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Cem Güçlü İstanbul Technical University Physics Department

Production of electron-positron pairs by nuclear dissociation in heavy ion collisons. Cem Güçlü İstanbul Technical University Physics Department. Particle production from E M Fields. * Lepton- pair production * Beam Lifetime (ele c tron capture ) * De t e ctor background

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Cem Güçlü İstanbul Technical University Physics Department

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  1. Production ofelectron-positron pairs by nuclear dissociation in heavy ion collisons Cem Güçlü İstanbul Technical University Physics Department Erice 2008

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

  3. “ 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) Erice 2008

  4. Collision Parameters : Erice 2008

  5. SPS 10 100 120 12 1.6 RHIC 100 10000 12000 1200 160 Relativistic Colliders Erice 2008

  6. Collisions of Heavy Ions Erice 2008

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

  8. Lepton-Pair Production Semi Clasical Action : Free Lagrangian : Interaction Lagrangian : Erice 2008

  9. Four Vector Potentials of the Colliding Ions : Erice 2008

  10. Ion 1 Ion 2 time Pair Production Emits photon Emits photon Erice 2008

  11. Direct and exchange diagrams : Erice 2008

  12. Total Cross Section Erice 2008

  13. Scalar part of EM Fields in momentum space of moving heavy ions Erice 2008

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

  15. Impact Parameter Dependence Cross Sections : Erice 2008

  16. Erice 2008

  17. Erice 2008

  18. Erice 2008

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

  20. Erice 2008

  21. Diagrams which are not included : ( 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 Erice 2008

  22. An example of a diagram which is included Erice 2008

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

  24. One pair production probability Poisson distribution Erice 2008

  25. Erice 2008

  26. Experiments at CERN Super Proton Synchroton SPS Erice 2008

  27. 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). Erice 2008

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

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

  30. Why do we study the reaction ? • 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? Erice 2008

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

  32. 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 Erice 2008

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

  34. Results: Baur at al. : σ = 1.9 mb Erice 2008

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

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

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

  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 5-x I.Mishustin; L. Satarov, HSt; W Greiner; Cold Nuclear Compressionby Vector Attraction of p-bars in medium

  39. 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.! Erice 2008

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