Recent results from BLAST detector Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
Bates Linear Accelerator center Siberian Snake • • 850 Me. V cw polarized electron beam • Beam polarization longitudinal at target • Storage ring filled to 225 m. A; 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 Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
Electron beam polarization Compton polarimeter Nucleon 05 Oct. 12 -14, 2005 • Compton polarimeter provides online control of stored beam polarization • Laser beam helicity flipped with a Pockels cell (~10 Hz) • Backscattered photons are detected with Cs. I crystal • Electron beam polarization flipped every new fill • Average beam polarization 67% Evgeni Tsentalovich MIT
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 Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
BLAST • • BEAM TARGET BEAM Nucleon 05 Oct. 12 -14, 2005 Toroidal field 3. 8 k. G 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
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) p Electron Left B Electron Right e’ e Nucleon 05 q Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
BLAST physics program Pol Vect. -Pol -production Tens. -Pol Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
Measurements of neutron form factor Product of beam and target polarizations (h. Pz) is determined from 2 H(e, e’p)n reaction and verified with 2 H(e, e’n)p in parallel kinematics The Form Factors ratio is measured in perpendicular kinematics Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
Preliminary results Small systematic errors: • The largest contribution (5%) – from the uncertainty in the target polarization angle (~12 % per degree) • Uncertainty in h. Pz 2. 5% • Uncertainty in magnetic Form Factor 1. 5 % • Model dependency < 3% • Radiative effects <1% Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
Measurements of deuteron form factors Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
Preliminary results The largest systematic error(~5%) – from the normalization on low-q points Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
, In the Born approximation vanishes in the L=0 model for deuteron (no L=2 admixture) => is a good measure of L=2 component and reaction mechanisms : MEC, IC, RC Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
Vector Asymmetry Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
Tensor Asymmetry Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
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) Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
World Data Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
Scattering of polarized electrons on polarized protons Super ratio Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
Preliminary Results from BLAST Left Sector Nucleon 05 Oct. 12 -14, 2005 BLAST Right Sector Evgeni Tsentalovich MIT
Preliminary Results from BLAST Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
Preliminary Results from BLAST with World Data Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
Preliminary results from BLAST Conclusion quasi-elastic d(e n) ( ) elastic d(e d) (T 20) quasi-elastic d(e p) elastic p(e p) ( ) Factor of two more data to analyze Also analyzing data on production, resonance, T 10/T 11, inclusive…. More results to come ! Nucleon 05 Oct. 12 -14, 2005 Evgeni Tsentalovich MIT
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