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Recent results from BLAST detector

Recent results from BLAST detector. Bates Linear Accelerator center. Siberian Snake. 850 MeV cw polarized electron beam Beam polarization longitudinal at target Storage ring filled to 225 mA; helicity flipped each fill Lifetime 25 to 30 minutes

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Recent results from BLAST detector

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  1. Recent results from BLAST detector Evgeni Tsentalovich MIT

  2. Evgeni Tsentalovich MIT

  3. Bates Linear Accelerator center Siberian Snake • 850 MeV cw polarized electron beam • Beam polarization longitudinal at target • Storage ring filled to 225 mA; helicity flipped each fill • Lifetime 25 to 30 minutes • Automated synchronization of ring fill, detector HV ramp, data taking, ring dump using the EPICS control system Evgeni Tsentalovich MIT

  4. Electron beam polarization Compton polarimeter • Compton polarimeter provides online control of stored beam polarization • Laser beam helicity flipped with a Pockels cell (~10Hz) • Backscattered photons are detected with CsI crystal • Electron beam polarization flipped every new fill • Average beam polarization 67% Evgeni Tsentalovich MIT

  5. Polarized Internal Target • ABS (Atomic Beam Source) produces flux of Hydrogen or Deuterium atoms • ABS intensity ~ • Dri-film coated T-shaped storage cell. • Target thickness ~ • Hydrogen polarization Pz78% • Deuterium polarization Pz72%, Pzz 68% • Target polarization flipped every 5 min Evgeni Tsentalovich MIT

  6. TARGET BEAM BEAM BLAST • Toroidal field 3.8 kG • 2 instrumented sectors in the horizontal plane - Drift chambers - Cerenkov detectors - Time of Flight scintillators - Neutron detectors BLAST DATA: 2004, Hydrogen - Pz78%, 81 pb-1 2004, Deuterium - Pz84%, 130 pb-1 Pzz68% 2005, Deuterium - Pz72%, 180 pb-1 Pzz56% Evgeni Tsentalovich MIT

  7. Electron Left Electron Right Kinematics for spin-dependent electron scattering Electron scattering into left sector : q vector ~ perpendicular to target spin (perpendicular kinematics) Electron scattering into right sector : q vector ~ parallel to target spin (parallel kinematics) B p e’ q e Evgeni Tsentalovich MIT

  8. BLAST physics program Pol Vect.-Pol -production Tens.-Pol Evgeni Tsentalovich MIT

  9. Measurements of neutron form factor Product of beam and target polarizations (hPz) is determined from 2H(e,e’p)n reaction and verified with 2H(e,e’n)p in parallel kinematics The Form Factors ratio is measured in perpendicular kinematics Evgeni Tsentalovich MIT

  10. Preliminary results • Small systematic errors: • The largest contribution (5%)– from the uncertainty in the target polarization angle (~12 % per degree) • Uncertainty in hPz 2.5% • Uncertainty in magnetic Form Factor 1.5 % • Model dependency < 3% • Radiative effects <1% Evgeni Tsentalovich MIT

  11. Measurements of deuteron form factors Evgeni Tsentalovich MIT

  12. Preliminary results The largest systematic error(~5%) – from the normalization on low-q points Evgeni Tsentalovich MIT

  13. , In the Born approximation vanishes in the L=0 model for deuteron (no L=2 admixture) => is a good measure of L=2 component is a good measure of L=2 component and reaction mechanisms : MEC, IC, RC Evgeni Tsentalovich MIT

  14. Vector Asymmetry Evgeni Tsentalovich MIT

  15. Tensor Asymmetry Evgeni Tsentalovich MIT

  16. Separation of charge and magnetic proton form factors Existing data: 1.Rosenbluth separation 2.Polarization transfer measurements (scattering of polarized electrons on Hydrogen target and measuring a polarization of recoil protons) Evgeni Tsentalovich MIT

  17. World Data Evgeni Tsentalovich MIT

  18. Scattering of polarized electrons on polarized protons Super ratio Evgeni Tsentalovich MIT

  19. Preliminary Results from BLAST BLAST Left Sector BLAST Right Sector Evgeni Tsentalovich MIT

  20. Preliminary Results from BLAST Evgeni Tsentalovich MIT

  21. Preliminary Results from BLAST with World Data Evgeni Tsentalovich MIT

  22. Conclusion • Preliminary results from BLAST • quasi-elastic d(en) ( ) • elastic d(ed)(T20) • quasi-elastic d(ep) • elastic p(ep)( ) • Factor of two more data to analyze • Also analyzing data on  production,  resonance, T10/T11, • inclusive…. • More results to come ! Evgeni Tsentalovich MIT

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