Recent results from BLAST detector
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Transcript of Recent results from BLAST detector
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
Recent results from BLAST detector
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
Bates Linear Accelerator center
• • 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
SiberianSnake
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
Electron beam polarization
• 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%
Compton polarimeter
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
• ABS (Atomic Beam Source) produces flux of Hydrogen or Deuterium atoms
• ABS intensity ~• Dri-film coated T-shaped storage
cell.• Target thickness ~• Hydrogen polarization Pz78%• Deuterium polarization Pz72%,
Pzz 68%• Target polarization flipped every 5
min
213 cm/at10*5
Polarized Internal Target
sec/at10*2 16
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
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 - Pz78%, 81 pb-1
2004, Deuterium - Pz84%, 130 pb-1
Pzz68%2005, Deuterium - Pz72%, 180
pb-1
Pzz56%
BEAM
BEAM TARGET
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
Kinematics for spin-dependent electron scattering
ElectronLeft
ElectronRight
q
q
B
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)
e
e’
q
p
*
*
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
BLAST physics program
H
Pol
Vect.-Pol D
Tens.-Pol D@
)'e,e(p
)p'e,e(p
n)'e,e(p
0)p'e,e(p
)n'e,e(p
)'e,e(d
)p'e,e(d
)n'e,e(d
)d'e,e(d
)d'e,e(d@
)p'e,e(d@ -production
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
)n'e,e(d
Measurements of neutron form factor n
EG
)}APAPA(hAPAP1{SddEd
d Tedzz
Vedze
Tdzz
Vdz0
CMee
**nM
nE*
2nM
2nE
**nM
nE
*2nMV
ed cossinG
Gbcosa
GcG
cossinGbGcosaGA
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
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
)n'e,e(d
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%
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
Measurements of deuteron form factors
)d'e,e(d@
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
Preliminary results)d'e,e(d@
The largest systematic error(~5%) – from the normalization on low-q points
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
)}APAPA(hAPAP1{SddEd
d Tedzz
Vedze
Tdzz
Vdz0
CMee
In the Born approximation
)p'e,e(d
)p'e,e(d@
,
0AAA Tede
Vd
TdA vanishes in the L=0 model for deuteron (no L=2 admixture)
TdA=> is a good measure of L=2 component
VedA is a good measure of L=2 component and reaction
mechanisms : MEC, IC, RC
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
Vector Asymmetry )p'e,e(d
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
Tensor Asymmetry )p'e,e(d@
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
)p'e,e(p
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)
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
)p'e,e(p
World Data
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
Super ratio
)p'e,e(p Scattering of polarized electrons on
polarized protons
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
Preliminary Results from BLAST
BLAST Left Sector BLAST Right Sector
)p'e,e(p
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
Preliminary Results from BLAST)p'e,e(p
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
Preliminary Results from BLAST with World Data)p'e,e(p
Nucleon05Oct. 12-14, 2005
Evgeni TsentalovichMIT
Preliminary results from BLASTquasi-elastic d(en) ( )
elastic d(ed) (T20) quasi-elastic d(ep)
elastic p(ep) ( )
Factor of two more data to analyze
Also analyzing data on production, resonance, T10/T11,inclusive….
More results to come !
Conclusion
pM
pE G/G
nEG