1. presented by Werner Boeglin Florida International University Miami
Deuteron Electro-Disintegration at Very High Missing Momenta PR Hall C Collaboration Experiment
presented by
Werner Boeglin
Florida International University
Miami

2. Why the Deuteron only bound two-nucleon system
fundamental system in nuclear physics
testing ground for any model of the NN interaction
hope to find new phenomena at short distances
prototype short range correlation (SRC)

3. All these problems are interconnected
Challenges
Reaction dynamics:
photon interacts with a deeply bound nucleon
what is the EM current structure
Final State Interactions
high Q2 : eikonal approximations
Deuteron wave function
probe NN wave function at small distances
search for manifestations of new degrees of freedom
All these problems are interconnected
New data are necessary !

4. Aim of Experiment
Determine cross sections at missing momenta up to 1 GeV/c
Measure at well defined kinematic settings
Selected kinematics to minimize contributions from FSI
Selected kinematics to minimize effects of delta excitation
Why ?
Explore a new kinematical region of the 2-nucleon system
Practically no data exist so far
SRC studies cover similar region on missing momenta e.g. experiment E need deuteron data for interpretation

5. From proposal PR07-006
unexplored
1 GeV/c

6. D(e,e’p) Reaction Mechanisms
reduced at certain kinematics ?
expected to be small at large Q2
supressed for x>1

7. Experiments at low(er) Q2
IC+MEC
large FSI
FSI included
JLAB Q2 = (GeV/c)2
Ulmer et al.
MAMI Q2 = 0.33 (GeV/c)2 Blomqvist et al.

8. Eikonal Approximation successfully describes D(e,e’p)n at high Q2
FSI described as sequential (soft) scatterings
successfully used in hadron scattering
for nucleons at rest  Glauber approximation
for moving nucleons  Generalized Eikonal Approximation
angle between q and outgoing nucleon small (< 10o)

9. Calculations Compared to Experiment
Data: Egyian et al. (CLAS) PRL 98 (2007)
pm = 250 ± 50 MeV/c
pm = 500 ± 100 MeV/c
Calculation. Sargsian

10. Momentum Dependence from CLAS
cross sections averaged over CLAS acceptance !

11. Selection of Kinematics
minimize FSI
pm = 500 MeV/c
pm = 400 MeV/c
pm = 200 MeV/c
pm bin width : ± 20 MeV/c

12. Angular Distributions up to pm = 1GeV/c
FSI depend weakly on pm
Calculation: M.Sargsian

13. FSI Reduction b determined by nucleon size
cancellation due to imaginary rescattering amplitude
valid only for high energy (GEA)

14. FSI contribution estimates
M.Sargsian (GEA)

15. Measurements in Hall C Beam: Energy: 11 GeV Current: 80mA
Electron arm fixed at:
SHMS at pcen = 9.32 GeV/c
qe = 11.68o
Q2 = 4.25 (GeV/c)2
x = 1.35
Vary proton arm to measure :
pm = 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 GeV/c
HMS 1.96 ≤ pcen ≤ 2.3 geV/c
Angles: 63.5o ≥ qp ≥ 53.1
Target: 15 cm LHD

16. Kinematic configurations
direct reaction proton is hit
indirect reaction neutron is hit
pn>1.9 GeV/c strongly suppressed

17. Estimated Counts per Setting
Estimate using SIMC and PWIA
Dpm=40 MeV/c, cut on acceptance > 20%

18. Accidentals expected to be small
E01-020: pm = 0.5 GeV/c I = 90mA

19. Expected Final Yield Applied Cuts: -0.05≤qe≤0.05 -0.025≤fe≤0.025
-0.08≤Dp/p≤0.04
-0.06≤qp≤0.06
-0.035≤fp≤0.035
-0.1≤Dp/p≤0.1
1.3≤xBj≤1.4

20. Expected Results

21. Cross Sections

22. What If ? Why would other models fail ?
These would indicate new phenomena

23. Beam Time Request
Time in hours

24. Summary Measure cross sections for pm up to 1 GeV/c
Errors are statistics dominated: 7% - 20%
Estimated systematic error ≈ 5 %
Probe NN interaction in new kinematic regions
Exploit cancellation of interference and rescattering terms (FSI small)
Very good theoretical support available
JLAB uniquely suited for high pm study
request 21 days of beam time

25. FSI as Rescattering

26. Angular Distribution lower Q2

27. Estimated Counts per Setting
Estimate using SIMC and PWIA
Dpm=40 MeV/c, no acceptance cut

28. TAP Reports H(e,e’p) for calibration purposes
rate at qe = 11.68o 125Hz for 80mA
20 cm target length: very little effect on rates
HMS defines target length acceptance
HMS at rel. large angles
cuts defined by coincidence acceptance
large Dp/p acceptance of SHMS does not match HMS momentum acceptance