1. QCD Town Meeting-January 2007 Probing Chiral Dynamics with photons Henry R. Weller Duke University and Triangle Universities Nuclear Laboratory HI  S PROGRAM

2. QCD Town Meeting-January 2007 A wide variety of physical processes can be used to study Chiral Dynamics, guided mainly by the results of ChPT, an expansion of the Lagrangian for low energy QCD about the chiral limit, m q =0. I want to mention a few of these today. Reference: International Workshop on Chiral Dynamics 2006 Organizers: H. Gao, B. Holstein, HRW www.tunl.duke.edu/events/cd2006/proceeding.html

3. QCD Town Meeting-January 2007 Chiral Anomaly (from Yelena Prok for the PrimEx Collaboration) The  0 decay rate is a fundamental prediction of confinement scale QCD. Chiral Anomaly – the closed-loop triangle diagram results in axial vector current non-conservation, even in the limit of vanishing quark masses. The anomaly leads to the reduced decay amplitude, in leading order (chiral limit) where F  = 92.42+/-0.25 MeV is the pion decay constant.

4. QCD Town Meeting-January 2007 Decay Width The  0   decay width is related to the amplitude: is presently known to 10% The goal of the PrimEx Experiment is to measure the decay width to an accuracy of 1.5%. ChPT calculations Including effects of m d -m u being non-zero Increase  by 4.5%.

5. QCD Town Meeting-January 2007 Success of ChPT at pion-threshold Linearly Polarized Photon asymmetry for the  p   0 p reaction at an average energy of 159.5 MeV MAINZ 2001

6. QCD Town Meeting-January 2007 Difficulties! e + p  e’ + p +   at low Q 2 --MAINZ

7. QCD Town Meeting-January 2007 Precision Measurement of the Electroproduction of  0 Near Threshold at JLAB: A Test of Chiral QCD Dynamics Co-spokespersons J. Annand, D. Higinbotham, R. Lindgren, V. Nelyubin, and B. Norum,  )

8. LH2 Target 10 - 15 cm Liquid Hydrogen( LH2) 125  m Al Foil Luminosity 3 - 5 x 10 37 Hz/cm 2 HRS Electron BigBite Beam Dump HRS Luminosity Monitor MWDC(15 Planes) p Two Segmented Scintillator Arrays Electron Beam 15  A e Pion Electro-Production in the US  BigBite Collaboration

9. QCD Town Meeting-January 2007 This experiment (now E04-007) is scheduled to be run in Nov 2007, but may be delayed until April 2008 due to budget problems.

10. QCD Town Meeting-January 2007 New measurements of  P –   for the proton and neutron at LEGS using the (SPHICE) frozen-spin solid HD target

11. QCD Town Meeting-January 2007 LEGS data for the ‘neutron’

12. QCD Town Meeting-January 2007 LEGS The LEGS group has now completed taking data for both polarized p and polarized d targets. They have used their recently commissioned TPC to measure the charged pion channels. This will provide very accurate results for the GDH and the forward-spin-polarizability integrals for both p and n. Measuring them simultaneously will provide accurate values of the GDH n-p difference, where the theoretical uncertainty is the smallest and the discrepancy with multipole analysis of pi-photo- production data the largest

13.  * + p    N N/Delta Physics at Mainz (IASA (Athens), MIT, Mainz,…)   N p u d u Detect: e' + p or e' +  + in coincidence

14. C2/M1 vs. Q 2 (  0 p channel) Lattice QCD Results Dynamical Model with pion cloud W=1232 MeV Dynamical Model without pion cloud Effective Field Theory Calculations Gail/Hemmert Pascalutsa/Vanderhaeghen

15. QCD Town Meeting-January 2007 HI  S –A free-electron laser generated  -ray source

16. QCD Town Meeting-January 2007 Upgraded Facility RF System with HOM Damping 1.2-GeV Booster Injector

17. QCD Town Meeting-January 2007 Upgrade Schedule Commissioning of Booster and Ring with OK-4—underway now! Nuclear Physics Program begins—March, 2007 March 07  Aug 07 Linear Pol.- Below 65 MeV, >2x10 8  /s Dec. 07  Circ. Pol. Up to 110 MeV, >10 8  /s These are TOTAL intensities. Beam on target is: TOTAL x 1.5 x % resolution (ex. 5% res. at 100 MeV: 7.5 x 10 6  s) Expect to have energies up to 160 MeV by Spring 09

18. QCD Town Meeting-January 2007 The GDH integrand for deuterium below pion threshold @ HI  S A 400 hour run will allow us to measure the GDH integrand between 5 and 100 MeV to an overall accuracy of about 3% or better, assuming a beam of 1 x 10 7  /s with ~5% energy spread. An experiment to measure the GDH integrand for 3 He below pion threshold is also being developed by Haiyan Gao et al.

19. QCD Town Meeting-January 2007 The upgraded BLOWFISH array as of January, 2005.

20. QCD Town Meeting-January 2007

21. Use the intense polarized beams at HI  S to obtain very precise values of the electric and magnetic polarizabilities of the proton and the neutron. Perform double polarization experiments to obtain precise values of the spin- polarizabilities of the proton and the neutron. Compton@HI  S Collaboration  see www.tunl.duke.edu/~mep/higs/compton.pdf)

22. QCD Town Meeting-January 2007 Recently NSF/MRI funded project—a high resolution-high acceptance gamma-ray spectrometer consisting of eight 10”x12” NaI detectors in 3” thick segmented NaI shields. The Compton@HI  S Collaboration The HINDA Array (  S NaI Detector Array)

23. QCD Town Meeting-January 2007

25. Electric and Magnetic Polarizability of the proton Recent results (B. Pasquini) of a free fit to data yield:  = 11.52 +/- 2.4 x 10 -4 fm 3  = 3.42 +/- 1.70 x 10 -4 fm  (with Baldin sum rule value of 13.82   11.0 +/- 1.4 ;  2.8 +/-1.4 ) A ~50% error in  – which will impact future measurements.

26. QCD Town Meeting-January 2007 100% Linearly polarized beams at HI  S can improve this Simulation (Blaine Norum) assumed: E  = 120 MeV Target: 80 mg/cm 2 10 7  /s 280 hours

27. QCD Town Meeting-January 2007 Determination of the electric and magnetic polarizabilities of the proton using 100% linearly polarized gammas@HI  S –a ~300 hr experiment will yield ~5% errors on both  now~  and  (now~50%).

28. QCD Town Meeting-January 2007 Compton scattering of  rays from the deuteron at LUND G. Feldman, M. Kovash, A. Nathan, B. Schroder, H.R. Weller et al. This will give us the so called isoscalar polarizabilities. Since the proton is “known”, this gives the values for the neutron. The following shows ChPT calculations O(p 4 ) (from Phillips and Choudhury)

29. QCD Town Meeting-January 2007 Solid curve->  N = 12;    Dashed curve->  N = 6;  N = 9

30. QCD Town Meeting-January 2007 Presently, results from 55 and 66 MeV disagree with those obtained from 94 MeV data. eg. 94 MeV (SAL) data yield    N ~ 2.5 while we expect a value of ~10 if the proton and neutron have the same values for this difference (as expected from Chiral Symmetry).

31. QCD Town Meeting-January 2007 The LUND experiment will make ~5% measurements at five angles and 3 energies between 40 and 110 MeV. The goal is to obtain errors for the isoscalar polarizabilities comparable to those which exist for the proton. This experiment will be run in 2007.

32. QCD Town Meeting-January 2007 Spin polarizabilities. Measuring these requires polarized beams and polarized targets. They are predicted (ChPT) to be different for the n and the p. There are four “dipole” spin polarizabilities:   which can be written in terms of      E1E1 ) and  4 (=    are the largest. 

33. QCD Town Meeting-January 2007 HI  S Proposal for measuring the proton spin- polarizabilities Spokesperson – Rory Miskimen A 200 hr. run at 120 MeV will give helicity dependent cross sections at the 3% level, which translates into ~10% measurments of spin- polarizabilities using the HINDA array. Sensitivity estimates for all four spin-polarizabilities are based upon calculations of Hildebrandt, Griesshammer and Hemmert.

34. QCD Town Meeting-January 2007

35. R. Miskimen, theory curves: Hildebrandt, Griesshammer, Hemmert, Nucl-th/0308054 100 hrs for each target spin orientation Projection for double-polarized Compton scattering from proton Total beam time for proton measurement: 450 hrs

36. QCD Town Meeting-January 2007 Experiments are being developed by Dr. Haiyan Gao at Duke/HI  S to measure the spin- polarizabilities of the neutron. Haiyan Gao has built a high pressure spin- polarized 3 He target. Target thickness will be about 10 22 atoms/cm 2 with a length of 40 cm. Polarizations of ~40% have been achieved. Effect of the reduced target thickness is offset by the increased sensitivity in the observables.

37. QCD Town Meeting-January 2007

38. Proposed set-up using the NaI detector array (HINDA) and the 88- neutron detector array for quasi-elastic Compton scattering studies using the polarized 3 He target.

39. QCD Town Meeting-January 2007 Present proposed experiments New theoretical calculations by Choudhury, Nogga and Phillips make extraction of spin-polarizabilities possible from elastic scattering data from 3 He. With a gamma intensity of 2 x 10 7 /sec and the target and detector system just described, a 350 hour experiment will give neutron spin polarizabilities with errors of about +/- 0.5 x 10 -4 fm 4.

40. QCD Town Meeting-January 2007 Estimate of the experimental uncertainties in the individual spin polarizabilities For example, at 90 o, the longitudinal cross section difference is sensitive to    while the transverse polarization cross section difference is sensitive to    The value of  0 for the proton was fixed from the Mainz experiment with an error of +/- 13%. (Could improve the resutls by considering additional constraints (B. Pasquini)). 

41. QCD Town Meeting-January 2007 Proton HI  S projected uncertainties Neutron HI  S projected uncertainties  p 1 =1.1  0.25  n 1 =3.7  0.40  p 2 =-1.5  0.36  n 2 =-0.1  0.50  p 3 =0.2  0.24  n 3 =0.4  0.50  p 4 =3.3  0.11  n 4 =2.3  0.35 Projected HI  S measurement on Nucleon Spin Polarizabilities (quasifree) (all in 10 -4 fm 4 ) McGovern et al. NLO heavy baryon Chiral Perturbation Theory

42. QCD Town Meeting-January 2007

43. Threshold pion-photoproduction from the proton @ HI  S p(  0 )p Co-spokesperson: Aron Bernstein The first experiment: A measurement of the Target analyzing power at E   MeV.

44. QCD Town Meeting-January 2007 These experiments will provide stringent tests of The predictions of Chiral Perturbation Theory Predictions of isospin breaking due to the mass differences of the up and down quarks.

45. QCD Town Meeting-January 2007 Phase I Calorimetry Only 60 CsI Crystals All Phases Veto Scint. Phase II Tracking 2 BGO Layers + 2 Sets of MWPC 14 Plastic Scintillators The Neutral Meson Spectrometer (NMS)

46. QCD Town Meeting-January 2007

47. A measurement of the imaginary part of the s-wave production amplitude (E 0 + ) provides a determination of the charge exchange scattering length a cex (   n    p). Requires measurement of the polarized target analyzing power T(  ). Motivation Isospin Symmetry Breaking

48. QCD Town Meeting-January 2007 Simulations (Bernstein et al.) The results indicate that we can measure ImE 0+ with a statistical uncertainty of 3.7% in 200 hours of actual data taking at 158 MeV. This gives us the value of a cex (  + n ->  0 p). Isospin conservation implies a cex (  + n ->  0 p) = -a cex (  - p ->  0 n). The latter is well known from the width of pionic hydrogen (0.1301 +/- 0.0059) after a decade of work. Our result will give a comparable accuracy for a cex (  + n ->  0 p).

49. QCD Town Meeting-January 2007 Resources at HI  S Mirror development is the key to pion threshold Physics at HI  S. Present mirrrors take us up to 110 MeV. Although a development plan is in place for 165 nm mirrors (140 MeV), additional resources are needed to assure that 160 MeV is reached (150 nm mirrors) with full flux in a timely manner. Funding presently limits operations to 1000 hrs/yr. In order to execute this program we would like to increase this to 3000 hours per year. This requires significant additional $upport.

50. QCD Town Meeting-January 2007 A wide variety of process can be used to study Chiral Dynamics, guided mainly by the results of CHPT, an expansion of the Lagrangian for low energy QCD about the chiral limit, m q =0. EXAMPLES: 1. PrimEx at JLAB—a precision measurement of the  0 lifetime. 2.Pion-electroproduction from the proton near threshold at Mainz and JLAB. ChPT at finite Q 2. 3.N/  Physics at Mainz: the pion-cloud to quark-parton transition. 4.Compton scattering from the deuteron at LUND—neutron polarizabilities. 5.Precision measurements of the polarizabilities of the proton at HI  S. Obtain ~5% measurements of  p and  p. 6.Double-polarization measurements at LEGS using the HD target. 7. Spin-polarizability measurements for both p and n at HI  S using polarized p, d and 3 He targets. Test ChPT and Lattice QCD results. 8.Pion-threshold measurements at HI  S using polarized beam and target.

51. QCD Town Meeting-January 2007 EXTRA SLIDES  HI  S –A free electron laser generated  -ray source

52. QCD Town Meeting-January 2007 HI  S Anticipated Schedule for 2007 Linearly polarized beams below ~65 MeV will be available in early 2007. Measure Compton scattering from the deuteron at ~50 MeV using a scintillating target (unpolarized). Circularly polarized beams (OK-5) will be available in late 2007 up to ~110 MeV. Measure GDH on the deuteron up to 50 MeV using Blowfish and the frozen-spin target.

53. QCD Town Meeting-January 2007 Spin-exchange optical pumping Optical pumping of alkali atoms (Rubidium) Spin-exchange of 3 He with Rubidium High pressure target (~10 bar), 3 He pol’n ~40 to 50% Target will be 40 cm in length giving 1 x 10 22 atoms/cm 2

54. QCD Town Meeting-January 2007 Extending Gamma Energy Range (4 kA Wiggler Op) Extending Wiggler Current 4 kA max Operational Concerns Saturated magnetic fields Additional power supplies Filter/bassbar system upgrades 1.2 GeV operation to reach 158 MeV with 150 nm mirrors 158 MeV

55. QCD Town Meeting-January 2007 190 nm mirrors have been proven to work in our environment…these will produce 110 MeV gammas. 165 nm mirrors will produce 140 MeV beams once OK-5 is operating at 4kA. Schedule for FEL Cavity Mirror R&D DateMilestone July 2006Delivery of 1 st mirror sets with coatings for 190, 180 and 165 nm May 2007Intracavity evaluation of 1 st set of 190, 180 and 165 nm mirrors Oct. 2007Delivery of 2 nd mirror sets with coatings for 180 and 165 nm Nov. 2007Intracavity evaluation of 2 nd set of 180 and 165 nm mirrors

56. QCD Town Meeting-January 2007 Recent results from Choudhury, Nogga and Phillips for elastic scattering from 3 He

57. QCD Town Meeting-January 2007

58. Primakoff Effect The  0 photoproduction from Coulomb field of the nucleus. Production (  *!  0 ) and decay (  0 !  ) mechanisms imply the Primakoff cross section is proportional to the  0 lifetime.

59. QCD Town Meeting-January 2007  0 production on 208 Pb Events/0.04 deg

60. QCD Town Meeting-January 2007 Frozen Spin Polarized Deuterium Target Butanol Polarization ~ 80 % Polarizing Field ~ 2.5 T Holding Field ~ 0.6 T ~4 x 10 23 d/cm 2

61. QCD Town Meeting-January 2007 COMPTON ON d WITH A SCINTILLATING TARGET Vertical axis : light output from target detector Horizontal axis: Missing energy (binding energy) Courtesy of Rory Miskimen

62. QCD Town Meeting-January 2007 Our measurement will determine  to +/- 0.10, where Im[E 0+ (  p ->  0 p)] =  p  /m  and  Re[E 0+ (  p ->  + n)] a cex (  + n ->  0 p) Re[E 0 + (  p ->  + n)] is well measured (=28.06 +/- 0.27 +/- 0.45), giving us a cex (  + n ->  0 p). Isospin conservation implies a cex (  + n ->  0 p) = -a cex (  - p ->  0 n). The latter is well known from the width of pionic hydrogen (-0.1301 +/- 0.0059) after a decade of work. Our measurement will give a comparable accuracy for a cex (  + n ->  0 p).

63. QCD Town Meeting-January 2007 Recent (PRC C71, 044002 (2005)) HBChPT calculations of Choudhury and Phillips indicate appreciable sensitivity of  x observed in Compton scattering from the deuteron to  1n at 135 MeV. Test for consistency!

64. QCD Town Meeting-January 2007