1. 1 Rapidity, Azimuthal and Multiplicity Dependences of Mean Transverse Momentum and Transverse Momentum Correlations in + p and K + p collisions at GeV The NA22 Collaboration Presented by Huang Yanping Institute of Particle Physics/Wuhan Aug. 10, 2005

2. Huang Yanping ISMD05,Aug.10 2 Outline Introduction Introduction Motivation Measures of p t fluctuation Advantages of the data Results and Discussion Results and Discussion Rapidity dependence Azimuthal dependence Multiplicity dependence Summary Summary

3. Huang Yanping ISMD05,Aug.10 3 Since transverse momenta of the final state particles are produced after the collision and carry the information of system expansion, their fluctuations are considered to be a good probe for QGP and a trace of local thermal equilibrium. Since transverse momenta of the final state particles are produced after the collision and carry the information of system expansion, their fluctuations are considered to be a good probe for QGP and a trace of local thermal equilibrium. Why e-by-e fluctuation of transverse momentum? Provide additional valuable insight into the particle production mechanism and dynamical evolution, which cannot be extracted from the conventional single-particle inclusive distribution. Provide additional valuable insight into the particle production mechanism and dynamical evolution, which cannot be extracted from the conventional single-particle inclusive distribution.

4. Huang Yanping ISMD05,Aug.10 4 Heavy ion collisions evolution(expansion) Collisions between two Lorentz-contracted “plates” Cool down and freeze out as hadrons How does the fluctuation behave, where no QGP is expected ?  How does the fluctuation behave, where no QGP is expected ? 1) What is the formed hot matter? QGP ? 2) How does the system expand? How does the transverse expansion relate to the longitudinal  How does the transverse expansion relate to the longitudinal expansion? expansion?

5. Huang Yanping ISMD05,Aug.10 5 Motivation evolution(expansion) Collisions between two Lorentz-contracted “plates” Cool down and freeze out as hadrons How does the fluctuation behave, where no QGP is expected ?  How does the fluctuation behave, where no QGP is expected ? 1) What is the formed hot matter? QGP ? 2) How does the system expand? Mean transverse momentum Expansion velocity Transverse momentum correlation Transverse expansion velocity [S.A.Voloshin, Nucl.Phys.A 727,287(2003)] How does the transverse expansion relate to the longitudinal  How does the transverse expansion relate to the longitudinal expansion? expansion?

6. Huang Yanping ISMD05,Aug.10 6 Current experimental results The non-monotonic dependence may be due to the effects of equilibration, jet quenching and radial flow saturation.

7. Huang Yanping ISMD05,Aug.10 7 Summary of Event-by-event Fluctuation Measures   pT,dyn F pT  pT  pT,n  pT

8. Huang Yanping ISMD05,Aug.10 8 Summary of Event-by-event Fluctuation Measures   pT,dyn F pT  pT  pT,n  pT

9. Huang Yanping ISMD05,Aug.10 9 Measures of p t correlation Event mean two-particle p t correlation Event mean two-particle p t correlation Which one is better ? Inclusive mean two-particle p t correlation Inclusive mean two-particle p t correlation

10. Huang Yanping ISMD05,Aug.10 10 A total of 44 524 NSD events 0.001GeV/c < p t < 10 GeV/c over full 4π acceptance over full 4π acceptance Advantages of the data

11. Huang Yanping ISMD05,Aug.10 11 Results and Discussion Rapidity Dependence Rapidity Dependence Azimuthal Dependence Azimuthal Dependence Multiplicity Dependence Multiplicity Dependence

12. Huang Yanping ISMD05,Aug.10 12 Rapidity Dependence of, or the expansion velocity of the system is longitudinal momentum related, or the expansion velocity of the system is longitudinal momentum related ▲ NA22 data ∆ PYTHIA Au+Au at 200GeV from star Similar to the sea-full effect. Pythia can’t describe the effect. The sea-gull effect is smeared in the nulceus collisions. Remnant effect exist.

13. Huang Yanping ISMD05,Aug.10 13 Rapidity Dependence of p t correlation R is independent of the size and position of the rapidity window.  R is independent of the size and position of the rapidity window.  is strongly dependent on rapidity. The transverse correlation is longitudinal momentum independent/boost invariant. R is well normalized and more robust than R'.

14. Huang Yanping ISMD05,Aug.10 14 Azimuthal Dependence NA22NA49 Acceptan ce cut 1.1<y<2.6 0.005<pt<1.5Gev collisio n nucleu s + +p + +p K + +p K + +pp+p  pt 10.91 ±1.54 2.2 ± 0.3 ▲ NA22 data ∆ PYTHIA » is independent of the azimuthal size » The dependence of R  the constraint of energy and momentum conservation

15. Huang Yanping ISMD05,Aug.10 15 Multiplicity Dependence  Both and R decrease with increasing multiplicity.  The smaller the event-multiplicity is, the stronger the event mean two-particle pt correlation is.

16. Huang Yanping ISMD05,Aug.10 16 Summary Both and R decrease with the increasing multiplicity, the smaller event-multiplicity is, the stronger the correlation is. Both and R decrease with the increasing multiplicity, the smaller event-multiplicity is, the stronger the correlation is. The mean transverse momentum is longitudinal momentum related, and the correlation is longitudinal momentum independent. PYTHIA can roughly describe the rapidity dependence of R but not for. The mean transverse momentum is longitudinal momentum related, and the correlation is longitudinal momentum independent. PYTHIA can roughly describe the rapidity dependence of R but not for. is uniformly distributed in plane, but due to energy-momentum conservation, R strongly depends on. is uniformly distributed in plane, but due to energy-momentum conservation, R strongly depends on.

17. Huang Yanping ISMD05,Aug.10 17