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Register a new userChemical Equilibrium in Collisions of Small Systems
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The system-size dependence of particle production in heavy-ion collisions at the top SPS energy is analyzed in terms of the statistical model. A systematic comparison is made of two suppression mechanisms that quantify strange particle yields in ultra-relativistic heavy-ion collisions: the canonical model with strangeness correlation radius determined from the data and the model formulated in the canonical ensemble using chemical off-equilibrium strangeness suppression factor. The system-size dependence of the correlation radius and the thermal parameters are obtained for p-p, C-C, Si-Si and Pb-Pb collisions at sqrt(s_NN) = 17.3 AGeV. It is shown that on the basis of a consistent set of data there is no clear difference between the two suppression patterns. In the present study the strangeness correlation radius was found to exhibit a rather weak dependence on the system size.
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The data on average hadron multiplicities in central A+A collisions measured at CERN SPS are analysed with the ideal hadron gas model. It is shown that the full chemical equilibrium version of the model fails to describe the experimental results. The agreement of the data with the off-equilibrium version allowing for partial strangeness saturation is significantly better. The freeze-out temperature of about 180 MeV seems to be independent of the system size (from S+S to Pb+Pb) and in agreement with that extracted in e+e-, pp and p{bar p} collisions. The strangeness suppression is discussed at both hadron and valence quark level. It is found that the hadronic strangeness saturation factor gamma_S increases from about 0.45 for pp interactions to about 0.7 for central A+A collisions with no significant change from S+S to Pb+Pb collisions. The quark strangeness suppression factor lambda_S is found to be about 0.2 for elementary collisions and about 0.4 for heavy ion collisions independently of collision energy and type of colliding system
We present a detailed study of chemical freeze-out in nucleus-nucleus collisions at beam energies of 11.6, 30, 40, 80 and 158A GeV. By analyzing hadronic multiplicities within the statistical hadronization approach, we have studied the strangeness production as a function of centre of mass energy and of the parameters of the source. We have tested and compared differe
We performed state-of-the-art QCD effective kinetic theory simulations of chemically equilibrating QGP in longitudinally expanding systems. We find that chemical equilibration takes place after hydrodynamization, but well before local thermalization. By relating the transport properties of QGP and the system size we estimate that hadronic collisions with final state multiplicities $dN_text{ch}/deta > 10^2$ live long enough to reach approximate chemical equilibrium for all collision systems. Therefore we expect the saturation of strangeness enhancement to occur at the same multiplicity in proton-proton, proton-nucleus and nucleus-nucleus collisions.
We present a detailed study of chemical freeze-out in nucleus-nucleus collisions at beam energies of 11.6, 30, 40, 80 and 158A GeV. By analyzing hadronic multiplicities within the statistical hadronization approach, we have studied the chemical equilibration of the system as a function of center of mass energy and of the parameters of the source. Additionally, we have tested and compared differe
The basic principles of the correlation femtoscopy, including its correspondence to the Hanbury Brown and Twiss intensity interferometry, are re-examined. The main subject of the paper is an analysis of the correlation femtoscopy when the source size is as small as the order of the uncertainty limit. It is about 1 fm for the current high energy experiments. Then the standard femtoscopy model of random sources is inapplicable. The uncertainty principle leads to the partial indistinguishability and coherence of closely located emitters that affect the observed femtoscopy scales. In thermal systems the role of corresponding coherent length is taken by the thermal de Broglie wavelength that also defines the size of a single emitter. The formalism of partially coherent phases in the amplitudes of closely located individual emitters is used for the quantitative analysis. The general approach is illustrated analytically for the case of the Gaussian approximation for emitting sources. A reduction of the interferometry radii and a suppression of the Bose-Einstein correlation functions for small sources due to the uncertainty principle are found. There is a positive correlation between the source size and the intercept of the correlation function. The peculiarities of the non-femtoscopic correlations caused by minijets and fluctuations of the initial states of the systems formed in $pp$ and $e^+e^-$ collisions are also analyzed. The factorization property for the contributions of femtoscopic and non-femtoscopic correlations into complete correlation function is observed in numerical calculations in a wide range of the model parameters.
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