Dmitriy Toporkov Budker Institute of nuclear physics Novosibirsk OLYMPUS collaboration meeting

1. Measurement of e+e- scattering cross section ratio off proton Dmitriy Toporkov Budker Institute of nuclear physics Novosibirsk OLYMPUS collaboration meeting DESY 31/08/2010

2. List of participants J. Arringtona, L.M. Barkovb, V.F. Dmitrievb, V.V. Gauzshtajnc , R.A. Golovinb A.V. Gramolinb, R.J. Holta, V.V. Kaminskyb, B.A.Lazarenkob, S.I. Mishnevb, N.Yu. Muchnoib, V.V. Neufeldb, D.M.Nikolenkob, A.V. Osipovc , I.A. Rachekb, R.Sh.Sadykovb, Yu.V.Shestakovb, V.N. Stibunovc , D.K. Toporkovb, H.de Vriesd, S.A.Zevakovb and V.N. Zhilichb. a ANL, Argonne, USA, b BINP, Novosibirsk, Russia, c INP TPU, Tomsk, Russia, d NIKHEF, Amsterdam, The Netherlands Measurement of e+e- scattering cross section ratio off proton

3. Form factor ratio – polarized and unpolarized data Measurement of e+e- scattering cross section ratio off proton

4. The problem caused the appearance of many new theoretical work performed in the various approaches P.A.M. Guichon, M. Vanderhaeghen.Phys. Rev. Lett. 91, 142303 (2003) P.G. Blunden, W. Melnitchouk and J.A. Tjon.Phys. Rev. Lett. 91, 142304 (2003) M.P, Rekalo and E.Tomasi-Gustafson. Eur. Phis. Jour. A22, 331 (2004) Y.C. Chen et al., Phys. Rev. Lett. 93, 122301 (2004) A.V. Afanasev and N.P. Merenkov. Phys. Rev. D70, 073002 (2004) A.V. Afanasev et al..Phys. Rev. D72, 013006 (2005) P.G. Blunden, W. Melnitchouk and J.A. Tjon. Phys. Rev. C72, 034612 (2005) Y.C. Chen et al.. Phys. Rev. C72, 034642 (2005) S. Kondratyuk et al.. Phys. Rev. Lett. 95, 172503 (2005) D. Borisyuk and A. Kobushkin. Phys. Rev. C78, 025206 (2008) N.Kivel and M.Vanderhaeghen. Phys. Rev. Lett. 103 (2009) etc. as well as the suggestions of new experiments for the determination of two-photonexchange contribution through the measurement of Re+/e−ratio, since the old data of 60thare not accurate enough. Novosibirsk/VEPP-3 operated OLYMPUS: DORIS/BLAST data taking 2012 TJNAF/CLAS/PR04-116 Measurement of e+e- scattering cross section ratio off proton

5. How to measure TPE R measures the real part of the two-photon amplitude Measurement of e+e- scattering cross section ratio off proton

6. Measurement of e+e- scattering cross section ratio off proton

7. R = s (e+) / s(e-), E=1600 MeV 10 –12 0.98 0.08–0.11 8.7.106 ---- 19 – 27 0.91 0.26–0.47 3.1.106 0.07 60 – 80 0.40 1.40–1.76 1.5.104 1.00 R/R % ee Q2(GeV/c)2 N+ events q • Systematic errors • Different energy of e+, e- beams (Ds/sfor three intervals 0.1, 0.2, 0.2 % / MeV) • Different position of beams (Ds/sfor three intervals 5.0, 1.4, 0.9 % / mm) • Drift of the efficiency over the time of experiment • Drift of the target thickness during the experiment • Difference of the radiation corrections for electrons and positrons Measurement of e+e- scattering cross section ratio off proton

8. VEPP-3 VEPP-4M COLLIDER, NOVOSIBIRSK VEPP-3 Energy : 2000 MeV Lifetime : 30000 s Av. curren : 100 mA Bunch : 0.7x0.3 mm Measurement of e+e- scattering cross section ratio off proton

9. Schematic side view of the particle detection system Measurement of e+e- scattering cross section ratio off proton

10. Middle angle scattering Large angle scattering Small angle scattering Moller/Bhabha monitor Measurement of e+e- scattering cross section ratio off proton

11. VEPP-3 Straight Section with Internal Target Measurement of e+e- scattering cross section ratio off proton

12. Storage cell cooled by cold head Measurement of e+e- scattering cross section ratio off proton

13. Measurement of e+e- scattering cross section ratio off proton

14. Typical picture of the e+/e− currents in VEPP-3 storage ring during the data taking. Measurement of e+e- scattering cross section ratio off proton

15. Initial current of the e+e- beams during the time of experiment Measurement of e+e- scattering cross section ratio off proton

16. Beam Integral Collected in shifts during the experiment at VEPP-3 Measurement of e+e- scattering cross section ratio off proton

17. Accumulation of integral beam current VEPP-3 during theexperiment. Measurement of e+e- scattering cross section ratio off proton

18. Compton back-scattering energy monitor Measurement of e+e- scattering cross section ratio off proton

19. Back Compton scattering set up for measurement energy of e+/e- beams. Spectrun fragment near wmax Measurement of e+e- scattering cross section ratio off proton

20. Energy of e+/e- beams being measured during one shift with the use of Back Compton scattering monitor E, MeV Positrons Electrons time Measurement of e+e- scattering cross section ratio off proton

21. Energy of e+/e- beams being measured with the use of Back Compton scattering monitor during the experiment Measurement of e+e- scattering cross section ratio off proton

22. Selection of the elastic e-p scattering events Measurement of e+e- scattering cross section ratio off proton

23. Event selection Energy in LA calorimeter Nev LA DATA-blue GEANT4-red DEe/Ee=14% MeV Measurement of e+e- scattering cross section ratio off proton

24. Information on the beams positions comes from: Beam position monitors of VEPP-3. They are located rather far from the target center and give only information on beams stability Four beam scrapers. They are located close to the target and provide information about absolute position of the beams. But they are rarely used because with them data taking should be interrapted Coordinate systems of the detector give the possibility off-line to determine both the horizontal and vertical relative shift of the electron or positron beams with an accuracy of ~ 0.1 mm Measurement of e+e- scattering cross section ratio off proton

25. The measurement of differences in the vertical position of e+/e+ beams on theevents of SA scattering. Nrun Measurement of e+e- scattering cross section ratio off proton

26. Dependence of counting rate of the detectors vs. vertical shift of the beam x102 Nev MA, GEANT4 x102 Nev LA, GEANT4 Measurement of e+e- scattering cross section ratio off proton

27. Dependence of counting rate of SA detector vs. vertical shift of the beam x102 NevSA, GEANT4 Absolute pozition 0.5+-0.2 mm with DZe+/e- = 0.1 mm D(N1+N2)/(N1+N2)=0.12% Measurement of e+e- scattering cross section ratio off proton

28. Raw ratio Re+/e− (no corrections) for MA are monitoring to SA. Preliminary result R=1.00412 +- 0.00094 Measurement of e+e- scattering cross section ratio off proton

29. Raw ratio Re+/e− (no corrections) for LA are monitoring to SA. Q2=1.43 (ГэВ/с)2 e = 0.50 R=1.057 +- 0.011 Preliminary result Measurement of e+e- scattering cross section ratio off proton

30. Radiative corrections Ispecially important for the determination of the difference of the e+e- elastic scattering off proton Measurement of e+e- scattering cross section ratio off proton

31. Born elastic electron vertex correction proton vertex correction vacuum polarization box diagram box diagram crossed-box diagram Measurement of e+e- scattering cross section ratio off proton

32. Bremsstrahlung initial electron radiation final electron radiation final proton radiation initial proton radiation Measurement of e+e- scattering cross section ratio off proton

33. Radiative corrections J. Schwinger, Phys.Rev. 76, 790(1949) D. R. Yennie, S. Frautschi and Suura, Ann.Phys. 13,379(1961) L. M. Mo and Y.S.Tsai, Rev.Mod.Phys. 41,205(1968) L. C. Maximon and J. A. Tjon, Phys. Rev. C, v.62, (2000) 054320 M. Vanderhaeghen et al., Phys. Rev. C, v. 62 (2000) 025501 R. Ent et al. Phys. Rev. C, v.64 (2001) 054610 F. Weissbach et al. Eur. Phys. J. A 30, 477-487 (2006) E. Tomasi-Gustafsson, Phys. of Part. and Nucl. Lett. 2007, Vol. 4, p. 281 Measurement of e+e- scattering cross section ratio off proton

34. Reaction: where k, k’ initial and final lepton four-momenta, p, p’ proton four-momenta, w - photon four-momentum. The total cross section for single-photon bremsstrahlung is given by where is Born electron-proton cross section. The first andthird terms in brackets have different signs in the case of e-pand e+p scattering. Soft Photon Approximation Measurement of e+e- scattering cross section ratio off proton

35. Angular distribution of first order bremsstrahlung photons Soft Photon Approximation Ee = 1.6 GeV Qe = 600 Eg> 100 MeV Qg Measurement of e+e- scattering cross section ratio off proton

36. Radiative corrections with real photons emission integrated over photon angles Ee=1.6 GeV Measurement of e+e- scattering cross section ratio off proton

37. SPA, LA, GEANT4. R dependence vs. cuts More correct calculation of radiative corrections (V.Fadin and A.Feldman,Private communication) with no restriction on the photon energy and proton form factor taken into account will be performed soon Measurement of e+e- scattering cross section ratio off proton

38. Preliminary result for Re+/e− in comparison with calculations of P.G. Blunden etal. e=0.50 Q2=1.43 GeV2 Measurement of e+e- scattering cross section ratio off proton

39. Рicture from Kivel talk PNPI Winter school 09 Measurement of e+e- scattering cross section ratio off proton

40. N. Kivel, private communication(Preprint MKPH-T-10-06) Measurement of e+e- scattering cross section ratio off proton

41. Future plans To apply new radiative corrections Make corrections on the beam’s position To repeat the experiment at the energy of 1000 MeV with larger scattering angle Measurement of e+e- scattering cross section ratio off proton

42. Part of participants 20.11.2009. VEPP-3 Measurement of e+e- scattering cross section ratio off proton

43. Measurement of e+e- scattering cross section ratio off proton

44. Measurement of e+e- scattering cross section ratio off proton

45. Measurement of e+e- scattering cross section ratio off proton

46. Measurement of e+e- scattering cross section ratio off proton

47. Measurement of e+e- scattering cross section ratio off proton

48. Parameters under control during the data taking Measurement of e+e- scattering cross section ratio off proton

49. Measurement of e+e- scattering cross section ratio off proton

50. e+/e scattering off proton at JLab Measurement of e+e- scattering cross section ratio off proton