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  Juan Carlos Cornejo Joaquin Lopez Herraiz

Impulse Approximation limitations to the (e,e'p) reaction on 208 Pb: 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  

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  Juan Carlos Cornejo Joaquin Lopez Herraiz

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  1. 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

  2. Physics motivation • 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

  3. 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

  4. E06-007 experiment 208Pb(ee’)p

  5. E06-007 experiment 208Pb(ee’)p • Extract the 208Pb(ee’)p crossection as a fonction of pmiss xB = 1 High pmiss predictions are robust at With correlations Without correlations 208Pb(e,e’p)207Tl(all 5 shells)

  6. 12C(ee’)p data • Carbon results for calibration and crosschecks

  7. 12C(e,e’p) (p-shell) REDUCED CROSS-SECTION

  8. SIMULATION DATA Q2 DEPENDENCE of the SPECTROSCOPIC FACTOR Recross-section for the p12 shell in duced 12C(e,e’p) are independent of Q2

  9. 208Pb(e,e’p) data • Cross section as function of pmiss • Extraction of individual excitation states for some kinematics Pmiss vs Emiss for the kin01 ( pmiss = 0, nominal) setting.

  10. Lead data EMISS RESOLUTION Lead data EMISS RESOLUTION (Pmiss=[-100,100] MeV/c)

  11. EMISS RESOLUTION (Pmiss=[280,380] MeV/c)

  12. 208Pb(e,e’p) (Valence shells) CROSS-SECTION

  13. Conclusions • 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

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