DIRECTED FLOW AND FREEZEOUT IN HEAVYION COLLISIONS IN

DIRECTED FLOW AND FREEZEOUT IN HEAVY-ION COLLISIONS IN THE ENERGY RANGE OF BES (RHIC) L. Bravina for Ui. O heavy-ion theory group International Workshop on Collectivity in Relativistic Heavy-Ion Collisions (Kolymbari, Crete, Greece, Sept. 15 -20, 2014)

Content • Flow: how to quantify this phenomenon • Connection to Equation of State • Directed flow at AGS and SPS energies • Freeze-out of hadrons in microscopic models • Flow and freeze-out • Summary of signals to study at BES (RHIC), FAIR, NICA

Flow: How to quantify it

They are predicted to provide unprecedented access to the properties of Nuclear matter W. Scheid, H. Muller, and W. Greiner, PRL 32, 741 (1974) Ne H. Stöcker, J. A. Maruhn, and W. Greiner, PRL 44, 725 (1980) M. I. Sobel, P. J. Siemens, J. P. Bondorf, an H. A. Bethe, Nucl. Phys. A 251, 502 (1975) G. F. Chapline, M. H. Johnson, E. Teller, and M. S. Weiss, PRD 8, 4302 (1973) E. Glass Gold et al. Annals of Physics 6, 1 (1959) The idea to use collective flow to Probe the properties of nuclear matter is long-standing

DEFINITIONS. NON-CENTRAL COLLISIONS (B>0 )

DISTRIBUTIONS Rapidity dependence Transverse momentum dependence n=1, 2, … Centrality dependence

Motivation: connection to Equation of State

DISAPPEARANCE OF DIRECTED FLOW Hung and Shuryak, PRL 75 (1995) 4003 In case of first order phase transition Braun-Munzinger, NPA 661 (1999) 261 c

DISAPPEARANCE OF DIRECTED FLOW Transition to Quark-Gluon Plasma leads to decrease in pressure and, therefore, to softening of the directed flow

DIRECTED FLOW OF NUCLEONS AND FRAGMENTS Plastic Ball Collaboration introduced a slope parameter W. Reisdorf, H. G. Ritter Annu. Rev. Nucl. Part. Sci. 47 (1997) 663 Directed flow of nucleons and fragments has linear slope in normal direction => normal flow

Directed flow (between AGS and SPS)

DIRECTED FLOW OF NUCLEONS. 1 -FLUID HYDRO VS MICROSCOPIC MODEL Changing of the slope in Px(y)/A distribution of baryons is observed in 1 -fluid hydro model only in case of the QGP formation. Microscopic model predicts weaker directed flow compared to FDM. L. B. , N. Amelin, L. Csernai, P. Levai, D. Strottman, NPA 566 (1994) 461 c

DIRECTED FLOW OF NUCLEONS. 3 -FLUID HYDRO The model predicts a local minimum in the excitation function of directed flow at energies between 10 and 20 AGe. V J. Brachmann et al. , PRC 61 (2000) 024909

DIRECTED FLOW OF NUCLEONS. 3 -FLUID HYDRO The antiflow component is a source of the reduction of directed flow at midrapidity NB! This is a very rare case when the antiflow behavior is reproduced in hydrodynamic model J. Brachmann et al. , PRC 61 (2000) 024909

C. Alt et al. (NA 49), PRC 68 (2003) 034903 Softening of directed flow of protons at midrapidi ty DIRECTED FLOW OF PIONS AND PROTONS AT 40 AGEV

C. Alt et al. (NA 49), PRC 68 (2003) 034903 Antiflow o f protons i n periphera l events DIRECTED FLOW OF PIONS AND PROTONS AT 158 AGEV

DIRECTED FLOW AT BES (RHIC) STAR Collab. , PRL 112 (2014) 162301 For pions the slope at y=0 is negative; for protons it changes the sign

SOFTENING OF DIRECTED FLOW

COMPARISON WITH EXPERIMENTAL DATA E. Zabrodin et al. , PRC 63 (2003) 034902; L. Bravina et al. , PRC 61 (2000) 064802

SOFTENING OF DIRECTED FLOW L. Bravina et al. , NPA 715 (2003) 665 c Although the normal flow component is always larger than the antiflow one, in central rapidity window the antiflow can overshadow its normal counterpart

DIRECTED FLOW IN DIFFERENT P_T - INTERVALS L. Bravina et al. , PRC 63 (2001) 034902 The directed flow of high-p. T pions (and other mesons) seems to have a normal slope

CONCLUSIONS (DIRECTED FLOW )

Flow and freeze-out

FREEZE-OUT OF HADRONS AT SPS L. B. , L. Csernai et al. , PRC 60 (1999) 044905

FREEZE-OUT OF HADRONS AT RHIC L. B. et al. , PLB 631 (2005) 109 Pions and nucleons are coming from different areas

SEQUENTIAL FREEZE-OUT SPS L. B. et al. , PRC 60 (1999) 044905 ; PLB 354 (1995) 196 AGS

ABSENCE OF SHARP FREEZE-OUT

CONCLUSIONS (FREEZE-OUT)

FREEZE-OUT AT RHIC: URQMD

FREEZE-OUT AT RHIC: QGSM

5. FREEZE-OUT AT RHIC: URQMD M. S. Nilsson, ”LHC and beyond” (Lund, Feb. 2009)

FREEZE-OUT AT RHIC: QGSM M. S. Nilsson , ”LHC and beyond” (Lund, Feb. 2009)

Main Conclusion • Collective phenomena, such as directed and elliptic flow, should be studied together with the freeze-out dynamics

Back-up Slides

ELLIPTIC FLOW AND FREEZE-OUT

DIRECTED FLOW OF PIONS AND PROTONS AT 158 AGEV Red, green, blue points What is this? C. Alt et al. (NA 49), PRC 68 (2003) 034903

QUARK-GLUON STRING MODEL (QGSM) AND ULTRA-RELATIVISTIC QUANTUM MOLECULAR DYNAMICS (URQMD) Excitation of color neutral strings