Particle spectra and HBT results from NA44

Murray, M.

doi:10.1063/1.48721

Cited by 3 publications

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“…with that of the preliminary three-dimensional measurements [27] at the highest RHIC energy of √ s = 200A GeV. We note that the m T dependence of the HBT radii R inv = A/ √ m T for these hadrons at RHIC are not consistent with one scaling coefficient as observed at the SPS energy [28]; the fitted values here are A = 3.81, 4.45, 5.32 fm GeV 1/2 for π − , K − , p. The measured single particle m T spectra for K − and K + [26] are fitted with an exponential function EdN/d 3 p = dN/dy exp[−(m T − m K )/T ]/(2πT (m K + T )) that results in a rapidity density of dN/dy = 38.2(42.1) for K − (K + ) using a slope parameter of T = 280 MeV. Inserting the spectra along with the the parameterization of R inv into Eq.…”

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confidence: 47%

Entropy production at RHIC

Pal¹,

Pratt²

2004

Physics Letters B

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For central heavy ion collisions at the RHIC energy, the entropy per unit rapidity dS/dy at freeze-out is extracted with minimal model dependence from available experimental measurements of particle yields, spectra, and source sizes estimated from two-particle interferometry. The extracted entropy rapidity density is consistent with lattice gauge theory results for a thermalized quark-gluon plasma with an energy density estimated from transverse energy production at RHIC. PACS numbers: 12.38.Mh, 24.85.+p, Lattice quantum chromodynamics (QCD) calculations indicate [1] that at zero net baryon density at a critical temperature of T c ∼ 170 MeV and energy density ǫ c ∼ 1 GeV/fm 3 a color deconfined and a chirally restored quark-gluon plasma (QGP) phase is formed. These energy densities are attained in relativistic heavy ion collisions, where it is believed that a dense system of quarks and gluons is created which undergoes rapid collective expansion before the partons hadronize and eventually decouple.The ongoing experimental program at RHIC is devoted to the search for the signals of QGP. Unfortunately, measurements are confined to final-state particles which are mostly hadrons. One interesting quantity that may provide valuable insight into the state of the matter in the early stages of the collision is the net entropy which is roughly conserved between initial thermalization and freeze-out [2,3]. After freeze-out, when particles are freestreaming, the entropy is fixed. Entropy would also be conserved during the expansion stage if the mean free paths were very short. Viscous effects, shock waves, and the decoupling process can only increase the entropy. Thus, the entropy from the final state provides an upper bound for the entropy of the initial state.Compared to a pion gas at the same energy density, the QGP is a high-entropy state as can be understood by considering the equation,where ∆S is the change in entropy resulting from the addition of an amount of heat Q into a fixed volume at temperature T . Lattice calculations show that the transition is nearly a first order with a distinct peak in the specific heat near T c . In this region, the temperature stays relatively fixed while the energy density changes substantially. Thus, the existence of a latent heat keeps the temperature lower than a pion gas at the same energy density, which results in a higher entropy as can be seen from Eq. (1). At high energy densities, the temperature of a QGP remains lower than that of the pion gas due to the disparity in the number of degrees of freedom.Asymptotically, the energy density of a QGP approaches that of a massless gas of quarks and hadrons,where N B and N F are the number of Bosonic and Fermionic degrees of freedom. Whereas a pion gas has 3 bosonic degrees of freedom, a QGP has 47.5 effective degrees of freedom if one considers gluons and the three light quark flavors. Thus, relative to a pion gas, the QGP has a lower temperature and higher entropy. If the partonic degrees of freedom were not fully liberated at RHIC, o...

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confidence: 47%

Entropy production at RHIC

Pal¹,

Pratt²

2004

Physics Letters B

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“…The K + /K − values for S+S [26] and Ni+Ni [2] are at mid-rapidity. The f Kin B values for S+S [28] and Pb+Pb [28,29] are determined from d/p at mid-rapidity. These values are approximated as for the total yield ratios with the systematic errors quoted in Table I.…”

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Correlation between the charged kaon ratio and the baryon phase-space density in heavy-ion collisions

Wang

2000

Physics Letters B

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It is found that the average baryon phase-space density obtained from the ratio of deuteron to proton yields is nearly constant over centrality in Au+Au collisions at the AGS. The finding offers an explanation for the puzzling centrality independence of the ratio of charged kaon total yields. The correlation between the charged kaon ratio and the average baryon phase-space density is studied for central heavy-ion collisions of various systems over a wide range of beam energy. It is found that the charged kaon ratio and the average baryon phase-space density both increase with decreasing beam energy, and are strongly correlated. Such study may provide a new approach to search for medium effects on the kaon mass. PACS number(s): 25.75.-q, 25.75.Dw

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Characterization of spindle assembly checkpoint in Xenopus egg extracts

Chen

Murray²

1997

Methods in Enzymology

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Particle spectra and HBT results from NA44

Cited by 3 publications

References 1 publication

Entropy production at RHIC

Entropy production at RHIC

Correlation between the charged kaon ratio and the baryon phase-space density in heavy-ion collisions

Characterization of spindle assembly checkpoint in Xenopus egg extracts

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