Impulse Approximation limitations to the (e,e'p) reaction on 208Pb: search for long range correlations at high missing
momenta Juan Carlos Cornejo Joaquin Lopez Herraiz
(Cal. State Univ., Los Angeles) (U. Comp. de Madrid)
Alexandre Camsonne
(Jefferson Lab)
for the Hall A collaboration
•Shell model (mean field) calculations: the shape of the cross-section is well described, but the measured spectroscopic factors are below the mean field prediction. How large/small must be the spectrocopic factors?
About 30% depletion is observed for states near the Fermi level. This cannot be explained only with short-range correlations
Shape at moderate pm and parallel kinematics is well understood
Long range correlations are predicted to be visible at large pm
Physics motivation
E06-007 experiment 208Pb(ee’)p
• Use of 2 Hall A High Resolution Spectrometer to detect the scattered electron and proton in coincidence
• Scattered electron beam energy = 2216 MeV• Need stable good resolution beam: keep beam vertical
distribution < 100 um and beam energy spread less than 3.10-5
• Diamond/lead/diamond sandwich cryogenic target for high beam currents:
0.2mm thick lead + 0.3mm diamond
E06-007 experiment 208Pb(ee’)pKinematic
sq
[GeV/c]Eo
[GeV]ω
[GeV]Ee
[GeV]θe
[degrees]Pp
[GeV]θp
[degrees]pm
[GeV/c]
Kin01 1.000 2.649 0.433 2.216 21.44 0.989 54.101 0.000
Kin02 1.000 2.649 0.433 2.216 21.44 0.989 59.830 0.100
Kin03 1.000 2.649 0.433 2.216 21.44 0.989 48.371 0.100
Kin04 1.000 2.649 0.433 2.216 21.44 0.989 65.625 0.200
Kin05 1.000 2.649 0.433 2.216 21.44 0.989 42.576 0.200
Kin06 1.000 2.649 0.433 2.216 21.44 0.989 71.440 0.300
Kin07 1.000 2.649 0.433 2.216 21.44 0.989 36.762 0.300
Kin08 1.000 2.649 0.433 2.216 21.44 0.989 77.299 0.400
Kin09 1.000 2.649 0.433 2.216 21.44 0.989 30.902 0.400
Kin10 1.000 2.649 0.433 2.216 21.44 0.988 83.222 0.500
Kin11 1.000 2.649 0.433 2.216 21.44 0.988 24.980 0.500
Kin12 1.400 2.649 0.745 1.904 30.60 1.388 43.816 0.000
Kin13 1.750 2.649 1.045 1.604 39.81 1.738 35.936 0.000
E06-007 experiment 208Pb(ee’)p
• Extract the 208Pb(ee’)p crossection as a fonction of pmiss
208Pb(e,e’p)207Tl(all 5 shells)
With correlations
Without correlations
High pmiss predictions are robust at
xB = 1
• Carbon results for calibration and crosschecks
12C(ee’)p data
12C(e,e’p) (p-shell) REDUCED CROSS-SECTION
Q2 DEPENDENCE of the SPECTROSCOPIC FACTOR
Recross-section for the p12 shell in duced
12C(e,e’p) are independent of Q2
SIMULATION
DATA
Pmiss
vs Emiss
for the kin01 ( pmiss
= 0, nominal) setting.
208Pb(e,e’p) data
• Cross section as function of pmiss
•Extraction of individual excitation states for some kinematics
Lead data EMISS RESOLUTION
Lead data EMISS RESOLUTION (Pmiss=[-100,100] MeV/c)
EMISS RESOLUTION (Pmiss=[280,380] MeV/c)
208Pb(e,e’p) (Valence shells) CROSS-SECTION
• Preliminary results on C are in good agreement with data and calculations this gives a good cross check Pb (ee’)p
• Finalizing the data analysis and corrections to have final systematics
• Within our current error bars standard long range correlation seems to be ruled out
Conclusions