Search

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., Comment: 12 pages, 6 figures

The quark combination mechanism of hadron production is applied to nucleus-nucleus collisions at the CERN Super Proton Synchrotron (SPS) and BNL Alternating Gradient Synchrotron (AGS). The rapidity spectra of identified hadrons and their spectrum widths are studied. The data of $\pi^{-}$, $K^{\pm}$, $\phi$, $\Lambda$, $\bar{\Lambda}$, $\Xi^{-}$, and $\bar{\Xi}^{+}$ at 80 and 40 AGeV, in particular at 30 and 20 AGeV where the onset of deconfinement is suggested to happen, are consistently described by the quark combination model. However at AGS 11.6 AGeV below the onset the spectra of $\pi^{\pm}$, $K^{\pm}$ and $\Lambda$ can not be simultaneously explained, indicating the disappearance of intrinsic correlation of their production in the constituent quark level. The collision-energy dependence of the rapidity spectrum widths of constituent quarks and the strangeness of the hot and dense quark matter produced in heavy ion collisions are obtained and discussed., Comment: 7 pages, 5 figures

Under the assignment of $D_s(3040)$ as a radially excited p-wave $\bar cs$ state with $J^P=1^+$, we compute the $B_s\to D_s (3040)$ form factors within the covariant light-front quark model. Two classification schemes for the p-wave $\bar cs$ meson are adopted. We also use our results to predict the branching ratios (BRs), polarization fractions and angular asymmetries in semileptonic $B_s\to D_s(3040)\ell\bar\nu(\ell=e,\mu,\tau)$. The BRs are found to have the order of $10^{-3}$ for $\ell=e,\mu$ and $10^{-5}$ for $\ell=\tau$. We find that the polarization fractions and the angular asymmetries could be useful to pin down the ambiguities of the quantum numbers for $D_s(3040)$. In addition, we investigate the nonleptonic $B_s\to D_s(3040)M$ decays under the factorization method, where $M$ denotes a charged pseudoscalar or a vector meson. The BRs of $B_s\to D_s(3040)\rho$ and $B_s\to D_s(3040)D_s^*$ reach the order of $10^{-3}$, while the other channels are typically smaller by 1-2 orders., Comment: 16 pages, 6 figures

Based on the assumption of the production of deconfined quark matter, we use a quark combination model to systematically investigate hadron yields in heavy ion collisions from RHIC $\sqrt{s_{NN}}=200, 130, 62.4$ GeV to SPS $E_{beam}=158, 80, 40, 30, 20 $ AGeV. We find that as the collision energy is greater than or equal to 30 AGeV the yields of various hadrons, their correlations, in particular, the observables $A=\frac{\bar{\Lambda} k^{-} p}{\Lambda k^{+} \bar{p}}$ and $B=\frac{\Lambda k^{-}\bar{\Xi}^{+}}{\bar{\Lambda} k^{+}\Xi^{-}}$, are all reproduced; however, as the collision energy drops to 20 AGeV quark combination fails. This indicates that the constituent quark degrees of freedom represent a decisive factor in thermal hadron production above 30 AGeV and seem to be invalid at 20 AGeV. In addition, hadron yields as well as particle ratios at midrapidity in the most central Pb+Pb collisions at $\sqrt{s_{NN}}=5.5$ TeV are predicted., Comment: 7 pages, 3 figures

We use two available methods, the Duhem-Gibbs relation and the entropy formula in terms of particle phase space distributions, to calculate the entropy in a quark combination model. The entropy of the system extracted from the Duhem-Gibbs relation is found to increase in hadronization if the average temperature of the hadronic phase is lower than that of the quark phase. The increase of the entropy can also be confirmed from the entropy formula if the volume of the hadronic phase is larger than 2.5-3.0 times that of the quark phase. So whether the entropy increases or decreases during combination depends on the temperature before and after combination and on how much expansion the system undergoes during combination. The current study provides an example to shed light on the entropy issue in the quark combination model., Comment: RevTex 4, 4 pages, 2 tables, 4 figures, discussions and references added, to appear in PRC

The philosophy on production of exotic hadrons (multi-quark states) in the framework of quark combination model is investigated, taking $f_0(980)$ as an example. The production rate and $p_T$ spectra of $f_0(980)$ considered as $(s\bar s)$ or $(s\bar q\bar s q)$ respectively, are calculated and compared in Au+Au collisions at $\sqrt{s_{NN}}=200GeV$. The unitarity of various combination models, when open for exotic hadron production, is addressed., Comment: 5 pages, 1 figure, new version with minor corrections and one ref. added

The quark combination mechanism of QGP hadronization is applied to nucleus-nucleus collisions at top SPS energy. The yields, rapidity and transverse momentum distributions of identified hadrons in most central Pb+Pb collisions at $\sqrt{s_{NN}}= 17.3$ GeV are systematically studied. The calculated results are in agreement with the experimental data from NA49 Collaboration. The longitudinal and transverse collective flows and strangeness of the hot and dense quark matter produced in nucleus-nucleus collisions at top SPS energy are investigated. It is found that the collective flow of strange quarks is stronger than light quarks, which is compatible with that at RHIC energies, and the strangeness is almost the same as those at $\sqrt{s_{NN}}=$ 62.4, 130, 200 GeV., Comment: 10 pages, 6 figures

Utilizing the three-fireball picture within the quark combination model, we study systematically the charged particle pseudorapidity distributions in both Au+Au and Cu+Cu collision systems as a function of collision centrality and energy, $\sqrt{s_{NN}}=$ 19.6, 62.4, 130 and 200 GeV, in full pseudorapidity range. We find that: (i)the contribution from leading particles to $dN_{ch}/d\eta$ distributions increases with the decrease of the collision centrality and energy respectively; (ii)the number of the leading particles is almost independent of the collision energy, but it does depend on the nucleon participants $N_{part}$; (iii)if Cu+Cu and Au+Au collisions at the same collision energy are selected to have the same $N_{part}$, the resulting of charged particle $dN/d\eta$ distributions are nearly identical, both in the mid-rapidity particle density and the width of the distribution. This is true for both 62.4 GeV and 200 GeV data. (iv)the limiting fragmentation phenomenon is reproduced. (iiv) we predict the total multiplicity and pseudorapidity distribution for the charged particles in Pb+Pb collisions at $\sqrt{s_{NN}}= 5.5$ TeV. Finally, we give a qualitative analysis of the $N_{ch}/$ and $dN_{ch}/d\eta/|_{\eta\approx0}$ as function of $\sqrt{s_{NN}}$ and $N_{part}$ from RHIC to LHC., Comment: 12 pages, 8 figures

The centrality dependence of transverse momentum spectra for identified hadrons at midrapidity in Au+Au collisions at $\sqrt{s_{NN}}= 200$ GeV is systematically studied in a quark combination model. The $\mathrm{{p}_{T}}$ spectra of $\pi^{\pm}$, $K^{\pm}$, $p(\bar{p})$ and $\Lambda(\bar{\Lambda})$ in different centrality bins and the nuclear modification factors ($R_{CP}$) for these hadrons are calculated. The centrality dependence of the average collective transverse velocity $<\beta (r)>$ for the hot and dense quark matter is obtained in Au+Au collisions, and it is applied to a relative smaller Cu+Cu collision system. The centrality dependence of $\mathrm{{p}_{T}}$ spectra and the $R_{CP}$ for $\pi^{0}$, $K_{s}^{0}$ and $\Lambda$ in Cu+Cu collisions at $\sqrt{s_{NN}}= 200$ GeV are well described. The results show that $<\beta (r)>$ is only a function of the number of participants $N_{part}$ and it is independent of the collision system., Comment: 7 pages, 6 figures

Within a quark combination model, we study systematically the yields and rapidity spectra of various hadrons in central Au+Au collisions at $\sqrt{s_{NN}}= 200$ GeV. We find that considering the difference in rapidity between net-quarks and newborn quarks, the data of multiplicities, rapidity distributions for $\pi^{\pm}$, $K^{\pm}$, $p(\bar{p})$ and, in particular the ratios of charged antihadron to hadron as a function of rapidity, can be well described. The effect of net-quarks on various hadrons is analysed, and the rapidity distributions for $K^{0}_{s}$, $\Lambda(\bar{\Lambda})$, $\Sigma^{+}(\bar{\Sigma}^{_-})$, $\mathrm{\Xi^{-}}$ ($\mathrm{\bar{\Xi}^{_+}}$) and $\mathrm{\Omega^{-}}(\mathrm{\bar{\Omega}}^{_+})$ are predicted. We discuss the rapidity distribution of net-baryon, and find that it reflects exactly the energy loss of colliding nuclei., Comment: 8 pages, 7 figures

The rapidity and transverse momentum spectra for identified hadrons in central Au+Au collisions at $\sqrt{s_{NN}}= 200$ GeV are computed in a quark combination model. The data of rapidity distributions for $\pi^{\pm}$, $K^{\pm}$, $p(\bar{p})$ and net protons $(p-\bar{p})$ are well described. We also predict rapidity distributions for $K^{0}_{s}$, $\Lambda(\bar{\Lambda})$, $\mathrm{\Xi^{-}}$ ($\mathrm{\bar{\Xi}^{_+}}$) and $\mathrm{\Omega^{-}}+\mathrm{\bar{\Omega}}^{_+}$. The multiplicity ratios of charged antihadrons to hadrons as a function of rapidity are reproduced. The results for ${p}_{T}$ spectra of $\pi^{\pm}$, $K^{\pm}$, $p(\bar{p})$ and for the $p/\pi$ ratios in a broader ${p}_{T}$ range agree well with the data. Finally the rapidity dependence of transverse momentum distributions for hadrons are given., Comment: 10 pages,11figures,3 tables

Rapidity/seudorapidity densities for charged particles and their centrality, rapidity and energy dependence in Au+Au collisions at RHIC are studied in a quark combination model. Using a Gaussian-type rapidity distribution for constituent quarks as a result of Landau hydrodynamic evolution, the data at $\sqrt{s_{NN}}=130, 200$ GeV at various centralities in full pseudorapidity range are well described, and the charged particle multiplicity are reproduced as functions of the number of participants. The energy dependence of the shape of the $dN_{ch}/d\eta$ distribution is also described at various collision energies $\sqrt{s_{NN}}=200, 130, 62.4$ GeV in central collisions with same value of parameters except 19.6 GeV. The calculated rapidity distributions and yields for the charged pions and kaons in central Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV are compared with experimental data of the BRAHMS Collaboration., Comment: 8 pages, 9 figures, 1 table

We carry out a detail study of elliptic flows in Au-Au collisions at 200 AGeV in a quark combination model. We find that elliptic flow data for a variety of hadrons can be well reproduced except pions if constituent quarks with equal parallel transverse momenta combine into initially produced hadrons. In a combination mechanism where initial hadrons are formed by quarks with unequal parallel transverse momenta, theoretical predictions agree with data for all available hadrons including pions. The mass hierarchy at low transverse momenta in elliptic flows can be understood in the same quark combination mechanism as in the mediate range of transverse momenta., Comment: In RevTex 4, 8 pages, 5 figures, references added

The hadron production in relativistic heavy ion collisions is well described by the quark combination model. The mixed ratios for various hadrons and the transverse momentum spectra for long-life hadrons are predicted and agree with recent RHIC data. The production rates for the pentaquarks $\Theta ^+$, $\Theta ^{*++}$ and the di-baryon $(\Omega\Omega)_{0^{+}}$ are estimated, neglecting the effect from the transition amplitude for constituent quarks to form an exotic state., Comment: The difference between our model and other combination models is clarified. The scaled transverse momentum spectra for pions, kaons and protoms at both 130 AGeV and 200 AGeV are given, replacing the previous results in transverse momentum spectra

We replace in the event generator JETSET the color singlet chain connection with the color separate state one as the interface between the hard and soft sectors of hadronic processes. The modified generator is applied to produce the hadronic events in $e^+ e^-$ annihilation. It describes the experimental data at the same level as the original JETSET with default parameters. This should be understood as a demonstration that color singlet chain is not the unique color connection. We also search for the difference in special sets of three-jet events arising from different color connections, which could subject to further experimental test., Comment: 23 pages, 8 figures, 4 tables, Revtex4

Hadronic events in $e^+ e^- \to Z^0$ are generated by a Monte-Carlo model including the production of colour separate states. These events are compared with those produced by the JETSET with default set of parameters where the colour connections are colour singlet chains. By selecting two-jet-like events and a sensitive observable, we find that these two kinds of colour connections lead to significant differences in the hadronic states., Comment: 9 figs, 4 pps in revtex