E06007, March 3 -> March 26, 2007

208Pb(e,e’p)207Tl, 209Bi(e,e’p)208Pb

Impulse Approximation limitations to the (e,e',p) reaction on 208Pb, identifying correlations and relativistic effects in the nuclear medium

Students:

Juan Carlos Cornejo (CSULA)

Joaquin Lopez (U. Madrid)

x=1, q = 1 GeV/c, w = 0.433 GeV, Q2 = 0.81 to 1.97 (GeV/c)2

1) Objectives of the Experiment

2) Run time experience

3) Activity to date

4) Anticipated direction for analysis

(I) Long Range Correlations search

a) Measure spectroscopic factors for states near the Fermi level. Spectroscopic factors depend on SRC and LRC.

b) Measure cross sections for these low lying states to 500 MeV/c in pmiss. Excess strength here is theoretically identified as due to LRC.

1) Objectives

c) Search for Q2 dependence of spectroscopic factors.

(II) Identify dynamical relativistic effects in nuclear structure.

1) Objectives

Measure cross section asymmetry ATL around the three momentum transfer. Relativistic mean field theory predicts an ATL dependence on pmiss< 300 MeV/c due to dynamical enhancement of the lower component of the nucleon wave function. Calculations which do not include the enhancement of the lower component predict a substantially different ATL behavior.

2) Run time experience

E=1.343 GeV, optics studies for RHRS, LHRS

E = 2.649 GeV, optics studies for LHRS

Aim to get dY<100 uM, dEbeam/Ebeam < 2.5 e-5

Internal and external sieve slits in/out

delta scans

raster on/off

OPTICS STUDIES

Online data base

sm

GEANT simulation using nominal spectrometer resolutions plus data with online optics data base.

12C(e,e’p)11B, small acceptance

815 keV

12C(e,e’p)11B, full acceptance cut

Emiss

GEANT simulation fitted to spectrometer resolutions plus data with online optics data base.

1 MeV

GEANT simulation fitted to spectrometer resolutions plus data with online optics data base.

12C(e,e’p)11B, raster off, full acceptance

Progress in data base change

Diamond sandwich targets, 4mmx4mm raster

Targets: C/Pb/C, C/Pb/C, C/Bi/C, C(non diamond)

2) Run time experience

Initially accelerator could not provide 100 uA with desired beam characteristics. Ran for 2 days at 55 uA on Pb tgt#4.

Beam current increased to 85 uA and target Pb#4 failed.

Bi target run at 80 uA for about 45 minutes with no sign of failure.

For next two weeks we ran at 45 uA on Pb tgt#3 and Bi with no sign of degradation.

Fracture in the diamond foil

Pb

C

Pmiss=0 MeV/c

GEANT simulation, C with Pb kinematics, pmiss = 0 MeV/c

Pb C11B gs and no 207Tl continuum

dp/p = +- 1.0e-4,

dh = +- 0.3mr,

dv = +- 1.0mr

Pb target, pmiss = 200 MeV/c

Pb tgt, 200 MeV/c simulation

Pb, pmiss = 300 MeV/c

Pb, simulation, pmiss = 300 MeV/c

Pb, pmiss = -300 MeV/c

Simulation, Pb, pmiss = -300MeV/c

3) Activity to date

Apply simulation to C data.

Analyze optics runs

4) Anticipated direction for analysis

Replay Pb and Bi data as C to get best carbon peaks.

Find values of spectrometer parameters to match carbon peaks.

Use spectrometer parameters to generate geant shapes for the unfolding of the Tl states.

Q2 = 1.40 GeV2, pmiss = 0 MeV/c

Q2 = 1.97 GeV2, pmiss = 0 MeV/c

pmiss=400 MeV/c, charge = 1.72 Coulombs, Pb

Simulation, pmiss = 400 MeV/c, charge = 7.2 Coulomb, Pb

High pmiss data

Pmiss Coul obtained Coul proposed

400 1.72 7.2

-400 1.15 10.8

500 1.37 8.6

-500 0.89 8.6

Emiss with Bi geant superposed

208Pb(e,e’p)207Tl

Using the online data base

3 MeV

0 100 200 MeV/c208Pb(e,e’p)207Tl

209Bi(e,e’p)208Pb, pmiss = 200 MeV/c, online optics data base

3 MeV

209Bi(e,e’p)208Pb, pmiss = 200 MeV/c, Guido’s recent optics update

2.2 MeV