1. September 23, 2008 Erice 2008 1 Cem Güçlü İstanbul Technical University Physics Department Production of electron-positron pairs by nuclear dissociation in heavy ion collisons

2. September 23, 2008Erice 20082 Particle production from EM Fields * Lepton-pair production * Beam Lifetime (electron capture) * Detector background * Non-perturbative and perturbative approach * Impact parameter dependence * Multi-pair production * Test of QED at high fields

3. September 23, 2008Erice 20083 “ The central and peripheral collisions of relativistic heavy ions may be compared to the case of two potential lovers walking on the same side of the street, but in opposite directions. If they do not care, they collide frontally... It could be a good opportunity for the beginning of strong interactions between them....On the other hand, if they pass far from from each other, they can still exchange glances ( just electromagnetic interactions!), which can even lead to their excitation....the effects of these peripheral collisions are sometimes more interesting than violent frontal ones. “ G. Baur and C.A. Bertulani Physics Reports 163, 299, (1989)

4. September 23, 2008Erice 20084 Collision Parameters :

5. September 23, 2008Erice 20085 Relativistic Colliders SPS RHIC 10 100 120121.6 10000120001200160

6. September 23, 2008Erice 20086 Collisions of Heavy Ions

7. September 23, 2008Erice 20087 Dirac wave-function of electrons/positrons Electromagnetic vector potential Electromagnetic field tensor

8. September 23, 2008Erice 20088 Lepton-Pair Production Semi Clasical Action : Free Lagrangian : Interaction Lagrangian :

9. September 23, 2008Erice 20089 Four Vector Potentials of the Colliding Ions :

10. September 23, 2008Erice 200810 time Ion 1 Ion 2 Emits photon Pair Production

11. September 23, 2008Erice 200811 Direct and exchange diagrams :

12. September 23, 2008Erice 200812 Total Cross Section

13. September 23, 2008Erice 200813 Scalar part of EM Fields in momentum space of moving heavy ions

14. September 23, 2008Erice 200814 SPS, γ=10, Au + Au, σ=140 barn RHIC, γ=100, Au + Au, σ=36 kbarn LHC, γ=3400, Pb + Pb, σ=227 kbarn RHIC, γ=100, Au + Au, σ=83 barn LHC, γ=3400, Au + Au, σ=161 barn Pb + Pb, σ=206 barn Free electron-positron pair production Bound- free electron-positron pair production

15. September 23, 2008Erice 200815 Impact Parameter Dependence Cross Sections :

16. September 23, 2008Erice 200816

17. September 23, 2008Erice 200817

18. September 23, 2008Erice 200818

19. September 23, 2008Erice 200819 Two Photon Method : Equivalent Photon Method: M. C. Güçlü, Nucl. Phys. A, Vol. 668, 207-217 (2000)

20. September 23, 2008Erice 200820

21. September 23, 2008Erice 200821 ( a ) Interaction between the created lepton and anti-lepton ( b ) Interaction of the created leptons with the EM fields of heavy ions ( c ) Fermion loops only which have exactly two vertices attached to each of the ions are included ( d ) Not included Diagrams which are not included :

22. September 23, 2008Erice 200822 An example of a diagram which is included

23. September 23, 2008Erice 200823 Güçlü M.C. et al, Annals of Physics, 272, 7-48 (1999)

24. September 23, 2008Erice 200824 One pair production probability Poisson distribution

25. September 23, 2008Erice 200825

26. September 23, 2008Erice 200826 Experiments at CERN Super Proton Synchroton SPS

27. September 23, 2008Erice 200827 Energy = 200 A GeV at fixed target frame Measured Cross Section for 1-17 MeV /c positron yield with 25% error for 1-17 MeV /c positron For all positron momenta Vane CR at al. Phys. Rev. A 50:2313 (1994).

28. September 23, 2008Erice 200828 What about experiments at SOLENOIDAL TRACKER ( STAR ) ? RHIC: Relativistic Heavy Ion Collider Energy =100 GeV/nucleon Au + Au collisions Circumference = 2.4 miles

29. September 23, 2008Erice 200829 Cross Section of electron-positron pairs accompanied by nuclear dissociation Giant Dipole Resonance

30. September 23, 2008Erice 200830 Why do we study the reaction ? 1.The test of QED at high fields – are there indications that at the available energies more than two photons are involved in an electron-positron pair creation? 2. Is pair production is independent of photonuclear excitation?

31. September 23, 2008Erice 200831 No hadronic probability, computed with Woods-Saxon nuclear form factor

32. September 23, 2008Erice 200832 Probability of mutual Coulomb nuclear excitation with breakup as a function of impact parameter G. Baur at al. Nuclear Physics A 729 (2003) 787-808

33. September 23, 2008Erice 200833 Rapidity: Invariant mass: Transverse momentum : Kinematic restrictions at STAR experiment Adams J. At al. Phys. Rev. A 63:031902 (2004)

34. September 23, 2008Erice 200834 Results: Baur at al. : σ = 1.9 mb

35. September 23, 2008Erice 200835 Adams J. At al. Phys. Rev. A 63:031902 (2004)

36. September 23, 2008Erice 200836 Adams J. At al. Phys. Rev. A 63:031902 (2004)

37. September 23, 2008Erice 200837 FAIR - Facility for Antiproton and Ion Research Completed in 2016 Cost : 1.2 billion Euro QED Strong Fields Ion -Matter Interactions

38. Flair @ FAIR: Research Topics with Low-Energy Antiprotons fundamental interactions - CPT (antihydrogen, HFS, magnetic moment) - gravitation of antimatter  atomic collision studies - ionization - energy loss - matter-antimatter collisions  anti- protonic atoms - formation - strong nuclear interaction and surface effects - trapping anti- protons in nuclei: short lived bound states? Later perhaps: Low Energy Anti- He Flair @ FAIR: Research Topics with Low-Energy Antiprotons fundamental interactions - CPT (antihydrogen, HFS, magnetic moment) - gravitation of antimatter  atomic collision studies - ionization - energy loss - matter-antimatter collisions  anti- protonic atoms - formation - strong nuclear interaction and surface effects - trapping anti- protons in nuclei: short lived bound states? Later perhaps: Low Energy Anti- He  x   I.Mishustin; L. Satarov, HSt; W Greiner; Cold Nuclear Compression by Vector Attraction of p-bars in medium

39. September 23, 2008Erice 200839 CONCLUSIONS: 1. We have obtained impact parameter dependence of lepton-pair production probability by using the semi-classical two photon method. 2. At SPS and RHIC energies, Monte Carlo QED calculations agree well with the experimantal results. 3. Can we use this method to calculate the production of other particles such as mesons, heavy leptons, may be Higgs particles ? 4. Can RHIC be used to test QED? NO… Wait for FAIR… 5. Cross section for bound-free pair production is very large and this will limit the maximum Pb-Pb luminosity at the LHC. Therefore we should understand these QED effects to a high degree of accuracy. Thank you for your attention.!