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Generation Of Resonant Particles In SPS - LHC Energy Region

Posted on:2017-01-07Degree:MasterType:Thesis
Country:ChinaCandidate:M S ZhangFull Text:PDF
GTID:2270330485474421Subject:Theoretical Physics
Abstract/Summary:PDF Full Text Request
Quantum chromodynamics (QCD) predicts that at extremely high energy and/or temperature the hadronic matter would turn into a new state of the matter called quark gluon plasma (QGP) in which quarks and gluon are deconfined. The study of this matter state is very important to understand the material microstructure and the early evolution of our universe. Collisions of heavy ions with ultra-relativistic energy can provide such an extreme condition (high temperature and energy density) of QGP creation in the laboratory. The running of Large Hadron Collider (LHC) at European Organization Nuclear Research and Relativistic Heavy Ion Collidier (RHIC) at the Brookhaven National Laboratory in 2000 has provided rich experimental data that greatly motivate the study of QGP creation and its properties.The outcomes of QGP are thousands of hadrons including various mesons and baryons (as well as letpons and photons). Among them, hadronic resonances that have a short lifetime of several fin/c are effective probes of evolution dynamics of the system produced in relativistic heavy ion collisions. Due to the short lifetime which is less than or comparable to the effective during time of the system in hadron multiple scattering stage, the production of hadronic resonance is nontrivial influenced by hadronic rescattering stage and, therefore, the observed resonance in experiments are compositive result of the initial production at hadronization and hadronic rescattering effects. The study of resonance production is one of the hottest subjects in high energy heavy ion physics both in experimental and theoretical sides. Resonances such as K*(892),φ(1020),Σ*(1385),Ξ*(1530) have been measured by NA49, NA60 collaboration at SPS, STAR collaboration at RHIC and recently ALICE collaboration at LHC, and rich experimental data of yields, transverse momentum spectra are reported. These data show the production of resonance in AA collisions has a complicated hadronic rescattering effect that is collisional energy and hadron species dependent. In the hadronc stage of collision evolution, resonance might be destructed by rescattering with other hadrons and be regenerated by the collisions of other hadrons. Also and most important, daughter particles of resonance will scatter with other particles, causing signal loss. The physical properties of resonances, e.g., their masses and widths, might be modified by the surrounding medium. In addition, the yields and momentum spectra of resonances might be changed. The experimentally reconstructed resonances are the compositive results of the hadronization and hadronic rescattering stage. Therefore, the production of hadronic resonance carries information of different evolution stage in heavy ion collisions. Resonances initially produced at QGP hadronization reflect the properties of QGP before hadronization and hadronization dynamics. Resonances produced in hadronic rescattering stage reveal important information of hadron interactions, in particular, interactions of strange hadrons. In addition, the extent of loss of initially produced resonance depends on the effective lifetime of hadronic rescattering stage. Therefore, it is important to distinguish the different prouction sources of resonances observed in experiment.In this paper, we study the production of K*(S92)、φ (1020)、Σ*(1385)、Ξ*(1530) in central Pb+Pb collisions at (?)= 17.3, central Au+Au collisions at 200 GeV and central Pb+Pb collisions at 2760 GeV by focusing on both initial production dynamics at hadronization and the effects of hadronic rescattering stage. The direct production of these resonances at system hadronization is described by the quark combination model developed by Shandong group (SDQCM) and the effects of hadron multiple-scattering stage are calculated by Ultra-relativistic Quantum Molecular Dynamics (UrQMD). We study the contribution of these two production sources in final observation and compare the final spectra with the available experimental data.The investigation contains two aspects (1) The study of yields and pT spectra of K*(892) and φ(1020) in relativistic heavy-ion collisions at (?)=17.3GeV,200 GeV and 2760 GeV. Firstly, we use the quark combination model developed by Shandong group to calculate the transverse momentum spectrum of K* (892), and find that the spectrum is explicitly higher than the experimental data at low pT and is close to the data at pt-2GeV. We further use the UrQMD to calculate the effects of hadronic rescattering stage on the pT spectrum of K* (892). Including this effect, the resulting pT spectrum is in good agreement with the experimental data at three collision energies. Following the same procedure, we study the production of φ(1020) and find that the influence of hadronic rescattering stage is weak at three energies. Including hadronic rescattering effect can slight improve the agreement between our results with the data at low pt, with overall agreement in all pT region studied.(2) The study of yields and pT spectra of Σ*(1385) and Ξ*(1530) in relativistic heavy-ion collisions at (?)=17.3 GeV,200 GeV and 2760 GeV. We firstly use the quark combination model to calculate the transverse momentum spectrum of Σ*(1385) and Ξ*(1530), and then use UrQMD to calculate the influence of hadronic rescattering stage. We find that the hadronic rescattering effects of Σ*(1385) is small and that of E*(1530) is slighter larger than the former, and both are smaller than that of K* (892). We predict their pT spectra at midrapidity for the future test in experiments.
Keywords/Search Tags:Relativistic heavy ion collisions, resonance production, SDQCM, UrQMD
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