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C. B. Yang

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

At least 55 records · Page 3Linked to original sources
arXiv2005

Stability of complex networks under the evolution of attack and repair

With a simple attack and repair evolution model, we investigate and compare the stability of the Erdos-Renyi random graphs (RG) and Barabasi-Albert scale-free (SF) networks. We introduce a new quantity, invulnerability I(s), to describe the stability of the system. We find that both RG and SF networks can evolve to a stationary state. The stationary value Ic has a power-law dependence on the average degree _rg for RG networks; and an exponential relationship with the repair probability p_sf for SF networks. We also discuss the topological changes of RG and SF networks between the initial and stationary states. We observe that the networks in the stationary state have smaller average degree but larger clustering coefficient C and stronger assortativity r.

cond-mat.stat-mech↗
arXiv2005

Stability in the evolution of random networks

With a simple model, we study the evolution of random networks under attack and reconstruction. We introduce a new quality, invulnerability I(s), to describe the stability of the system. We find that the network can evolve to a stationary state. The stationary value I_c has a power-law dependence on the initial average degree , with the slope is about -1.485. In the stationary state, the degree distribution is a normal distribution, rather than a typical Poisson distribution for general random graphs. The clustering coefficient in the stationary state is much larger than that in the initial state. The stability of the network depends only on the initial average degree , which increases rapidly with the decrease of .

cond-mat.dis-nn↗
arXiv2004

Forward Production in d+Au Collisions by Parton Recombination

Hadron production at forward rapidities in d+Au collisions is studied in the framework of parton recombination in the final state. Multiple scattering and gluon saturation in the initial state are not explicitly considered. The recombination of soft and shower partons is found to be important. The soft parton densities are determined by extrapolation from the parametrization fixed at η=0 with no unconstrained adjustments. The suppression of R_{CP} observed at high ηis understood as the simple consequence of the reduction of the soft parton density on the deuteron side compared to that on the gold side. The effect of momentum degradation responsible for baryon stopping is also considered. The asymmetry of backward-to-forward spectra can be reproduced within the same framework without any change in the basic physics.

nucl-th↗
arXiv2004

The origin of power-law distributions in self-organized criticality

The origin of power-law distributions in self-organized criticality is investigated by treating the variation of the number of active sites in the system as a stochastic process. An avalanche is then regarded as a first-return random walk process in a one-dimensional lattice. Power law distributions of the lifetime and spatial size are found when the random walk is unbiased with equal probability to move in opposite directions. This shows that power-law distributions in self-organized criticality may be caused by the balance of competitive interactions. At the mean time, the mean spatial size for avalanches with the same lifetime is found to increase in a power law with the lifetime.

cond-mat.stat-mech↗
arXiv2004

Dihadron Correlation in Jets Produced in Heavy-Ion Collisions

The difference between the structures of jets produced in heavy-ion and hadronic collisions can best be exhibited in the correlations between particles within those jets. We study the dihadron correlations in jets in the framework of parton recombination. Two types of triggers, $π^+$ and proton, are considered. It is shown that the recombination of thermal and shower partons makes the most important contribution to the spectra of the associated particles at intermediate $p_T$. In $pp$ collisions the only significant contribution arises from shower-shower recombination, which is negligible in heavy-ion collisions. Moments of the associated-particle distributions are calculated to provide simple summary of the jet structures for easy comparison with experiments.

nucl-th↗
arXiv2004

Recombination of shower partons in fragmentation processes

We develop the notion of shower partons and determine their distributions in jets in the framework of the recombination model. The shower parton distributions obtained render a good fit of the fragmentation functions. We then illustrate the usefulness of the distributions in a problem where a jet is produced in the environment of thermal partons as in heavy-ion collisions. The recombination of shower and thermal partons is shown to be more important than fragmentation. Application to the study of two-particle correlation in a jet is also carried out.

hep-ph↗
arXiv2004

Production of phi and Omega at RHIC in the Recombination Model

The recombination model is applied to the production of phi and Omega at all pt in central Au+Au collisions. Since no light quarks are involved in the hadronization, those hidden-strange particles present a clean slate for the study of the role of strange quarks in large-pt physics. We find that shower s quarks have negligible effect for pt<6 GeV/c, in which range the thermal s quarks make the dominant contributions to the formation of phi and Omega. We show that the same effective temperature of the s quarks is responsible for the shape of the spectra of both phi and Omega. We predict that the ratio of Omega to phi will show a peak at pt \approx 6 GeV/c due to the effect of the hard partons. We also give reasons on the basis of the pt dependence that phi cannot be formed by means of K+K- coalescence.

nucl-th↗
arXiv2004

Recombination of Shower Partons at High $p_T$ in Heavy-Ion Collisions

A formalism for hadron production at high \pt in heavy-ion collisions has been developed such that all partons hadronize by recombination. The fragmentation of a hard parton is accounted for by the recombination of shower partons that it creates. Such shower partons can also recombine with the thermal partons to form particles that dominate over all other possible modes of hadronization in the $3<p_T<8$ GeV range. The results for the high \pt spectra of pion, kaon, and proton agree well with experiments. Energy loss of partons in the dense medium is taken into account on the average by an effective parameter by fitting data, and is found to be universal independent of the type of particles produced, as it should. Due to the recombination of thermal and shower partons, the structure of jets produced in nuclear collisions is different from that in $pp$ collisions. The consequence on same-side correlations is discussed.

nucl-th↗
arXiv2004

Proton Production in d+Au Collisions and the Cronin Effect

Proton production in the intermediate p_T region in d+Au collisions is studied in the parton recombination model. The recombination of soft and shower partons is shown to be important in central collisions, but negligible in peripheral collisions. It is found that the large nuclear modification factor for proton production can be well reproduced by a calculation of the 3-quark recombination process.

nucl-th↗
arXiv2004

Critical Fluctuation of Wind Reversals in Convective Turbulence

The irregular reversals of wind direction in convective turbulence are found to have fluctuating intervals that can be related to critical behavior. It is shown that the net magnetization of a 2D Ising lattice of finite size fluctuates in the same way. Detrended fluctuation analysis of the wind reversal time series results in a scaling behavior that agrees with that of the Ising problem. The properties found suggest that the wind reversal phenomenon exhibits signs of self-organized criticality.

physics.flu-dyn↗
arXiv2004

Fragmentation or Recombination at High p_T?

All hadronization processes, including fragmentation, are shown to proceed through recombination. The shower partons in a jet turn out to play an important role in describing the p_T spectra of hadrons produced in heavy-ion collisions. Due to the recombination of the shower partons with the soft thermal partons, the structure of jets produced in AA collisions is not the same as that of jets produced in pp collisions.

nucl-th↗
arXiv2004

Final-State Interaction as the Origin of the Cronin Effect

Instead of adhering to the usual explanation of the Cronin effect in terms of the broadening of the parton transverse momentum in the initial state, we show that the enhancement of hadron production at moderate $p_T$ in d+Au collisions is due to the recombination of soft and shower partons in the final state. Such a mechanism can readily explain the decrease of the Cronin effect with increasing rapidity. Furthermore, the effect should be larger for protons than for pions.

nucl-th↗
arXiv2003

Fractional Energy Loss and Centrality Scaling

The phenomenon of centrality scaling in the high-\pt spectra of $π^0$ produced in Au-Au collisions at $\sqrt s=200$ GeV is examined in the framework of relating fractional energy loss to fractional centrality increase. A new scaling behavior is found where the scaling variable is given a power-law dependence on $N_{\rm part}$. The exponent $γ$ specifies the fractional proportionality relationship between energy loss and centrality, and is a phenomenologically determined number that characterizes the nuclear suppression effect. The implication on the parton energy loss in the context of recombination is discussed.

nucl-th↗
arXiv2003

Comparison of Nuclear Suppression Effects on Meson Production at High p_T and p_L

The medium effect on the pion distribution at high $p_T$ in $AA$ collisions is compared to that of the pion distribution at high $p_L$ in $pA$ collisions. Both the suppression of the spectra and the energy losses of the measured pions are studied. Although the medium effect on $p_T$ is larger than on $p_L$, the difference is found surprisingly to be not as big as one would naively expect.

nucl-th↗
arXiv2003

Scaling Distributions of Quarks, Mesons and Proton for all $p_T$, Energy and Centrality

We present the evidences for the existence of a universal scaling behavior of the production of $π^0$ at all transverse momenta in heavy-ion collisions at all centralities and all collision energies. The corresponding scaling behavior of the quarks is then derived just before the quarks recombine with antiquarks to form the pions. The degradation effect of the dense medium on the quark $p_T$ is derived from the scaling distribution. In the recombination model it is then possible to calculate the $p_T$ distributions of the produced proton and kaon, which are scaling also. Experimentally verifiable predictions are made. Implications of the existence of the scaling behavior are discussed.

nucl-th↗
arXiv2003

Scaling behavior at high p_T and the p/pi ratio

We first show that the pions produced at high $p_T$ in heavy-ion collisions over a wide range of high energies exhibit a scaling behavior when the distributions are plotted in terms of a scaling variable. We then use the recombination model to calculate the scaling quark distribution just before hadronization. From the quark distribution it is then possible to calculate the proton distribution at high $p_T$, also in the framework of the recombination model. The resultant $p/π$ ratio exceeds one in the intermediate $p_T$ region where data exist, but the scaling result for the proton distribution is not reliable unless $p_T$ is high enough to be insensitive to the scale-breaking mass effects.

nucl-th↗
arXiv2003

Centrality Scaling of the $p_T$ Distribution of Pions

From the preliminary data of PHENIX on the centrality dependence of the $π^0$ spectrum in $p_T$ at midrapidity in heavy-ion collisions, we show that a scaling behavior exists that is independent of the centrality. It is then shown that $ $ degrades with increasing $N_{\rm part}$ exponentially with a decay constant that can be quantified. A scaling distribution in terms of an intuitive scaling variable is derived that is analogous to the KNO scaling. No theoretical models are used in any part of this phenomenological analysis.

nucl-th↗