Centrality dependences of the pseudorapidity distributions of charged particles in Au+Au collisions at RHIC energies

By employing the Glauber model, we give the centrality dependences of the numbers of participants and binary nucleon-nucleon collisions in nucleus-nucleus collisions. By taking into account the energy loss of the participants in their multiple collisions, we then present the pseudorapidity distributions of charged particles in nucleus-nucleus collisions as a function of beam energy and impact parameter. Finally, we analyze the centrality dependence of the pseudorapidity of the charged particles in Au＋Au collisions at energies from √SNN=19.6 to 200 GeV. The theoretical results are in good agreement with the experimental observations of the RHIC-PHOBOS collaboration.     

Charged-particle pseudorapidity distributions in Au+Au collisions at RHIC

Using the Glauber model, we present the formulas for calculating the numbers of participants,spectators and binary nucleon-nucleon collisions. Based on this work, we get the pseudorapidity distributions of charged particles as the function of the impact parameter in nucleus-nucleus collisions. The theoretical results agree well with the experimental observations made by the BRAHMS Collaboration in Au+Au collisions at √SNN=200 GeV in different centrality bins over the whole pseudorapidity range.     

Pseudorapidity distribution of multiplicity in Au+Au collisions at √SNN=200 GeV

Using the Glauber model,we discuss the number of binary nucleon-nucleon collisions in heavy-ion collisions.Based on the latter,after considering the effect of energy loss of the nucleons in multiple collisions,we derive the pseudorapidity distribution of the multiplicity as a function of the impact parameter in nucleus-nucleus collisions.Using this,we analyze the experimental measurements carried out by the BRAHMS Collaboration in Au+Au collisions at √SNN=200 GeV.The results are in good agreement with the experimental observations.     

Centrality dependences of the pseudorapidity distributions of charged particles in Au+Au collisions at RHIC energies

By employing the Glauber model, we give the centrality dependences of the numbers of participants and binary nucleon-nucleon collisions in nucleus-nucleus collisions. By taking into account the energy loss of the participants in their multiple collisions, we then present the pseudorapidity distributions of charged particles in nucleus-nucleus collisions as a function of beam energy and impact parameter. Finally, we analyze the centrality dependence of the pseudorapidity of the charged particles in Au+Au collisions at energies from √sNN=19.6 to 200 GeV.The theoretical results are in good agreement with the experimental observations of the RHIC-PHOBOS collaboration.     

Pseudorapidity distribution of multiplicity in Au Au collisions at (S_(NN))~(1/2)=200 GeV

Using the Glauber model,we discuss the number of binary nucleon-nucleon collisions in heavy-ion collisions.Based on the latter,after considering the effect of energy loss of the nucleons in multiple colli- sions,we derive the pseudorapidity distribution of the multiplicity as a function of the impact parameter in nucleus-nucleus collisions.Using this,we analyze the experimental measurements carried out by the BRAHMS Collaboration in Au Au collisions at Pseudorapidity distribution of multiplicity in Au Au collisions at (S_(NN))~(1/2)=200 GeV)=200 GeV.The results are in good agreement with the experi- mental observations.     

高能Cu+Cu碰撞中末态带电粒子赝快度分布的能量与对心度依赖性

利用Glauber模型,给出了核-核碰撞中的参与者数及二元核子-核子碰撞数与碰撞参数的解析关系,并以此为基础,在考虑到参与者由于多重碰撞而引起的能量损失效应后,通过有效二元核子-核子碰撞末态带电粒子赝快度分布的加权叠加,建立起了以碰撞参数为自变量的核-核碰撞末态带电粒子的赝快度分布函数,并用其分析了RHIC-PHOBOS合作组在不同能量与不同对心度的Cu+Cu碰撞中所做的实验测量。所得结果与实验符合得较好。     

Open charm yields in d+Au collisions at squareroot[sNN]=200 GeV

Midrapidity open charm spectra from direct reconstruction of D0(D0)-->K-/+pi+/- in d+Au collisions and indirect electron-positron measurements via charm semileptonic decays in p+p and d+Au collisions at squareroot[sNN]=200 GeV are reported. The D0(D0) spectrum covers a transverse momentum (pT) range of 0.1相似文献   

N＊（1535） contribution in pp →ppη＇ and pn →dφ

In an effective Lagrangian model we find that the N＊（1535） resonance contribution might be important to the interpretation of the present data of the pp →ppη＇ and pn →dφ reactions. The strong coupling strength of N＊ （1535） to η＇ and φ are indicated, and the possible implication to the intrinsic component of N＊（1535） is explored. These results may provide hints to the real origin of the OZI rule violation. It is stressed that further measurements could be performed at China. the Cooling Storage Ring （CSR） at Lanzhou of     

xF （or y）-Dependence of Nuclear Absorption and Energy Loss Effects on J/ψ Production

By means of the nuclear parton distribution studied only with lepton deep-inelastic scattering experimental data, the J/ψ ＂normal nuclear absorption＂ and energy loss effects are studied in a GIauber formalism at HERA and RHIC energies. Assuming that the absorption cross section σabs increases with the charmonium-nucleon center of mass energy, the results reveal a significant dependence of the aabs on rapidity g at RHIC energies. The initial-state energy loss effect, which is found important only at HERA energies, is also considered, and its influence should be eliminated when we studied the absorption effect at low collision energies. Finally, we also present the theoretical prediction for LHC.     

Scaling property in one-nucleon removal reactions induced by exotic nuclei

Assuming a core plus valence nucleon structure, one-nucleon removal reaction is investigated within the framework of few-body Glauber theory. Fermi-type distribution is used for the core density, while the wavefunction of the valence nucleon is calculated by solving the single particle eigenvalue problem of the SchrSdinger equation with the Woods-Saxon potential. The parallel momentum distribution （P//） of the fragments is calculated for isotopes with 3 〈 Z 〈 18. A remarkable scaling property is observed from the dependence of the dimensionless quantity P^2 v/R^2 e on the full width at half maximum of the parallel momentum distribution （FWHMp//）. R^2 v/R^2 c is a measure of the exotic extent of the nuclear halo. Based on the obtained 2 2 scaling law, FWHMp// can be used as an experimental observable to extract R^2 v/R^2 c and measure the exotic extent for the nuclear halo.     

Measurement of single electrons and implications for charm production in Au+Au collisions at square root[s(NN)] = 130 GeV

Transverse momentum spectra of electrons from Au+Au collisions at square root[s(NN)] = 130 GeV have been measured at midrapidity by the PHENIX experiment at the Relativistic Heavy Ion Collider. The spectra show an excess above the background from photon conversions and light hadron decays. The electron signal is consistent with that expected from semileptonic decays of charm. The yield of the electron signal dN(e)/dy for p(T) > 0.8 GeV/c is 0.025+/-0.004(stat)+/-0.010(syst) in central collisions, and the corresponding charm cross section is 380+/-60(stat)+/-200(syst) microb per binary nucleon-nucleon collision.     

Measurement of the total reaction cross section for the mirror nuclei ^12N and ^12B

The mirror nuclei ^12N and ^12B are separated by the Radioactive Ion Beam Line in Lanzhou （RIBLL） at HIRFL from the breakup of 78.6 MeV/u 14N on a Be target. The total reaction cross-sections of ^12N at 34.9 MeV/u and ^12B at 54.4 MeV/u on a Si target have been measured by using the transmission method. Assuming ^12N consists of a ^11C core plus one halo proton, the excitation function of ^12N and ^12B on a Si target and a C target were calculated with the Glanber model. It can fit the experimental data very well. The characteristic halo structure for ^12N was found with a large diffusion of the protons density distribution.     

高能重离子碰撞中的参与者数和核子-核子碰撞数

采用核-核碰撞的Glauber模型, 给出了高能重离子碰撞中的参与者数和核子-核子碰撞数随碰撞参数的分布方程, 并用其讨论了\{s_NN\}^1/2=200GeV的Au+Au碰撞中的参与者数与核子-核子碰撞数随对心度的变化关系, 所得结果与PHENIX合作组所给出的实验结果符合得很好. 关键词： Glauber 模型 参与者数 核子-核子碰撞数     

用光学极限的Glauber模型结合相对论平均场对8Li和8B的半径的研究

We study the reaction cross sections （σR） and root-mean-square （RMS） radii of ^8Li and ^8B, the halo-like nuclei, with stable target ^12C, ^27Al and ^9Be within the standard optical-limit Glauber model, using densities obtained from relativistic mean-field （RMF） formalisms and other types of distributions. It is found that the experimental σR can be reproduced well at high energy. The RMS radius and Ar extracted by RMF- theory and harmonic oscillator distribution are compared. larger than those of SLi. In addition, we analyze in detail the We find that the RMS radius and Ar of SB are relationship between σR and density distribution.     

Microscopic Three-Body Force Effect on Nucleon-Nucleon Cross Sections in Symmetric Nuclear Matter

We provide a microscopic calculation of neutron-proton and proton-proton cross sections in symmetric nuclear matter at various densities, using the Brueckner Hartree-Fock approximation scheme with the Argonne Va4 potential including the contribution of microscopic three-body force. We investigate separately the effects of three-body force on the effective mass and on the scattering amplitude. In the present calculation, the rearrangement contribution of three-body force is considered, which will reduce the neutron and proton effective mass, and depress the amplitude of cross section. The effect of three body force is shown to be repulsive, especially in high densities and large momenta, which will suppress the cross section markedly.     

Common suppression pattern of eta and pi0 mesons at high transverse momentum in Au + Au collisions at square root S(NN) = 200 GeV

Inclusive transverse momentum spectra of eta mesons have been measured within p(T) = 2-10 GeV/c at midrapidity by the PHENIX experiment in Au + Au collisions at square root S(NN) = 200 GeV. In central Au+Au the eta yields are significantly suppressed compared to peripheral Au + Au, d + Au, and p + p yields scaled by the corresponding number of nucleon-nucleon collisions. The magnitude, centrality, and p(T) dependence of the suppression is common, within errors, for eta and pi0. The ratio of eta to pi0 spectra at high p(T) amounts to 0.40 < R(eta/pi)0 < 0.48 for the three systems, in agreement with the world average measured in hadronic and nuclear reactions and, at large scaled momentum, in e+e- collisions.     

Determination of the nucleon-nucleon interaction in the ImQMD model by nuclear reactions at the Fermi energy region

The nucleon-nucleon interaction is investigated by using the improved quantum molecular dynamic （ImQMD） model with three sets of parameters IQ1, IQ2 and IQ3, in which the corresponding incompressibility coefficients of nuclear matter are different. The charge distributions of fragments are calculated for various reaction systems at different incident energies. The parameters strongly affect the charge distributions and the fragment multiplicity spectrum below the threshold energy of nuclear multifragmentation. The fragment multiplicity spectrum for 238U＋197Au at 15 A MeV and the charge distributions for 129Xe＋12~Sn at 32 and 45 A MeV, and 197Au＋197Au at 35 A MeV are reproduced by the ImQMD model with the set of parameter IQ3. It is found that： 1） The charge distribution of the fragments and the fragment multiplicity spectrum are good observables for testing the model and the parameters. 2） The Fermi energy region is a sensitive energy region for studying nucleon-nucleon interaction.     

Pade Expansion and Nucleon-Nucleon Scattering in Coupled Channels

We extend our Pade-aided analysis of the nonperturbative renormalization of nucleon-nucleon scattering to the case of coupled channels.     

A higher-dimensional model of the nucleon-nucleon central potential

Based on a theory of extra dimensional confinement of quantum particles [E. R. Hedin, Physics Essays, 2012, 25（2）： 177], a simple model of a nucleon nucleon （NN） central potential is derived which quantitatively reproduces tile radial profile of other models, without adjusting any free pa- rameters. It is postulated that a higher-dimensional simple harmonic oscillator confining potential localizes particles into three-dimensional （3D） space, but allows for an ewmescent penetration of the particles into two higtmr spatial dimensions. Producing an effect identical with the relativistic quan- tum phenolnenon of zitterbewegung, the higher-dimensional oscillations of amplitude h（mc） call be alternatively viewed as a localized curvature of 3D space back and forth into the higher dimensions. The overall spatial curvature is proportional to the particle＇s extra-dimensional ground state wave function in tile higher-dimensional harmonic confining potential well. Minimizing the overlapping curvature （proportional to the energy） of two particles in proximity to each other, subject to the constraint that for the two particles to occupy the same spatial location one of them must be excited into the 1st excited state of the harmonic potential well, gives the desired NN potential. Specifying only the imcleon masses, the resulting potential well and repulsive core reproduces the radial profile of several published NN central potential models. In addition, the predicted height of the repulsive core, when used to estimate the maximum neutron star mass, matches well with the best estimates from relativistic theory incorporating standard nuclear matter equations of state. Nucleon spin, Coulomb interactions, and internal nucleon structure are not considered in the theory as presented in this article.     

Suppressed pi(0) production at large transverse momentum in central Au+Au collisions at sqrt[s(NN)]=200 GeV

Transverse momentum spectra of neutral pions in the range 1相似文献