Dissertation > Mathematical sciences and chemical > Physics > Nuclear physics,high energy physics > High-energy physics > Particle physics > Interaction > Strong interaction

Nuclear energy - Nuclear Collisions new substances and hadron physics research oriented

Author ZhuLiLin
Tutor YangChunBin
School Central China Normal University
Course Theoretical Physics
Keywords Quark-gluon plasma (QGP) Relativistic heavy ion collisions Thermal and chemical properties Recombination model Particle generation rate Momentum attenuation Quark regeneration Nuclear correction factor ridge yield Elliptic flow coefficient ν2 Two particle correlation Axial angle Scaling behavior Particle generation mechanism String fragmentation mechanism Mission fragmentation mechanism
CLC O572.243
Type PhD thesis
Year 2010
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QCD predictions at very high energy density, will produce a made of quarks and anti-quarks and gluons composition of the new physical form, which is the quark-gluon plasma (QGP). The relativistic heavy ion collisions is the in-depth study of this new material forms an important experimental means, it is hoped by this method, from hadronic matter to quark matter phase transition. The final state of high energy collision observables, such as: the distribution of particles in the final state spectrum, particle correlation, undulating ...... is to understand the evolution of high-energy heavy ion collisions and particle generation mechanisms important way. In this paper, in 布鲁克海汶 National Laboratory Relativistic Heavy Ion Collider (RHIC) data on the four experimental groups, in-depth study of the generation mechanism of final state particles and their distribution characteristics. This article first briefly reviews the relativistic heavy ion collision experiments and theoretical status quo. Then describes the calculation of basic physical concepts and the required phenomenological model, including a description of nucleus - nucleus collisions, the nuclear geometry of the Glauber model; weight combination model (Recombination / Coalescence (ReCo) Model), especially the Oregon team (Hwa / Yang) model of the basic ideas; and Peter Levai team ALgebraic COalescence Rehadronization model (ALCOR). First, the use of statistical mechanics methods discussed energy heavy ion collisions resulting thermodynamic properties of QGP. At high temperatures, the asymptotic freedom, weak interactions between partons, so you can put quarks and gluons as free gas to deal with. However, the critical temperature (Tc) near the coupling constant is relatively large, it is difficult to re-use analytical method. If starting from first principles using lattice QCD calculations, but also requires a lot of time and computer resources. Therefore, in this paper, the second chapter, will use a self-consistent phenomenological model of quasi-particle QGP thermal and chemical properties. Assuming parton interactions can all be included in its quality among the system so that you can handle as an ideal gas, and then use statistical mechanics to calculate various thermodynamic quantities. In T gt; Tc region, can be a good point to be qualified QCD data. ALCOR model based on discussions strange particle wave function in different combinations of the generation rate. The results show that hadron production rate depends on the gluon mass, but is not sensitive to temperature; resulting rate ratio is almost independent of the mass and gluons. Then select the energy of s 1/2 = 200AGeV, Au Au particles in the central collision ratio Φ / K * = 0.60 ± 0.15 as a starting point, calculate the wave function in different combinations than hadron results show that The ratio of the particle wave function of choice is not sensitive. In addition, the article also utilize the latest experimental data p / π and p / p, in the heavy quark combination model (Recombination Model) framework, re-examine the high energy heavy ion collisions at forward rapidity region (η = 3.2) final state hadrons produced. Central to reconsider the system of molecular momentum and quark decay regenerative effect, got charged with the experimental data hadron spectroscopy and larger ratio of proton and π mesons, but also predicted the anti-proton and proton ratio. In-depth study of nuclear - nuclear collision geometry based on the overlap region, unified description of the low transverse momentum region (pT lt; 2GeV / c), π0 meson and axial azimuth all relevant observables: Nuclear correction factor RAA ( φ, Np), elliptic flow v2 (Np) and ridge yield YR (φs, Np), and agrees well with the experimental data. Two basic starting point is: the system causes the surface of the semi-hard scattering particle axial ridge opposite sex and trigger particle generation and independent of the choice. Although the RAA is a measure of the single-particle distribution, and YR is the trigger particle and its accompanying particle correlation measurements, but in between there is a close link. Throughout the physical picture, the most critical point is the single-particle distribution dNAAπ / pTdptdφ is divided into two parts: the azimuth angle φ does not depend on the bulk component (B (pT, Np)) and depends on the ridge component φ (R (pT, φ, Np)). Finally, this paper RHIC experimental data, in-depth study of different centrality, (pseudo) rapidity and collision system, π mesons, protons and antiprotons transverse momentum spectra scaling behavior. The results showed that: π meson scaling behavior does not depend and centrality, (pseudo) rapidity, and the center of mass energy of the collision system exists. For protons and antiprotons in the SNN 1/2 = 200 GeV under, Au Au collisions, there are also not dependent on the centrality and rapidity scaling behavior. However, the scaling behavior of the three there are differences, which particles quarks are closely linked. In these processes, the characterization of these particles scaling behavior of only one parameter: the average particle transverse momentum , it depends on the centrality, rapidity, collision energy and collision system. Once you know , so low pT region of the soft part of the process and the high pT region of the hard part of the process can be made of particles determines the scaling function. Then use π mesons and protons scaling behavior of charged hadrons in pp collisions at different multiplicity of transverse momentum distribution under the scaling behavior. Found that different spectral distribution under multiplicity still has a scaling behavior, and can use π mesons and protons scaling function of the linear superposition to represent. And momentum are different, the kinetic energy is a scalar, and directly with the hot dense matter temperature. Effects because of the quality, the different particles, the same momentum corresponding to different kinetic energy. Thus, in the ultra-relativistic heavy ion collisions, the kinetic energy distribution more effectively reveal the system's thermal and chemical properties. Therefore, further research Chapter protons and π meson transverse energy distribution scaling behavior, and its transverse momentum scaling behavior were compared, results showed that at low and high momentum (transverse energy) region, transverse energy scale better. Scaling can be used as a mechanism to explore particle generation is an important message. Through analysis, we found string fragmentation and fragmentation mechanisms regiment π mesons and protons, respectively, describe the scaling behavior, but can not get the scaling behavior of the two particles, so these two mechanisms is not a universal mechanism of particle generation, need to find a new mechanism to explain the generation of particles in the final state.

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