Hadronization Of Quark-gluon Plasma Research Articles

Baryon number fluctuations induced by hadronic interactions at low temperature and large chemical potential

We investigate the density fluctuations induced by hadronic interactions at low temperatures and large chemical potentials after the hadronization of quark-gluon plasma~(QGP). We analyze the structures of net-baryon number kurtosis and skewness and elaborate on their relations with the nuclear liquid-gas~(LG) phase transition and hadronic interactions above the critical temperature. Combining with the relevant experimental projects at RHIC/NICA/FAIR/J-PARC/HIAF with collision energies from $200\,$GeV to $1.8\,$GeV, we propose a double-peak structure of kurtosis (skewness) as a function of collision energy, which can be taken to identify the chiral phase transition and the nuclear liquid-gas phase transition. In particular, the fluctuation distributions at low temperatures provide a new method to explore hadronic interactions and nuclear liquid-gas transition.

Entropy production during hadronization of a quark-gluon plasma

We revisit the physical pictures for the hadronization of quark-gluon plasma, concentrating on the problem of entropy production during processes where the number of degrees of freedom is seemingly reduced due to color confinement. Based on observations on Regge trajectories we propose not having an infinite tower of hadronic resonances. We discuss possible entropy production mechanisms far from equilibrium in terms of stochastic dynamics.

The Rapidity Distributions and the Thermalization Induced Transverse Momentum Distributions in Au-Au Collisions at RHIC Energies

It is widely believed that the quark-gluon plasma (QGP) might be formed in the current heavy ion collisions. It is also widely recognized that the relativistic hydrodynamics is one of the best tools for describing the process of expansion and hadronization of QGP. In this paper, by taking into account the effects of thermalization, a hydrodynamic model including phase transition from QGP state to hadronic state is used to analyze the rapidity and transverse momentum distributions of identified charged particles produced in heavy ion collisions. A comparison is made between the theoretical results and experimental data. The theoretical model gives a good description of the corresponding measurements made in Au-Au collisions at RHIC energies.

Strangeness in QGP: Hadronization Pressure

We review strangeness as signature of quark gluon plasma (QGP) and the hadronization process of a QGP fireball formed in relativistic heavy-ion collisions in the entire range of today accessible reaction energies. We discuss energy dependence of the statistical hadronization parameters within the context of fast QGP hadronization. We find that QGP breakup occurs for all energies at the universal hadronization pressure $P = 80\pm 3\,\mathrm{MeV/fm}^3 $.

Baryon Anomaly in Heavy-Ion Collisions and Colour Correlations in QGP

Abstract A baryon anomaly – an increased baryon-to-meson production ratio at intermediate p T in heavyion collisions when compared to pp collisions – is observed at RHIC and the LHC. This effect is usually explained by recombination of constituent quarks during QGP hadronization, or as a consequence of a strong radial flow developed during the heavy-ion collision. In this contribution, an additional mechanism to favour baryon over meson production is proposed: when hadrons are formed in the recombination of nearby quarks and antiquarks, only colour-singlet combinations can be chosen. Hadron formation, in particular the probability to create baryons or mesons, depends on the distribution of colour charges among quarks. If the distribution is random – a reasonable assumption for Quark–Gluon Plasma (QGP) – the baryon-to-meson ratio is nearly twice higher than in the situation where quark colours are pre-arranged to obtain a white hadron in the combination of nearest quarks and antiquarks. The correlation of colour charges in the QGP also influences the distance over which recombination occurs. A study of the dependence of the baryon-to-meson ratio on the size of the colour correlation domain is presented.

K*0andΣ*production in Au+Au collisions atsNN=200GeV and 62.4 GeV

Applying a quark combination model for the hadronization of Quark Gluon Plasma (QGP) and A Relativistic Transport (ART) model for the subsequent hadronic rescattering process, we investigate the production of $K^{*0}$ and $\Sigma^*$ resonances in central Au+Au collisions at $\sqrt{s_{NN}}=$ 200 GeV and 62.4 GeV. The initial $K^{*0}$ produced via hadronization is higher than the experimental data in the low $p_T$ region and is close to the data at 2-3 GeV/c. We take into account the hadronic rescattering effects which lead to a strong suppression of $K^{*0}$ with low $p_T$, and find that the $p_T$ spectrum of $K^{*0}$ can be well described. According to the suppressed magnitude of $K^{*0}$ yield, the time span of hadronic rescattering stage is estimated to be about 13 fm/c at 200 GeV and 5 fm/c at 62.4 GeV. The $p_T$ spectrum of $\Sigma^*$ directly obtained by quark combination hadronization in central Au+Au collisions at 200 GeV is in well agreement with the experimental data, which shows a weak hadronic rescattering effects. The elliptic flow v2 of $\Sigma^*$ in minimum bias Au+Au collisions at 200 GeV and $p_T$ spectrum of $\Sigma^*$ at lower 62.4 GeV are predicted.

Color-singlet clustering of partons and recombination model for hadronization of quark-gluon plasma

SU$({N}_{c})$ color-singlet restriction, along with flavor and spin symmetry, on a thermal partonic ensemble is shown to recombine the partons with internal color structure into color-singlet multiquark clusters, which can be identified with various hadronic modes at a given temperature. This can provide a possible basis for a recombination model for hadronization of quark-gluon plasma. This also leads to a natural explanation for the ratio of (anti)protons to pions and the quark number scaling of the elliptic flow coefficient in relativistic heavy-ion collisions.

Hadron spectra and quark-gluon plasma hadronization inAu+Aucollisions at relativistic energies

The transverse mass spectra of $\ensuremath{\Omega}$ hyperons and $\ensuremath{\varphi}$ mesons measured recently by STAR Collaboration in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{\mathrm{NN}}}=130\mathrm{GeV}$ are described within a hydrodynamic model of the quark-gluon plasma expansion and hadronization. The flow parameters at the plasma hadronization extracted by fitting these data are used to predict the transverse mass spectra of $J/\ensuremath{\psi}$ and ${\ensuremath{\psi}}^{\ensuremath{'}}$ mesons.

Formula omitted], J/ψ and ψ′ transverse mass spectra at RHIC

The transverse mass spectra of J/ψ and ψ′ mesons and Ω hyperons produced in central Au+Au collisions at RHIC energies are discussed within a statistical model used successfully for the interpretation of the SPS results. The comparison of the presented model with the future RHIC data should serve as a further crucial test of the hypothesis of statistical production of charmonia at hadronization. Finally, in case of validity, the approach should allow to estimate the mean transverse flow velocity at the quark–gluon plasma hadronization.

Transverse momentum spectra of J/ψ and ψ′ mesons from quark gluon plasma hadronization at CERN SPS

A popular derivation of the apparent temperature of the particle transverse momentum spectra and its inconsistency are considered. An improved formula for the apparent temperature is discussed. It is shown that recent results on transverse mass spectra of J/ψ and ψ′ mesons support a hypothesis of statistical production of charmonia at hadronization and suggest the early thermal freeze-out of these mesons. Using the apparent temperature formula the collective transverse velocity of the hadronizing quark gluon plasma is extracted to be ⟨vT⟩ ≈ 0.2. Predictions for transverse mass spectra of hidden and open charm mesons along with bottomonium at SPS and RHIC energies are discussed.

Transverse momentum spectra of J/ψ and ψ′ mesons from quark gluon plasma hadronization in nuclear collisions

Recent results on transverse mass spectra of $J/\psi$ and $\psi^{\prime}$ mesons in central Pb+Pb collisions at 158 A$\cdot$GeV are considered. It is shown that those results support a hypothesis of statistical production of charmonia at hadronization and suggest the early thermal freeze--out of $J/\psi$ and $\psi^{\prime}$ mesons. Based on this approach the collective transverse velocity of hadronizing quark gluon plasma is estimated to be $<v^H_T> \approx 0.2$. Predictions for transverse mass spectra of hidden and open charm mesons at SPS and RHIC are discussed.

Preface

A baryon anomaly – an increased baryon-to-meson production ratio at intermediate pT in heavyion collisions when compared to pp collisions – is observed at RHIC and the LHC. This effect is usually explained by recombination of constituent quarks during QGP hadronization, or as a consequence of a strong radial flow developed during the heavy-ion collision. In this contribution, an additional mechanism to favour baryon over meson production is proposed: when hadrons are formed in the recombination of nearby quarks and antiquarks, only colour-singlet combinations can be chosen. Hadron formation, in particular the probability to create baryons or mesons, depends on the distribution of colour charges among quarks. If the distribution is random – a reasonable assumption for Quark–Gluon Plasma (QGP) – the baryon-to-meson ratio is nearly twice higher than in the situation where quark colours are pre-arranged to obtain a white hadron in the combination of nearest quarks and antiquarks. The correlation of colour charges in the QGP also influences the distance over which recombination occurs. A study of the dependence of the baryon-to-meson ratio on the size of the colour correlation domain is presented.

Glueball production from the quark-gluon plasma.

We suggest that there might be a production of a large number of glueballs in relativistic nucleus-nucleus collisions if the quark-gluon plasma (QGP) phase is realized. The ratio of the number of the produced glueball to that of the neutral pions directly produced in the process of QGP hadronization is estimated phenomenologically. Being a function of the phase transition temperature and chemical potential, it can be as large as a few percents. Considering the fact that the hadronization is very complicated, we anticipate that the abundant population of glueballs from the quark-gluon plasma at least may exert influences on the final-state ${\mathit{K}}^{+}$/${\mathrm{\ensuremath{\pi}}}^{+}$ ratio.

Hadron production from quark-gluon plasma via mixed phase

Well-controlled hadronization of the quark-gluon plasma via a mixed phase is described by a set of rate equations supplemented with the one-dimensional scaling hydrodynamics. The reaction rates for the hadronization processes are constrained by the equilibrium condition for the static mixed phase using the fractional volume formalism. As an example, two models of hadronization of baryon-free quark-gluon plasma are constructed according to different choices of the constituents of the free hadron gas: the meson-baryon model and the pseudoscalar-vector model. Time evolution of the flavor composition and hadron multiplicity is studied in detail. It was found that (i) the abundance of strange hadrons at the final stage of the phase transition is insensitive to the strangeness abundance in the initial stage, (ii) the K π ratio in the final stage is essentially given by the equilibrium value for the hadronic phase, (iii) the baryon/meson ratio is sensitive to the transition temperature, (iv) the entropy is approximately conserved or increases slightly, and (v) the period of the mixed phase era depends on both the critical temperature and the effective number of hadronic degrees of freedom. The time-integrated ratio of the vector meson yields 〈 φ>/<ρ 0 + ω〉 is found to be twice as large as the maximum enhancement observed by the NA38 experiment on muon pair production. It is suggested that suppression of resonance production relative to direct pseudoscalar meson production may serve as a signature of thermal equilibrium in the hadronic phase.

Intermittency, Kadanoff scaling and hadronization

We show that Kadanoff scaling near the critical point of the Feynman-Wilson fluid leads to intermittency in the rapidity-space. A minimum rapidity interval δ 0, below which intermittency disappears, naturally emerges and its magnitude is evaluated. We argue that the characteristic pattern of the factorial moments, when compared with data, especially in relativistic ion collisions, may signal a higher-order phase transition related to the quark-gluon plasma hadronization.

Shock stability criterion in relativistic hydrodynamics and quark-gluon plasma hadronization

The shock stability condition in the relativistic hydrodynamics is found. This criterion is applied to a quark-gluon plasma shock-like hadronization transition.