| Theoretically,the positive matter should have been the same with the antimatter when the universe began,but antimatter has been hard to find in the real world.The asymmetry between antimatter and ordinary matter is a fundamental problem in modern physics.The deep physics of this asymmetry has been a hot topic in the past few decades.In high-energy heavy-ion collision experiments,the environment in which hot and dense nuclear matter was initially produced is similar to the "fireball"environment in the initial stage of the big bang,which provides a possible way to study antimatter in experiments.It also provides an ideal place for scientists to study the early forms of matter in the evolution of the universe,looking for exotic matter and antimatter.With the help of modern accelerator technology,scientists have successfully produced and captured antihydrogen atoms in high-energy collision experiments,and conducted extensive studies on light(anti)nuclear and(anti)hypernuclear matter.In particular,the discovery of(anti)hypernuclear matter has greatly facilitated the work of nuclear physicists in the exploration of exotic matters(such as hypernuclei,antihypernuclei,and bound states containing exotic quarks)and hyperon-nucleon interactions.This thesis uses parton and hadron cascade model(PACIAE)to simulate the production of final-state multiparticles in Cu+Cu collisions at(?)=200 GeV with pseudo-rapidity |?|<0.5 and transverse momentum 0<PT<8 GeV/c,then produce the light(anti)nuclei(d,(?),3He,(?),4He,(?))and(anti)hypernuclei(?3H,(?))using the dynamically constrained phase-space coalescence model(DCPC).In this way,the production and properties of light(anti)nuclei and(anti)hypernuclei in relativistic heavy-ion collisions are studied.The model parameters were determined by fitting the existing experimental data under the same conditions in the STAR experiments.Firstly,the produce of light(anti)nuclei(d,(?),3He,(?),4He,(?))in different centrality bins is discussed.Calculating their yields and yield ratios and studying their centrality dependence and mass scale characteristics.The results show that there is a strong centrality dependence of yields,i.e.,their yields decrease rapidly with the increase of centrality;whereas their ratios of antinuclei to nuclei remain constant as the centrality increases.Moreover,the greater the mass of the(anti)nuclei is,the greater the yields decrease,indicating that the(anti)nuclei have an exponential scale behavior of the mass,that is,the yields of the(anti)nuclei decrease by about three orders of magnitude for each reduction in the number of the nucleon per unit.At the same time,with the increases of the number of nucleons involved in the collisions(Npart),the relative yields of light(anti)nuclei generated per nucleon involved in the collision increase rapidly;and the heavier(anti)nuclei increase faster than the lighter ones,suggesting that the more nucleon involved in the collision,the easier it is to produce the lighter(anti)nuclei.In addition,this thesis also discusses the difficulty of synthesizing nuclei with coalescence parameter BA.It turns out that producing heavier(anti)nuclei is harder than producing lighter ones.Our results are consistent with the STAR experimental data.Thus,this thesis predicts the yields and yield ratios of light(anti)nuclei in different centrality bins in high-energy Cu+Cu collisions,and verifies the mass scale characteristics of light(anti)nuclei in relativistic heavy-ion collisions.Secondly,the production of(anti)hypertriton(?3H,(?))in Cu+Cu collisions is studied in three different centrality bins of 0-10%,10-30%,and 30-60%.They are compared with 3He,(?),3H,and (?).The results show that the yields of ?3H,(?) are similar to the 3He,(?),3H,and (?),they all increase rapidly from peripheral to central collisions;while the ratio of antihypertriton to hypertriton remains unchanged and has nothing to do with the centrality;the mixing ratios(?3H/3He,(?)/(?),?3H/3H,(?)/(?))are all less than 1,indicating that the yields of the(anti)hypertriton are lower than that of the normal(anti)nuclei.In addition,the strangeness population factor S3=?3H/(3HeŚ?/p)of the hypertriton and antihypertriton are also calculated,whose values are close to unity.This result further confirms that the phase-space population of strange quarks is similar to the ones of light quarks in the relativistic heavy-ion collisions,indicating that the high-temperature unconfined quark matter has been formed in the high-energy Cu+Cu collisions.Our results are also in good agreement with the existing STAR experimental data.Thus,this thesis uses the model to predict the yields,yield ratios and strangeness population factor of the hypertriton and antihypertriton in different centrality bins in high-energy Cu+Cu collisions.Finally,the study of the collective flow for mesons(?+,?-,k+,k-,kS0)baryons(P,P,?,?),and light(anti)nuclei(d,(?),3H,(?),3He,(?))produced from Cu+Cu collisions at(?)=200 GeV is presented in this thesis by comparing the difference of collective flow between the positive matter and antimatter.The PACIAE and DCPC model are used to calculate the transverse momentum distribution of elliptic flow v2 for mesons,baryons,and light(anti)nuclei,respectively.The results show that the light(anti)nuclei produced in the high-energy Cu+Cu collisions also have a collective flow behavior;in particular,the transverse momentum distribution of the elliptic flow of the positive matter and corresponding antimatter is exactly the same within uncertainties,that is,the generation and evolution of the positive matter and antimatter are completely symmetric.These results further confirm that QGP matter has been produced in relativistic heavy-ion collisions.The calculated transverse momentum distribution of the elliptic flow are similar to the experimental data,at the low transverse momentum region,the model results of v2 are compatible with the experimental data;while there has some difference between them at the high transverse momentum region,which may be contributed by the different centrality criteria for model and experiment. |
PDF Full Text Request