1. Chris Crawford Blast Analysis Meeting 2004/05/21
H(e,e’p) Analysis
Chris Crawford
Blast Analysis Meeting
2004/05/21

2. Monte Carlo Dataset used DGen, epel channel
KINE (note .’s)
4 states, q=25±  90±, f=-17±  17±
gen. 2.5M events ! 1.5M recon (75 bud hrs)
momentum resolution: 15 MeV
6th order t2d function (before 2nd q bug-fix)
standard wire resolution (200!120!400 m)
LOSS=1 MULS=1

3. MC Cross Section
theta

4. MC Asymmetry

5. MC Form Factor Ratio

6. Fit Method Super-ratio Method 2 equations in P, R
i = left,right
j = Q2 bin (1..n)
b = spin angle
Fit Method
Super-ratio Method
2 equations in P, R
for fixed bin j
independent polarization in each bin!
2n parameters Pj, Rj
Global Fit Method
fit ALj, ARj to above formalism with P, Rj
n+1 parameters
n+2 (+spin angle?)
same advantage as super-ratio method
PbPt still cancels

7. Outbending Data (Dec)

8. Inbending Data(Feb, Apr)

9. Combined Dataset

10. Spin angle: 35± § 10± (errors also insensitive?)
Fit of Spin Angle
Spin angle: 35± § 10± (errors also insensitive?)

11. Systematic Errors 4 measured states ) 2 False Asymmetries Two options:
a) assume beam and target symmetric, use Ab, At to estimate uncertainty in charge
b) use measured beam/target asymmetry to calculation physics asymmetry dilution

12. False Asymmetries

13. MC Resolution Studies T2D, bkg 0m 200m 500m 2mm linear 1.8 3.0 6.7 94
intrinsic wire resolution
T2D, bkg 0m
200m
500m
2mm
linear
1.8
3.0
6.7 94
linear, phys
3.5
4.7
6th order
6.6
6th ord, phys
12.8
Momentum Resolution (MeV)

14. Track Fit Data vs MC

15. Tools for Improving Reconstruction/Analysis
wcb_ntuple.C
entry for each stub
track info (p,q,f,z)
stub coordinates
t0-2, x0-2, d0-2
qtrk in cell, B field 16 48 8 24 32 40 56

16. nsed + init.C

17. Cosmics

18. Todo List refine cuts (TOF, CC), subtract background
cuts on epics variables (current, WC HV)
detector efficiencies w/unpol buffer system
more statistics in MC, radiative corrections
unfold b(z), acceptance dependence of s
improve WC resolution, do a kinematic fit
investigate low value of b fit