Quasi-elastic 3 He(e,e’p) experiment (E89-044) at Jefferson Lab :

E. Penel-Nottaris

Laboratoire de Physique Subatomique et de Cosmologie de Grenoble

1July, 7th, 2004

Quasi-elastic 3He(e,e’p) experiment (E89-044) at Jefferson Lab :

study of the 2-bbu parallel kinematics.

E. Penel - Nottaris

Expérience E89-044 de diffusion quasi-élastique sur l’3Heau Jefferson Laboratory :

analyse des sections efficaces 3He(e,e’p)den cinématique parallèle.

Hall A collaboration

2 other PhD students : F. Benmokhtar and M. Rvachev

E. Penel-Nottaris


2July, 7th, 2004

Electromagnetic probe

- interaction described by QED- electron is a point like particle- small coupling (Z1)- kinematical flexibility

(e,e’p) experiments study the nucleon inside the nucleus

- energy and momentum distribution of nucleon- electromagnetic properties of bound proton

3He nucleus- exact calculations for 3-body systems- ingredients of complex nuclei

NN and 3-body forcesShort range correlationsRelativistic effects

E. Penel-Nottaris


3July, 7th, 2004

Plane Wave Impulse Approximation- absorbed by the detected nucleon- independent particles model for the nucleus- particles described by plane waves.

misspp )p,S(E

dΩ

σd

dE'dΩdΩ

σdmissmiss

e'

ep2

p'e'

5

ep : electron-(off shell) proton elastic cross section

Born Approximation : one photon exchange

S(Emiss, pmiss) : spectral function

of 3He

E. Penel-Nottaris


4July, 7th, 2004

• 2-body-break-up : 3He(e,ep)d

Emiss = 5.5 MeV

• 3-body-break-up : 3He(e,ep)pn

Emiss 7.7 MeV

Emiss = Mp + Mrecoil – M3He

Missing energy :

Emiss = - Tp - Tr

Emiss (MeV)

2.2 MeV energy separation between the 2 processes

E. Penel-Nottaris


5July, 7th, 2004

misspp

)p',p,(ESdΩ

σd K

de'dΩdΩ

σdmissmiss

D

e'

ep2

p'e

5

• Meson Exchange Currents (MEC) and Isobaric Currents (IC) :

• Exchange term :• Final State Interactions (FSI) :

• modify the extracted nuclear information• involve more general cross-section formulation

E. Penel-Nottaris


6July, 7th, 2004

• Virtual photon polarization :

- h=0 longitudinal polarization

- h=1 transverse polarizations

qh=0 ε

qh=-1

ε

qh=+1

ε

TT

LT

σ

σinterference terms

Lσ : longitudinal response function coupling to nuclear charge

Tσ : transverse response function coupling to nuclear transverse current

E. Penel-Nottaris


7July, 7th, 2004

• Parallel kinematics :

q//pmiss

)cos2 εcos 1)ε(ε εΓ(dE'dΩdΩ

σdTTLTLT σσσσ

p'e

5

ε1

1

Q

q

E

E'Γ

20

)

2

θtan

Q

q2(1ε e2

2

2

) εΓ(dE'dΩdΩ

σdL

p'e

5

σσT pmiss

p’

E. Penel-Nottaris


8July, 7th, 2004

)ε(εΓΓ

σ εΓσ εΓσ

)ε(εΓΓ

σ Γσ Γσ

BwFwBwFw

BwFwFwFwBwBwT

BwFwBwFw

BwFwFwBwL

pmiss

(MeV/c)

q

(GeV/c)Fw - Bw

0 1.0 0.7

0 1.5 0.7

0 2.0 0.6

0 3.0 0.5

- 300 1.0 0.4

- 300 2.0 0.7

+ 300 1.0 0.6

• Extracting the response functions :

- forward electron angles : Fw (Fw 1)

- backward electron angles : Bw (Bw 0)at fixed hadronic vertex variables

E. Penel-Nottaris


9July, 7th, 2004

- Coincidence experiment => 100% duty cycle- High luminosity (1038 cm-2 s-1) => high beam current and target density-Identification of processes separated by 2.2 MeV at momenta of few GeV => low beam energy dispersion (2.10 -5) and high momentum resolution (2.10 -4)

Jefferson Lab Hall A Basic Equipment

E. Penel-Nottaris


10July, 7th, 2004

Duty cycle 100 %

Beam energy 0.8 – 6 GeV

Energy dispersion 2.5 10-5

Beam emittance 2 10-9

Beam current 200 A

Frequency = 1497 MHz 499 MHz in the halls

E. Penel-Nottaris


11July, 7th, 2004

E. Penel-Nottaris


12July, 7th, 2004

High density : T = 6.3 K P 7.6 or 11 atm = 0.055 or 0.070 g.cm-3

• Density measurements :

- temperature and pressure sensors + state equation of 3He

- elastic electron scattering on 3He at each beam energy

Cylindrical target (tuna can) : = 10.3 cm

Preliminary normalization by density from sensorsSystematic error on density from sensors : 7 %

E. Penel-Nottaris


13July, 7th, 2004

• Luminosity monitoring

charge

-e singles nb.rate

L

• Target density stability : max. fluctuation < 3% ( 0.6 %)

corrected for dead time and prescales

refrate_ref

rate ρρL

L

density of the 1st run

density from luminosity monitoring density from P and T sensors

run number

rela

tive

den

sity

E. Penel-Nottaris


14July, 7th, 2004

Acceptance Resolution

Momentum ± 5 % 2.5 10-4

Horizontal angle 30 mrad 2.0 mrad

Vertical angle 65 mrad 6.0 mrad

Separates momentum resolution (vertical plane) from vertex position resolution (horizontal plane)

45° vertical deflexion

(FWHM)

E. Penel-Nottaris


15July, 7th, 2004

E. Penel-Nottaris


16July, 7th, 2004

pe > 17 MeV/cp > 4.8 GeV/c

Relative calibration by analysis software

Gas Cerenkov detector Shower counters

Absolute gains calibration (pe = 3581 MeV/c)

preshower and shower counters

-

-

e-e-

Cerenkov (channel) preshower + shower (MeV)

E. Penel-Nottaris


17July, 7th, 2004

Two planes of 6 scintillator paddles in each arm : S1 and S2 planes

Trigger electronics :

- Coincidence between the 2 PM of the hit paddle.

Single event

S1 & S2 & 45° track

Relative calibration by analysis software

Coincidence event

Electron event & Hadron eventS1 ADC (channel) S1 ADC (channel)

xrot (m)

S1

AD

C (

chan

nel)

S1

AD

C (

chan

nel)

xrot (m)

E. Penel-Nottaris


18July, 7th, 2004

VDC tracks detector variables

Spectrometer focal plane variables

Spectrometer target variables

Vertex variables

detector position offsets / focal plane

spectrometer absolute position / hall

spectrometer optics tensor + beam position

• In each detection arm :

)Φ , y,θ ,(xfpfpfpfp

δ) ,Φ , y,θ ,(xtgtgtgtg

variableslkinematica

(react_z) positionvertex

)Φ , y,θ ,(xdetdetdetdet

E. Penel-Nottaris


19July, 7th, 2004

ztg

ytg

beam

scattered e-

tg

ytg

react_z

target

Transverse position tensor coefficients optimized from vertex position along beam line (react_z)

Scattering off 4 targets : - carbon foil at z = 0 - aluminum foils at z = ± 2 cm

z = ± 5 cm z = ± 7.5 cm

zlab

ylab

E. Penel-Nottaris


20July, 7th, 2004

before after

Low electronmomentum

High protonmomentum

hadron react_z (cm) hadron react_z (cm)

Ph = 2999 MeV/c

Ph = 1295 MeV/c

electron react_z (cm)

Pe = 694 MeV/c

Pe = 3850 MeV/c

electron react_z (cm)electron react_z (cm)

hadron react_z (cm)

E. Penel-Nottaris


21July, 7th, 2004

Momentum tensor coefficients optimized on missing energy spectra : remove dependence on dispersive variables (xfp, fp)

Em

iss (

MeV

)

Em

iss (

MeV

)

hadron rot (rad) hadron rot (rad)

E. Penel-Nottaris


22July, 7th, 2004

- May not point at the hall center- Angle orientation may be different from floor marks

Use scattering off carbon foil at z = 0

electron react_z (mm) electron react_z (mm)

E. Penel-Nottaris


23July, 7th, 2004

- Background rejection => experimental 3He(e,e’p) events

- 2-bbu and 3-bbu separation- Radiative corrections- Phase space calculation=> Monte Carlo Simulation

Data Analysis and Simulation

=> Simulated 3He(e,e’p) events

3He(e,e’p)dCross-sections=>

E. Penel-Nottaris


24July, 7th, 2004

• Corrected time of coincidence : tc_cor

Time of coincidence window width = 12 ns

2 ns beam structure

resolution 0.6 ns

tc (ns) tc_cor (ns)

E. Penel-Nottaris


25July, 7th, 2004

signal in the Cerenkov detector+ signal in the showers

e-

-

-

e-

shower (MeV)

pres

how

er (

MeV

)

shower (MeV)

pres

how

er (

MeV

)

tc_cor (ns)

E. Penel-Nottaris


26July, 7th, 2004

| react_z | < 4 cm cut on the arm with best resolution on react_z

| react_ze arm – react_zh arm | < 2 cm

electron react_z (cm) electron react_z - hadron react_z (cm)

E. Penel-Nottaris


27July, 7th, 2004

p

d

+

before cuts after cuts

No need to remove deuterons or pions

hadron hadron

hadr

on S

2 A

DC

hadr

on S

2 A

DC

E. Penel-Nottaris


28July, 7th, 2004

pmiss

bq

p'pq

q

Parallel configuration : q//pmiss

Cone aperture = 45 °

bq (°) bq (°)bq (°)

pmiss=+300 MeV/cpmiss=0 MeV/c pmiss=-300 MeV/c

E. Penel-Nottaris


29July, 7th, 2004

Subtraction of missing energy spectra :accidbbu-2

12/50 – SS

12nsΔt

50nsΔtΔt

bbu2

f2f1before accidental subtractionafter accidental subtraction

tc_cor (ns) Emiss (MeV)

E. Penel-Nottaris


30July, 7th, 2004

Emiss (MeV)Emiss (MeV)

Emiss (MeV) Emiss (MeV)

pmiss = 0 MeV/c

pmiss = +300 MeV/c

forward backward

forward backward

E. Penel-Nottaris


31July, 7th, 2004

• Limit simulated and experimental phase space to the same volume

• Optimize statistics by considering maximal phase space volume

Cuts on target variables :

tgtgtgy,Φ ,θ δ,

(same cuts for both arms)

ytg (m) tg (rad)

tg (

rad)

tg (

rad)

tg (

rad)

tg (

rad)

(R-function defined by M. Rvachev)

E. Penel-Nottaris


32July, 7th, 2004

• Angular resolutions : FWHM tg = 2 mrad

FWHM tg = 4 mrad

• Transverse position resolution : fitted from ytg distributions on scattering off carbon foils data

1.4 mm < FWHM ytg < 9.7 mm

Carbon foil data Quasi-elastic 3He data

data simulation

ytg (mm)electron react_z - hadron react_z (cm)

E. Penel-Nottaris


33July, 7th, 2004

• Adjusted in the simulation to get same resolution on missing energy for 2-bbu as experimental resolution same momentum resolution for electron and hadron arms.

kin # FWHM

16 4.8 10-4

01 4.0 10-4

18 4.8 10-4

20 5.2 10-4

22 6.2 10-4

24 5.2 10-4

26 4.3 10-4

kin # FWHM

17 6.5 10-4

03 6.3 10-4

19 5.8 10-4

21 4.4 10-4

23 7.0 10-4

25 6.5 10-4

27 8.0 10-4

4 10-4 < FWHM < 8 10-4

data simulation

Emiss (MeV)

E. Penel-Nottaris


34July, 7th, 2004

’

By fitting simulated missing energy spectrum to experimental data

• takes into account 3-bbu contribution (1 % systematic error on subtraction)• simulates energy losses and radiative effects• extracts unradiated cross-section averaged on phase-space

Two theoretical models :

- unit cross-section

- PWIA model )S(pσdΩdΩde'

σdmisscc1

pe

5

Emiss (MeV)

Emiss (MeV)

data

simulation

E. Penel-Nottaris


35July, 7th, 2004

• Experimental data analysis shows reliable background control and pretty good transport variables resolutions

• Simulation reproduces rather well kinematical variables resolutions => used to extract unradiated cross-section averaged on phase-space

• Possible improvements could come from spectrometer optics optimization, simulated resolutions and absolute normalization by density from elastic data.

• Systematic error on preliminary cross-sections is 8.8 % (mainly due to target density)

Preliminary results

E. Penel-Nottaris


36July, 7th, 2004

De Forest / Salme PWIALaget PWIALaget full calculation

pmiss (MeV/c) pmiss (MeV/c)cr

oss-

sect

ion

(b.

MeV

-1.s

r-2)

cros

s-se

ctio

n (

b.M

eV-1.s

r-2)

Backwardelectron angles

Forward electron angles

E. Penel-Nottaris


37July, 7th, 2004

De Forest / Salme PWIALaget PWIALaget full calculation

Pmiss (MeV/c)

cros

s-se

ctio

n (

b.M

eV-1.s

r-2)

Pmiss (MeV/c)

cros

s-se

ctio

n (

b.M

eV-1.s

r-2)

Salmewave function Urbanna

Paris


Backward electron angles

E. Penel-Nottaris


38July, 7th, 2004

De Forest / Salme PWIALaget PWIA

Pmiss (MeV/c)

cros

s-se

ctio

n (

b.M

eV-1.s

r-2)

Pmiss (MeV/c)

cros

s-se

ctio

n (

b.M

eV-1.s

r-2)

Salmewave function Urbanna

Paris


Backward electron angles

E. Penel-Nottaris


39July, 7th, 2004

• and q matching for forward and backward kinematics• 50 MeV/c pmiss bins• achieving forward and backward cross-sections

De Forest / SalmePWIA

Sensitivity to interference terms and imperfect (, q) matching

Pmiss (MeV/c) Pmiss (MeV/c)

L (b

.sr-2

)

T (b

.sr-2

)

E. Penel-Nottaris


40July, 7th, 2004

•Preliminary results show unexpected effects for forward electron angles kinematics at pmiss = 0 and rather good agreement for the other kinematics that should constraint theoretical models.• Elastic data analysis would allow final cross-sections extraction.• Longitudinal and transverse separation looks promising

• Very interesting results on perpendicular kinematics (2-bbu and 3-bbu) that constrained models.

• Other experiments at Jlab study few body interactions models through (e,e’p)

Overview on E89-044 resultsParallel kinematics

Quasi-elastic 3 He(e,e’p) experiment (E89-044) at Jefferson Lab :

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