L/T separation in the 3 He(e,e’p) reaction at parallel kinematics Freija Descamps Supervisors:

L/T separation in the 3He(e,e’p) reaction at parallel kinematics Freija Descamps Supervisors: Ron Gilman Eric 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 Change in structure? Free nucleon Bound nucleon 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 E89-044 experiment: December 1999! April 2000

Missing momentum : undetected momentum Missing energy : separation energy Quasi-elastic: Parallel: pm≈ 0 Quasi-elastic scattering: 3He(e,e’p)B • Only e’ and p are detected • Residual system B: Leptonic plane • Kinematical regime Hadronic plane

Quasi-elastic scattering 2 body break-up peak 2-bbu 3 body break-up threshold 3-bbu

: Kinematic electron coupling coefficients : Nuclear response functions σM: Mott cross section R: Recoil factor 3He(e,e’p)d cross section

 KIN01≠ KIN03 change photon polarization 2 points in space 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.

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

Experimental setup d, np

Experimental setup 0 TOF p Electron Arm Hadron Arm

Raw Data Filter Coincidence events Background rejection Real coincidence events Accidental coincidence rejection Experimental Yield In pm and Em bins 1 Experimental data

Experimental Data: Background rejection Some examples... 1 Hadron and Electron Arm Electron Arm • Events that are not reconstructed at • the same point by each spectrometer • Pion contamination Demand |zlabh-zlabe| < 0.02. Demand hit in Čerenkov counter.

Experimental Data: Accidental coincidences 1 Bin experimental data in pm Per pm bin: bin in Em First bin in Em = 2-bbu bin Substract flat background: Bin in Em Accidental coincidences Experimental yield per pm, Em bin

Raw Data All events Efficiency study Detector Efficiencies total deadtime target density Normalization factor 2 Luminosity

Luminosity: Scintillator efficiency study 2 Scintillator efficiency study Start losing ‘good events’! Kin 03: S1-study in Hadron arm

Luminosity: target density monitoring 2 Target density monitoring: Single rates Increase in target density Kin 03: Single rates vs. Run number

3 Monte Carlo simulation Experimental conditions Resolutions, Offsets, Target density Input Monte Carlo Raw simulated events Acceptance cuts Simulated Yield In pm and Em bins

Monte Carlo simulation: matrix-method 3 Em Vertex Radiation effects Resolution effects Em Asymptotic Weights associated to each vertex bin Binning in EmV Binning In EmA

Monte Carlo simulation: example 3 Em Vertex Radiation effects Resolution effects Em Asymptotic Resolution effect to 1st asymptotic bin Event drawn in 2nd bin Vertex Contribution to N12 Binning in EmV Binning In EmA

Radiation to 3rd asymptotic bin Event drawn in 2-bbu bin Vertex (1) Contribution to N31 Monte Carlo simulation: example 3 Em Vertex Radiation effects Resolution effects Em Asymptotic Resolution effect to 1st asymptotic bin Event drawn in 2nd bin Vertex Contribution to N12 Binning in EmV Binning In EmA

Cross section results Previous Analysis Current Analysis Kin 01 Kin 03

Bq pq Cross section results Why this difference? Current analysis: no angle selection Bq > 90° Bq < 90° Previous Analysis Current Analysis Kin 01

Cross section results Bq pq Pm>0(<0)!Bq<45°(>135°) Bq pq Previous Analysis Current Analysis pq<2°

L/T Separation: status report q vs ω for Kin01 and Kin03 • 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.

L/T Separation: status report σ

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 Conclusion and prospects • Detector in-beam efficiency study • 3He(e,e’p)d Cross section extraction • Preliminary L/T separation • 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

L/T separation in the 3 He(e,e’p) reaction at parallel kinematics Freija Descamps Supervisors: