Phase Space Dependences of E-by-E Fluc. in  + p and K + p Collisions at 250 GeV/ c

1. Phase Space Dependences of E-by-E Fluc. in +p and K+p Collisions at 250 GeV/c Wu Yuanfang for NA22 Coll. 1. Introduction. 2. Main results and simple discussions. 3. Summary and conclusions. Institute of Particle Physics, Huazhong Normal University, Wuhan 430079 China. • M. R. Atayan et al. (NA22 Coll.), Phys. Rev.Lett. 89, 121802(2002); • 2. M. R. Atayan et al. (NA22 Coll.), submitted to PRL.

2. 1. Introduction. • Motivations ♠ Why event-by-event fluc. ? ∆ Additional valuable insight into theparticle production mechanism& dynamical evolutionof the system, which cannot be extracted from the conventional single-particle inclusive distribution. ∆ Various theoretical works predict that the formation of Quark Gluon Plasma (QGP) could produce significant event-by-event fluc. M. Gazdzicki and St. Mrowczynski, Z. Phys. C54, 127(1992); L. Stodolsky, PRL75, 1044 (1995); M. Stephanov, K. Rajagopal and E. Shuryak, PRL81, 48816(1998); M. Asakawa, U. Heinz and B. Muller, Phys. Rev. Lett. 85, 2072(2000). S. Jeon & V. Koch, Phys. Rev. Lett. 85, 2076(2000);

3. ♠ Advantages of the data. A total of 44 524 NSD events 0.001GeV/c< pt < 10 GeV/c over its full 4π acceptance M. Adamus et al. (NA22 Coll.), Z. Phys. C32, 476(1986); ibid C39, 311(1988); M. R. Atayan et al. (NA22 Coll.), Eur. Phys. J. C21, 271(2001). 1. Introduction. • Motivations ♠ Why phase space dependences of e-by-e fluc. ∆ For transverse momentum fluc., whether the fluctuation is boost invariant & whether the momenta in transverse & longitudinal directions are correlated. ∆ For charge fluc., if the global charge conservation and baryon stopping effects are properly deduced from the measure or not.

4. 1. Introduction. (B) Measures of the charge fluc. Net charge fluc.: Charge ratio fluc.: Corrected version: global charge conservation baryon stopping The theoretical predictions for the D-measure in : QGP D ~ 1 resonance gas D ~ 2.9; quark coalescence model D~ 3.26; random D~ 4. S. Jeon & V. Koch, Phys. Rev. Lett. 85, 2076(200); M. Asakawa, U. Heinz and B. Muller, Phys. Rev. Lett. 85, 2072(2000); J. T. Mitchell, nucl-ex/0404005; H. Appelshauser, nucl-ex/0405005.

5. 1. Introduction. (C) Measure of transverse momentum fluc. Independent production: It is supposed to be a good probe for thermal equilibrium & QCD tri-critical point. S. Gavin, PRL92, 162301(2004); M. Stephanov, K. Rajagopal and E. Shuryak, PRL81, 48816(1998); M. Gazdzicki & St. Mrowczynski, Z. Phys. C54, 127(1992).

6. 2. Main results and simple discussions. (A) The dependency of net charge fluc. on the size of y windows Random quark coalescence resonance gas QGP ● Random ○ NA22 data ◊ PYTHIA » For random case, it is 4 as expected and confirms that e-by-e analysis can be used in low n.(A. Bialas & V. Koch, Phys. Lett. B456, 1(1999)) » keep decreasing with the size of central rapidity windows. » the scaling ofappears when the size of rapidity window is larger than 4 unit, showing that the influence of charge conservation and leading-particle stopping have been well deduced from the measure.

7. 2. Main results and simple discussions. (B) The dependency of charge ratio fluc. on the size of y windows. » both of them have behavior very different from net charge fluc. » both and are above independent emission and increase rapidly with the size of central rapidity window. ○ NA22 data ◊ PYTHIA

8. 2. Main results and simple discussions. (C) The dependency of on the size and position of y windows. » increase with size of central rapidity window and saturate when the size of central rapidity window is larger than 4 unit; »PYTHIA underestimate the fluc. in all central rapidity windows; »The contribution of particles in the fragmentation region to the fluc. is negligible.

9. 2. Main results and simple discussions. (D) The correlation between ‹pt›n and n in above central rapidity windows. »This implies that the correlation between〈pt〉n and nis not as closely related to the fluctuations as it was expected. M. Gazdzicki & St. Mrowczynski, Z. Phys. C54, 127(1992); M. Gazdzicki, A. leonidov & G. Roland, Eur. Phys. J. C6, 365(1999).

10. 2. Main results and simple discussions. (E) The dependency of Φpt on the low pt-cut. ▲ NA22 data ∆ PYTHIA » The higher the ptcut , the samller are the fluc.. »The strongest correlation subsample has the smallestΦpt!

11. 3. Summaryand conclusions. • On charge fluc. : • D(Q) depends strongly on the size of the central rapidity window . • Its corrected version well deduce the influence of global charge • conservation and leading-particle stopping. The scaling behavior • is observed when the central rapidity window is wider than 4 • rapidity units. • The same corrections are invalid for charge ratio fluctuations. • D(Q)is a better record in charge fluctuations • On transverse momentum fluc. : • Transverse momentum fluctuation strongly depends on the rapidity • region under consideration. Only the measurements in the whole • central rapidity plateau region are representative for the behavior in • the full rapidity region. • The loss of low-ptparticles due to detector acceptance will significantly • reduce the Φpt measurement. • The correlation between average transverse momentum and multiplicity is not the main origin of the fluctuations.

12. 3. Summaryand conclusions. On PYTHIA : PYTHIA underestimates the transverse momentum fluc. in all logitudinal and samll transverse phase space region, despite of the fact that it can reproduce the correlations between ‹pt›n and n in all rapidity intervals and all the data for charge fluc.. These results show that thedynamical evolutionin longitudinal andtransverse momentum directions arestrongly correlatedin hadron-hadron collisions, which hasnotbeen well taken into account in PYTHIA.

13. Thanks!