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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 - PowerPoint PPT Presentation
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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