1. Andrzej Rybicki, Kraków, 6 Feb 2007 Strong and Electromagnetic Interactions in Heavy-Ion Collisions Andrzej Rybicki Dept. of Ultrarelativistic Nuclear Physics in collaboration with: Antoni Szczurek, Andrzej Górski Dept. of Strong Interactions and Mechanisms of Nuclear Reactions H. Niewodniczański Institute of Nuclear Physics of the Polish Academy of Sciences, Kraków 1)Introduction 2)Experimental results 3)Theory 4)Conclusions

2. Andrzej Rybicki, Kraków, 6 Feb 2007 Introduction: heavy-ion collisions Proton What is the nature of the strong force? Nucleus

3. Andrzej Rybicki, Kraków, 6 Feb 2007 Wounded Nucleons What is the nature of the strong force? Nucleus Spectator system Produced particles ( mesons ) Introduction: heavy-ion collisions Proton

4. Andrzej Rybicki, Kraków, 6 Feb 2007 What is the nature of the strong force? Nucleus Spectator system Pb+Pb s N+N = 17 GeV Introduction: heavy-ion collisions Produced particles ( mesons ) Proton Wounded Nucleons

5. Andrzej Rybicki, Kraków, 6 Feb 2007 NA49 @ CERN SPS (SPS = Super Proton Synchrotron) The Geneva Lake LEP/LHC CERN Pb beam, 158 GeV/N SPS

6. Andrzej Rybicki, Kraków, 6 Feb 2007 NA49 @ CERN SPS (SPS = Super Proton Synchrotron) CERN The Geneva Lake LEP/LHC Pb beam, 158 GeV/N SPS NA49

7. Andrzej Rybicki, Kraków, 6 Feb 2007 Experimental Results

8. Andrzej Rybicki, Kraków, 6 Feb 2007 x F = 0.05 Pb+Pb x F = 0.10 Pb+Pb x F = 0.15 Pb+Pb x F = 0.20 Pb+Pb x F = 0.25 Pb+Pb A.Rybicki, to appear in Int. J. Mod. Phys. A, 2007 NA49 Preliminary Produced m /m N = 0.15

9. Andrzej Rybicki, Kraków, 6 Feb 2007 A.Rybicki, to appear in Int. J. Mod. Phys. A, 2007 NA49 Preliminary Produced x F = 0.05 Pb+Pb x F = 0.10 Pb+Pb x F = 0.15 Pb+Pb x F = 0.20 Pb+Pb x F = 0.25 Pb+Pb m /m N = 0.15

10. Andrzej Rybicki, Kraków, 6 Feb 2007 A.Rybicki, to appear in Int. J. Mod. Phys. A, 2007 NA49 Preliminary Produced Coulomb repulsion ( for ) and attraction ( for ) m /m N = 0.15 x F = 0.05 Pb+Pb x F = 0.10 Pb+Pb x F = 0.15 Pb+Pb x F = 0.20 Pb+Pb x F = 0.25 Pb+Pb

11. Andrzej Rybicki, Kraków, 6 Feb 2007 Theory

12. Andrzej Rybicki, Kraków, 6 Feb 2007 t = t E Model of peripheral collision: the spectator systems are modelled as two spheres; the pion emission region is reduced to a single point in space; the emission time t E is a free parameter. A.Rybicki, A.Szczurek, nucl-th/0610036, to appear in PRC, 2007 A.Szczurek, A.Rybicki, A.Górski, nucl-th/0701056, to appear in J. Phys. G, 2007

13. Andrzej Rybicki, Kraków, 6 Feb 2007 xF xF 25 MeV/c 75 MeV/c 125 MeV/c 175 MeV/c 325 MeV/c p T = t E = 0 fm/c t E = 1.5 fm/c t E = 1 fm/c t E = 0.5 fm/c t = t E Strong dependence on initial conditions Model of peripheral collision:

14. Andrzej Rybicki, Kraków, 6 Feb 2007 Conclusions The interplay between strong and electromagnetic interactions results in visible distortions of the ratios measured in high energy heavy-ion collisions. These distortions bring new information on the dynamics of the collision.

15. Andrzej Rybicki, Kraków, 6 Feb 2007 Acknowledgements This work was supported by the Polish State Committee for Scientific Research under grant no. 1 P03B 097 29.