Hanna Paulina Gos 1, 2

for the STAR collaboration

1 Faculty of Physics

Warsaw University of Technology

2 SUBATECH

Nantes

Hanna Paulina Gos	Hot Quarks, 2006

Villasimius, 16 May 2006

Proton-proton correlations in Au+Au collisions

measured by STAR at RHIC

Baryon correlations:

Interactions present in baryon correlations

Identical vs. nonidentical (anti)proton combinations

The contribution of Residual Correlations + their estimation

The fraction of pure p -p correlation

Results of correlation functions

mT dependence (validity of flow description checked)

Conclusions

Outline

Proton- (anti)proton

correlations

Identical baryon- baryon

- Quantum Statistics- QS

- Final State Interactions- FSI

- Coulomb

- Strong

Nonidentical baryon- (anti)baryon

- Final State Interactions- FSI

- Coulomb

- Strong

0.1

k* [GeV/c]

0.05

Baryon-baryon: Quark Matter 2005 status

2 different sizes!

2 different sources?

The input

- 10 000 events generated (central collisions) using

THERMal heavy IoN generATOR

(Broniowski, Florkowski, Kisiel, Tałuć: nucl-th/0504047)

- Access to information: unique id, pid, space-time coordinates,

mass, momentum four-vector, identification number of

father

- weak decay channels of interest:

Λ -> p + π-, Λbar -> pbar + π+

Σ+ -> p + π0, Σ+bar -> pbar + π0

Contribution to measured correlation function

+

+

The fraction of proton-proton pairs

The estimation of p-Λ residual correlation

=

=

Normalized in each k*p-p slice

STAR preliminary

Proton-proton

correlations

STAR preliminary

Proton-antiproton

correlations

STAR preliminary

Proton-proton, antiproton-antiproton, proton- antiproton

STAR preliminary

mT dependence

Not taking into account the residual correlations- may lead to the misunderstanding of results!

STAR preliminary

Conclusions – part II

- Proton-proton, antiproton-antiproton, proton-antiproton correlations

for Au+Au @ 200GeV and 62 GeV are shown

- Proton femtoscopy is a new insight into baryon production and

interaction processes thanks to the large STAR data collections

- It allows to extract proton and antiproton source size parameters with

a very good accurancy

- Preliminary results indicate that the residual correlations play a crucial role

in baryon systems

- Residual correlations affect non-id systems more

- We record a very good agreement between the experimental results and

the theoretical predictions

- After removing RC- there are still small discrepancies (according gaussian

parametrization of source)

- Systematic uncertainty studies are underway

- Proton source sizes scales as predicted by flow

The End

Few words about femtoscopy

Single- and two- particle distributions

The correlation function

S(x,p) – emission function: the distribution

of source density probability of finding particle

with x and p

The estimation of p-Σ residual correlation

=

=

Normalized in each k*p-p slice

The estimation of Σ-Σ residual correlation

=

=

Normalized in each k*p-p slice

The scattering lengths

Annihilation

Repulsive interaction (negative)

pp

STAR preliminary

2006-05-03T14:37:57