H(e,e’p) Analysis

H(e,e’p) Analysis

Chris Crawford

Blast Analysis Meeting

2004/05/21

Monte Carlo Dataset

used DGen, epel channel KINE 10 1. 1. 0. 45. 0. 21. 0. 11. (note .’s) 4 states, =25± 90±, =-17± 17±

gen. 2.5M events ! 1.5M recon (75 bud hrs) momentum resolution: 15 MeV

6th order t2d function (before 2nd bug-fix) standard wire resolution (200!120!400 ) LOSS=1 MULS=1

MC Cross Section

theta

MC Asymmetry

MC Form Factor Ratio

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

i = left,right

j = Q2 bin (1..n)

= spin angle

Outbending Data (Dec)

Inbending Data(Feb, Apr)

Combined Dataset

Fit of Spin Angle

Spin angle: 35± § 10± (errors also insensitive?)

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

False Asymmetries

MC Resolution Studies

T2D, bkg 0 200 500 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)

intrinsic wire resolution

Track Fit Data vs MC

Tools for Improving Reconstruction/Analysis

0 16 48

8 24 32

40 32 56

wcb_ntuple.C entry for each stub track info (p,,,z) stub coordinates t0-2, x0-2, d0-2 trk in cell, B field

nsed + init.C

Cosmics

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 (z), acceptance dependence of improve WC resolution, do a kinematic fit investigate low value of fit