Deuteron Electro-Disintegration at Very High Missing Momenta
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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

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Deuteron Electro-Disintegration at Very High Missing MomentaPR10-003Hall C Collaboration Experiment

presented by

Werner Boeglin

Florida International University

Miami


Why the deuteron
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
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
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
D(e,e’p) Reaction Mechanisms

reduced at certainkinematics ?

expected to be small at large Q2

supressed for x>1


Experiments at low er q 2
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)2Blomqvist et al.


Eikonal approximation successfully describes d e e p n at high q 2
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
Calculations Compared to Experiment high Q

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

pm = 250 ± 50 MeV/c

pm = 500 ± 100 MeV/c

Calculation. Sargsian


Momentum dependence from clas
Momentum Dependence from CLAS high Q

cross sections averagedover CLAS acceptance !


Selection of kinematics
Selection of Kinematics high Q

minimize FSI

pm = 500 MeV/c

pm = 400 MeV/c

pm = 200 MeV/c

pm bin width : ± 20 MeV/c


Angular distributions up to p m 1gev c
Angular Distributions up to p high Qm = 1GeV/c

FSI depend weakly on pm

Calculation: M.Sargsian


Fsi reduction
FSI Reduction high Q

  • b determined by nucleon size

  • cancellation due to imaginary rescattering amplitude

  • valid only for high energy (GEA)


Fsi contribution estimates
FSI contribution estimates high Q

M.Sargsian (GEA)


Measurements in hall c
Measurements in Hall C high Q

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 high Q

direct reactionproton is hit

indirect reactionneutron is hit

pn>1.9 GeV/cstrongly suppressed


Estimated counts per setting
Estimated Counts per Setting high Q

Estimate using SIMC and PWIA

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


Accidentals expected to be small high Q

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


Expected final yield
Expected Final Yield high Q

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




What if
What If ? high Q

Why would other models fail ?

These would indicate new phenomena


Beam time request
Beam Time Request high Q

Time in hours


Summary
Summary high Q

  • 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




Estimated counts per setting1
Estimated Counts per Setting high Q

Estimate using SIMC and PWIA

Dpm=40 MeV/c, no acceptance cut


Tap reports
TAP Reports high Q

  • H(e,e’p) for calibrationpurposes

  • 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


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