118652542
Study of triangular flow v3 in Au+Au and Cu+Cu collisions with a multiphase transport model
We studied the relation between the initial geometry anisotropy and the anisotropic flow in a multiphase transport model for both Au+Au and Cu+Cu collisions at = 200 GeV. It is found that unlike the elliptic flow v2, little centrality dependence of the triangular flow v3 is observed. After removing the initial geometry effect, v3/e3 increases with the transverse particle density, which is similar to v2/e2. The transverse momentum (pT) dependence of v3 from identified particles is qualitatively similar to the pT dependence of v2.
122409394
Energy dependence of the v2-scaling and the QCD phase boundary
In high-energy nuclear collisions at RHIC ( = 60–200 GeV), quark coalescence has been suggested as one of the processes for hadronization. As a result, one observes a scaling in the elliptic flow parameter v2 and hadron-type dependence (within the 2 < pT < 5 GeV/c region) in the nuclear modification parameter RAA. On the other hand, in a given collision when the center of mass energy is not sufficiently high to create partonic matter, one would not expect the scaling in the final observed v2. Hence, the scaling provides us a sensitive tool for the search for the possible phase boundary in the hot/dense matter dominated by either partonic or hadronic degrees of freedom. In this paper, we will report the results from analyzing the energy dependence of v2 for identified hadrons from Au+Au collisions. Data from transport models are used in our analysis. In this model calculation, without the partonic coalescence the scaling in v2 is absent.
119211238
Directed flow of transported and non-transported protons in Au+Au collisions from UrQMD model
The directed flow of inclusive, transported and non-transported (including produced) protons, as well as antiprotons, has been studied in the framework of Ultra-Relativistic Quantum Molecular Dynamics approach (UrQMD model) for Au+Au collisions at √ sNN =7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV. The rapidity, centrality and energy dependence of directed flow for various proton groups are presented. It is found that the integrated directed flow decreases monotonically as a function of collision energy for √ sNN =11.5 GeV and beyond. However, the sign-change of directed flow of inclusive protons, seen in experimental data as a function of centrality and collision energy, can be explained by the competing effect of directed flow between transported and non-transported protons. Similarly the difference in directed flow between protons and antiprotons can be explained. Our study offers a conventional explanation on the cause of the v1 sign-change other than the antiflow component of protons alone which is argued to be linked to a phase transition.
118540594
Energy and Centrality Dependence of Chemical Freeze-out Thermodynamics parameters
energy and somehow saturates at certain values of Tch in collisions near √ sNN=10 GeV, indicating the limiting temperature in hadronic interactions; meanwhile the baryon chemical potential µB decrease with the collision energy. The saturation temperature is also found to be dependent on partonic interaction. At a given collision energy, it is found that both Tch and µB decrease towards more peripheral collisions in the grand canonical approach. The energy and centrality dependence of other chemical freeze-out parameters, strangeness chemical potential µS , strangeness undersaturation factor S , and the volume of the fireball V are also presented in this paper. The chemical potential ratio µs/µB is also compared with lattice QCD calculation. The AMPT default model gives better descriptions on both the particle yields and the chemical freeze-out parameters than those from the AMPT string-melting model.
120498489
Elliptic flow in a hadron transport model
We present elliptic flow v2 as a function of freeze-out time, transverse momentum for π, K, nucleon, Λ, Ξ and Ω in Au+Au collisions at within two transport approaches (RQMD and UrQMD). The presence of mass ordering and NCQ scaling in the string-hadron model suggests that hadronic interactions do contribute to the observed particle-type dependence of v2 as well.
120089995
The large-scale organization of the hadron decay network
The standard model of particle physics predicts a complex structure of decay modes for hadrons, which opens up an avenue for observing the internal forces governing the decay dynamics. In this paper, we present the decay modes of hadrons as a network in which the nodes are particles and directed links are pointing from the mother particles to daughter particles. Using the database of decay modes collected from the Particle Data Group, we try to unveil the topological structure and possible intrinsic nature of hadron decays in the light of recent investigations of complex networks. We study distributions of the numbers of daughter and mother particles, and explore scaling laws that may govern the underlying decay structure of the system. We find that it is a small-world network with symmetrical structure. We also study the influence of constraints arising from conservation laws on the network structure, and our analysis suggests that the constraints of conservations of momentum-energy, charge, lepton number and baryon number play important roles in the topology of the decay network. Finally, we classify the hadrons into communities according to their quark component, and uncover the relationship between the particle roles and connection patterns in the communities.
122359446
Dependence of elliptic flow on participant nucleon number in Au + Au collisions at sNN=200 GeV
Elliptic flows of charged particles produced in nucleus-nucleus collisions at high energy are studied in the framework of a multisource ideal-gas model. The participant nucleon number at a fixed impact parameter is calculated by a geometrical picture of the participant-spectator model. Then, the dependence of elliptic flow on participant nucleon number is obtained in the combined framework of the two models. Our calculated results are approximately in agreement with the experimental data of the PHENIX Collaboration.
118718956
Dependence of elliptic flow on transverse momentum in $\sqrt{\mathrm{\it s_{NN}}}=200$ GeV Au-Au and $\sqrt{\mathrm{\it s_{NN}=2.76$ TeV Pb-Pb collisions
We investigate the dependence of elliptic flows $v_2$ on transverse momentum $P_T$ for charged hadrons produced in nucleus-nucleus collisions at high energy by using a multi-source ideal gas model which includes the interaction contribution of the emission sources. Our calculated results are approximately in agreement with the experimental data over a wider $P_T$ range from the STAR and ALICE Collaborations. It is found that the expansion factor increases linearly with the impact parameter from most central (0-5%) to mid-peripheral (35-40%) collisions.
124273608
Strange Quark Matter and Strangelets in a Strong Magnetic Field
We study the stability properties of magnetized strange quark matter and strangelets under a strong magnetic field in the MIT bag model. The free energy per baryon of strange quark matter feels a great influence from the magnetic held. At the held strength about 1017 G, the magnetized strange quark matter becomes more stable. Considering the finite size effect, the magnetic influence on strangelets becomes complicated. For a given magnetic held, there exists a critical baryon number, below which the magnetized strangelets have lower energy than the non-magnetized strangelets. For the held strength of 5 × 1017 G, the critical baryon number is Ac ~ 100. Generally, the critical baryon number increases with the decreasing external magnetic held. When the held strength is smaller than 1017 G, the critical baryon number goes up to Ac ~ 105. The stable radius, electric charge, and quark flavor fractions of magnetized strangelets are shown.
121855629
Charged-particle pseudorapidity (rapidity) distribution in nucleus- nucleus collisions at alternating- gradient synchrotron energy
The charged-particle pseudorapidity (rapidity) distributions in nucleus-nucleus collisions at the alternating-gradient synchrotron energy (11-15A GeV) have been described by the thermalized cylinder picture. The calculated results are in agreement with the experimental data of the reactions 28 Si + Au, Ag, Cu, and Al at 14.6A GeV/c bombarding energy. It is shown that the target stopping power (the leading participant target nucleon rapidity shift with respect to the projectile) increases with the target size, and the projectile penetrating power (the leading participant projectile nucleon rapidity shift with respect to the target) decreases with the increasing of target size.
117946057
Final-state energy spectrum in relativistic nuclear electromagnetic dissociation
The final-state energy spectrum in the electromagnetic dissociation is calculated by a simple method. The final-state energy curves obtained from the calculation are in agreement with the experimental data of Si-28 into p + Al-27 at an energy of 14.6 GeV/N.