1. Compton Scattering at HIGS with Polarized Photons George Washington University  George Washington University  Jerry Feldman  Mark Sikora  Duke University/TUNL Luke Myers  Luke Myers  Henry Weller  Mohammad Ahmed  Jonathan Mueller  Seth Henshaw Compton@HIGS Collaboration  University of Kentucky  Mike Kovash

2. Outline What (and where) is HIGS?  What (and where) is HIGS? What have we done so far at HIGS?  What have we done so far at HIGS?  polarized Compton scattering study of IVGQR  elastic Compton scattering on 6 Li high energy (60-86 MeV) and low energy (3-5 MeV) What are we planning to do at HIGS?  What are we planning to do at HIGS?  elastic Compton scattering on deuterium neutron polarizability  polarized Compton scattering on proton proton electric polarizability  double-polarized Compton scattering on proton proton spin polarizability

3. Background Information on HIGS

4. United States

5. North Carolina

6. Duke University

7. TUNL HIGS TUNL Triangle Universities Nuclear Laboratory

8. Duke Free-Electron Laser Lab

9. Storage Ring and Booster Circularly and linearly polarized  rays, nearly monoenergetic (E   2 – 90 MeV) Utilizes Compton backscattering to generate  rays Booster Injector LINAC RF Cavity Mirror Optical Klystron FEL

10. HIGS Photon Beam to target room

11. HIGS Photon Beam  monoenergetic photons up to ~90 MeV  energy will reach ~160 MeV by 2015  100% linear or circular polarization  high photon beam intensity  ~10 7 Hz at 20-60 MeV  ~10 8 Hz below 15 MeV  low beam-related background  no bremsstrahlung typical of tagged photons

12. Polarized Compton Scattering for IVGQR Systematics

13. Giant Resonances L = 1 L = 2 T = 0T = 1  collective nuclear excitations  GDR and ISGQR well known IVGQR poorly known  IVGQR poorly known isovector  photon as isovector probe use pol. photons for IVGQR  use pol. photons for IVGQR  map systematics vs. A  nuclear symmetry energy neutron star eqn. of state ratio of H/V scattered photons is sensitive to E1/E2 interference ratio of H/V scattered photons is sensitive to E1/E2 interference sign difference in interference term at forward/backward angles sign difference in interference term at forward/backward angles

14. Photon Asymmetry in IVGQR pure E1 E1/E2 interference

15. HINDA Array HINDA HIGS NaI Detector Array 55 o 125 o

16. 209 Bi Results for 209 Bi

17. Results for 89 Y measured 124 Sn last month!  measured 124 Sn last month!  lease 142 Nd target from ORNL for $15k  other targets include A ~ 56, 180, 238 extend measurements to 89 Y  extend measurements to 89 Y 89 Y preliminary

18. Results for 124 Sn

19. IVGQR Systematics 89 Y 209 Bi Pitthan 1980 124 Sn

20. Compton Scattering on 6 Li

21. World Data Set D(,)D  Lucas – Illinois (1994) E  = 49, 69 MeV  Hornidge – SAL (2000) E  = 85-105 MeV  Lundin – Lund (2003) E  = 55, 66 MeV  Myers and Shonyozov (coming 2013) (coming 2013) Illinois, GW, UK, Lund E  = 58-115 MeV

22. EFT Fits to Deuteron Data Lundin Lucas Lucas, Lundin Hornidge Griesshammer 2012

23. Summary of Neutron Results  Neutron scattering  Schmiedmayer (91)  n = 12.6  1.5(stat)  2.0(syst)  Quasi-free Compton scattering  Kossert (03)  n = 12.5  1.8(stat)(syst)  1.1(model) +1.1 –0.6  n = 2.7 1.8(stat) (syst) 1.1(model) +0.6 –1.1    Elastic Compton scattering  data from Lucas (94), Hornidge (00), Lundin (03)  n = 11.6  1.5 (stat)  0.6 (Baldin)  n = 3.6 1.5 (stat)  0.6 (Baldin)  Hildebrandt 05  n = 11.1  1.8 (stat)  0.4 (Baldin)  0.8 (theory)  n = 4.1 1.8 (stat)  0.4 (Baldin)  (0.8 (theory)  Griesshammer 12

24. Experiment on 6 Li at HIGS E  = 60, 86 MeV  energies: E  = 60, 86 MeV   = 40°-160°  angles:   = 40°-160° ( = 17°) 12.7 cm long 6 Li  target: solid 12.7 cm long 6 Li cylinder (plus empty) eight 10”12” NaI’s  detectors: eight 10”12” NaI’s (HINDA array)  good photon energy resolution (E  /E  < 5%)  experiment motivation  exploit higher nuclear cross section to measure  and  cross section scales as Z 2, so factor of 9x higher than 2 H  solid 6 Li target is simple provided by Univ. of Saskatchewan  no previous Compton data on 6 Li exists (except Pugh 1957)

25. HINDA Array HINDA HIGS NaI Detector Array

26. Experimental Setup

27. Sample Spectra 6 Li( ,  ) 6 Li E  = 60 MeV Full and Empty Targets Full  Empty subtraction

28. Cross Section for 16 O(,) 16 O

29. Cross Section for 6 Li(,) 6 Li sum rule:   +  = 14.5 L. Myers et al. Phys. Rev. C86 (2012) E  = 60 MeV

30. (, ) = (10.9, 3.6)  = 2  = 2  sum rule:   +  = 14.5 E  = 60 MeV  7.4% E  = 80 MeV  12.8% E  = 100 MeV  20.9%

31. E  = 86 MeV Cross Section for 6 Li(,) 6 Li preliminary

32. Bampa 2011 Lundin (Lund) – 55 MeV Lucas (Illinois) – 49 MeV D(,)D LIT Method for Compton Scattering

33. Nuclear Polarizability of 6 Li (and 4 He?)

34. Nuclear Polarizability  nuclear polarizability affects energy levels of light atoms  non-negligible corrections for high-precision tests of QED  extraction of nuclear quantities from atomic spectroscopy  nuclear charge radius from Lamb shift in muonic atoms  usually determined from photoabsorption sum rule

35. Nuclear Polarizability of 6 Li  E = 0.163  0.064  M = 0.018  0.012

36. E  = 3.0 MeV 6 Li( ,  ) 6 Li  = 55   = 90   = 55   = 0   = 125   = 0   = 125   = 90 

37. E  = 4.2 MeV 6 Li( ,  ) 6 Li  = 55   = 90   = 55   = 0   = 125   = 0   = 125   = 90 

38. Compton Scattering on the Proton and Deuteron

39. Compton Scattering on Deuterium  unpolarized photon beam and unpolarized deuterium target  first use of our new LD 2 cryogenic target  scattering angles 45 o, 80 o, 115 o, 150 o (E  = 65, 100 MeV)  requires 300 hrs (65 MeV) + 100 hrs (100 MeV)  detectors: eight 10”12” NaI’s (HINDA array)  arranged symmetrically left/right

40. LH 2 /LD 2 /LHe Cryogenic Target  paid by GWU and TUNL  procured from vendors  assembled at HIGS  first run Oct. 2013? (3.5 K  24 K)

41. HINDA Array HINDA HIGS NaI Detector Array 55 o 125 o 55 o 125 o

42. Sum-Rule-Independent Measurement of  p linearly polarized  linearly polarized photon beam (unpolarized target)  scintillating active target (detect recoils in coincidence) measure scattered photons at 90 o  measure scattered photons at 90 o (E  = 82 MeV)  scattering cross section is independent of  p  extraction of  p is independent of the Baldin sum rule  extraction of  p is model-independent  requires 300 hrs for 5% uncertainty in  p  detectors: four 10”12” NaI’s (HINDA array)  located left, right, up, down

43. Sum-Rule-Independent Measurement of  p (point)

44. Polarizability of the Proton

45. Scintillating Target simulations: R. Miskimen

46. Nucleon Spin Polarizability forward and backward spin polarizabilities

47. Polarization Observables RCP (+) LCP (  ) Circular polarization Linear polarization

48. Spin Polarizabilities of the Proton first determination of proton  E1E1  measure  2x for first determination of proton  E1E1  circularly polarized photon beam transverse  scintillating active transverse polarized target (P ~ 80%)  scattering angles 65 o, 90 o, 115 o (E  = 100 MeV)  requires 800 hrs for  E1E1 = 1  detectors: eight 10”12” NaI’s  4 in plane, 4 out of plane Circular polarization

49. Spin Polarizabilities of the Proton expand simulations: R. Miskimen

51. Summary Early measurements of Compton scattering at HIGS  Early measurements of Compton scattering at HIGS  polarized A(,)A for A = 89-209 (IVGQR systematics)  6 Li(,) 6 Li at 60, 86 MeV (nucleon polarizability)  polarized 6 Li(,) 6 Li at 3.0-4.2 MeV (nuclear polarizability) Next generation of experiments on light nuclei  Next generation of experiments on light nuclei  D(,)D at 65 and 100 MeV (neutron polarizability) polarized  polarized p(,)p at 82 MeV (proton electric polarizability) polarized  polarized 4 He(,) 4 He at 3-15 MeV (nuclear polarizability) double-polarized  double-polarized Compton scattering on proton/deuteron nucleon spin polarizability HIGS can contribute high-quality polarized data!  HIGS can contribute high-quality polarized data!  stay tuned for further developments in the future…

52. Extra slides

53. Phenomenological Formalism

54. Cross-Section Ratios for Deuterium  N = 1

55. Level Scheme of 6 Li

56. Nuclear Polarizability

57. Calculations by Trento Group Bacca 2002  photoabsorption on 6 Li Lorentz Integral Transform method extend calculations to case of Compton scattering

58. NaI Detectors Pb collimator Paraffin n shield 10"  10" NaI core detector 3" thick optically isolated NaI shield segments (8 in total)

59. E  = 3.0 MeV E  = 4.2 MeV  = 55   = 125 

60. Nuclear Polarizability of 4 He  E = 0.061  0.007 (stat)  0.020 (syst)  M = 0.007  0.001 (stat)  0.002 (syst)

61. Nuclear Polarizability of 4 He  E = 0.061  0.007 (stat)  0.020 (syst)  M = 0.007  0.001 (stat)  0.002 (syst)

62. Compton Scattering with scintillating target Light Output Missing Energy (MeV) deuteronproton simulations: R. Miskimen

63. Nucleon Spin Polarizability  classical analogy: Faraday rotation of linearly polarized light in a spin-polarized medium  four spin polarizabilities:  1, …, 4  forward spin polarizability:  0 =  1 –  2 – 2 4  backward spin polarizability:   =  1 +  2 + 2 4  expt. asymmetries with circularly polarized photons   x : target spin  photon helicity (in reaction plane)   z : target spin parallel to photon helicity