Strangeness conservation constraints in hadron gas models

Abstract

We examine the implications of the constraints arising due to strangeness conservation on the strangeness production in various existing thermal hadron-gas models. The dependence of strangeness chemical potential S on the baryon chemical potential B and temperature T is investigated. The incorporation of finite-size, hard-core, repulsive interactions in the thermodynamically consistent description of hot and dense hadron gas alters the results obtained for pointlike particles. We compare results in two extreme alternative cases: ͑1͒ K and K* mesons are treated as point particles and they can penetrate all volumes occupied by baryons and antibaryons and ͑2͒ the volume occupied by the baryons and antibaryons is not accessible to them. We find that the results indeed depend on the assumptions made. Moreover, the anomalous results obtained for the ratios ⌶/⌶ and ⌳/⌳ rule out the second possibility.PACS number͑s͒: 25.75. Ϫq, 12.38.Mh, 21.65.ϩf, 24.85.ϩp

Chemical equilibration of strangeness

“…In [23,29] the effect is minimal since the mean field coupling K B = 680 MeV fm 3 of baryons and anti-baryons is similar to the one of mesons K M = 600 MeV fm 3 . The studies in [30] show the repulsion effect for the heavy baryons. The extracted µ B in [30] differs from the other results of table 1.…”

“…Therefore the resonance states are included in the partition function of all calculations in table 1 except for [19,20]. On the other hand, their decay is sometimes neglected [26,30] when calculations are compared with experimental data. Some of the publications restrict their discussion to strange baryon ratios.…”

“…If V 0 j or K j are different for various j then they influence the particle ratios. The only publications in table 1 which have such an influence on particle ratios due to repulsions are [23,29,30]. In [23,29] the effect is minimal since the meanfield coupling K B = 680 MeV fm −3 of baryons and antibaryons is similar to the one of mesons K M = 600 MeV fm −3 .…”

On local and global equilibrium in heavy ion collisions

“…In heavy ion collisions one may be even closer to thermodynamic behaviour due to secondary interactions. Therefore a big effort is going on to study thermal behaviour in these collisions by microscopic models [4][5][6] as well as to classify directly the experimental final hadronic state by a thermal model [7][8][9][10][11][12][13][14][15][16][17][18]. While within the thermal model applied at low incident energies the whole system may be regarded as one fireball in approximate global thermal and chemical equilibrium this is not anymore justified in ultra-relativistic heavy ion collisions.…”

“…The mentioned problem of rapidity cuts leads to the second method for a chemical analysis, i.e. a global thermal model to 4π integrated data [16][17][18]. This method implicitly assumes global chemical equilibrium in the above mentioned sense.…”