1. Recent results from BLAST detector
Nucleon05
Oct , 2005
Evgeni Tsentalovich
MIT

2. Nucleon05
Oct , 2005
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
Nucleon05
Oct , 2005
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%
Nucleon05
Oct , 2005
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
Nucleon05
Oct , 2005
Evgeni Tsentalovich
MIT

6. 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%
BEAM
TARGET
Nucleon05
Oct , 2005
Evgeni Tsentalovich
MIT

7. Kinematics for spin-dependent electron scattering
Electron scattering into left sector : q vector ~ perpendicular to target spin (perpendicular kinematics)
Electron
Left
Right
Electron scattering into right sector : q vector ~ parallel to target spin (parallel kinematics) B p e’ q e
Nucleon05
Oct , 2005
Evgeni Tsentalovich
MIT

8. BLAST physics program Pol Vect.-Pol Tens.-Pol -production
Nucleon05
Oct , 2005
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
Nucleon05
Oct , 2005
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%
Nucleon05
Oct , 2005
Evgeni Tsentalovich
MIT

11. Measurements of deuteron form factors
Nucleon05
Oct , 2005
Evgeni Tsentalovich
MIT

12. Preliminary results
The largest systematic error(~5%) – from the normalization on low-q points
Nucleon05
Oct , 2005
Evgeni Tsentalovich
MIT

13. In the Born approximation,
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
Nucleon05
Oct , 2005
Evgeni Tsentalovich
MIT

14. Vector Asymmetry
Nucleon05
Oct , 2005
Evgeni Tsentalovich
MIT

15. Tensor Asymmetry
Nucleon05
Oct , 2005
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)
Nucleon05
Oct , 2005
Evgeni Tsentalovich
MIT

17. World Data
Nucleon05
Oct , 2005
Evgeni Tsentalovich
MIT

18. Scattering of polarized electrons on polarized protons
Super ratio
Nucleon05
Oct , 2005
Evgeni Tsentalovich
MIT

19. Preliminary Results from BLAST
BLAST Left Sector BLAST Right Sector
Nucleon05
Oct , 2005
Evgeni Tsentalovich
MIT

20. Preliminary Results from BLAST
Nucleon05
Oct , 2005
Evgeni Tsentalovich
MIT

21. Preliminary Results from BLAST with World Data
Nucleon05
Oct , 2005
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 !
Nucleon05
Oct , 2005
Evgeni Tsentalovich
MIT