1. Tests of beam-beam effects with strong field QED experiments in crystals Ulrik I. Uggerhøj Department of Physics and Astronomy Aarhus University, Denmark

2. Beamstrahlung

3. Electric field from one bunch boosted by 2  2 as seen by particles in the other bunch Small beams, high Lorentz factors => Strong electromagnetic fields => Beam focusing Increase of luminosity Beamstrahlung Beam-beam interaction

4. Synchrotron radiation ’Typical’ fraction of energy radiated classically B photons electrons

5. Beamstrahlung

6. High energy, high luminosity ’Typical’ fraction of energy radiated classically For high energy and high luminosity (unless ’ribbon pulses’ are used):

7. Classical synchrotron-radiation

8. D. Schulte

9. Strong, but partial, suppression compared to classical beamstrahlung

10. From the ’locals’

11. But do we know (i.e. do experiments show) that these formulas are correct?

12. Strong fields Other kinds of motivation…

13. heavy ion collisions Superstrong field, but of short duration E 1s / E 0 =  3 Z 3 Extended nucleus: Z  172

14. Coherent pair production “The total capture cross sections are dominated by electron capture from pair production...”

15. Strong lasers () Strong lasers (  -collisions ) Laser wavelength (and  energy) limited by non-linear Compton scattering χ (or  )  1  -collision scheme (Telnov et al.)

16. Plasma wakefields Transverse focusing forces: Lead to values for realistic parameters:

17. Magnetars B  10 10 T relativistic gyration: ħ  /mc 2 =  B/B 0 Electrosphere of strange stars:  ≈ 5-100 T=0.01 MeV T=15 MeV

18. The strong magnetic field of the Earth

19. Hawking radiation as a strong field effect Gravitatonal acceleration at Schwarzschild radius: g(R S )=c 4 /4GM R S =2GM/c 2 Set equal to critical field acc.: g 0 =e E 0 /m=c 2 / c Light (small) black holes are hotter: c =2R S

20. Beamstrahlung | V Crystals ?

21. What are the invariants? Motion perpendicular to an electric field: Recall:

22. Synchrotron-radiation in a critical field J. Schwinger, 1954 See, e.g. Berestetskii, Pitaevskii, Lifshitz – Quantum electrodynamics

23. Similar situations ? ILC / CLIC Bunch-size: 300  0.6  0.006 μm 3, 2·10 10 particles Density: 0.005 Å -3, 0.6 Å -3 (at IP) Si crystal Density: 0.05 Å -3, of Z = 14 Blankenbecler, Drell (PRD 36, 277 (1987), Quantum treatment of beamstrahlung: ”Pulse transforms into a very long narrow ’string’ of N charges.”

24. Strong fields in crystals

25. Experiments on strong field QED in crystals (CERN NA43 and NA63) J.U. Andersen, H. Knudsen, S.P. Møller, A.H. Sørensen, E. Uggerhøj, U.I. Uggerhøj Department of Physics and Astronomy, Aarhus University, Denmark P. Sona Dipartimento di Fisica, Universitá degli Studi di Firenze, Polo Scientifico, Sesto F.no, Italy S. Connell, S. Ballestrero Schonland Research Institute, Johannesburg, South Africa T. Ketel NIKHEF, Amsterdam, Holland S. Kartal, A. Dizdar Department of Physics, Istanbul University, Turkey A. Mangiarotti Laboratório de Instrumentação e F í sica Experimental de Part í culas, Coimbra, Portugal

26. Strong crystalline fields

27. Crystals Extremely strong electric fields 10 10 -10 11 V/cm 50 V / 0.1 Å = 5·10 10 V/cm Channeling transverse potential

28. ’Super-critical’ fields Relativistic invariant:

29. Formation length High particle energy, low photon energy: Long formation length 250 GeV e -, 1 GeV γ: 0.1 mm

30. NA63 experiment

31. Crystal on goniometer

32. Total length of setup: 65 m => good angular resolution (few μrad)

33. Strong crystalline fields Critical fields can be simulated in a crystal. Example: Radiation emission in diamond (CERN NA43)

34. One of the complications - Setting up within a few days: Electronics, hardware, crystal target….

35. Strong crystalline fields Critical fields can be simulated in a crystal. Example: Pair production in Ge (CERN NA43) Similar results obtained in W and Ir

36. Quantum synchrotron χ << 1

37. Synchrotron-radiation Schwinger, Proc. Nat. Acad. Sci. 1954; Berestetskii, Lifshitz, Pitaevskii

38. Beamstrahlung – synchr.rad. Classical: -> 0 => C b -> infty

39. Quantum-synchrotron Classical = linear (CERN NA43)

41. Beamstrahlung, D. Schroeder

42. Spin-flip

44. ’Polarization time’

45. Similar situations ILC / CLIC Bunch-size: 300  0.6  0.006 μm 3, 2·10 10 particles Density: 0.005 Å -3, 0.6 Å -3 (at IP) Si crystal Density: 0.05 Å -3, of Z = 14 Blankenbecler, Drell (PRD 36, 277 (1987), Quantum treatment of beamstrahlung: ”Pulse transforms into a very long narrow ’string’ of N charges.”

46. Spin contr. to beamstrahlung Blankenbecler and Drell, ”Quantum treatment of beamstrahlung”, PRD 36, 277 (1987) Radiation from crystal C ≈ 1/ χ Spin-flip contribution:

47. Blankenbecler and Drell, ”Quantum treatment of beamstrahlung”, PRD 36, 277 (1987) Spin contr. to beamstrahlung

48. Trident production (electroproduction) ’Coherent pairs’ ’Landau-Lifshitz process’

49. Electroproduction “The probability of photon radiation during beam-beam collision in linear colliders turns out to be of the order of unity and the density of accompanying photons becomes comparable to the density of the charged particles in the colliding beams. At these photons are converted with high probability in electron-positron pairs in the field of the counter-moving beam.”

50. Electroproduction of electron-positron pair in a medium Authors: V. N. Baier, V. M. KatkovV. N. Baier V. M. Katkov arXiv:0805.0456v1 arXiv:0805.0456v1 [hep-ph] Amorphous case Sequential Direct Direct process dominates below 30 GeV

51. Non-aligned crystal JETP Lett.88:80-84,2008 Small multi- hit capability Geometric acceptance

52. Aligned crystal Phys. Lett. A, accepted

53. Summary Experiments in crystals may address today: –Coherent pairs –Electroproduction –Beamstrahlung (radiation) Quantum reduction Spin-flip processes in the >> 1 regime relevant for beamstrahlung in future linear colliders.

54. More about these and related effects in: H.D. Hansen, U.I. Uggerhøj, C. Biino, S. Ballestrero, A. Mangiarotti, P. Sona, T. Ketel and Z.Z. Vilakazi: Is the electron radiation length constant at high energies?, Phys. Rev. Lett. vol. 91, 014801 (2003)Is the electron radiation length constant at high energies? H.D. Hansen, U.I. Uggerhøj, C. Biino, S. Ballestrero, A. Mangiarotti, P. Sona, T. Ketel and Z.Z. Vilakazi: The LPM effect for multi-hundred GeV electrons, Phys. Rev. D vol. 69, 032001 (2004) The LPM effect for multi-hundred GeV electrons U.I. Uggerhøj, H. Knudsen, S. Ballestrero, A. Mangiarotti, P. Sona, T.J. Ketel, A. Dizdar, S. Kartal and C. Pagliarone: Formation length effects in very thin targets, Phys. Rev. D vol. 72, 112001 (2005)Formation length effects in very thin targets H.D. Thomsen, K. Kirsebom, H. Knudsen, E. Uggerhøj, U.I. Uggerhøj, P. Sona, A. Mangiarotti, T.J. Ketel, A. Dizdar, M. Dalton, S. Ballestrero and S. Connell: On the macroscopic formation length for GeV photons, subm. to Phys. Lett. B (2008)On the macroscopic formation length for GeV photons T. Virkus, U.I. Uggerhøj, H. Knudsen, S. Ballestrero, A. Mangiarotti, P. Sona, T.J. Ketel, A. Dizdar, S. Kartal and C. Pagliarone (CERN NA63): Direct measurement of the Chudakov effect, Phys. Rev. Lett. vol. 100, 164802 (2008)Direct measurement of the Chudakov effect J. Esberg, K. Kirsebom, H. Knudsen, H.D. Thomsen, E. Uggerhøj, U.I. Uggerhøj, P. Sona, A. Mangiarotti,, T.J. Ketel, A. Dizdar, M. Dalton, S. Ballestrero, S. Connell (CERN NA63): Addressing the Klein paradox by trident production in strong crystalline fields, in preparation (2008)Addressing the Klein paradox by trident production in strong crystalline fields Thank you for your attention!