Motivation. Experimental Details. Three-body forces & other nuclear dynamics studied in 3. He(e,e pp)n reactions

Transcription

1 Scottish Universities Physics Alliance Motivation Three-body forces & other nuclear dynamics studied in 3 He(e,e pp)n reactions Analyse e2b data taken at low electron beam energy get significant yield with energy transfers (ω) below π production threshold and moderate momentum transfer (q) 1) Test recent exact theories of 3 He electrodisintegration (e.g Faddeev) Dan Watts (University of Edinburgh) Dan Protopopescu Dave Ireland (University of Glasgow) 2) Test the diagrammatic approaches (e.g. Laget model) in new kinematic regimes ω=0 GeV π production threshold ω=0.5 GeV ω=1 GeV 3 He disintegration measurements AmPSNikhef Virtual photon A1@MAMI CLAS@JLAB (2.2 GeV) CLAS@JLAB (0.9 GeV) Livermore &Illinois Saskatchewan Real photon Daphne@MAMI LEGS@BNL TAG-X Experimental Details Run: e2b (June 2002) Beam energy: GeV No. of triggers: 1042 M Events with 2 protons: 18.4 M 3 He(e,e pp)n passing all cuts: 1.5 M Events with ω < m π : 0.75 M ω=1.5gev

2 e2b analysis status Energy transfer distribution Electron ID Proton ID Vertex cut Electron momentum corrections Proton energy loss corrections Fiducial cuts Definition of Variables Variation with angles P n <0.2 GeV/c P n >0.2 GeV/c

3 Circular Dalitz Plots Spectator or Active Neutron? p n LAB < 0.2 GeV/c ( spectator ) ω = p n LAB > 0.2 GeV/c ( active ) ω = Variation with β Variation with β All β All β < β < < β < < β < < β < < β < < β < < β < < β < < β < < β < 90 0 Experimental Data 30 0 < β < < β < 90 0 Three-body passed through CLAS simulation

4 Variation with γ Variation with γ All γ All γ 0 0 < γ < < γ < < γ < < γ < < γ < < γ < < γ < < γ < < γ < < γ < Experimental Data < γ < < γ < Three-body passed through CLAS simulation Obtaining theoretical comparisons Preliminary sampling of calculations Exact Faddeev calculations : Obtained computer code for Krakow/Bochum Faddeev calculations Implemented a sampling procedure to allow theory to be filtered through CLAS acceptance preliminary results Diagrammatic approach : Laget is preparing calculations from events generated within the CLAS acceptance for the e2b data. Calculations based on complete diagrammatic expansion in the future (Gross)? Three-body generator to produce events sampling the full Apply minimum energy threshold (no fiducial cuts yet but soon!) For each event apply a weight proportional to the cross section for that kinematics (calculated by e.g. Faddeev) Uniform population of Dalitz plot

5 Preliminary Faddeev comparisons Preliminary Faddeev comparisons Spectator neutron P n <0.2 GeV/c ω cm = 0.1 GeV q=0.5 GeV/c Experimental data ω cm = 0.1±0.025 GeV q = 0.5 ±0.05 GeV/c Active neutron P n >0.2 GeV/c ω cm = 0.1 GeV q=0.5 GeV/c Experimental data ω cm = 0.1±0.02 GeV q = 0.5 ±0.05 GeV/c +3NF +3NF Plane wave calculation (No FSI) +3NF 3NFs predicted to give noticeable effects +3NF 3NFs predicted to give noticeable effects Summary Present Status Analysis of 3 He(e,e pp) ~complete Setup a procedure to compare Faddeev calculations (Gloeckle/Golak) with data CLAS analysis note ~complete To Do Radiative corrections to experimental data Faddeev: Improve statistical sample and add fiducial cuts. Also compare with other exact 3 He electrodisintegration calculations based on different framework (Deltuva/Sauer) Laget (/Gross?) : Comparison with diagrammatic calculations at higher ω More plots on