WA97 results on strangeness production in lead-lead collisions at 158 A GeV/c

Andersen, E.; Andrighetto, A.; Antinori, F.; Armenise, N.; Bán, J.; Barberis, D.; Beker, H.; Benayoun, M.; Beusch, W.; Böhm, J.; Campbell, M.; Cantatore, Eugenio; Carrer, N.; Catanesi, M. G.; Chesi, E.; Dameri, M.; Darbo, G.; Davies, J.; Diaczek, A.; Bari, D. Di; Liberto, S. Di; Mauro, A. Di; Elia, D.; Evans, D.; Fanebust, K.; Farthouat, P.; Fini, R. A.; Fontaine, J.-C.; French, B. R.; Ftáčnik, J.; Geist, W.; Ghidini, B.; Grella, G.; Guida, M.; Heijne, E.H.M.; Helstrup, H.; Holme, A.K.; Huss, D.; Jachołkowski, A.; Jovanović, P.; Jusko, A.; Kachanov, V.A.; Kachelhoffer, T.; Kinson, J.B.; Kirk, A.; Klempt, W.; Knudson, K.; Králik, I.; Lassalle, J. C.; Lenti, V.; Leruste, Ph.; Lien, J.; Lietava, R.; Loconsole, R.A.; López, L.; Løvhøiden, G.; Luptak, M.; Macha, I.; Mack, V.; Manzari, V.; Martinengo, P.; Mazzoni, M. A.; Meddi, F.; Michalon, A.; Michalon-Mentzer, M.E.; Middelkamp, P.; Morando, M.; Muciaccia, M. T.; Nappi, E.; Narjoux, J. L.; Navach, F.; Norman, K.L.; Osculati, B.; Pastirčák, B.; Pellegrini, F.; Piska, K.; Posa, F.; Quercigh, E.; Ricci, R. A.; Romano, G.; Rosa, G. De; Rossi, L. P.; Rotscheidt, H.; Šafařı́k, K.; Saladino, S.; Salvo, C.; Šándor, L.; Scognetti, T.; Segato, G.; Sené, M.; Sené, R.; Sennels, P.; Simone, S.; Singovski, A.; Sopko, B.; Staroba, P.; Šťastný, J.; Storås, T.; Szafran, S.; Thorsteinsen, T.F.; Tomasicchio, G.; Urbán, J.; Vanickova, M.; Vassiliadis, G.; Venables, M.; Baillie, O. Villalobos; Virgili, T.; Volte, A.; Voltolini, C.; Votruba, M.F.; Závada, P.

doi:10.1016/s0375-9474(96)00352-1

Cited by 25 publications

(43 citation statements)

References 14 publications

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“…More precisely the ratio between yields in central AA and pA (or pp) collisions will obey to the hierarchy : ∆Ω > ∆Ξ > ∆Λ > ∆p. This is in agreement with the results of the WA97 [14] and NA49 [1,13] collaborations.…”

Section: Net Hyperon Enhancementsupporting

confidence: 92%

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Baryon stopping and hyperon enhancement in the improved dual parton model

Capella

Salgado

1999

Phys. Rev. C

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We present an improved version of the dual parton model which contains a new realization of the diquark breaking mechanism of baryon stopping. We reproduce in this way the net baryon yield in nuclear collisions. The model, which also considers strings originating from diquark-antidiquark pairs in the nucleon sea, reproduces the observed yields of p and Λ and their antiparticles and underestimates cascades by less than 50 %. However, Ω's are underestimated by a factor five. Agreement with data is restored by final state interaction, with an averaged cross-section as small as σ = 0.14 mb. Hyperon yields increase significantly faster than antihyperons, in agreement with experiment.

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Section: Net Hyperon Enhancementsupporting

confidence: 92%

“…This increase obeys to the hierarchy Ω > Ξ > Λ (i.e. the large number of strange quarks in Y , the larger the increase) [13,14]. In two recent publications [12] [15], it has been shown that a baryon stopping mechanism of the type described above produces a substantial increase of the hyperon yields according to this hierarchy.…”

Section: Introductionmentioning

confidence: 93%

Baryon stopping and hyperon enhancement in the improved dual parton model

Capella

Salgado

1999

Phys. Rev. C

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“…The implied quantum number coalescence mechanism can be directly tested in hyperon to antihyperon production ratios [23,30]. Very recent such data [22] by WA97 and NA49 appear to support the evidence for a parton to hadron transition by statistical flavour coalescence.…”

Section: Discussionmentioning

confidence: 88%

“…However, other thermal models for SPS collisions dispense with the additional parameter of strangeness saturation [21] still obtaining reasonable fits to the hadronic production ratios. The eventual decision concerning strangeness as a diagnostic of the flavour composition prior to hadronization will come from new precision data [22] on hyperon production (Λ(1520), Ξ, Ω). In fact Bialas [23] has just shown that the observed hyperon to antihyperon yield ratios can be well understood in a flavour coalescence model (see next section) based on the partonic strangeness concentration.…”

Section: Transverse Energy Density Estimatesmentioning

confidence: 99%

The parton-hadron phase transition in central nuclear collisions at the CERN SPS

Stock

1999

Progress in Particle and Nuclear Physics

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A selection of recent data referring to P b + P b collisions at the SPS CERN energy of 158 GeV per nucleon is presented which might describe the state of highly excited strongly interacting matter both above and below the deconfinement to hadronization (phase) transition predicted by lattice QCD. A tentative picture emerges in which a partonic state is indeed formed in central P b + P b collisions which hadronizes at about T = 185 M eV , and expands its volume more than tenfold, cooling to about 120 M eV before hadronic collisions cease. We suggest further that all SPS collisions, from central S + S onward, reach that partonic phase, the maximum energy density increasing with more massive collision systems. Relativistic Nuclear CollisionsAstrophysical objects and processes, both connected with very early and very late phenomena in the cosmological evolution of strongly interacting matter, present an enormous challenge to modern nuclear and particle physics: we can recreate the conditions prevailing during the late nanosecond era of the cosmological expansion (when free quarks and gluons hadronized to isolated protons and neutrons), or during the late stages of a violent supernova stellar implosion (when the properties of highly compressed nuclear matter decide the final avenue leading either into a superdense neutron star or into a black hole) in experiments carried out in the terrestrial laboratory, by colliding heavy nuclei at relativistic energy.These studies culminate, for the time being, in the CERN SPS 208 P b beam facility which accelerates P b nuclei to 158 GeV per nucleon (about 33 T eV total energy). Ongoing programs at BNL and CERN will vastly extend the energy domain from √ s ≈ 17 GeV at the SPS to collider mode experiments with √ s = 200 GeV (RHIC) and √ s ≈ 5 T eV (LHC).The common idea of these investigations is to create extended "fireball" volumes of strongly interacting matter in head-on collisions of heavy nuclei, creating an average energy density reaching (at the SPS) or far exceeding (at RHIC and LHC) the "critical" value of about 1.5 GeV /f m 3 , at which modern Lattice QCD theory predicts a sudden departure, concerning the specific heat, the number density of degrees of freedom, the constituent quark mass scale etc., away from the expected behaviour of a densely packed liquid of hadrons. Does the hadron degree of freedom melt away at this transition point, giving rise to a continuous QCD state in which massive "constituent" quarks turn into nearly massless "current" (QCD)quarks -a phenomenon associated with the concept of chiral symmetry restoration -and in which colour carrying partons acquire a finite mobility, i.e. they approach deconfinement in an extended plasma state of nuclear dimension, i.e. 10 f m, large in comparison to typical confinement scales of about 1 f m.The present state of the art in lattice QCD finite temperature calculations [1] is illustrated in F ig. This interpretation is supported by a concurrent steep jump in the energy density E/T 4 (not illustrated).We t...

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“…Results are compared to recent WA97 P bP b → YȲ X data. 24.10.Lx Typeset using REVT E X Striking nonlinear nuclear enhancements of multistrange hyperons and anti-hyperons have been recently reported for central P b + P b collisions at incident momentum of 158A GeV [1][2][3]. For example, the midrapidity density of Ξ − (ssd) is claimed [3] to be enhanced by an order of magnitude relative to the linear A 1.0 ∼ 200 extrapolation from pp data.…”

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confidence: 99%

Antihyperon Enhancement through Baryon Junction Loops

1999

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The baryon junction exchange mechanism recently proposed to explain valence baryon number transport in nuclear collisions is extended to study midrapidity anti-hyperon production. Baryon junction-antijunction (JJ) loops are shown to enhanceΛ,Ξ,Ω as well as lead to long range rapidity correlations. Results are compared to recent WA97 P bP b → YȲ X data.25.75.-q,24.10.LxTypeset using REVT E X 1

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WA97 results on strangeness production in lead-lead collisions at 158 A GeV/c

Cited by 25 publications

References 14 publications

Baryon stopping and hyperon enhancement in the improved dual parton model

Baryon stopping and hyperon enhancement in the improved dual parton model

The parton-hadron phase transition in central nuclear collisions at the CERN SPS

Antihyperon Enhancement through Baryon Junction Loops

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