# Presentation: 182759

## Statistical model fitting

-  Particle ratios well reproduced
-  Resonance ratios not reproduced(Braun-Munzinger, QM 2004)
-               too low
-  K*/K too high

- Braun-Munzinger et al.

- Marcus Bleicher, TBS Berkeley 2005

## Hadronic vs leptonic channel

- Hot and dense
- medium

**Au+Au**

- Particle yields

- Particle spectra

**time**

****

**p**

**K**

****

**p**

**K**

****

- Marcus Bleicher, TBS Berkeley 2005

## Yields and scaling in AA

- Baryon resonances:

- Meson resonances:

**All ratios a smooth,****	****no sudden resonance disappearance**

- Marcus Bleicher, TBS Berkeley 2005

## Baryon resonances at RHIC

- All decaying resonances

- Finally observed resonances

**Signal loss due to rescattering of daughters**

- Marcus Bleicher, TBS Berkeley 2005

## Meson resonances at RHIC

- All decaying resonances

- Finally observed resonances

**Note that                  yields information about all decays (l.h.s),  ****while             yields information about r.h.s. **

- Marcus Bleicher, TBS Berkeley 2005

## What about the centrality dependence?

-  Where is the suppression?
-  K*/K deceases!
-              stays constant!

- Marcus Bleicher, TBS Berkeley 2005

## Data vs. models 

**Thermal model [1]:**
- T = 177 MeV
- B = 29 MeV

- [1] P. Braun-Munzinger et.al., PLB 518(2001) 41
-       D.Magestro, private communication
- [2] Marcus Bleicher and Jörg Aichelin
-       Phys. Lett. B530 (2002) 81.   M. Bleicher and
-       Horst Stöcker .Phys.G30 (2004) 111.

**UrQMD [2]**

**Life time [fm/c] :**
******(1020)    =  40 **
******(1520)    =  13 **
** ****K(892)     =    4 **
** ********++                  ****=  1.7 **
****

- Rescattering and refeeding are needed        rather long living hadron stage

- Marcus Bleicher, TBS Berkeley 2005

## How can we understand these differences?

-  Strong decrease in kinetic freeze-out temperature from peripheral to central
-  Kinetic freeze-out as low as 80 - 90 MeV
-  Consequences  for resonance re-feeding

- Marcus Bleicher, TBS Berkeley 2005

**Notes:**
Chemical fo: thermal, kinetic: blast wave

## Estimate of re-feeding prob.

-         can re-created until end of the reaction
-         re-creation is only possible near chemical freeze-out

- Estimate of available energy for re-feeding at different reaction stages

- Marcus Bleicher, TBS Berkeley 2005

## Decay time analysis

- Decay time analysis

-  In the model rho mesons are not re-created after T=120 MeV.Check with mass shift.Check hadronic vs leptonicCheck centrality dependence
-  Deltas can be re-created until T=80-90 MeV.No centrality dependence

- RHIC

- Marcus Bleicher, TBS Berkeley 2005

- Pb+PB @ 160AGeV

- Do resonances know about the chemical freeze-out?

- Marcus Bleicher, TBS Berkeley 2005

- Delta

- rho

- Pb+Pb @ SPS

- phi

- Marcus Bleicher, TBS Berkeley 2005

- Pb+PB @ 160AGeV

- Delta does not know  about chem. f-o.
-  rho/K* know a bit   (30% effect)
-  phi reflects the  chemical f-o.

- Marcus Bleicher, TBS Berkeley 2005

- Pb+PB @ 160AGeV

- midrapidity

- PRELIMINARY

- Marcus Bleicher, TBS Berkeley 2005

## Simple    mass shift

-  Breit-Wiegner distr. for the rho mass
-  Fold with thermal distribution
-     Temperature dependent mass

-  For T=150-100 MeV the mass is shifted by 10-20 MeV downwards

- Marcus Bleicher, TBS Berkeley 2005

## Rho mass shift predictions

-  Mass drops towards central reactions

-  Mass drops towards low pt

- Marcus Bleicher, TBS Berkeley 2005

## Conclusion

- Scaled elliptic flow  saturates
- K/pi ratio enhanced
- Large dynamical  fluctuations

- Another interesting energy range, because:

- Marcus Bleicher, TBS Berkeley 2005

- Marcus Bleicher, TBS Berkeley 2005

- Marcus Bleicher, TBS Berkeley 2005

- Marcus Bleicher, TBS Berkeley 2005

## K/ fluctuations increase towards lower beam energy
Significant enhancement over hadronic cascade model 
p/ fluctuations are negative
indicates a strong contribution from resonance decays 

- K/ fluctuations increase towards lower beam energy
- Significant enhancement over hadronic cascade model
- p/ fluctuations are negative
- indicates a strong contribution from resonance decays

**NA49  Preliminary**

**NA49  Preliminary**

- Fluctuation studies

- Taken from Christoph Roland

- Marcus Bleicher, TBS Berkeley 2005

## Longitudinal pressure:Is it Landau or Bjorken? 

-  **Bjorken**: Boost invariant flow (transparency of projectile and target)
-   Rapidity density plateau!
-  **Landau**:  instant thermalization  followed by expansion
-   Rapidity density is Gaussian!
-  (with                         )

- Marcus Bleicher, TBS Berkeley 2005

## Particle dependent rapidity widths 

-  Rapidity widths of all particles are different

- Au+Au (Pb+Pb), central

- particles

- anti-particles

- Marcus Bleicher, TBS Berkeley 2005

## Landau or Bjorken?None of both! 

- Rapidity width decreases   with mass
- No universal scaling of   the rapidity width
- Maximal |y-ycm| of the ‘Bjorken plateau’ is 0.75 units

- Marcus Bleicher, TBS Berkeley 2005