Sixth International Conference on Perspectives in Hadronic Physics

1. Sixth International Conference on Perspectives in Hadronic Physics Hard Photodisintegration of a proton Pair E. Piasetzky Tel Aviv University, Tel Aviv, Israel 12 - 16 May 2008(Miramare - Trieste, Italy)

2. Kinematics : n/p d/pp d/pp n/p p p LAB CM photodisintegration is an efficient way to reach the hard regime. To obtain the same s in NN scattering Pp ~ 2 Pγ.

3. p p d n Electron Photon n Radiator High – energy photodisintegration of the deuteron The bremsstrahlumg endpoint technique: It is enough to measure the proton momentum vector The incident photon energy The recoil neutron kinematics Assuming two-body reaction To ensure two-body reaction the reconstructed photon energy Is limited to the endpoint – the π mass

4. p Electron Photon Radiator n d HRS 3He p Backgrounds are subtracted by “radiator out” and empty target runs Build in quality-control – empty region beyond the endpoint

5. scaling For N = 1 + 6 + 3 + 3 – 2 = 11 Notice: Exclusive large-momentum-transfer scattering • Dimensional(Constituents) counting rule:

7. Δ(1232) N*(1520)D13 ?

8. Leading orderpQCD underestimates cross sections for intermediate energy photo - reactions Deuteron elastic form factor Farrar, Huleihel, Zhang PRL 74, 650 (1955) FF (Q2 = 4 GeV2) calculation/data < 10-3 Meson photoproduction Farrar, Huleihel, Zhang NP B 349, 655 (1991) Real Compton scattering Brooks, Dixon PRD 62 114021 (2000) (pQCD  scaling scaling --\ pQCD )

9. d p n Theoretical models: How the photon is coupled What diagrams can be neglected The observation of the scaling indicates the onset of the quark – gluon degrees of freedom, the appropriate underlying physics is not Leading order perturbative QCD. Millions of diagrams like this How to use experimental data to replace sum over many diagrams

10. F (p) F (p) F (n) F (n) d p n RNA (Reduced Nuclear Amplitude) Brodsky , Hiller PRC 28, 475 (1983) Experimental nucleon FF  gluon exchanges within the nucleons Neglect diagrams with gluon exchanges between the nucleons Photon can interacts with any quarks

11. F (p) F (p) F (n) F (n) d p n TQC (Two - Quark Coupling) Radyushkin gluon exchanges within the nucleons  Experimental nucleon FF gluon exchanges between the nucleons  neglected Photon interacts with the exchange pair of quarks

12. d p n HRM (Hard rescattering Model) Frankfurt, Miller, Sargsian, Strikman PRL 84, 3045 (2000). Convolution of large angle pn scattering amplitude , hard photon – quark interaction vertex, and low momentum nuclear wave function The pn scattering amplitude is obtained from large angle pn data

13. Quark – Gluon String model (QGS) Grishina et al. EUR. J. Phys. A 10, 355 (2000) 3 q exchange with an arbitrary number of gluon exchanges Regge theory - nonlinear trajectory

14. See M. Sargsian talk F) F F F N N g d d p n RNA p d n HRM QGS CQM See Sargsian talk

15. How are such large transverse - momentum nucleons produced ? But comparing calculations with the data do not reveal the underlying physics. Breaking a transverse compact object formed before the absorption ? RNA Double hard scattering ? HRM

16. Hard Photodisintegration of a proton pair What new can we learn from that? Howare such large transverse momentum nucleons produced ? Transitions from meson exchange to quark exchange Scaling Oscillations

17. p Electron Photon Radiator p High – energy photodisintegration of a proton pair in 3He The bremsstrahlumg endpoint technique 3He HRS p n p a spectator neutron kinematics. Experiment E03-101 HRS JLab. June 2007

18. Experiment E03-101 Experimental setup Jefferson Lab 0.8-6 GeV A B C Hard photodisintegration of a proton pair

19. Experiment E03-101 Experimental setup Experimental Hall A HRS HRS Beam line Hard photodisintegration of a proton pair

20. 3He cryotarget Electrons Experiment E03-101 Experimental setup Target Chamber Photons Radiator Copper foils 1-6% r.l Hard photodisintegration of a proton pair

21. Backgrounds are subtracted by “radiator out” and empty target runs With radiator No radiator Build in quality-control – empty region beyond the endpoint counts Radiator in Radiator out Beam energy

22. 3He p p n p p Correcting for the finite acceptance of the second spectrometer Simulation assumes photon energy distribution based on Matthews and Owens NIM 111, 157-168 (73). Neutron momentum distribution based on 3He Wave function of R. Schiavilla, et al., PRL. 98, 132501 (2007), and references therein.

23. HRS_right HRS_left simulation Momentum of the proton [MeV/c] Momentum of the proton [MeV/c] data HRS_right HRS_left angle of the proton [Deg.] angle of the proton [Deg.] Target position [mm] Momentum of the neutron [MeV/c]

24. MC 100% DATA 100% MC 2.1% DATA 2.9% Δ/D=-37% MC 5.9% DATA 5.1% Δ/D=12.5% MC 5.4% DATA 6.4% Δ/D=-19% MC 8.6% DATA 10.9% Δ/D=-28% MC 13.6% DATA 11.9% Δ/D=13% MC 16.3% DATA 16.6% Δ/D=-1.5% MC 13.5% DATA 15.3% Δ/D=-13% MC 19.7% DATA 18.8% Δ/D=5% MC 13.6% DATA 11.9% Δ/D=12.5% Box number We (temporarily) assigned an extrapolation error of 15% to the data

25. p p p p Expected Results Magnitude of pp vs. pn hard photodisintegration At low photon energy MEC is the dominant process pp pair : only a neutral pion can be exchanged , its coupling to the photon is weak. Laget NP A497 (89) 391, (Saclay data).

26. Expected Results See M. Sargsian talk Normalized to deuteron Absolute for 3He

27. ? 10 1 Expected Results What are the relevant degrees of freedom ? In contrast to low energy observations, nonperturbative models predict a large cross section for the pp break up. This is an indication for quark – gluon dynamics The energy dependence of the pp/pn break up can map the transition from hadronic to quark – gluon domain The exchange particles in the diproton photodisintegration reaction are: Neutral at low energies where meson exchange dominates. Charged at high energy where quark exchanges dominate.

28. Preliminary Results N*(1675)D15, N*(1680)F15 Δ(1620)S31, N*(1650)S11 Δ(1230) preliminary preliminary The new data were normalized to the preliminary CLAS data !

29. Preliminary Results N*(1675)D15, N*(1680)F15 Δ(1620)S31, N*(1650)S11 Δ(1230) preliminary The new data were normalized to the preliminary CLAS data !

30. Δ(1230) Preliminary Results N*(1520) Δ(1230) Δ(1620)S31, N*(1650)S11 N*(1675)D15, N*(1680)F15 Δ(1230) preliminary

31. Preliminary Results

32. Outlook ? ? Improved statistic

33. Outlook We can utilize the recoil neutron to study how such large transverse- momentum nucleons are produced. α=( E - PZ) / m Breaking a transverse compact object formed before the absorption ? RNA Double hard scattering ? HRM Physics Letters B 578 (2004) 69–77

34. scaling γ p n αn 1 p αn 1 γ p p n ±3% HRM, α(1-1.2) / α(0.8-1) ±1 Verify the scaling for another hard exclusive reaction Extend the verification of photodisintegrartion scaling α=( E - PZ) / m Utilize the recoil neutron to study scaling

35. Outlook energy oscillation If HRM is valid (see Sargsian talk) and photodisintegration amplitude can be factorized Hard photodisintegration data can be related to NN scattering data

36. We also have data Outlook

37. Acknowledgment Physics Letters B 578 (2004) 69–77 “Hard Photodisintegration of a Proton Pair in 3He” Brodsky, Frankfurt, Gilman, Hiller, Miller,Radyushkin, Piasetzky, Sargsian, Strikman Experiment E03-101 collaboration Hall A / JLab. Spokespersons: R. Gilman, E. Piasetzky Graduate student: Ishay Pomerantz (Tel Aviv University) Theoretical support : M. Sargsian

43. p n HRS 3He γ p

44. p 3He γ p n p p High – energy photodisintegration of a proton pair in 3He HRS HRS