1. New Results for Compton Scattering on Deuterium: A Better Determination of the Neutron Electromagnetic Polarizabilities University of Kentucky

2.  George Washington University Jerry Feldman  Jerry Feldman  Lund University Bent Schröder  Bent Schröder  Lennart Isaksson  Kevin Fissum  Magnus Lundin  Kurt Hansen  Jason Brudvik  University of Illinois Alan Nathan  Alan Nathan Luke Myers  Luke Myers  University of Kentucky Mike Kovash  Mike Kovash Khayrullo Shoniyozov  Khayrullo Shoniyozov  Duke University  Sean Stave  Seth Henshaw  University of Glasgow  John Annand  Theory support  H. Griesshammer (GWU)  J. McGovern (Manchester)  D. Phillips (Ohio)

3. Introduction  polarizability – measure of induced dipole moment in external field  for the free nucleon:  fundamental structure constants (and not so well known)  test of models of nucleon structure electric magnetic D =  E M =  B  = – d · E – ½   |E| 2  = –  · B – ½   |B| 2 q,   1 st order response ,   2 nd order response internal (lowest order response of internal structure)

4. electric polarizability: separation of charge D = 0D = 0D = 0D = 0 D = ED = ED = ED = E paramagnetic polarizability: moments align with B M = 0M = 0M = 0M = 0 M =  para B + diamagnetic polarizability: induced current opposes B M =  dia B

5. Measuring Nucleon Polarizability  Neutron  difficulties no free neutron targets neutron is uncharged (no Thomson scattering)  techniques neutron scattering by heavy nucleus quasi-free Compton scattering: D (, n ) p D (,) D elastic Compton scattering: D (,) D  Proton  Compton scattering  p  p ()  r 0 2 – 2 r 0  p  2  n 2  n ()   n 2  4 (  p  n )  D ()  r 0 2 – 2 r 0 (  p   n )  2

6. Proton Polarizability

7. Neutron Polarizability Experiments Alexandrov (Dubna – 1986) Koester (Munich – 1986) Schmiedmayer (Vienna/Harwell – 1986) Koester (Munich – 1988) Schmiedmayer (Vienna/ORNL – 1991) Koester (Munich – 1995) Enik (Dubna – 1997) Laptev (Gatchina – 2002) n scattering D(,n)pD(,n)pD(,n)pD(,n)p Rose (Gottingen/Mainz – 1990) Kolb (SAL – 2000) Kossert (Mainz – 2003)  n = 12.6  1.5(stat)  2.0(syst)  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  

8. Elastic Compton Scattering on D  Motivation sum  sum of proton and neutron polarizabilities ( p +  n )   D ()  r 0 2 – 2 r 0 ( p +  n )  2  Requirements elastic  must separate elastic from breakup! monoenergetic (tagged) photons high-resolution photon detector (E/E < 2% at 100 MeV)  Data  Lucas – Illinois (1994)E  = 49, 69 MeV  Hornidge – SAL (2000)E  = 85-105 MeV  Lundin – Lund (2003)E  = 55, 66 MeV  Theory  diagrammatic approach (Levchuk/L’vov)  EFT (Griesshammer, McGovern, Phillips)

9. World Data Set  Lucas – Illinois (1994) E  = 49, 69 MeV  Hornidge – SAL (2000) E  = 85-105 MeV  Lundin – Lund (2003) E  = 55, 66 MeV  Myers – Lund (2014) E  = 65-115 MeV   = 60 º, 120 º, 150 º

10. Status of Nucleon Polarizability proton neutron  deuteron data set is much smaller than proton  29 vs. 170 data points  deuteron data covers much narrower energy range  49-95 MeV vs. 40-170 MeV

11. Experiment at Lund E  = 65-115 MeV using tagged photons  energies: E  = 65-115 MeV using tagged photons  two tagger settings: 65-97 and 81-115 MeV  bin data in E = 8 MeV energy bins   = 60°, 120°, 150°90°  angles:   = 60°, 120°, 150° (plus recent 90°)  with 3 NaI detectors simultaneously  detectors: 3 large-volume (50 cm  50 cm) NaI’s  excellent photon energy resolution (E  /E  ~ 2%) BUNI: Boston Univ. CATS: Mainz Univ. UK: Univ. of Kentucky UK CATS BUNI 120 o

12. Kinematic Coverage (23) (5) (18) (6)

13. Washington Location of MAX-Lab

14. MAX1 PSR MAX2 MAX3 125 MeV Linacs Nuclear Physics  Upgrade to double linac in 2002-04  Install SAL tagger magnet in 2005 First beam delivered in Sept. 2005  First beam delivered in Sept. 2005

15. Experimental Area at MAX-Lab CATS 60° BUNI 120° DIANA 150° Tagging Spectrometer

16. NaI Detectors

17. CATS NaI Detector 48 cm 27 cm Front View 64 cm Side View 2 MeV E  = 100 MeV

18. Timing Cuts

19. Carbon Deuterium Carbon vs. Deuterium 1 day 15 days!!

20. Background Subtraction

21. Data Analysis  Extraction of yields  subtraction of cosmics  subtraction of accidentals  Determination of photon flux  tagging efficiency ( N  =  tag N e )  Simulation of expt. geometry and NaI response  effective solid angle and target thickness  overall detector efficiency  Corrections for rate-dependent effects  stolen coincidences  ghost events in tagger focal plane  beam time structure profile

22. Rate-Dependent Corrections Myers et al. (2013) Preston et al. (2014)

23. d  /d  (nb/sr) E  (MeV) Myers et al. (2014)

24. d  /d  (nb/sr) E  (MeV) Myers et al. (2014) o Lucas  Lundin  Hornidge ● Myers

25. d  /d  (nb/sr)   (deg) 0 30 60 90 120 150   (deg) Lucas Lundin Myers Myers et al. (2014)

26. d  /d  (nb/sr)   (deg) 0 30 60 90 120 150   (deg) Myers Hornidge Myers et al. (2014)

27. Summary and Outlook  New elastic Compton scattering data on deuterium roughly doubles world data set (first new data since 2003)  roughly doubles world data set (first new data since 2003) higher energy  extends data to higher energy, more backward angles  reduces statistical uncertainty by 30% for  n and  n  More data coming! (Shoniyozov – Kentucky)  concentrate on measurements in the 81-115 MeV range greater sensitivity to polarizabilities  more angles covered (60 º, 90 º, 120 º, 150 º )  better statistics, smaller rate-dependent corrections