1 / 18

HBT search for new states of matter in A+A collisions

HBT search for new states of matter in A+A collisions. Yu. Sinyukov, BITP, Kiev Based on the paper S.V. Akkelin, Yu. S. nucl-th 0505045, submitted to PRC. Basic ideas.

feng
Download Presentation

HBT search for new states of matter in A+A collisions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. HBT search for new states of matter in A+A collisions Yu. Sinyukov, BITP, Kiev Based on the paper S.V. Akkelin, Yu. S. nucl-th 0505045, submitted to PRC Quark Matter 2005

  2. Basicideas • The goal of experiments with heavy ion collisions is to study the new forms of matter which can be created under an extreme conditions at the early stage of the evolution. • The bulk of hadronic observables (“soft physics”) are related, however, to the very last period of the matter evolution, so called kinetic freeze-out - the end of the collective expansion of hadronic gas when the system decays. • The main idea is to use integrals of motion - the ''conserved observables'' which are specific functionals of spectra and correlations functions. • A structure of the integrals of motion, besides the trivial ones associated with energy, momentum and charges, dependson a scenario of the matter evolution. • Our analysis is based on hydrodynamic picture of the evolution. Quark Matter 2005

  3. Approximately conserved observables t Thermal f.-o. • APSD - Phase-space density averaged over some hypersurface , where all particles are already free and over momen- tum at fixed particle rapidity,y=0. (Bertsch) Chemical. f.-o. n(p) is single- , n(p1, p2 ) is double (identical) particle spectra, correlation function is C=n(p1, p2)/n(p1)n(p2) z p=(p1+ p2)/2 q= p1- p2 • APSD is conserved during isentropic and chemically frozen evolution: S. Akkelin, Yu.S. Phys.Rev. C 70 064901 (2004): Quark Matter 2005

  4. Approximately conservedobservables • (1) ENTROPY and (2) SPECIFIC ENTROPY (1) (i =pion) (2) For spin-zero (J=0) bosons in locally equilibrated state: On the face of it the APSD and (specific) entropy depend on the freeze-out hypersurface and velocity field on it, and so it seems that these values cannot be extracted in a reasonably model independent way. Quark Matter 2005

  5. “Model independent” analysis of pion APSD and specific entropy • The thermal freeze-out happens at some space-time hypersurface with T=const and =const. • Then, the integrals over of contain the common factor, “effective volume ” is rapidity of fluid), that completely absorbs the flow and form of the hypersurface in mid-rapidity. For instance, if then • where is thermal density of equilibrium B-E gas and similar for • (APSD-numerator) and (entropy). • Thus, the effective volume is cancelled in the corresponding ratios: APSD • and specific entropy. Quark Matter 2005

  6. Pion APSD and specific entropy as observables • The APSD will be the same as the totally averaged phase-space density in the static homogeneous Bose gas: , =0.6-0.7 accounts for resonances where • Spectra + BE correlations Chemical potential + Tf.o. • Pion specific entropy: Quark Matter 2005

  7. The averaged phase-space density Non-hadronic DoF Limiting Hagedorn Temperature Quark Matter 2005

  8. The statistical errors The statistical uncertainties caused by the experimental errors in the interferometry radiiin the AGS-SPS energy domain. The results demonstrate the range of statistical signicance ofnonmonotonic structures found for a behavior of pion averaged phase-space densities as functionof c.m. energy per nucleon in heavy ion collisions. Quark Matter 2005

  9. The chemical potential Quark Matter 2005

  10. Interferometry volumes and pion densities at different (central) collision energies Quark Matter 2005

  11. Energy dependence of the interferometry radii Energy- and kt-dependence of the radii Rlong, Rside, and Rout forcentral Pb+Pb(Au+Au) collisions from AGS to RHICexperiments measurednear midrapidity. (Kniege, NA49, 2004) Quark Matter 2005

  12. HBT PUZZLE • The interferometry volume only slightly increases with collision energy (due to the long-radius growth) for the central collisions of the same nuclei. Explanation: • only slightly increases and is saturated due to limiting Hagedorn temperature TH =Tc (B = 0). • grows with A is fixed Quark Matter 2005

  13. HBT PUZZLE & FLOWS • Possible increase of the interferometry volume with due to geometrical volume grows is mitigated by more intensive transverse flows at higher energies: ,  is inverse of temperature • Why does the intensity of flow grow? More more initial energy density  more (max) pressure pmax BUT the initial acceleration is ≈ the same ! HBT puzzle puzzling developing of initial flows (< 1 fm/c). Quark Matter 2005

  14. The interferometry radii vs initial system sizes • Let us consider time evolution (in  ) of the interferometry volume if it were measured at corresponding time: • for pions does not change much since the heat energy transforms into kinetic energy of transverse flows (S. Akkelin, Yu.S. Phys.Rev. C 70 064901 (2004)); • The <f> is integral of motion; • is conserved because of chemical freeze-out. is fixed Thus the pion interferometry volume will approximately coincide with what could be found at initial time of hadronic matter formation and is associated with initial volume Quark Matter 2005

  15. The interferometry radii vs initial system sizes Quark Matter 2005

  16. Rapidity densities of entropy and number of thermal pions vs collision energy (bulk) viscosity Quark Matter 2005

  17. Anomalous rise of pion entropy/multiplicities and critical temperature Quark Matter 2005

  18. Conclusions • A method allowing studies the hadronic matter at the early evolution stage in A+A collisions is developed. It is based on an interferometry analysis of approximately conserved values such as the averaged phase-space density (APSD) and the specific entropy of thermal pions. • The plateau founded in the APSD behavior vs collision energy at SPS is associated, apparently, with the deconfinement phase transition at low SPS energies; a saturation of this quantity at the RHIC energies indicates the limiting Hagedorn temperature for hadronic matter. • An anomalously high rise of the entropy at the SPS energies can be interpreted as a manifestation of the QCD critical end point, while at the RHIC energies the entropy behavior supports hypothesis of crossover. • It is shown that if the cubic power of effective temperature of pion transverse spectra grows with energy similarly to the rapidity density (that is roughly consistent with experimental data), then the interferometry volume is inverse proportional to the pion APSD that is about a constant because of limiting Hagedorn temperature. This sheds light on the HBT puzzle. Quark Matter 2005

More Related