Author
Vaclav Kosar
Abstract
This work provides a review of theories of properties of high energy density matter originating in heavy-ion high energy collisions (GeV/nucleus). The work contains an introduction to the extreme state of matter called quark-gluon plasma, quantum statistical mechanics, and theory of longitudinally boost-invariantly expanding fireball of a hot matter.
Particular intention is given to the blast-wave model with resonances, whose basic assumptions are longitudinally boost-invariant expansion, transverse expansion, and the existence of a particular hypersurface in space-time, on which hadronic matter abruptly decouples from fireball.
In the final part two most important parameters of the blast-wave model are extracted from fits to the transverse momentum spectra obtained from STAR experiment, using a modification of the program DRAGON [B. Tomasik, Comp.Phys.Commun. 180 (2009) 1642-1653].
Conclusion
With the help of software modification of some outputs of the DRAGON program, I have fitted the two most important parameters of the Blastwave model with resonances to the normalized (see sub-chapter 4.3.1) spectra in transverse momentum from the STAR experiment : E [GeV] ηf Tf o [GeV] χ^2 min(E) 62.4 0.8 0.08 2.66 130 0.8 0.08 2.35 200 0.9 0.08 0.81 Table 4.2: Values of parameter ηf, Tf o [GeV] for found minima of function χ^2(ηf, Tf o) (see sub-chapter 4.3.2) and for different energies see also tables in Appendix A.3.
It is interesting that even though the spectra for the fitted values correspond quite well (see graphs in sub-chapter 4.3.2). However, the freeze-out temperature Tf o values are approximately half compared to previous estimates. There could be several explanations:
- Even though the chosen parameters are significant, it is necessary to adjust the others as well.
- The region in transverse momentum I analyzed is too narrow.
- It is necessary to adjust the chemical composition parameter for energy 62.4 [GeV].
- The choice of the freeze-out super-surface of the Blastwave model is not suitable.
A possible continuation of this work would be to add the results of the influence of symmetrization - HBT interferometry as additional data (see sub-chapter 3.6).
Key words
ultrarelativistic nuclear collisions, logitudinally boost-invariat expanding fireball, Blastwave model, transverse momentum spectra, DRAGON
