Nonequilibrium Pion Distribution within the Zubarev Approach

Blaschke, D.; Röpke, G.; Voskresensky, D. N.; Morozov, V. G.

doi:10.3390/particles3020029

Cited by 8 publications

(6 citation statements)

References 53 publications

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“…for heavy-ion collisions with √ s N N > 8 GeV, in the region of meson dominance, where also a low-momentum enhancement of pion production has been observed. Such an effect is best described by a nonequilibrium pion distribution function, which according to Zubarev's concept of the nonequilibrium statistical operator requires an additional Lagrange multiplier, the pion chemical potential, for a consistent description [22]. Within the Beth-Uhlenbeck approach we have provided fit functions for the x-dependence of the pion and strange quark chemical potentials that lead to a simultaneous description of the x-dependence of both kaon-to-pion ratios in accordance with the experimental data, with a strong horn effect for the K + /π + ratio.…”

Section: Resultsmentioning

confidence: 99%

Mott Dissociation and Kaon to Pion Ratio in the EPNJL Model

et al. 2021

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The behaviour of pseudoscalar mesons within the SU(3)PNJL-like models is considered for finite T and µB. We compare the pole approximation (Breit-Wigner) with the Beth-Uhlenbeck approach. We evaluate the K/π ratios along the phase transition line in the T-µB plane with constant and T /µB-dependent pion and strange quark chemical potentials. Using the model, we can show that the splitting of kaon and anti-kaon masses appears as a result of introduction of density and this explains the difference in the K + /π + ratio and K − /π − ratio at low √ sNN and their tendency to the same value at high √ sNN . A sharp "horn" effect in the K + /π + ratio is explained by the enhanced pion production which can be described by occurrence of a nonequilibrium pion chemical potential of the order of the pion mass. We elucidate that the horn effect is not related to the existence of a critical endpoint in the QCD phase diagram.

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Section: Resultsmentioning

confidence: 99%

Mott Dissociation and Kaon to Pion Ratio in the EPNJL Model

et al. 2021

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“…The proper explanation of the origin of such a chemical potential has been given within the Zubarev approach to nonequilibrium statistical thermodynamics that introduces the concept of a nonequilibrium statistical operator [50]. The number of produced pions is a quasi-conserved number for the duration of the collision event until its detection and has therefore to be included as an additional observable that characterizes the nonequilibrium state into the statistical operator with the pion chemical potential as the Lagrange multiplier conjugate to it.…”

Section: "Horn" Effect In the Kaon-to-pion Ratiomentioning

confidence: 99%

“…Since the theoretical concept of introducing a pion chemical potential is the nonequilibrium generalization of the Gibbs ensembles within Zubarev's method of the nonequilibrium statistical operator [50], it is natural to assume a dependence of this Lagrangian multiplier on the pion multiplicities, which are directly related collision energy and the specific entropy variable x. Consistent with this new explanation of the horn effect by a step-like increase in the pion chemical potential at √ s N N = 8 GeV is that within the thermal statistical model at this very collision energy the entropy density of the system changes its character from being baryon-dominated to meson-dominated [73].…”

Section: "Horn" Effect In the Kaon-to-pion Ratiomentioning

confidence: 99%

“…Therefore, the adequate approach to this nonequilibrium situation is the Zubarev approach of the generalized Gibbs ensemble where the quasi conserved pion number requires an additional Lagrange multiplier, the pion chemical potential µ π , as an additional parameter of the statistical operator. For details, see [50]. The resulting nonequilibrium pion distribution function with the pion chemical potential has been successfully used in the phenomenological description of the transverse momentum spectra of pions produced in heavy-ion collision experiments, see [51,52].…”

Section: Introductionmentioning

confidence: 99%

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Chiral phase transition and kaon-to-pion ratios in the entanglement SU(3) PNJL model

Blaschke

Friesen

Kalinovsky

et al. 2020

Eur. Phys. J. Spec. Top.

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Within the three-flavor PNJL and EPNJL chiral quark models we have obtained pseudoscalar meson properties in quark matter at finite temperature T and baryochemical potential μB. We compare the meson pole (Breit-Wigner) approximation with the Beth-Uhlenbeck (BU) approach that takes into account the continuum of quark-antiquark scattering states when determining the partial densities of pions and kaons. We evaluate the kaon-to-pion ratios along the (pseudo-)critical line in the T − μB plane as a proxy for the chemical freezeout line, whereby the variable x = T∕μB is introduced that corresponds to the conserved entropy per baryon as initial condition for the heavy-ion collision experiments. We present a comparison with the experimental pattern of kaon-to-pion ratios within the BU approach and using x-dependent pion and strange quark potentials. A sharp “horn” effect in the energy dependence K+∕π+ ratio is explained by the enhanced pion production at energies above √sNN=8 GeV, when the system enters the regime of meson dominance. This effect is in line with the enhancement of low-momentum pion spectra that is discussed as a precursor of the pion Bose condensation and entails the occurrence of a nonequilibrium pion chemical potential of the order of the pion mass. We elucidate that the horn effect is not related to the existence of a critical endpoint in the QCD phase diagram.

show abstract

Section: "Horn" Effect In the Kaon-to-pion Ratiomentioning

confidence: 99%

Chiral phase transition and kaon-to-pion ratios in the entanglement SU(3) PNJL model

Blaschke,

Friesen,

Kalinovsky

et al. 2020

Preprint

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Within the three-flavor PNJL and EPNJL chiral quark models we have obtained pseudoscalar meson properties in quark matter at finite temperature T and baryochemical potential µB. We compare the meson pole (Breit-Wigner) approximation with the Beth-Uhlenbeck (BU) approach that takes into account the continuum of quark-antiquark scattering states when determining the partial densities of pions and kaons. We evaluate the kaon-to-pion ratios along the (pseudo-)critical line in the T − µB plane as a proxy for the chemical freezeout line, whereby the variable x = T /µB is introduced that corresponds to the conserved entropy per baryon as initial condition for the heavy-ion collision experiments. We present a comparison with the experimental pattern of kaon-to-pion ratios within the BU approach and using x-dependent pion and strange quark potentials. A sharp "horn" effect in the energy dependence K + /π + ratio is explained by the enhanced pion production at energies above √ sNN = 8 GeV, when the system enters the regime of meson dominance. This effect is in line with the enhancement of low-momentum pion spectra that is discussed as a precursor of the pion Bose condensation and entails the occurrence of a nonequilibrium pion chemical potential of the order of the pion mass. We elucidate that the horn effect is not related to the existence of a critical endpoint in the QCD phase diagram.

show abstract

Nonequilibrium Pion Distribution within the Zubarev Approach

Cited by 8 publications

References 53 publications

Mott Dissociation and Kaon to Pion Ratio in the EPNJL Model

Mott Dissociation and Kaon to Pion Ratio in the EPNJL Model

Chiral phase transition and kaon-to-pion ratios in the entanglement SU(3) PNJL model

Chiral phase transition and kaon-to-pion ratios in the entanglement SU(3) PNJL model

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