presented by Werner Boeglin Florida International University Miami Deuteron Electro-Disintegration at Very High Missing Momenta PR10-003 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)

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 !

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 E07-006 need deuteron data for interpretation

From proposal PR07-006 unexplored 1 GeV/c

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

Experiments at low(er) Q2 IC+MEC large FSI FSI included JLAB Q2 = 0.67 (GeV/c)2 Ulmer et al. MAMI Q2 = 0.33 (GeV/c)2 Blomqvist et al.

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

Momentum Dependence from CLAS cross sections averaged over CLAS acceptance !

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

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

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 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

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

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

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

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

Expected Results

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 Dpm=40 MeV/c, no acceptance cut

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