arXiv subjects

C. B. Yang

Publications and source records attributed to C. B. Yang.

At least 73 records · Page 4Linked to original sources

arXiv2002

Strangeness Enhancement in the Parton Model

Strangeness enhancement in heavy-ion collisions is studied at the parton level by examining the partition of the new sea quarks generated by gluon conversion into the strange and non-strange sectors. The CTEQ parton distribution functions are used as a baseline for the quiescent sea before gluon conversion. By quark counting simple constraints are placed on the hadron yields in different channels. The experimental values of particle ratios are fitted to determine the strangeness enhancement factor. A quantitative measure of Pauli blocking is determined. Energy dependence between SPS and RHIC energies is well described. No thermal equilibrium or statistical model is assumed.

nucl-th↗

arXiv2002

Inclusive Distributions for Hadronic Collisions in the Valon-Recombination Model

Inclusive distributions of soft production of mesons in hadronic collisions are calculated in the valon-recombination model. The new determination of the valon distributions from hard scattering data makes possible a tightly interrelated treatment of pion and kaon production in the fragmentation regions of proton, pion and kaon. Only one free parameter is used in the determination of the valon distribution in the kaon. No other adjustable parameter is needed to fit the $x$-distributions of the data on inclusive cross sections, except for the normalizations since the data are at fixed $p_T$. The success of the model in reproducing seven inclusive distributions suggests that there are two important mechanisms at work in soft production. One is that the structure of the hadron that fragments is highly relevant. The other is that the produced particles are formed by the recombination of quarks and antiquarks. These two aspects about hadrons in soft processes can be well described in the framework of the valon-recombination model.

hep-ph↗

arXiv2002

Charge Fluctuations at Disoriented Chiral Transition

The signatures of the creation of a disoriented chiral condensate in heavy-ion collisions are studied in the Ginzburg-Landau description of chiral phase transition. Scaling properties are found that characterize the fluctuations of charged particles. There exists also an explicitly calculable measure that can directly be measured. Experimental procedures needed to find the signatures are discussed.

hep-ph↗

arXiv2002

Parton Distributions in the Valon Model

The parton distribution functions determined by CTEQ at low $Q^2$ are used as inputs to test the validity of the valon model. The valon distributions in a nucleon are first found to be nearly $Q$ independent. The parton distribution in a valon are shown to be consistent with being universal, independent of the valon type. The momentum fractions of the partons in the valon add up separately to one. These properties affirm the validity of the valon model. The various distributions are parameterized for convenient application of the model.

hep-ph↗

arXiv2001

Centrality Dependence of Baryon and Meson Momentum Distributions in $pA$ Collisions

The proton and neutron inclusive distributions in the projectile fragmentation region of $pA$ collisions are studied in the valon model. Momentum degradation and flavor changes due to the nuclear medium are described at the valon level using two parameters. Particle production is treated by means of the recombination subprocess. Pion inclusive distributions can be calculated without any adjustable parameters.

hep-ph↗

arXiv2001

Centrality Dependence of Baryon and Meson Momentum Distributions in Proton-Nucleus Collisions

The proton and neutron inclusive distributions in the projectile fragmentation region of $pA$ collisions are studied in the valon model. Momentum degradation and flavor changes due to the nuclear medium are described at the valon level using two parameters. Particle production is treated by means of the recombination subprocess. The centrality dependences of the net proton and neutron spectra of the NA49 data are satisfactorily reproduced. The effective degradation length is determined to be 17 fm. Pion inclusive distributions can be calculated without any adjustable parameters.

nucl-th↗

arXiv2001

Understanding $K/π$ ratio distribution in the mixed events

The event mixing method is analyzed for the study of the event-by-event $K/π$ ratio distribution. It is shown that there exists some correlation between the kaon and pion multiplicities in the mixed events. The $K/π$ ratio distributions in the mixed events for different sets of real events are shown. The dependence of the distributions on the mean $K/π$ ratio, mean and variance of multiplicity distribution in the real events is investigated systematically. The effect of imperfect particle identification on the $K/π$ ratio distribution in the mixed event is also considered.

hep-ph↗

arXiv2001

Influence of statistical fluctuations on $K/π$ ratios in relativistic heavy ion collisions

The influence of pure statistical fluctuations on $K/π$ ratio is investigated in an event-by-event way. Poisson and the modified negative binomial distributions are used as the multiplicity distributions since they both have statistical background. It is shown that the distributions of the ratio in these cases are Gaussian, and the mean and relative variance are given analytically.

hep-ph↗

arXiv2000

Spatial-temporal correlations in the process to self-organized criticality

A new type of spatial-temporal correlation in the process approaching to the self-organized criticality is investigated for the two simple models for biological evolution. The change behaviors of the position with minimum barrier are shown to be quantitatively different in the two models. Different results of the correlation are given for the two models. We argue that the correlation can be used, together with the power-law distributions, as criteria for self-organized criticality.

physics.bio-ph↗

arXiv2000

Perturbative calculation of the scaled factorial moments in second-order quark-hadron phase transition within the Ginzburg-Landau description

The scaled factorial moments $F_q$ are studied for a second-order quark-hadron phase transition within the Ginzburg-Landau description. The role played by the ground state of the system under low temperature is emphasized. After a local shift of the order parameter the fluctuations are around the ground state, and a perturbative calculation for $F_q$ can be carried out. Power scaling between $F_q$'s is shown, and a universal scaling exponent $ν\simeq 1.75$ is given for the case with weak correlations and weak self-interactions.

hep-ph↗

arXiv1998

Effect of spatial fluctuations on the scaled factorial moments in second-order quark-hadron phase transition within Ginzburg-Landau description

The scaled factorial moments in second-order quark-hadron phase transition are reexamined within the Ginzburg-Landau description, with the spatial fluctuations of phase angle of the complex field $ϕ$ taken into account rigorously. Scaling behaviors between $F_q$ and $F_2$ are shown, and the exponent $ν$ is found very close to the one without spatial fluctuations.

hep-ph↗

arXiv1998

Novel Scaling Behavior for the Multiplicity Distribution under Second-Order Quark-Hadron Phase Transition

Deviation of the multiplicity distribution $P_q$ in small bin from its Poisson counterpart $p_q$ is studied within the Ginzburg-Landau description for second-order quark-hadron phase transition. Dynamical factor $d_q\equiv P_q/p_q$ for the distribution and ratio $D_q\equiv d_q/d_1$ are defined, and novel scaling behaviors between $D_q$ are found which can be used to detect the formation of quark-gluon plasma. The study of $d_q$ and $D_q$ is also very interesting for other multiparticle production processes without phase transition.

hep-ph↗

arXiv1998

Scaling Behavior of Multiplicity Distribution under First-Order Quark-Hadron Phase Transition

Multiplicity distribution in small bins is studied within the Ginzburg-Landau description for first-order quark-hadron phase transition. Direct comparison of the distribution with a Poisson one (with the same average) is made. Dynamical factor $d_q$ for the distributionand ratio $D_q\equiv d_q/d_1$ are studied, and novel scaling behaviors between $D_q$ are found which can be used to detect the formation of quark-gluon plasma.

hep-ph↗

arXiv1998

Local Spontaneous Symmetry Breaking for Film System Within Scalar $ϕ^4$ Model for Phase Transition

The difficulty is analysed in evaluating fluctuations in phase transition of finite-size system at temperature far below the critical point. Film system is discussed with one-component order parameter $ϕ^4$ model for phase transition. Non-trivial vacuum state corresponding to minimum Hamiltonian is given approximately for various boundary conditions. It is shown that the spontaneous symmetry breaking plays an important role for such systems, and that perturbative calculations can be done safely when the effect of the vacuum state or the local spontaneous symmetry breaking is taken into consideration.

cond-mat↗

arXiv1997

Multiplicity difference correlators under first-order QGP phase transition

The multiplicity difference correlators between two well-separated bins in high-energy heavy-ion collisions are studied as a means to detect evidence of a first-order quark-hadron phase transition. Analytical expressions for the scaled factorial moments of multiplicity difference distribution are obtained for small bin size $δ$ with mean multiplicity in the bin ${\bar s}\le 1.0$ within Ginzburg-Landau description. The scaling behaviors between the moments are still valid, though they behave completely different from the so-called intermittency patterns. A universal exponent $γ=1.4066$ is given to describe the dynamical fluctuations in the phase transition in small $δ$ limit.

hep-ph↗

arXiv1997

Analytical investigation for multiplicity difference correlators under QGP phase transition

It is suggested that the study of multiplicity difference correlators between two well-separated bins in high-energy heavy-ion collisions can be used as a means to detect evidence of a quark-hadron phase transition. Analytical expressions for the scaled factorial moments of multiplicity difference distribution are obtained in a kinetical region ${\bar s}\le 0.3$ within Ginzburg-Landau description. It is shown that the scaling behaviors between the moments are still valid, though the behaviors of the moments with respect to the bin size are completely different from the so-called intermittency patterns. A universal exponent $γ$ is given to describe the dynamical fluctuations in the phase transition.

hep-ph↗

arXiv1997

Finite-Size Effects in Critical Phenomena from Mean Field Approach with $ϕ^4$ Model

The finite-size effects in critical phenomena of a thin film system are studied from a mean field (MF) approach with $ϕ^4$ model for second-order phase transition. The influence of boundary condition on the critical properties are emphasized. Scaling functions for relative free-energy and relative specific heat capacity are given.

cond-mat↗

arXiv1996

On the Polarization Dependence of Electromagnetic Vertex for Proton

The polarization dependence of the electromagnetic vertex for polarized proton is discussed. Such a dependence is shown to be a result of gluon polarization and gluon interactions with the constituents within proton. One more form factor is introduced to give such a dependence in the electromagnetic vertex for proton. Due the polarization dependence of the vertex, a nonzero single-spin asymmetry for unpolarized lepton scattering off transversely polarized proton is predicted.

hep-ph↗