HALL A COLLABORATION MEETING 16 DECEMBER 2009 STATUS OF THE E06-007 EXPERIMENT Impulse Approximation...

HALL A COLLABORATION MEETING16 DECEMBER 2009

STATUS OF THE E06-007 EXPERIMENTSTATUS OF THE E06-007 EXPERIMENT Impulse Approximation limitations Impulse Approximation limitations

to the (e,e’p) reaction to the (e,e’p) reaction on on 208208Pb, Pb, 209209Bi Bi and and 1212CC

StudentsStudents:: Juan Carlos Cornejo, Joaquin Lopez HerraizJlab staff:Jlab staff: Alexandre CamsonneSpokepersons:Spokepersons: K. Aniol, A. Saha, J. M. Udias, G. Urciuoli

and the Jefferson Lab Hall A Collaboration


INDEXMOTIVATION and THEORY DATA ANALYSIS

- Checks - Some results on 12C(e,e’p) and 208Pb(e,e’p)

from J.L.Herraiz, June 2009 Hall A meetingNEW RESULTS FROM MEASURED DATA

- 209Bi(e,e’p)SUMMARY


Nuclear States of interest in E06-007

207Tl

0.0 3s1/2

0.351 2d3/2

1.348 1h11/2

1.683 2d5/2

3.470 1g7/2

MeV

208PbMeV

0.0 0+~4.1 1p1h~5.4 1p1h

209Bi

MeV

0.0 1h9/2, proton


xB = 0.18

E. Quint, thesis, 1988,

NIKHEF

I. Bobeldijk et al., PRL 73 (2684)1994

J. M. Udías et al. PRC 48(2731) 1994

J.M. Udías et al. PRC 51(3246) 1996

If long range correlations are the reason for the small spectroscopic factors, then they should produce a large effect at high missing momentum. An experiment was performed at NIKHEF-K to measure the large momentum region, but the kinematics was far from XB=1. Additional strength was indeed found, but this can be explained either via long-range correlations or by relativistic effects in the mean field model.

Long Range Correlations ? Ambiguous Interpretation


With correlations

Without correlations

Previous experiment at NIKHEF (Bobeldijk, PRL 1994) found an excess of strength at high pmiss in 208Pb(e,e’p). This was explained by two approaches: (1) Quasiparticle orbits plus non-relativistic DWIA. (2) Relativistic DWIA using independent particle orbit solutions to Dirac equation.

Measuring the high pmiss region at the quasielastic peak with good statistics will reveal if long-range correlations are needed to describe the data.

At XB = 1 both a

relativistic and nonrelativistic theoretical treatment agree and excess strength at high p

miss is predicted by both

approaches if LRC exist.

Simulated theoretical calculations

Choice of Kinematics

208Pb(e,e’p)


209Bi(e,e'p)208Pb is also an interesting study

A previous study of electron and photon induced knockout from 209Bi

D. Brandford et al.,PRC 63 014310 (2000)

208Pb(g.s.) 208Pb(hole states)

(e,e'p)

gamma,p

(e,e'p)-parallel kinematics, Ee=293,412 MeV, Tp = 100 MeV110<p

miss<290 MeV/c

E06007- primary goal here is to isolate the 208Pb gs by the knockout of the 1h9/2 proton in 209Bi. The first excited state of 208Pb is at 2.6 MeV(3-) which is weakly excited in (e,e'p)

2nd goal is to excite the 1p1hProton configurations in 208Pb


Proton orbitals which are important for the low lying states. In 209Bi, 208Pb and 207Tl.

209Bi – model structure

From earlier proton removal experiments and the data of Brandford the strong excitations at 4.1 and 5.4 MeV have proton particle hole configurations given by

[1h9/2,(3s1/2)-1]

[1h9/2,(2d3/2)-1]

[1h9/2,(1h11/2)-1]

[1h9/2,(2d5/2)-1]

There are many states in this energy region which also have large neutron particle-hole configurations(PRC 74 034303 (2006)) but the

(e,e'p) reaction is selecting the proton hole configuration.


1. EXPERIMENT E06-007

• We measured 208Pb(e,e’p), 209Bi(e,e’p) and 12C(e,e’p) cross sections at true quasielastic kinem. (xB=1, q=1GeV/c, ω=0.433GeV/c) at both sides of q.

1. Determine momentum

distributions: 0< pmiss< 500MeV/c

2. Determine ATL by measuring cross

sections on either side of q

3. Determine the spectroscopic

factors dependence with Q2

(0.81, 1.40, 1.97 GeV2)

OBJECTIVES


Data acquisition: RUN 1 – (March, 3-26, 2007) RUN 2 – (January 2008) Additional

measurements in Lead in the high pmiss

region. With thin and thick lead target.

1. EXPERIMENT E06-007

Targets:-Diamond/Lead/Diamond -Diamond/Bismuth/Diamondsandwich cryogenic target 0.2mm Pb + 0.3mm Diamond0.2mm Bi + 0.3mm Diamond (needed for high beam current).

Requirements:- Good Energy Resolution

- Raster Correction

- Normalization Factors

- Use 12C as a reference


3. DATA ANALYSIS: Emiss Resolution

Pmiss = 0-100MeV/c

PROTONS

2.13

0.27

0.27

2.68 0.67


3. DATA ANALYSIS: Emiss Resolution

Two peaks can be separated in this 208Pb(e,e'p)207Tl Emiss spectrum (Pmiss=0). Both of them are composed of two peaks.

Thallium

Valence states

Boron states from 12C(e,e'p)11B

Ex=[0-2.5]

Ex=[2.5-7.5]


3. DATA ANALYSIS: Luminosity and Raster

1 )1 ) In order to get Absolute Cross Sections we should know the Luminosity very precisely.

2 )2 ) Nevertheless C+Bi+C target had a problem and Bismuth only covered one-half of the target. Furthermore, the raster pattern was not uniform at the edges.

3 ) 3 ) A simple approach (ratio between areas) may not be entirely accurate. To estimate luminosities, we compared the measured cross-section in the region of the target with only diamond foils against the events measured with the graphite target, both with Raster on and off.

GRAPHITE

DIAMOND

X

Y


4. RESULTS: 209Bi(e,e’p)208Pb Emiss spectrum,pmiss = 200 MeV/c

Lead g.s. From Bismuth

1h9/2 state

boron

Ex=[0-3.0]

leadhole States


209Bi(e,e’p)208Pb ground state CROSS-SECTION

Integrated over the detector acceptancesgeant simulation, Coulombs scaled by area of Bismuth to

total area in the raster pattern.

pmiss

(MeV/c)

<>exp

(nb/MeV/sr2)

<>theory

(nb/MeV/sr2)

-0.3 0.038 0.043 0.006

-0.2 0.171 0.065 0.179

-0.1 0.113 0.078 0.060

0.1 0.075 0.039 0.095

0.2 0.362 0.095 0.382

0.3 0.011 0.019 0.026

Emiss

PRELIMIN

ARY

PRELIMIN

ARY

Cro

ss

-Sec

tio

n

209Bi(e,e’p)208Pb ground state

Independent analysis using MCEEP simulation for kinematic runs at pmiss

= 100, 200 and 300 MeV/c. Luminosities estimated from the comparison to carbon(graphite) data.

PRELIMINARY


Pmiss

= 200 MeV/c

The two spectra have been normalized by the luminosities . The Raster cut has been applied so that the carbon/metal ratios are the same in the two spectra.

11B states

208Pb(e,e'p)207Tl

208Pb, g.s.

209Bi(e,e'p)208Pb, hole states

Comparison of hole states in 208Pb and valence states in 207Tl

Integrated cross section over the particle hole states in 208Pb

PRELIMINARY

Luminosities were estimated by comparing the carbon events from the diamond-foils-only region of the target to the same kinematics with the graphite target.

The shape of the pmiss

distribution is fitted well assuming the same proton orbitals are important for the 1p1h states in 208Pb as the proton orbitals used in


4. RESULTS: 208Pb(e,e’p) RED. CROSS-SECTION(Emiss region –Ex=0..7.5MeV-)

SIMULATION

DATA

PRELIMIN

ARY

PRELIMIN

ARY

207Tl states


Results from D. Brandford etal., PRC 63 014310 (2000)


Summary

Analysis is ongoing for the 209Bi data – extract cross sections on both sides of the three momentum transfer.

Theses writing is being finished

Papers on the results are being written: - long range correlation implications for 208Pb(e,e'p)207Tl - Q2 dependence on the spectroscopic factors for 208Pb(e,e'p)207Tl and 12C(e,e'p)11B- A

TL dependence on p

miss

- 209Bi(e,e'p)208Pb cross sections


BACKUP SLIDES

Bismuth

1h9/2 state

boronlead

hole States

DATA

SIMULATION

pmiss = 200MeV/c


Results from D. Brandford etal., PRC 63 014310 (2000)


HOW MUCH HYDROGEN IS THERE?

· LEAD TARGET: NucleiH ~0.12% NucleiPb (.t)H~5.8E-6 (.t)Pb = 1.13E-6 g/cm2 tH ~ 1E-8m

· GRAPHITE TARGET (RUN 1): NucleiH ~0.016% NucleiC (.t)H~2.2E-5 (.t)C = 1.9E-6g/cm2 tH ~ 2E-8m


2. THEORY AND SIMULATIONSINPUT PARAMETERINPUT PARAMETER OPTIONOPTION

BOUND-NUCLEON

WAVE FUNCTION

NLSH

OPTICAL MODEL EDAI-C (12C) & EDAD (208Pb, 209Bi)

NUCLEAR SPINOR DISTORTION RELATIVISTIC AND

PROJECTED (NON-RELATIVISTIC DYNAMICS)

ELECTRON DISTORTION NONE (yet)

KINEMATICS RELATIVISTIC

CURRENT OPERATOR CC2

NUCLEON FORM FACTORS J.ARRINGTON (ROSENBLUTH DATA FIT)

GAUGE COULOMB

RADIATION SIMULATED BUT NOT UNFOLDED


- The first part of the data analysis consisted in: Improving the Optics Database to get 1MeV resolution. Improving the Coincidence Time (resolution 2.5ns). Establishing the Raster Correction (we used a large raster) Normalization factors (Dead-time,Multitracks correction)

- This part of the analysis is almost finished and

we obtain reasonable good results:

3. DATA ANALYSIS – Calibration

Good

Coincidence

Time

RASTER

ON

RASTER

OFF


• For each kinematics, the cross-section is obtained as:

3. DATA ANALYSIS: Cross-Section (e,e’p)

5 _ _ _

e p e p

d Number of counts correctedd d d L

sw w

=W W DW ×DW ×D ×

Live time and

Multitrack corrections

Solid angles Electron Energy Range

Luminosity

5 5

1

1red

e p p p CC e p

d dd d d E P d d d

s sw s w

= ×W W W W

CC1 - Prescription of De Forest Form Factors from J. Arrington

fit of Rosenbluth data. PRC 69, 022201 (2004).

• Using MCEEP we can simulate the Phase-space

population and bin the acquired data in (pmiss,q,,)

• Reduced cross-section was obtained as:


4. RESULTS: 12C(e,e’p) REDUCED CROSS-SECTION

PRELIMINARY

Simulations: RDWIA with and w/o relativistic dynamical

effects in the wave function (projected)


4. RESULTS: 12C(e,e’p) REDUCED CROSS-SECTIONCOMPARATIVE WITH PREVIOUS EXPERIMENTS

PRELIMIN

ARY

PRELIMIN

ARY

(*)


4. RESULTS: 12C(e,e’p) ATL

PRELIMIN

ARY

PRELIMIN

ARY


4. RESULTS: Study of dependence with Q2 in 12C

Reduced cross-section for the 1p32 shell (Emiss=[14-23] MeV)in 12C(e,e’p) are independent of

Q2

SIMULATION

DATA

No need to adjust simulation for the experiments at different Q2 within error bars (5%)


4. RESULTS: 208Pb(e,e’p) RED. CROSS-SECTIONCOMPARATIVE WITH PREVIOUS EXPERIMENTS


4. RESULTS: 208Pb(e,e’p) ATL

PRELIMIN

ARY

PRELIMIN

ARY


4. RESULTS: 208Pb(e,e’p) Study of dependence with Q2 in 208Pb

Reduced cross-section for the valence states in 208Pb(e,e’p) are also independent of Q2

SIMULATION

DATA


5. CONCLUSIONS Most of the data analysis of E06-007 experiment has already been done and preliminary results have been obtained.

In the last few months, we have focused on Bismuth data.

CARBON and LEAD:

Results show no significant dependence of spectroscopic factors with Q2

both in Carbon and Lead.

Simulations obtained from just relativistic mean field calculations (without long-range correlations included) seem to compare fairly well with data at both low and high missing momentum and the ATL has the expected shape.

These results are being checked in more detail. Specially radiative corrections, systematic errors and different theoretical models.

BISMUTH:

Cross-section for the state 1h9/2 has been obtained for different kinematics. These preliminary results are in fairly good agreement with RMF predictions with an occupancy of ~0.7 protons in that shell.


2. THEORY AND SIMULATIONS

With correlations

Without correlations

Non relativistic dynamics(Projected)

Relativistic dynamics

Previous experiment at NIKHEF (Bobeldijk, PRL 1994) found an excess of strength at high pmiss in 208Pb(e,e’p). This was explained by two approaches: (1) Quasiparticle orbits plus non-relativistic DWIA. (2) Relativistic DWIA using independent particle orbit solutions to Dirac equation.

The ATL is an excellent observable to check both models.

Measuring the high pmiss region at the quasielastic peak with good statistics will reveal if long-range correlations are needed to describe the data.

HALL A COLLABORATION MEETING 16 DECEMBER 2009 STATUS OF THE E06-007 EXPERIMENT Impulse Approximation...

Documents

Transcript of HALL A COLLABORATION MEETING 16 DECEMBER 2009 STATUS OF THE E06-007 EXPERIMENT Impulse Approximation...