L/T separation in the 3He(e,e’p) reactionat parallel kinematics
Freija Descamps
Supervisors:Ron GilmanEric Voutier
Co-supervisor:Jean Mougey
L/T separation in the 3He(e,e’p) reactionat parallel kinematics
• Motivations• Quasi-elastic scattering
• 3He(e,e’p) cross section• L/T separation
• Experimental setup• Cross section extraction
• Experimental data• Normalization• Monte Carlo simulation• Results
• L/T separation• Status report
• Conclusion and prospects
Motivations
E89-044 experiment: December 1999! April 2000
Free nucleon Bound nucleonChange in structure?
Study bound nucleon by (e,e’p) quasi-elastic scattering
Extract electromagnetic response functions for various transfered four-momenta Q (i.e. various probing resolutions).
•High Q2 : unexplored domain•Variable Q2 •High precision measurements
L/T separation in the 3He(e,e’p) reactionat parallel kinematics
• Motivations• Quasi-elastic scattering
• 3He(e,e’p) cross section• L/T separation
• Experimental setup• Cross section extraction
• Experimental data• Normalization• Monte Carlo simulation• Results
• L/T separation• Status report
• Conclusion and prospects
Quasi-elastic scattering: 3He(e,e’p)B
Bpm ppqp
BpHeBpm TTMmmE 3*
Missing momentum : undetected momentum
Missing energy : separation energy
GeV/c5.1 ppqGeV837.0
Leptonic plane
Hadronic plane
• Only e’ and p are detected
• Residual system B:
Quasi-elastic: 12
2
pm
Qx
Parallel: 0pq
pm ≈ 0
• Kinematical regime
2 body break-up peak2-bbu
3 body break-up threshold3-bbu
Quasi-elastic scattering
3He(e,e’p)d cross section
)2(cos)(cos)2( 3
5
TTTTLTLTTTLLM
pp
pff
RVRVRVRVREp
dddE
d
),,,( TTLTTL RRRR : Nuclear response functions
R: Recoil factor
σM: Mott cross section
),,,( TTLTTL VVVV : Kinematic electron coupling coefficients
L/T separation:
•Separation of longitudinal/transverse response functions
•Interference terms ! 0 if pq! 0 (parallel kinematics)
•Averaging over out-of-plane angle: ! 0
Separation using Rosenbluth method:
•Extraction of the 3He(e,e’p)d cross section at different kinematic settings
•Keep same hadronic vertex and change leptonic vertex.
TL RR and
)cos(2),cos(
)2(cos)(cos)2( 3
5
TTTTLTLTTTLLM
pp
pff
RVRVRVRVREp
dddE
d
KIN01≠ KIN03 change photon polarization
2 points in space
T
M
VR,
L/T separation in the 3He(e,e’p) reactionat parallel kinematics
• Motivations• Quasi-elastic scattering
• 3He(e,e’p) cross section• L/T separation
• Experimental setup• Cross section extraction
• Experimental data• Normalization• Monte Carlo simulation• Results
• L/T separation• Status report
• Conclusion and prospects
Experimental setup
Jefferson Laboratory (CEBAF, Newport News, USA), continuous electron beam : •Beam Energy up to 6 GeV•Beam Intensity up to 200 A
•Recirculation arcs
•0.6 GeV LINAC
•67 MeV injector
•3 experimental areas
•Extraction elements
Experimental setup
e He3
p
e
d, np
Experimental setup
Experimental setup
Electron Arm Hadron Arm
TOF
p
0
Electron Arm Hadron Arm
Tracking Vertical Drift Chamber (2 planes) Vertical Drift Chamber (2 planes)
Triggers S1, S2 scintillator planes (Čerenkov) S1, S2 scintillator planes (S0)
PID Čerenkov, Shower counters
S1, S2 ! TOF
S0
S1, S2 ! TOF
L/T separation in the 3He(e,e’p) reactionat parallel kinematics
• Motivations• Quasi-elastic scattering
• 3He(e,e’p) cross section• L/T separation
• Experimental setup• Cross section extraction
• Experimental data• Normalization• Monte Carlo simulation• Results
• L/T separation• Status report
• Conclusion and prospects
Experimentaldata
1
Raw Data
Coincidence
events
Real coincidence
events
Filter
Background rejection
Accidental coincidence
rejection
Experimental YieldIn pm and Em bins
1 Experimental Data: Background rejectionSome examples...
Electron ArmHadron and Electron Arm
• Events that are not reconstructed atthe same point by each spectrometer
• Pion contamination
Demand |zlabh-zlabe| < 0.02. Demand hit in Čerenkov counter.
1 Experimental Data: Accidental coincidences
Bin experimental data in pm
Per pm bin: bin in Em
First bin in Em = 2-bbu bin
Substract flat background:
BininEm
Experimental yield per pm, Em binAccidental coincidences
Luminosity
2
Raw Data
All
events
Detector Efficiencies
Efficiency study
total deadtimetarget density
Normalizationfactor
2 Luminosity: Scintillator efficiency study
Scintillator efficiency study
Kin 03: S1-study in Hadron arm
Start losing ‘good events’!
2 Luminosity: target density monitoring
Target density monitoring: Single rates
Kin 03: Single rates vs. Run number
Increase in
target density
Monte Carlosimulation
3
Experimentalconditions
Input
Raw simulatedevents
Resolutions,Offsets,
Target density
Monte Carlo
Acceptance cuts
Simulated YieldIn pm and Em bins
3 Monte Carlo simulation: matrix-method
Em
Vertex
Em
Asymptotic
Binning in EmV
BinningIn
EmA
Radiation effects
Resolution effects
Weights associated to each vertex
bin
3 Monte Carlo simulation: example
Em
Vertex
Em
Asymptotic
Binning in EmV
BinningIn
EmA
Radiation effects
Resolution effects
Eventdrawn in 2nd bin
Vertex
Resolution effect to
1st asymptotic bin
Contributionto N12
3 Monte Carlo simulation: example
Em
Vertex
Em
Asymptotic
Binning in EmV
BinningIn
EmA
Radiation effects
Resolution effects
Eventdrawn in 2nd bin
Vertex
Resolution effect to
1st asymptotic bin
Contributionto N12
Eventdrawn in 2-bbu bin
Vertex (1)
Radiation to
3rd asymptotic bin
Contributionto N31
Cross section results
1w
Kin 03 Kin 01Previous AnalysisCurrent Analysis
Cross section results
Kin 01Previous AnalysisCurrent Analysis
Why this difference?
Bq
pq
qp
mp
Bq > 90° Bq < 90°
Current analysis: no angle selection
Cross section results
Previous AnalysisCurrent Analysis
pq
pq
Bq
Bq
Pm>0(<0)! Bq<45°(>135°)
pq<2°
L/T separation in the 3He(e,e’p) reactionat parallel kinematics
• Motivations• Quasi-elastic scattering
• 3He(e,e’p) cross section• L/T separation
• Experimental setup• Cross section extraction
• Experimental data• Normalization• Monte Carlo simulation• Results
• L/T separation• Status report
• Conclusion and prospects
L/T Separation: status report
• Kin01, Kin03: keep same hadronic vertex
•ω/q and pm/q phase spaces need to be matched
•Mean values have to be checked to be equal for Kin01 and Kin03
•Extract 2-bbu cross sections for the two kinematics at the average kinematic point.
q vs ω for Kin01 and Kin03
L/T Separation: status report
TTLLMpp RVRVREp 3333
3
)2(
)2(cos)(cos)2( 3
5
TTTTLTLTTTLLM
pp
pff
RVRVRVRVREp
dddE
d
σ
TTLLMpp RVRVREp 1113
1
)2(
L/T separation in the 3He(e,e’p) reactionat parallel kinematics
• Motivations• Quasi-elastic scattering
• 3He(e,e’p) cross section• L/T separation
• Experimental setup• Cross section extraction
• Experimental data• Normalization• Monte Carlo simulation• Results
• L/T separation• Status report
• Conclusion and prospects
Conclusion and prospects
• Next steps?
• Generalization of the matrix-method to deconvolute radiative effects between pm bins
• Additional binning in Q2
• Cross section extractions and L/T separations for the remaining Q2 at parallel kinematics
• Good understanding of efficiencies• Optimization of good-event-selection
• Matrix method• Gain in statistics• Iteration of matrix method • Results consistent with previous analysis
• Understanding of the different aspects concerning the separation• First results seem reasonable
• Detector in-beam efficiency study
• 3He(e,e’p)d Cross section extraction
• Preliminary L/T separation