- and anti-Omega+ can be performed, over a wide range of momenta (e.g. from 0.6 to 8.5 GeV/c for Xi-, with the present statistics analysed). The production at central rapidity (|y| < 0.5) as a function of transverse momentum, dN/dptdy, is presented. These results are compared to PYTHIA Perugia 2011 predictions.; Comment: 6 pages, 3 figures, 1 table. Strangeness In Quark Matter (SQM 2011), 18-24 Sept. 2011, Krakow. To be published in Acta Physica Polonica B (APPB)

## ‣ Multi-strange baryon elliptic flow in Pb-Pb collisions at \sqrt{s_{NN}} = 2.76 TeV measured with the ALICE detector

Yin, Zhongbao
Tipo: Artigo de Revista Científica
Publicado em 02/02/2012 Português
Relevância na Pesquisa
59.050117%
We present the results on elliptic flow with multi-strange baryons produced in Pb-Pb collisions at \sqrt{s_{NN}} = 2.76 TeV. The analysis is performed with the ALICE detector at LHC. Multi-strange baryons are reconstructed via their decay topologies and the v_2 values are analyzed with the two-particle scalar product method. The p_T differential v_2 values are compared to the VISH2+1 model calculation and to the STAR measurements at 200 GeV in Au+Au collisions. We found that the model describes \Xi and \Omega v_2 measurements within experimental uncertainties. The differential flow of \Xi and \Omega is similar to the STAR measurements at 200 GeV in Au+Au collisions.; Comment: Prepared for the Proceedings of the International Conference on "Critical Point and Onset of Deconfinement - CPOD 2011", Wuhan, November 7-11, 2011

## ‣ Probing bulk properties and partonic collectivity via multi-strange baryons in Au+Au collisions at top RHIC energy

Estienne, Magali
Tipo: Artigo de Revista Científica
Publicado em 18/11/2004 Português
Relevância na Pesquisa
59.050117%
The study of the multi-strange production in the final state of ultra-relativistic Au+Au collisions at top RHIC energy gives information on the freeze-out conditions and probably on earlier stages of the collision. The chemical freeze-out temperature as well as the strangeness phase space occupancy factor gamma_s extracted from statistical models are studied as a function of the collision centrality. Within the framework of a hydrodynamically-inspired model the transverse collectivity of the collision is investigated. In this view, multi-strange particles seem to develop significant radial transverse flow. Furthermore, they present an elliptic flow as stronger as previously measured baryons supporting the idea that a fraction of the final collective motion has been developed at an early partonic stage of the collision.; Comment: 5 pages, 4 figures. Talk presented in Phase transitions in strongly interacting matter Prague, 23.8.-29.8. 2004 18th Nuclear Physics Division Conference of the EPS (NPDC18) Europhysics Conference

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

Estienne, Magali
Tipo: Artigo de Revista Científica
Publicado em 20/12/2004 Português
Relevância na Pesquisa
59.316%
We report STAR preliminary results on multi-strange baryon production in Au+Au collisions at sqrt(s_NN)=200 GeV 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 Lambda, Xi and Omega is also presented. Its suppression at p_T>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 prior than lighter particles and that their flow may be mostly developed at a partonic level. This idea is emphasized by the measurement of the v_2 of Xi+AntiXi and Omega+AntiOmega whose behaviour is close to the Lambda+AntiLambda baryon elliptic flow in the intermediate p_T region where a constituent quark scaling of v_2 is observed.; Comment: 8 pages, 8 figures, Strange Quark Matter 2004 conference proceedings

## ‣ Multi-strange baryon elliptic flow in Au+Au collisions at sqrt(s_NN)= 200 GeV

STAR Collaboration; Adams, J.
Tipo: Artigo de Revista Científica
Publicado em 22/04/2005 Português
Relevância na Pesquisa
59.66624%
We report on the first measurement of elliptic flow $v_2(p_T)$ of multi-strange baryons $\Xi+\bar{Xi}$ and $\Omega+\bar{Omega} in heavy-ion collisions. In minimum bias Au+Au collisions at sqrt(s_NN) = 200 GeV, a significant amount of elliptic flow, comparable to other non-strange baryons, is observed for multi-strange baryons which are expected to be particularly sensitive to the dynamics of the partonic stage of heavy-ion collisions. The$p_T$dependence of$v_2\$ of the multi-strange baryons confirms the number of constituent quark scaling previously observed for lighter hadrons. These results support the idea that a substantial fraction of the observed collective motion is developed at the early partonic stage in ultra-relativistic nuclear collisions at RHIC.; Comment: 6 pages, 3 figures, submitted to PRL

## ‣ The Effects of Varying the Correlation Volume on Strangeness Production in High Energy Collisions

Caines, Helen
Tipo: Artigo de Revista Científica
Publicado em 10/01/2006 Português
Relevância na Pesquisa
38.494155%
Preliminary results on strange particle production versus collision centrality are presented. STAR measurements from \sqrts = 200 GeV heavy-ion and \pp collisions are compared to SPS measurements. A systematic study of strange particle production is presented with the aim of establishing how the correlation volume of the produced source affects the scale of strange particle creation, including that of the multi-strange baryons. A linear increase of strangeness production with volume has been suggested by thermal models as an indication that the collision region has reached sufficient size such that small volume effects can be neglected. Analysis of preliminary results from STAR show that, using the assumption that the number of participants is linearly correlated with the volume, no such regime was obtained. This suggests that the correlation volume ''seen" by strange quarks is not merely that of the initial overlap.; Comment: 4 pages, 4 figures, Poster write-up from QM2005

## ‣ Multi-strange baryon production in pp collisions at (s)^1/2 = 7 TeV with ALICE

ALICE Collaboration