Few-body studies at HI g S

1. Few-body studies at HIgS Sean Stave Duke University & Triangle Universities Nuclear Laboratory (TUNL) And Mohammad Ahmed, Henry Weller Supported in-part by DOE grant DE-FG02-97ER41033 www.tunl.duke.edu www.tunl.duke.edu/higs/

2. Few-body experiments at HIgS Exploring A=2 and 3 Photodisintegration of the Deuteron & 3He • Importance • Theoretical understanding of A=2,3 systems • Global state of the experiments • The role HIGS plays in the understanding of these systems • What is on the horizon for HIGS

3. Overview of A=2 The Deuteron Fundamental Sum Rules The BBN Importance Ideal Laboratory for the study of 2-body NP system “Baryometer” • Test of EFT and PM • Calculations d Target Beam d

4. Understanding Few-Nucleon Systems 2H, the simplest of Few-Body Systems The Theoretical Framework, A=2 • Potential Model • Effective Field Theory • Sum Rules for Deuteron: • Gerasimov-Drell-Hearn (GDH) & • Forward Spin Polarizability (g0)

5. The A=2 Theoretical Framework Potential Model Calculations [H. Arenhovel, M. Schwamb et al.] • High precision NN-potentials, MEC, RC and D degrees of freedom The Pion-less Effective Field Theory Approach (EFT) [M. Savage, J-W. Chen & G. Rupak] • E1 is computed up to N4LO and M1 is calculated up to N2LO, • n-p radiative capture cross section predicted to an accuracy of • 1% at CM energies ~ 1 MeV Most accurate theory describing 2-Nucleon system, Minimal data exist to test the predictions in this energy region

6. The Experimental Effort at HIgS Few-Body Studies at TUNL are carried out at HIgS Duke Free-Electron Laser Laboratory (HIgS)

7. HIgS g-ray beam generation RF Cavity Optical Klystron FEL Booster Injector Mirror LINAC High Intensity Gamma-Ray Source:

8. HIgS Parameters • Circularly and Linearly Polarized nearly monoenergetic g-Rays • from 2 to 60 MeV (90 MeV in the next 1 to 2 years) • Total Gamma-Ray Flux ~ 108 to 109g/s

9. A=2 Experiments at HIgS • S(135°) Eg = 3.58 MeV Eric Schrieber et al., 2000 • S(90°) Eg = 2.39 to 4.05 MeV Werner Tornow et al., 2003 • s(q); S(q) Eg = 4 to 10 MeV Brad Sawatsky et al., 2005 • S(90°) Eg = 2.44 to 4.0 MeV Mohammad Ahmed et al., 2007 • s(q); S(q) Eg = 14 and 16 MeV Matthew Blackston et al., 2007 • s(q); stotalEg = 2.44 to 4.0 MeV Mohammad Ahmed et al., 2008 All experiments were performed using linearly polarized beams Liquid Scintillating Detectors in Blowfish Array Li-Glass Detectors in an Array Liquid Scintillating Detectors Schreiber Tornow Sawatsky Blackston Sawatsky Blackston Ahmed

10. Status of the “baryometer” • Very little data in energy region for BBN

11. d(g,n)p Cross section Expansion Polarized beam, unpolarized target (M1) (E1) Photon analyzing power measurement is proportional to the %E1 contribution to the total cross section

12. A=2 Results at HIgS Tornow et al. [PLB 574, 8 (2003)] Excellent agreement between data and PM and EFT 4-neutron detectors at a polar angle of 90 degrees and azimuthal angles of 0,90,180, and 270 degrees PRC 61, 061604 (2000) Curves from EFT (Rupak et al.)

13. d(g,n)p at HIgS: Ahmed et al. No significant d-wave contributions are present at these low energies 4.0 MeV 3.5 MeV 2.44 MeV

14. Sum Rules for the Deuteron Spin-flip part of forward Compton scattering amplitude: GDH : Arenhoevel et al.

15. GDH on the deuteron: Theory With relativistic corrections Without relativistic corrections Negative at low energies Crosses zero at low energies Arenhoevel et al. [NPA 631, 612c (1998)]

16. Cross section difference expansion Polarized beam, polarized target ] If ignore d-waves and splitting of p-waves at low energies then

17. A=2 Global Impact First-ever indirect determination of the GDH Sum Rule for Deuteron at low energies: -603 ± 43 mb (Fit from thr. to 4 MeV, integrated from thr. to 6 MeV) Remember Ds =-3s(M1) Ahmed et al. [PRC 77, 044005 (2008)]

18. A=2 GDH Comparison: Data and Theory • Theory and Data integrated from threshold to 6 MeV • Data: -603 ± 43 mb • Arenhoevel: -627 mb • -3sM1: -662 mb • Experimentally confirmed negative value at low energy Ahmed et al. [PRC 77, 044005 (2008)]

19. A=2 Results at HIgS Blowfish • 88-cell Liquid Scintillating • detector array • 25% of 4p coverage • q = 22.5 to 157.5 degrees

20. d(g,n)p: Weller/Blackston’s Results Blackston et al. [PRC 78, 034003 (2008)] 16 MeV • Cross section and analyzing power at 16 MeV as a function of angle compared with Schwamb/Arenhoevel potential model • High quality of data allowed a fit using 7 reduced transition matrix element amplitudes (phases fixed by np elastic scattering, SAID)

21. d(g,n)p: Weller/Blackston’s Results 16 MeV First-ever observation of the splittings of the E1 (p-wave) amplitudes in low energy deuteron photo-disintegration [PRC 78, 034003 (2008)] Note: d-wave results negligible and consistent with theory Value if no p-wave splitting Compared with Schwamb/Arenhoevel Potential Model

22. A=2 Global Impact First-ever observation of the p-wave splittings and confirmation of the relativistic corrections in the theory [PRC 78, 034003 (2008)]

23. Sum Rules for the Deuteron Spin-flip part of forward Compton scattering amplitude: Forward Spin-Polarizability: NLO, EFT calculation by X. Ji et al.

24. A=2 g0 Comparison: Data and Theory First-ever indirect determination of g0 for deuteron at low energies Data integrated from threshold to 6 MeV • Data: 3.75 ± 0.18 fm4 • Ji-LO: 3.762 fm4 • Ji-NLO: 4.262 fm4 • Arenhoevel: 4.1 fm4 Ahmed et al. [PRC 77, 044005 (2008)]

25. What is our understanding of Few-Nucleon systems? 3He, the simplest of Few-body Systems with 3NF and no excitation spectrum System being considered • 3He breakup • Two-body • Three-body

26. The A=3 Experiments at HIgS • Photodisintegration of 3He between 7 and 20 MeV • Total and differential Cross Section • Total cross section for the 2-body breakup from 7 to 20 MeV, • Tornow et al. • Total and differential cross sections for the 3-body breakup, • 12.8, 13.5, and 14.7 MeV, Perdue et al.

27. The A=3 Theoretical Framework Recent efforts in understanding 3-body systems [Deltuva, Fonseca, Sauer] • Coulomb Interaction in the 2- and 3-body • photodisintegration channels • CD-Bonn + D, with D isobar mediating an effective 3NF and • 2-, 3-nucleon currents, and still consistent with 2NF • Still has issues at low-energies (3 Nucleon Analyzing Power Puzzle still stands!) The problem is also being worked upon by [Witala, Glockle, Nogga, and Golak, et al.]

28. Current Status of the 3He breakup cross section Shima & Nagai [PRC 73, 034003 (2006)] Compared with previous data and AV18 and AV18+Urbana IX 2-body • No measurement that is consistent across the energy range • Clearly calls for a set of measurements with the same experimental conditions across the energy range 3-body total Factor of 3 below theory

29. A=3 at HIgS: 2-body breakup of 3He, Tornow et al. • High Pressure 3He/Xe cell Data are still under analysis for absolute normalization Two-body peaks clearly separated

30. 3He 3-body Breakup at HIgS: Weller, Perdue et al. 12.8, 13.5, and 14.7 MeV

31. 3He 3-body Breakup: Theoretical Framework No coulomb interaction With coulomb interaction No sensitivity to coulomb interaction in the analyzing power Deltuva et al. [PRC 72, 054004 (2005)]

32. Weller, Perdue et al. Initial Results From an APS talk by B. Perdue - HIgS Data - Deltuva - 3-body phase space • Phase-Space (PS) to • PS + NP transition near • 12.8 MeV • About 25% below theory

33. Summary What have we accomplished? • Confirmation of PM/EFT for the deuteron near BBN region • First determination of the splitting of the p-waves in the • photodisintegration of the deuteron • First confirmation of GDH sum rule for the deuteron • Confirmed large negative strength • Confirmed positive going above 8 MeV and that it arises fromthe splitting of the p-waves • First determination of the g0 sum rule for deuteron • Precision 3-body photodisintegration cross section for 3He • disagree with state-of-the-art theory at low energies

34. Future plans at HIgS New era of precision measurements at HIgS - PAC-09 has approved the following experiments for the next two years: • Continue to measure deuteron photodisintegration cross section • at lower energies (below 2.4 MeV) (Using OTPC) • Direct measurements of the GDH on deuteron • Compton scattering on the deuteron • Measurement of two- and three-body cross sections of g + 3He • GDH Sum rule for 3He • Cross section measurement of g + 4He

35. Acknowledgments • Calvin Howell et al. • Werner Tornow et al. • Henry Weller et al. • Ying Wu et al. Thank you!

36. Additional slides

37. Weller, Perdue et al. Initial Results • Results from Gorbunov (1976) coarsely binned but consistent with current results 8-12 MeV 12-16 MeV A. N. Gorbunov, Proc. Of the P.N. Lebedev Phys. Inst., p. 1 (1976)

38. A=2 Introduction ( ( ( ( ( ( ) ) ) ) ) ) d d d n n p γ p n p p γ , , , , , , Few-Nucleon Systems and BBN Network Light-element abundances depends on WMAP determines and11 nuclear reaction rates n-p capture reaction rate becomes a “baryometer”

39. Understanding the photodisintegration of the deuteron In 1936, H. A. Bethe and R. F. Bacher wrote … “… the transition from the ground state to the state of positive energy . . . can be produced by a magnetic moment, this ‘magnetic dipole’ photoelectric effect is, however, small compared to the ‘electric dipole’ effect …, except for very low energies . . . the final state must be a P-state” [ Rev. Mod. Phys. 8, 82-229 (1936) ]

40. The A=2 Experiments at HIgS In the near-threshold region, the photodisintegration cross section can be expanded in terms of S and P wave amplitudes. We can ignore the D-waves and The P-wave splittings (evidence will be presented soon) : Bethe, 1936 Photon analyzing power measurement is proportional to the %E1 contribution to the total cross section

41. A=2 Global Impact (Ahmed et al.) • First-ever indirect determination of g0 for deuteron at low energies Ahmed et al. [PRC 77, 044005 (2008)]