NE X US 3

1. (Basic ideas, baryon production in pp NEXUS+Hydro for AA) Fuming Liu Sergej Ostapchenko Tanguy Pierog Klaus Werner hep-ph/0007198 Physics Reports 350 (2001) 93-289 hep-ph/0102194 Phys. Rev. Lett. 86 (2001) 3506 Hajo Drescher Michael Hladik Joerg Aichelin Marcus Bleicher SUBATECH, Nantes NEXUS 3 Consistent treatment of multiple scattering LOPWDHAB Model

2. Problems with the String Model Approach Particle production in pp scattering via string fragmentation pp ==> 2 strings Strings decay into chains of hadrons Not enough multiplicity fluctuations ==>

3. Two Pairs of strings In general: n pairs of strings

4. Probability of n pairs ? Gribov Regge : Pomeron (= pair of strings) ... 2 / 2

5. String model -- Gribov-Regge String model: first and subsequent pairs are of different nature Gribov-Regge: all Pomerons are identical String model: energy-momentum is properly shared among strings Gribov-Regge: energy-sharing is not considered inconsistent

6. The new approach Aim: connecting properly string model and Gribov-Regge Theory … and the parton model Extending work by Gribov, Kaidalov, Capella ...

7. Basic Features Result of a pp collisions: 2 remnants and n Pomerons (all identical) Pomeron = 2 strings Energy-momentum properly shared Same formalism for particle production and probability calculations

8. Notations Consider parton-parton scattering

9. Symbols: full and dashed line  elastic and cut diagram Very useful for nucleus-nucleus

10. The elastic amplitude: soft hard semihard (one of three) Soft: parameterization - hard: pQCD - semihard: convolution soft/hard

11. Amplitude: Squared amplitude => interference terms: Inelastic scattering in pp: => Symbolic notation

12. Inelastic scattering in AB: (Elastic and inelastic elem. Interactions) Squaring amplitude  sum over many interference terms expressed via cut and uncut elementary diagrams full energy conservation!!

13. Pomeron-Pomeron Interactions  • Diffraction • Screening • Shadowing • Saturation • Increasing mult. fluctuations • Solving F2-tot puzzle

14. Parton language: Consider a cut Pomeron as a succession of parton emissions = parton cascade At high energies, more and more parton cascades contribute They overlap and interact

15. Important consequence Consider the different contributions to inclusive particle production in pp scattering at given rapidity ()  non-factorizable Contribution zero (complete cancellation) factorizable  inclusive cross section is factorizable So does this mean one can hide all these complicated diagrams in a simple measurable function f ?

16. NO - if one is interested in total cross sections: tot = factorizable + non-factorizable diagrams Very important! NO - if one is interested in Monte Carlo applications topological cross sections = factorizable + non-factorizable diagrams Very important! YES - if one is only interested in inclusive spectra

17. Total and elastic cross section in pp Red: complete calculation Blue: calculation without Pomeron-Pomeron interactions Big difference!!! Important contributions from nonfactorizable diagrams

18. Hadronization Multiple scattering theory determines how many Pomerons are involved in each nucleon-nucleon interaction and the momenta of each Pomeron. Then: Pomeron  strings Strings  hadrons

19. From Pomerons to Strings In the multiple scattering theory a dashed line represents a cut Pomeron The complicated hadronic structure is “hidden” What is the precise structure of a cut Pomeron? Pomeron = 2 strings

20. pp scattering: 1 Pomeron 2 Pomerons etc Projectile remnant q, q-bar or qq qq-bar (sea quarks) strings Target remnant Crucial: separation of Pomerons and rennants otherwise completely wrong baryon yields (FM Liu, M Bleicher, J Aichelin, T. Pierog, KW et al)

21. Baryon ratios in pp at 158 GeV 3

22. Why does the conventional string model give more antiomegas than omegas? A string end flavor u or d prevents the production of omegas NEXUS : projectile/target flavor is in the remnants not in the strings

23. Baryon spectra in pp at 158 GeV Leading particles (mainly from remnants) Theory: NEXUS (FM Liu et al) Data: NA49

24. Theory: NEXUS (FM Liu et al) PYTHIA (Sjostrand et at) Data: NA49

25. Other hadrons

26. Energy dependence charged pions kaons antiprotons Spectra at low energies?

27. Nucleus-nucleus collisions: particle densities are too high for independent string fragmentation NEXUS + Hydro • Use NEXUS for the initial stage (0) • Calculate energy density and velocity field at =0 • Apply hydro evolution for 0 Efficient hydro code = SPHERIO C.E. Aguiar, T. Kodama U.F. Rio de Janeiro T. Osada,Y. Hama U. São Paulo Coupling: O. Socolowski, KW Nantes

28. NEXUS generates partons (from cut Pomerons) so one may calculate (x) and v(x) of partons BUT: soft part ignored Better: Pomerons  partons  strings  (x) and v(x)

29. Preliminary result NEXUS 3 optimised for pp (mainly 100-200GeV) + SPHERIO default

30. Summary Considerable improvement of the GRT approach by considering energy conservation properly Pomeron-Pomeron interactions are crucial but contribute differently for inclusive spectra and cross sections Multi-strange baryon production in pp understood Final stage: hydro-evolution first results for RHIC