Chemical freeze-out of light nuclei in high energy nuclear collisions and resolution of the hyper-triton chemical freeze-out puzzle
K. A. Bugaev, O. V. Vitiuk, B. E. Grinyuk, N. S. Yakovenko, E. S. Zherebtsova, V. V. Sagun, O. I. Ivanytskyi, D. O. Savchenko, L. V. Bravina, D. B. Blaschke, G.… 展开作者
K. A. Bugaev, O. V. Vitiuk, B. E. Grinyuk, N. S. Yakovenko, E. S. Zherebtsova, V. V. Sagun, O. I. Ivanytskyi, D. O. Savchenko, L. V. Bravina, D. B. Blaschke, G. R. Farrar, S. Kabana, S. V. Kuleshov, E. G. Nikonov, A. V. Taranenko, E. E. Zabrodin, G. M. Zinovjev
We present a summary of the recent results obtained with the novel hadron resonance gas model with the multicomponent hard-core repulsion which is extended to describe the mixtures of hadrons and light (anti-, hyper-)nuclei. A very accurate description is obtained for the hadronic and the light nuclei data measured by STAR at the collision energy $\sqrt{s_{NN}} =200$ GeV and by ALICE at $\sqrt{s_{NN}} =2.76$ TeV. The most striking result discussed here is that for the most probable chemical freeze-out scenario for the STAR energy the found parameters allow us to reproduce the values of the experimental ratios $S_3$ and $\overline{S}_3$ without fitting.
The recently developed hadron resonance gas model with multicomponent hard-core repulsion is used to address and resolve the long standing problem to describe the light nuclear cluster multiplicities including the hyper-triton measured by the STAR Collaboration, known as the hyper-triton chemical freeze-out puzzle. An unprecedentedly accurate description is obtained for the hadronic and other light nuclear cluster data measured by STAR at the collision energy $\sqrt{s_{NN}} =200$ GeV and by ALICE at $\sqrt{s_{NN}} =2.76$ TeV. This success is achieved by applying the new strategy of analyzing t…
We study the transverse momentum spectra of light nuclei (deuteron, anti-deuteron and triton) produced in Gold-Gold (Au-Au) collisions in different centrality bins by the blast wave model with Tsallis statistics. The model results are in agreement with the experimental data measured by STAR Collaboration in special transverse momentum ranges. We extracted the kinetic freezeout temperature, transverse flow velocity and kinetic freezeout volume. It is observed that kinetic freezeout temperature and transverse flow velocity increases initially, and then saturates from 14.5-39 GeV, while the kinet…
We used blast wave model with Tsallis statistics to analyze the experimental data measured by ALICE Collaboration in proton-proton collisions at Large Hadron Collider and extracted the related parameters (kinetic freeze-out temperature, transverse flow velocity and kinetic freeze-out volume of emission source) from transverse momentum spectra of the particles. We found that the kinetic freeze-out temperature and kinetic freeze-out volume are mass dependent. The former increase while the latter decrease with the particle mass which is the evidence of a mass as well as volume differential kineti…
A finite unbound system which is equilibrium in one reference frame is in general nonequilibrium in another frame. This is a consequence of the relative character of the time synchronization in the relativistic physics. This puzzle was a prime motivation of the Cooper--Frye approach to the freeze-out in relativistic hydrodynamics. Solution of the puzzle reveals that the Cooper--Frye recipe is far not a unique phenomenological method that meets requirements of energy-momentum conservation. Alternative freeze-out recipes are considered and discussed.
The single-freeze-out model with parametrized hypersurface and flow geometry is employed to analyze the transverse-momentum spectra of hadrons produced in the Pb+Pb collisions at the collision energy of {$\sqrt{s_{\rm NN}}=2.76$ TeV} at the CERN Large Hadron Collider (LHC). With the notable exception for protons and antiprotons, we find a very good agreement between the model results and the data for the measured hadron species. The additional analysis of the HBT radii of pions helps us to select, from several different types of freeze-out studied in this work, the most realistic form of the f…
The evolution of (non-strange) antibaryon abundances in the hadronic phase of central heavy-ion collisions is studied within a thermal equilibrium framework, based on the well-established picture of subsequent chemical and thermal freezeout. Due to large annihilation cross sections, antiprotons are, a priori, not expected to comply with this scheme. However, we show that a significant regeneration of their abundance occurs upon inclusion of the inverse reaction of multipion fusion, $n_ππ\to p\bar p$ (with $n_π$=5-6), necessary to ensure detailed balance. Especially at SPS energies, the build-u…
We analyze the transverse momentum ($p_T$) spectra, $1/N_{ev}$[(1/2$π$$p_T$) $d^2$$N$/$dyd$$p_T$], of kaon, proton, deuteron and triton in different centrality events in gold-gold (Au-Au) collisions at Relativistic Heavy Ion Collisions (RHIC) by Hagedorn thermal model and extracted the excitation function of effective temperature, kinetic freeze-out volume, initial temperature and kinetic freeze-out temperature. We perceived that the effective temperature, initial temperature and kinetic freeze-out temperature sharply increases from 7.7 GeV to 14.5 GeV and then remain static from 14.5-39 GeV, …
We analyzed the transverse momentum spectra of proton, deuteron and triton in Boron-Boron (B-B), Oxygen-Oxygen (O-O), and Calcium-Calcium (Ca-Ca) central collisions, as well as in several centrality bins in Gold-Gold (Au-Au) collisions at 39 GeV by using the blast wave model with Tsallis statistics. The bulk properties in terms of kinetic freeze-out temperature, transverse flow velocity and kinetic freeze-out volume are extracted from the model by the least square method. We observed that with increasing the rest mass of the particle, the kinetic freeze-out temperature becomes larger, while tr…
Using a transport model that includes a first-order chiral phase transition between the partonic and the hadronic matter, we study the development of density fluctuations in the matter produced in heavy ion collisions as it undergoes the phase transition, and their time evolution in later hadronic stage of the collisions. Using the coalescence model to describe the production of deuterons and tritons from nucleons at the kinetic freeze out, we find that the yield ratio $ N_\text{t}N_\text{p}/ N_\text{d}^2$, where $N_\text{p}$, $N_\text{d}$, and $N_\text{t}$ are, respectively, the proton, deute…
We show that the measured yield ratio $^3_Λ$H/$^3$He ($^3_{\overlineΛ}\overline{\text{H}}$/$^3\overline{\text{He}}$) in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV and in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV can be understood within a covariant coalescence model if (anti-)$Λ$ particles freeze out earlier than (anti-)nucleons but their relative freezeout time is closer at $\sqrt{s_{NN}}=2.76$ TeV than at $\sqrt{s_{NN}}=200$ GeV. The earlier (anti-)$Λ$ freezeout can significantly enhance the yield of (anti)hypernucleus $^4_Λ$H ($^4_{\overlineΛ}\overline{\text{H}}$), leading to that $^4_{…
We use a simple hard-core gas model to study the dynamics of small exploding systems. The system is initially prepared in a thermalized state in a spherical container and then allowed to expand freely into the vacuum. We follow the expansion dynamics by recording the coordinates and velocities of all particles until their last collision points (freeze-out). We have found that the entropy per particle calculated for the ensemble of freeze-out points is very close to the initial value. This is in apparent contradiction with the Joule experiment in which the entropy grows when the gas expands irr…
Based on an improved multiphase transport (AMPT) model, which gives a good description of proton production with a smooth quark matter to hadronic matter transition in relativistic heavy ion collisions, we study deuteron and triton production from the coalescence of nucleons at the kinetic freezeout of these collisions. For Au+Au collisions at center-of-mass energies $\sqrt{s_\text{NN}}$ from 7.7 GeV to 200 GeV available at the Relativistic Heavy Ion Collider (RHIC), we find that the yield ratio $N_\text{t}N_\text{p}/N_\text{d}^2$ of proton, deuteron\com{,} and triton is essentially a constant…
We introduce a new scenario for heavy ion collisions that could solve the lingering problems associated with the so-called HBT puzzle. We postulate that the system starts expansion as the perfect quark-gluon fluid but close to freeze-out it splits into clusters, due to a sharp rise of bulk viscosity in the vicinity of the hadronization transition. We then argue that the characteristic cluster size is determined by the viscosity coefficient and the expansion rate. Typically it is much smaller and independent of the total system volume. These clusters maintain the pre-existing outward-going flow…
We give an review the HBT puzzle, and argue that its resolution requires the introduction of new physics close to the phase transition scale. We argue that a candidate for this new physics is bulk viscosity, recently postulated to peak, and even diverge, close to the phase transition temperature. We show that such a viscosity peak can force the system created in heavy ion collisions to become unstable, and filament into fragments whose size is weakly dependent on the global size of the system, thereby triggering freeze-out.
In this talk we present the results of two-pion HBT correlation at freeze-out in heavy ion collisions (HICs) from AGS to RHIC energies. The UrQMD hadron-string transport model as well as the CRAB analyzing program are adopted. Based on the cascade mode, in general, the calculations are satisfying and well in line with the experimental data although discrepancies are not negligible. Such as: I), the HBT time-related puzzle exists at all energies. II), at low AGS energies, the calculated volume as well as the mean free path of pion source at freeze-out are lower than data. It implies that a bett…
We show that the recently observed suppression of the yield ratio of deuteron to proton and of helium-3 to proton in p+p collisions compared to those in p+Pb or Pb+Pb collisions by the ALICE Collaboration at the Large Hadron Collider (LHC) can be explained if light nuclei are produced from the coalescence of nucleons at the kinetic freeze-out of these collisions. This suppression is attributed to the non-negligible sizes of deuteron and helium-3 compared to the size of the nucleon emission source in collisions of small systems, which reduces the overlap of their internal wave functions with th…
Using the nucleon coalescence model based on kinetic freeze-out nucleons from the 3D MUSIC+UrQMD and the 2D VISHNU hybrid model with a crossover equation of state, we study the multiplicity dependence of deuteron ($d$) and triton ($t$) production from central to peripheral Au+Au collisions at $\sqrt{s_\mathrm{NN}}=$ 7.7, 14.5, 19.6, 27, 39, 62.4 and 200 GeV and Pb+Pb at $\sqrt{s_\mathrm{NN}}=2.76$ TeV, respectively. It is found that the ratio $N_t N_p/N_d^2$ of the proton yield $N_p$, deuteron yield $N_d$ and triton yield $N_t$ exhibits a scaling behavior in its multiplicity dependence, i.e., …
We show that the new data on mean multiplicities measured in p+p and A+A collisions together with the updated list of resonances lead to the significant changes of the obtained freeze-out lines. The new A+A line gives much smaller temperatures at high collision energies and agrees with the values obtained at the LHC. The newly obtained p+p line is much closer to the A+A line than previously expected, and even touches it in the region where the $K^+/π^+$ horn appears in the data. It indicates that the temperatures that will be obtained in the beam energy and system size scan by the NA61/SHINE C…
We estimate the feeddown contributions from decays of unstable $A = 4$ and $A = 5$ nuclei to the final yields of protons, deuterons, tritons, $^3$He, and $^4$He produced in relativistic heavy-ion collisions at $\sqrt{s_{\rm NN}} > 2.4$ GeV, using the statistical model. The feeddown contribution effects do not exceed 5% at LHC and top RHIC energies due to the large penalty factors involved, but are substantial at intermediate collision energies. We observe large feeddown contributions for tritons, $^3$He, and $^4$He at $\sqrt{s_{\rm NN}} \lesssim 10$ GeV, where they may account for as much as 7…
We study the collision energy dependence of (anti-)deuteron and (anti-)triton production in the most central Au+Au collisions at $\sqrt{s_\mathrm{NN}}=$ 7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV, using the nucleon coalescence model. The needed phase-space distribution of nucleons at the kinetic freeze-out is generated from a new 3D hybrid dynamical model (\texttt{iEBE-MUSIC}) by using a smooth crossover equation of state (EoS) without a QCD critical point. Our model calculations predict that the coalescence parameters of (anti-)deuteron ($B_2(d)$ and $B_2(\bar{d})$) decrease monotonically as t…
With the kinetic freeze-out nucleons and antinucleons obtained from the quark combination model, we study the production of light nuclei and antinuclei in the (anti-)nucleon coalescence mechanism in relativistic heavy ion collisions. We derive analytic formulas of the momentum distributions of different light nuclei and apply them to compute transverse momentum ($p_T$) spectra of (anti-)deuterons ($d$, $\bar d$) and (anti-)tritons ($t$, $\bar t$) in Au-Au collisions at $\sqrt{s_{NN}}=$7.7, 11.5, 19.6, 27, 39, 54.4 GeV. We find that the experimental data available for these $p_T$ spectra can be…
The light-nuclei yield ratio is one of the candidates to probe the critical fluctuations of hot QCD matter. In this paper, we investigate the \textit{background effects}, namely the non-critical effects coming from the non-trivial thermal background, on the light-nuclei production within the framework of the coalescence model. Specifically, we analyze the impact of the equilibrium phase-space distribution function of nucleons, $f(\mathbf{r},\mathbf{p})$, on the light-nuclei yield ratio $N_tN_p/N_d^2$, where $N_t$, $N_p$, and $N_d$ denote triton, proton, and deuteron yields. By considering the …
