arXiv subjects

Feng-lan Shao

Publications and source records attributed to Feng-lan Shao.

At least 37 records · Page 2Linked to original sources

arXiv2017

New insights into hadron production mechanism from $p_{T}$ spectra in $pp$ collisions at $\sqrt{s}=7$ TeV

We show that the experimental data of mid-rapidity $p_{T}$ spectra for proton, $Λ$, $Ξ$ , $Ω^{-}$, $\text{K(892)}^{*0}$ and $Ξ(1530)^{*0}$ in minimum-bias $pp$ collisions at $\sqrt{s}=7$ TeV can be systemically explained by the quark combination mechanism of hadronization. The averaged transverse momentum $\langle p_{T}\rangle$ and spectra ratios such as $Ξ/Λ$ and $Ω/ϕ$ calculated from quark combination reproduce the data much better than those from traditional string and/or cluster fragmentation. The available data of hadronic $p_{T}$ spectra released by ALICE collaboration in the first three high-multiplicity classes of $pp$ collisions at $\sqrt{s}=7$ TeV are also well explained. We make predictions for other hadrons, and propose two scaling behaviors among decuplet baryons and vector mesons as the effective probe of hadron production mechanism at such high collision energy.

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arXiv2017

Yield ratios of identified hadrons in p+p, p+Pb, Pb+Pb collisions at the Large Hadron Collider

Yield ratios of identified hadrons observed in high multiplicity p+p and p+Pb collisions at LHC show remarkable similarity with those in Pb+Pb collisions, indicating some important and universal underlying dynamics in hadron production for different quark gluon final states. We use the quark combination model to explain the data of yield ratios in these three collision systems. The observed $p/π$ and $Λ/K_s^0$ can be reproduced simultaneously by quark combination, and these two ratios reflect the rate of baryon production at hadronization which is the same in light sector and strange sector and is roughly constant in p+p, p+Pb and Pb+Pb collision systems over three orders of magnitude in charged particle multiplicity.The data of $K_s^0/π$, $Λ/π$, $Ξ/π$ and $Ω/π$ show a hierarchy behavior relating to the strangeness content, and are naturally explained by quark combination both in the saturate stage at high multiplicity and in the increase stage at moderate multiplicity. Our results suggest that the dynamical characteristic of quark combination is necessary in describing the production of hadrons in small systems created in p+p and p+Pb collisions.

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arXiv2017

Quark number scaling of hadronic $p_T$ spectra and constituent quark degree of freedom in $p$-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV

We show that the experimental data of $p_T$ spectra of identified hadrons released recently by ALICE collaboration for $p$-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV exhibit a distinct universal behavior --- the quark number scaling. We further show that the scaling is a direct consequence of quark (re-)combination mechanism of hadronization and can be regarded as a strong indication of the existence of the underlying source with constituent quark degree of freedom for the production of hadrons in $p$-Pb collisions at such high energies. We make also predictions for production of other hadrons.

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arXiv2017

Multiplicity fluctuation and correlation of identified baryons in quark combination model

The dynamical fluctuation and correlation of multiplicity distributions of identified baryons and antibaryons produced by the hadronization of the bulk quark system are systematically studied in quark combination model. Starting from the most basic dynamics of quark combination which are necessary for multiplicity study, we analyze moments (variance, skewness and kurtosis) of inclusive multiplicity distribution of identified baryons, two-baryon multiplicity correlations, and baryon-antibaryon multiplicity correlations after the hadronization of quark system with given quark number and antiquark number. We obtain a series of interesting findings, e.g., binomial behavior of multiplicity moments, coincide flavor dependent two-baryon correlation and universal baryon-antibaryon correlation, which can be regarded as general features of quark combination. We further take into account correlations and fluctuations of quark numbers before hadronization to study their influence on multiple production of baryons and antibaryons. We find that quark number fluctuation and flavor conservation lead to a series of important results such as the negative $p\barΩ^{+}$ multiplicity correlation and universal two-baryon correlations. We also study the influence of resonance decay in order to compare our results with future experimental data in ultra-relativistic heavy ion collisions at LHC.

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arXiv2016

Energy dependence of resonance production in relativistic heavy ion collisions

The production of hadronic resonances $K^{*}(892)$, $ϕ(1020)$, $Σ^{*}(1385)$, and $Ξ^{*}(1530)$ in central AA collisions at $\sqrt{s_{NN}}=$ 17.3, 200, and 2760 GeV are systematically studied. The direct production of these resonances at system hadronization are described by the quark combination model and the effects of hadron multiple-scattering stage are dealt with by a ultra-relativistic quantum molecular dynamics model (UrQMD). We study the contribution of these two production sources to final observation and compare the final spectra with the available experimental data. The $p_T$ spectra of $K^{*}(892)$ calculated directly by quark combination model are explicitly higher than the data at low $p_T \lesssim 1.5$ GeV and taking into account the modification of rescattering effects the resulting final spectra well agree with the data at all three collision energies. The rescattering effect on $ϕ(1020)$ production is weak and including it can slightly improve our description at low $p_T$ on the basis of overall agreement with the data. We also predict the $p_T$ spectra of $Σ^{*}(1385)$ and $Ξ^{*}(1530)$ to be tested by the future experimental data.

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arXiv2015

Hadronization effects on the baryon-strangeness correlation in quark combination models

The baryon-strangeness correlation in the hadronization of the quark matter is studied within the quark combination mechanism. We calculate the correlation coefficient $C_{BS} = -3\big(\langle B S \rangle -\langle B\rangle \langle S\rangle\big)/\big( \langle S^2 \rangle-\langle S \rangle^2 \big)$ of initial hadrons produced from the deconfined free quark system with $C^{(q)}_{BS}=1$. The competition of the production of baryons against that of mesons is the key dynamics that is most relevant to the change of baryon-strangeness correlation during system hadronization. Results of quark combination under the Poisson statistics agree with the statistical model predictions for a hadron resonance gas at vanishing chemical potential but differ from those at relatively large chemical potentials. Results beyond Poisson statistics are also obtained and are compared with calculations of Lattice QCD in the phase boundary, giving the best agreement at temperature $T =163$ MeV. We predict the dependence of the $C_{BS}$ of hadron system on the baryon chemical potential and strangeness. These predictions are expected to be tested by the future Lattice QCD calculations at non-zero chemical potentials and/or by the Beam Energy Scan experiment of STAR Collaboration at RHIC.

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arXiv2014

Probing charge correlations of quark gluon plasma by identified two-hadron rapidity correlations in ultra-relativistic AA collisions

We propose a new kind of two-particle correlation of identified hadrons in longitudinal rapidity space, called $G_{αβ}(y_α,y_β)$, which can reflect clearly the charge correlations of hot quark system produced in AA collisions at LHC energies. It is derived from the basic scenario of quark combination mechanism of hadron production. Like the elliptic flow of identified hadrons at intermediate transverse momentum, this correlation is independent of the absolute hadronic yields but dependent only on the flavor compositions of hadrons, and thus exhibits interesting properties for different kinds of hadron species. We suggest the measurement of this observable in AA collisions at LHC to gain more insights into the charge correlation properties of produced hot quark matter.

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arXiv2013

Baryon-anti-baryon Flavor Correlation in Quark Combination Models in Heavy Ion Collisions

We extend the study of hadron yield correlation in combination models in a recent publication to baryon-anti-baryon flavor correlations in heavy ion collisions. We show that the universal behaviors of the anti-baryon to baryon yield ratios as functions of that of $K^-$ to $K^+$ are naturally explained. We study also the "mixed ratios" and propose other measurements that might be sensitive to the hadronization mechanism.

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arXiv2013

Yield correlations and $p_T$ dependence of charm hadrons in Pb + Pb collisions at $\sqrt{s_{NN}}= 2.76$ TeV

Recently the ALICE Collaboration has published a few data of charm hadrons in Pb + Pb collisions at the CERN Large Hadron Collider (LHC). We extend the quark combination to the charm sector and point out that the measurement of charm hadron yields can provide important insights into charm quark hadronization mechanism and properties of the hot and dense matter produced in high energy reactions. We propose several types of yield ratios, e.g. $D^{*+}/D^0$, $D_s^+/D^+$ and $Λ_c^+/D_s^+$, to measure various properties of low $p_T$ charm quark hadronization. We argue that ratios $D_s^+/D^0$ and $2D_s^+/(D^0+D^+)$ as the function of transverse momentum can serve as good probes for the dynamics of charm quark hadronization. We further make predictions for the yields and $p_T$ spectra of identified charm hadrons in central Pb + Pb collisions at $\sqrt{s_{NN}}= 2.76$ TeV.

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arXiv2013

Baryon-antibaryon production asymmetry in relativistic heavy ion collisions

Experimental data at RHIC and SPS energies suggest a systematic correlation between yield ratio $\bar{p}/p$ and $K^{-}/K^{+}$, which reveal some universality of hadron production in relativistic heavy ion collisions. We propose an explanation based on the quark combination mechanism in which the production asymmetry between baryons and antibaryons is focused on especially. We start from the basic ideas of quark combination to carry out a general analysis of the properties of the global production of baryons and mesons and obtain the yields of baryons, antibaryons and mesons as functions of the number of constituent quarks and antiquarks just before hadronization. In particular, we study effects of quark-antiquark asymmetry on the ratio of (anti-)baryons to mesons and that of antibaryons to baryons. We use these formula to well explain the data of $\bar{p}/p$ and $K^{-}/K^{+}$ at different of collision energies and rapidities and suggest further measurements at moderate RHIC energies in the mid-forward rapidity regions to make the decisive test of this universality.

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arXiv2012

Hadron Yield Correlation in Combination Models in High Energy AA Collisions

We study the hadron yield correlation in the combination models in high energy heavy ion collisions. We derive the relationship between the average yields of different hadrons produced in the combination of a system consisting of equal number of quarks and antiquarks. We present the results for the directly produced hadrons as well as those for the final hadrons including the strong and electromagnetic decay contributions. We also study the net quark influence by considering the case when the number of quarks is larger than that of the antiquarks. We make comparison with the data wherever possible.

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arXiv2012

Quark charge balance function and hadronization effects in relativistic heavy ion collisions

We calculate the charge balance function of the bulk quark system before hadronization and those for the directly produced and the final hadron system in high energy heavy ion collisions. We use the covariance coefficient to describe the strength of the correlation between the momentum of the quark and that of the anti-quark if they are produced in a pair and fix the parameter by comparing the results for hadrons with the available data. We study the hadronization effects and decay contributions by comparing the results for hadrons with those for the bulk quark system. Our results show that while hadronization via quark combination mechanism slightly increases the width of the charge balance functions, it preserves the main features of these functions such as the longitudinal boost invariance and scaling properties in rapidity space. The influence from resonance decays on the width of the balance function is more significant but it does not destroy its boost invariance and scaling properties in rapidity space either. The balance functions in azimuthal direction are also presented.

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arXiv2012

$K^{0}$ and $Σ^$ production in Au+Au collisions at $\sqrt{s_{NN}}=$ 200 GeV 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 $Σ^*$ 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 $Σ^*$ 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 $Σ^*$ in minimum bias Au+Au collisions at 200 GeV and $p_T$ spectrum of $Σ^*$ at lower 62.4 GeV are predicted.

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arXiv2011

Hadronic Rapidity Spectra in Heavy Ion Collisions at SPS and AGS energies in a Quark Combination Model

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 $π^{-}$, $K^{\pm}$, $ϕ$, $Λ$, $\barΛ$, $Ξ^{-}$, and $\barΞ^{+}$ 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 $π^{\pm}$, $K^{\pm}$ and $Λ$ 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.

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arXiv2010

$B_s\to D_s(3040)$ form factors and $B_s$ decays into $D_s(3040)$

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 $B_s\to D_s(3040)\ell\barν(\ell=e,μ,τ)$. The BRs are found to have the order of $10^{-3}$ for $\ell=e,μ$ and $10^{-5}$ for $\ell=τ$. 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 $B_s\to D_s(3040)ρ$ 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.

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arXiv2010

The entropy puzzle and the quark combination model

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.

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arXiv2010

Hadron yield correlation and constituent quark degree of freedom in heavy ion collisions

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 $A=\frac{\barΛ k^{-} p}{Λk^{+} \bar{p}}$ and $B=\frac{Λk^{-}\barΞ^{+}}{\barΛ k^{+}Ξ^{-}}$, 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.

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arXiv2009

Hadron production by quark combination in central Pb+Pb collisions at $\sqrt{s_{NN}}= 17.3$ GeV

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.

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