Enhanced antiproton production in Pb(160 A GeV)+Pb reactions: evidence for quark gluon matter?

Bleicher, Marcus; Belkacem, M.; Bass, Steffen A.; Soff, S.; Stöcker, H.

doi:10.1016/s0370-2693(00)00643-2

Cited by 18 publications

(26 citation statements)

References 26 publications

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“…A consistent enhancement of hyperons and anti-protons is necessary to support this scenario. In fact, it has been shown that this approach is consistent with the measured anti-proton and hyperon yields at SPS energies, if rescattering effects are taken into account [25,26].…”

Section: Lbnl-preprint: Lbnl-46167supporting

confidence: 64%

Strangeness enhancement from strong color fields at relativistic heavy ion energies

et al. 2000

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In ultra-relativistic heavy ion collisions, early stage multiple scatterings may lead to an increase of the color electric field strength. Consequently, particle production -especially heavy quark (and di-quark) production -is greatly enhanced according to the Schwinger mechanism. We test this idea via the Ultra-relativistic Quantum Molecular Dynamics model (UrQMD) for Au+Au collisions at the full RHIC energy ( √ s = 200 AGeV). Relative to p+p collisions, a factor of 60, 20 and 7 enhancement respectively, for Ω (sss), Ξ (ss), and Λ, Σ (s) is predicted for a model with increased color electric field strength. LBNL-preprint: LBNL-46167One of the major goals of the relativistic heavy ion collider (RHIC) at Brookhaven National Laboratory is to explore the phase diagram of hot and dense matter near the quark gluon plasma (QGP) phase transition. The QGP is a state in which the individual hadrons dissolve into a gas of free (or almost free) quarks and gluons in strongly compressed and hot matter (for recent reviews on the topic, we refer to [1,2]). The achievable energyand baryon densities depend on the extend to which the nuclei are stopped during penetration, thus on centrality and bombarding energy.Strange particles, especially multi-strange baryons (which have more than one strange quark) carry vital information about the collision dynamics [3][4][5][6][7][8][9][10]. Relative strangeness abundancies have been proposed as a powerful tool for searching the transition from hadronic matter to partonic matter in high energy nuclear collisions [3][4][5]. Indeed, strangeness enhancement has be observed in heavy ion collisions at all collision energies with different colliding systems.Recently, measurements by the WA97 and the NA49 collaborations clearly demonstrated the relative enhancement of the (anti-)hyperon yields (Λ, Ξ, Ω) in Pb-Pb collisions as compared to p-Pb collisions [11][12][13][14][15][16]. The observed enhancement increases with the strangeness content (|S| = 1, 2, 3) of the probe under investigation * Feodor Lynen Fellow of the Alexander v. Humboldt Foundation, E -mail: bleicher@nta2.lbl.gov [11][12][13][14][15][16]. For the (Ω − + Ω − )-yield the enhancement factor is as large as 15.A number of different mechanisms are under debate to understand this strong increase in strangeness production with centrality and beam energy:• Equilibrated (gluon rich) plasma phase: Chemical and flavour equilibration times are predicted to be shorter in a plasma phase than in a thermally equilibrated hadronic fireball of T ∼ 160 MeV [3]. Thus, a dominant production mechanism for strangeness in an equilibrated gluon rich plasma phase (Hot glue scenario [17]), might be the production of ss pairs via gluon fusion (gg → ss) [3]. This might allow for strangeness equilibration within the lifetime of the QGP, resulting in strong strangeness enhancement compared to hadronic scenarios.• Baryon-junctions: A baryon junction exchange mechanism was proposed to explain valence baryon number transport in nuclear collisions. Recently it wa...

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Section: Lbnl-preprint: Lbnl-46167supporting

confidence: 64%

Strangeness enhancement from strong color fields at relativistic heavy ion energies

et al. 2000

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“…With new data coming up on antibaryon production from nucleus-nucleus collisions at the AGS [26,27,28] and SPS [29,30,31,32,33] thep,Λ enhancement factors seen experimentally were no longer that dramatic as at SIS energies, however, traditional cascade calculations employing free production and annihilation cross sections again were not able to reproduce the measured abundancies and spectra [34,35,36,37,38] especially for Ξ,Ξ and Ω,Ω. Here additional collective mechanisms in the entrance channel have been suggested such as color rope formation [39] or hot plasma droplet formation [40].…”

Section: Introductionmentioning

confidence: 99%

Antibaryon production in hot and dense nuclear matter

Cassing

2002

Nuclear Physics A

158

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The production of antibaryons is calculated in a microscopic transport approach employing multiple meson fusion reactions according to detailed balance relations with respect to baryon-antibaryon annihilation. It is found that the abundancies of antiprotons as observed from peripheral to central collisions of $Pb + Pb$ at the SPS and $Au + Au$ at the AGS can approximately be described on the basis of multiple interactions of 'formed' hadronic states which drive the system to chemical equilibrium by flavor exchange or quark rearrangement reactions.Comment: 39 pages, LaTeX, 14 postscript figures; revised version includes 3 additional figures; to appear in Nucl. Phys.

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“…With new data coming up on antibaryon production from proton-nucleus and nucleus-nucleus collisions at the AGS [21,22,23,24,25] and SPS [26,27,28,29] thep,Λ enhancement factors seen experimentally were no longer that dramatic as at SIS energies, however, traditional cascade calculations employing free production and annihilation cross sections again were not able to reproduce the measured abundancies and spectra [30,31,32,33] especially for Ξ,Ξ and Ω,Ω. Here additional collective mechanisms in the entrance channel have been suggested such as color rope formation [34] or hot plasma droplet formation [35].…”

Section: Introductionmentioning

confidence: 99%

Probing hadronic formation times with antiprotons in p+A reactions at AGS energies

Cassing

Bratkovskaya²,

Hansén

2002

Nuclear Physics A

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The production of antiprotons in p + A reactions is calculated in a microscopic transport approach employing hadronic and string degrees of freedom (HSD). It is found that the abundancies of antiprotons as observed by the E910 Collaboration in p + A reactions at 12.3 GeV/c as well as 17.5 GeV/c can approximately be described on the basis of primary proton-nucleon and secondary meson-baryon production channels for all targets. The transport calculations demonstrate that the antiproton rapidity distributions for heavy targets are sensitive to thep (or hadron) formation time in the nuclear medium. Within our analysis the data from the E910 Collaboration are reasonably described with a formation time of 0.4 − 0.8 fm/c in the hadron rest frame.

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Enhanced antiproton production in Pb(160 A GeV)+Pb reactions: evidence for quark gluon matter?

Cited by 18 publications

References 26 publications

Strangeness enhancement from strong color fields at relativistic heavy ion energies

Strangeness enhancement from strong color fields at relativistic heavy ion energies

Antibaryon production in hot and dense nuclear matter

Probing hadronic formation times with antiprotons in p+A reactions at AGS energies

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