Scaling of deuteron production in ultrarelativistic nucleus-nucleus collisions

Sorge, H.; Nagle, J. L.; Kumar, B. S.

doi:10.1016/0370-2693(95)00763-b

Cited by 23 publications

(25 citation statements)

References 21 publications

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“…An obvious deviation from a single exponential at small m t , the so called "shoulder-arm shape" of the transverse mass distributions [34], is observed for all three energies. The above observations, an increase with mass of the inverse slope parameter, a deviation of the m t spectra from an exponential shape at small transverse mass as well as the evolution of these features with centrality and beam energy are the predicted characteristics of radial collective expansion [20][21][22]. In agreement with the measurement these are expected to be stronger in central than in peripheral collisions.…”

Section: Discussionsupporting

confidence: 84%

“…Thermal and density matrix coalescence models [5,6] had already been developed which considered a significant expansion of the collision volume, albeit no correlations between position and momentum of the nucleons. The presence of collective motion (flow) leads not only to an expansion of the collision volume but also to significant positionmomentum correlations between particles at freeze-out [20][21][22] affecting the process of cluster formation. Indeed, the overall expansion of the system tends to reduce the coalescence probability B A by spatially isolating nucleons from each other, whereas the collective flow increases B A .…”

Section: Introductionmentioning

confidence: 99%

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Energy and centrality dependence of deuteron and proton production inPb+Pbcollisions at relativistic energies

Antičić¹,

Baatar²,

Barna³

et al. 2004

Phys. Rev. C

129

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The transverse mass m t distributions for deuterons and protons are measured in Pb+ Pb reactions near midrapidity and in the range 0 Ͻ m t − m Ͻ 1.0 ͑1.5͒ GeV/ c 2 for minimum bias collisions at 158A GeV and for central collisions at 40 and 80 A GeV beam energies. The rapidity density dn / dy, inverse slope parameter T and mean transverse mass ͗m t ͘ derived from m t distributions as well as the coalescence parameter B 2 are studied as a function of the incident energy and the collision centrality. The deuteron m t spectra are significantly harder than those of protons, especially in central collisions. The coalescence factor B 2 shows three systematic trends. First, it decreases strongly with increasing centrality reflecting an enlargement of the deuteron coalescence volume in central Pb+ Pb collisions. Second, it increases with m t . Finally, B 2 shows an increase with decreasing incident beam energy even within the SPS energy range. The results are discussed and compared to the predictions of models that include the collective expansion of the source created in Pb+ Pb collisions.

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Section: Discussionsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Energy and centrality dependence of deuteron and proton production inPb+Pbcollisions at relativistic energies

Antičić¹,

Baatar²,

Barna³

et al. 2004

Phys. Rev. C

129

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“…We do not believe that the existence of strong transverse flow in the Pb͑158A GeV͒ on Pb reactions belongs to the unresolved questions. The difference between flow-a space-momentum correlation-and excitations purely in momentum space (temperature or random kicks) shows up in observables which are sensitive to the phase-space densities of the finally emitted hadrons (such as nucleon cluster formation [17] and pion interferometry [18]). Indeed, transport calculations [16] and fits to experimental data based on the fireball model [19] consistently give transverse flow velocities in the range of ϳ0.4c 0.6c for the Pb on Pb reactions.…”

mentioning

confidence: 99%

Evidence of Early Multistrange Hadron Freeze-Out in High Energy Nuclear Collisions

1998

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Recently reported transverse momentum distributions of strange hadrons produced in Pb͑158A GeV͒ on Pb collisions and corresponding results from the relativistic quantum molecular dynamics approach are examined. We argue that the experimental observations favor a scenario in which multistrange hadrons are formed and decouple from the system rather early at large energy densities (at about 1 GeV͞fm 3 ). The systematics of the strange and nonstrange particle spectra indicate that the observed transverse flow develops mainly in the late hadronic stages of these reactions.[S0031-9007(98)07927-7] PACS numbers: 25.75.Ld, 24.10.Lx, 25.75.Dw The purpose of the current and forthcoming heavy ion programs at the high energy laboratories CERN (Switzerland) and Brookhaven National Laboratory (US) is to probe strongly interacting matter under extreme conditions, i.e., at high densities and temperatures. The central subject of these studies is the transition from the quark-gluon plasma to hadronic matter. In the early phases of ultrarelativistic heavy ion collisions, when a hot, dense region is formed in the center of the reaction, there is copious production of up, down, and strange quarks. Transverse expansion is driven by the numerous scatterings among the incoming and produced particles. As the medium expands and cools, the quarks combine to form the hadrons that are eventually observed.On the experimental side, the presence of strong radial transverse flow in the Pb͑158A GeV͒ on Pb collisions was deduced from the systematics of nonstrange particle spectra some time ago [1,2]. The long awaited spectra of multiple strange baryons J 2 and V, measured at midrapidity, were reported during the Quark Matter '97 conference [3]. Quite surprisingly, the reported slopes of these hadrons are much softer than expected from an interpolation based on the measured slope parameters of nonstrange particles, hadrons with a single strange quark only and deuterons [2,4]. A compilation of the experimental data as obtained by the NA44, NA49, and WA97 collaborations is shown in Fig. 1.In this Letter we argue that the transverse momentum spectra encode valuable information on the decoupling process of strange and nonstrange hadrons in the medium and the time development of flow during the evolution [5]. It has been recognized for a long time [6] that hadron momentum spectra reflect the collective flow developing in ultrarelativistic heavy ion collisions. The flows may be related to bulk and transport properties in the ultradense matterlike transient pressure and viscosities. Hydrodynamic behavior may be expected at least for truly large colliding systems such as Pb 1 Pb.Concerning the search for the quark-gluon plasma, one would like to identify the regions in energy density at which the equation of state (EOS) softens, presumably due to the phase transition or crossover between hadronic and quark matter. Another topic of interest is to see the EOS becoming hard again at yet higher densities. At temperatures much larger than the critical tempera...

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“…On the experimental side, the predicted presence of strong radial transverse flow in the Pb(158AGeV) on Pb collisions (0.4 to 0.6 c) [6] has been deduced from the systematics of non-strange particle spectra already some time ago [7,8]. The long awaited spectra of multiple strange hadrons Φ, Ξ, and Ω, measured at mid-rapidity, were reported during the Quark Matter '97 conference [9,10].…”

mentioning

confidence: 99%

“…It is well-known that the difference between flow -a space-momentum correlation -and excitations purely in momentum space (temperature or random kicks [16]) shows up in observables which are sensitive to the phase-space densities of the finally emitted hadrons (like nucleon cluster formation [6] and HBT [17]). Let us turn now to the recent data and interpret them in the light of these ideas.…”

mentioning

confidence: 99%

Evidence of early multi-strange hadron freeze-out in high energy nuclear collisions

Hecke

Sorge

1999

Nuclear Physics A

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Recently reported transverse momentum distributions of strange hadrons produced in Pb(158AGeV) on Pb collisions and corresponding results from the relativistic quantum molecular dynamics (RQMD) approach are examined. We argue that the experimental observations favor a scenario in which multi-strange hadrons are formed and decouple from the system rather early at large energy densities (around 1 GeV/fm 3 ). The systematics of the strange and non-strange particle spectra indicate that the observed transverse flow develops mainly in the late hadronic stages of these reactions.The purpose of the current and forthcoming heavy ion programs at the high-energy laboratories CERN (Switzerland) and Brookhaven National Laboratory (USA) is to probe strongly interacting matter under extreme conditions, i.e. at high densities and temperatures. The central subject of these studies is the transition from the quark-gluon plasma to hadronic matter. In the early phases of ultrarelativistic heavy ion collisions, when a hot, dense region is formed in the center of the reaction, there is copious production of up, down, and strange quarks. Transverse expansion is driven by the numerous scatterings among the incoming and produced particles. As the medium expands and cools, the quarks combine to form the hadrons that are eventually observed.In this Letter we are going to address the question whether data from heavy ion experiments allow one to make statements about the existence of strange hadrons in a medium of high energy density ǫ > 1GeV/fm 3 . So far, experimental information about survival or "melting" of quark bound states was restricted to charmonium states only [1]. On the other side, the strange quark mass is intermediate between charm and the very light flavors (up and down). Strangeness should in fact not be considered as an "external probe" of the hot medium like charm, as it may influence fundamental characteristics of the QCD phase transition itself, e.g. its order [2]. Furthermore, we argue in this Letter that the strange and non-strange hadron spectra encode information on the timing of flows and pressures. It has been recognized for a long time [3] that hadron momentum spectra are a valuable source of information on the collective flow developing in ultrarelativistic heavy ion collisions. The flows may be related to bulk and transport properties in the ultra-dense matter like transient pressure and viscosities. Presence of hydrodynamic behavior is expected at least for truly large colliding system such as Pb+Pb. Concerning the search for the quark-gluon plasma one would like to identify the regions in energy density at which the Equation of State (EOS) softens, presumably due to the phase transition or a cross-over between hadronic and quark matter. Another topic of interest is to see the EOS becoming hard again at yet higher densities. Asymptotically, the EOS approaches the Stefan-Boltzmann limit p = ǫ/3, where p is the pressure, according to recent lattice calculations [4]. Note, however, that the regime of perturbativ...

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Scaling of deuteron production in ultrarelativistic nucleus-nucleus collisions

Cited by 23 publications

References 21 publications

Energy and centrality dependence of deuteron and proton production inPb+Pbcollisions at relativistic energies

Energy and centrality dependence of deuteron and proton production inPb+Pbcollisions at relativistic energies

Evidence of Early Multistrange Hadron Freeze-Out in High Energy Nuclear Collisions

Evidence of early multi-strange hadron freeze-out in high energy nuclear collisions

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