presented by werner boeglin florida international university miami

Deuteron Electro-Disintegration at Very High

Missing MomentaPR10-003

Hall C Collaboration Experiment

presented by

Werner Boeglin

Florida International University

Miami

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)

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 interconnectedNew data are necessary !

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

• 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 E07-006 need deuteron data for interpretation

Why ?

From proposal PR07-006

unexplored

1 GeV/c

D(e,e’p) Reaction Mechanisms

expected to be small at large Q2 supressed for

x>1

reduced at certainkinematics ?

Experiments at low(er) Q2

MAMI Q2 = 0.33 (GeV/c)2 Blomqvist et al.

JLAB Q2 = 0.67 (GeV/c)2

Ulmer et al.

FSI included

IC+MEC

large FSI

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)

Calculations Compared to Experiment

pm = 250 ± 50 MeV/c pm = 500 ± 100 MeV/c

Data: Egyian et al. (CLAS) PRL 98 (2007)

Calculation. Sargsian

Momentum Dependence from CLAS

cross sections averagedover CLAS acceptance !

Selection of Kinematics

minimize FSI

R =σ EXP

σ PWIA

pm = 500 MeV/cpm = 500 MeV/c

pm = 400 MeV/cpm = 400 MeV/c

pm = 200 MeV/cpm = 200 MeV/c

pm bin width : ± 20 MeV/c

Calculation: M.Sargsian

Angular Distributions up to pm = 1GeV/c

FSI depend weakly on pm

FSI Reduction

• b determined by nucleon size• cancellation due to imaginary rescattering amplitude• valid only for high energy (GEA)

FSI contribution estimates

M.Sargsian (GEA)

Measurements in Hall C

Beam: Energy: 11 GeVCurrent: 80A

Electron arm fixed at:SHMS at pcen = 9.32 GeV/ce = 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/cHMS 1.96 ≤ pcen ≤ 2.3 geV/cAngles: 63.5o ≥ p ≥ 53.1

Target: 15 cm LHD

Kinematic configurations

direct reactionproton is hit

indirect reactionneutron is hit

pn>1.9 GeV/cstrongly suppressed

Estimated Counts per Setting

Estimate using SIMC and PWIA

pm=40 MeV/c, cut on acceptance > 20%

Accidentals expected to be small

E01-020: pm = 0.5 GeV/c I = 90A

Expected Final Yield

Applied Cuts:-0.05≤e≤0.05-0.025≤e≤0.025-0.08≤p/p≤0.04

-0.06≤p≤0.06-0.035≤p≤0.035-0.1≤p/p≤0.1

1.3≤xBj≤1.4

Expected Resultsfm2

MeV ⋅Sr2

pm

Cross Sections

What If ?

Why would other models fail ?

These would indicate new phenomena

Beam Time Request

Time in hours

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

FSI as Rescattering

Angular Distribution lower Q2

Estimated Counts per Setting

Estimate using SIMC and PWIA

pm=40 MeV/c, no acceptance cut

TAP Reports

• H(e,e’p) for calibration purposes• rate at e

= 11.68o 125Hz for 80A• 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 p/p acceptance of SHMS does not match HMS momentum acceptance