1. Nuclear Size Fluctuations in Nuclear Collisions V.Uzhinsky, A.Galoyan The first RHIC result – Large elliptic flow of particles

2. Hydrodynamic model Nucleus is a quantum mechanical system. How can one consider quantum fluctuations? Especially size fluctuations.

3. Idea - A nucleus is a superposition of homogeneous spheres!

4. Pb-208, R Pb =5.3 fm

5. Size fluctuations are rather large! They must be taken into account in hydrodynamic calculations. AGS SPSRHIC Mid-rapidity elliptic flow measurements from various energies and centralities combined in a single plot of v2 divided by relevant initial spatial eccentricity vs. charged-particle rapidity density per unit transverse area in the A + A overlap region. The figures, taken from Ref. [100], highlight the smooth behavior of flow vs. energy and centrality. The rightmost points represent near-central STAR results, where the observed v2/ ǫ ratio becomes consistent with limiting hydrodynamic expectations for an ideal relativistic fluid. The hydrodynamic limits are represented by horizontal lines [100] drawn for AGS, SPS and RHIC energies (from left to right), for one particular choice of EOS that assumes no phase transition in the matter produced.

6. STAR NA 49 Where can it be used? What processes are dominated in high multiplicity events – multiple fluctuations in elementary (NN) collisions, or interactions of compact objects? Sizes of interacting nuclei can be an essential parameter as the impact parameter.

7. Glauber approach

8. Size of a nucleus? Standard Monte Carlo techniques 1)Sample nucleon coordinates according to the density; 2)Take center-of-mass correlations into account: Shift center of mass of generated set to zero; Sample for half of nucleons and ascribe to other half

9. One-half Shift

10. One-half Shift

11. How can one simulate uniform distribution? Standard procedure +/- CM correlations

12. INTERACTIONS

13. A=44 A=216 Lattice nucleus N.D. Cook, T. Hayashi, Lattice model for quark, nuclear structure and nuclear reaction studies, J.Phys. G23: 1109-1126, 1997

14. Weighted simulation

15. Conclusion 1.It is shown that nuclear size fluctuations are quite strong. They must be taken into account in hydrody- namic model. 2.According to the Glauber theory in ordinary approach the average nuclear size changes within 6-10 % in AA-interactions. 3.New method of weighted simulation of nucleus- nucleus interactions with high multiplicity of intra- nuclear collisions is proposed. 4.It is shown that in high multiplicity events nuclei with small sizes play essential role. 5.Effects of nuclear structure, especially nuclear size fluctuation, can be very important in nucleus-nucleus interactions with high multiplicity! (Multi-nucleon correlations)

16. PP-interaction P n jet =? A.Sissakian, J.Manjavidze P n jet > O(e -n ) (condensation) P n jet = O(e -n ) (Hard QCD) P n jet < O(e -n ) (Peripheral