# Presentation: 265570

## Anisotropic flow at RHIC

- Aihong Tang for the                    Collaboration

- Aihong Tang                                           Hot Quarks 04, Taos City

## Outline

- Directed flow
- Theoretical predictions (anti-flow/3rd flow component, *v**1* wiggle)
*v**1* at RHIC
-  Elliptic flow
- How does azimuthal correlation evolve from elementary collisions (p+p) through collisions involving cold nuclear matter (d+Au), and then on to hot, dense heavy ion collisions (Au+Au) ?
*v**2* at intermediate *p**t*

- Aihong Tang                                           Hot Quarks 04, Taos City

## Directed flow Do we see wiggle ?

- Aihong Tang                                           Hot Quarks 04, Taos City

## Directed flow (v1) and phase transition 

**Directed flow (*****v******1*****) and phase transition **

- Brachmann, Soff, Dumitru, Stocker, Maruhn, Greiner Bravina, Rischke ,  PRC 61 (2000) 024909. L.P. Csernai, D. Roehrich PLB 458, 454 (1999)   M.Bleicher and H.Stocker, PLB 526,309(2002)

- Anti-flow/3rd flow component, with QGP  *v**1* flat at middle rapidity.

- Aihong Tang                                           Hot Quarks 04, Taos City

## Directed flow (v1) and baryon stopping 

- R.Snellings, H.Sorge, S.Voloshin, F.Wang, N. Xu, PRL (84) 2803(2000)

- Positive space-momentum correlation, no QGP necessary  *v**1* wiggle.

- Aihong Tang                                           Hot Quarks 04, Taos City

## Directed flow at RHIC - 200 GeV

**Directed flow at RHIC - 200 GeV**

- Shows no sign of  a “wiggle” (although does not exclude the magnitude as predicted)

- nucl-ex/0310029, PRL 92 062301(2004)

- Aihong Tang                                           Hot Quarks 04, Taos City

## Directed flow at RHIC - 62 GeV

**Directed flow at RHIC - 62 GeV**

- v1{3} and v1{EP1,EP2} give the same result.

- STAR Preliminary

-  v1{EP1,EP2} from M. Oldenburg

- No Wiggle in Nch v1 !

- Aihong Tang                                           Hot Quarks 04, Taos City

## Directed flow at RHIC - 62 GeV

- No Wiggle in Nch v1 !

- STAR
- Preliminary

- Aihong Tang                                           Hot Quarks 04, Taos City

## Directed flow at RHIC - Limiting fragmentation

- STAR Preliminary

- Aihong Tang                                           Hot Quarks 04, Taos City

##  Directed flow : conclusions 

-  No wiggle is found in Nch *v**1 *at 62 GeV.
-  Viewed in the projectile frame, *v**1* at RHIC agrees with NA49 result.

- Aihong Tang                                           Hot Quarks 04, Taos City

## Elliptic flow (I) How does azimuthal correlation evolve from elementary collisions (p+p) through collisions involving cold nuclear matter (d+Au), and then on to hot, dense heavy ion collisions (Au+Au) ?

- Aihong Tang                                           Hot Quarks 04, Taos City

## We need a fair comparison of “v2” on three different systems

- V2 does not scale  ---  need to find a multiplicity (or Nbinary) independent quantity to compare azimuthal correlations between two different systems.

-     Multiplicity independent

-     Scaling !

- Aihong Tang                                           Hot Quarks 04, Taos City

## In S. Voloshin’s language

- Aihong Tang                                           Hot Quarks 04, Taos City

## In J.-Y Ollitrault & N. Borghini’s language

- Log(G(z)) then should scale linearly with the number of pp collisions, so should cumulants, which is the coefficient of z of Log(G(z)).

- It is good for extracting v2, but it does not scale. If we change it to

- The format of generating function used in cumulant analyses is:

- Then for a system that is superposition of two independent system 1 and 2, and only “nonflow” correlations are present, we have

- So if a Nucleus-Nucleus is a simple superposition of N  independent pp collisions, then

- In the case of a second order cumulant, this is

- Aihong Tang                                           Hot Quarks 04, Taos City

## How does elliptic flow evolve from pp to dAu, and AuAu collisions ? 

**How does elliptic flow evolve from pp to dAu, and AuAu collisions ? **

- STAR
- Preliminary

- Aihong Tang                                           Hot Quarks 04, Taos City

## Elliptic flow (II) v2 at intermediate pt  

- Aihong Tang                                           Hot Quarks 04, Taos City

**v****2**** at intermediate p****t**** **

- Aihong Tang                                           Hot Quarks 04, Taos City

**v****2**** at intermediate p****t**** **

- v2 at intermediate pt is too large for recombination + fragmentation, Hydro remnants ?

- Aihong Tang                                           Hot Quarks 04, Taos City

##  We can compare azimuthal correlation in three different collision systems by Scalar Product method. 

-  Azimuthal correlations in AuAu collisions show strong real collective motion.
-  As to date, yet no theoretical work can completely explain the high v2 at moderate pt.

**Elliptic flow : conclusions**

- Aihong Tang                                           Hot Quarks 04, Taos City

## THE END

- Aihong Tang                                           Hot Quarks 04, Taos City