elastics

Elastic analysis summary 05/30/06

In the plot below, the solid line represents the random and scale uncertainty added in quadrature, while the dashed line represents the random systematic uncertainty. The model uncertainty has not been included. The error bars on the data points are the statistical uncertainty.

Elastic settings

New Hee'p offsets

Ebeam(GeV)	P hms(GeV)	TH hms(deg)	P sos(GeV)	TH sos(deg)	dE	dth_ss	dp_ss	dth_hs	dp_hs	dssxptar	dhsxptar
2.038	-1.692	25.005	0.874	54.90	0.59	0.0	0.48	0.6	0.9	-0.0032	-0.0011
5.012	4.116	18.70	-1.7227	50.00	0.79	-1.0	11.0	0.6	0.9	-0.0032	-0.0011
5.766	4.867	16.19	-1.6868	51.61	0.2	0.0	8.11	0.0	0.9	-0.0032	-0.0011
4.021	3.232	22.15	-1.588	50.00	-0.75	-1.0	3.85	1.0	0.9	-0.0032	-0.0011

The format of the offsets "d[variablename]" are the same as those in "heepcheck.f". For example, for the electron in the sos
         p_e = ssp*(1-dp_ss/1000.0)
         th_e = mysstheta-dth_ss/1000.0 [rad]
         p_p = hsp*(1-dp_hs/1000.0)
         th_p = myhstheta-dth_hs/1000.0   [rad]
         newE=e_beam*(1+dE/1000.0)
     newssxptar= ssxptar- dssxptar [rad]
         newhsxptar=hsxptar-dhsxptar [rad]
The plots for the previously fitted heep offset results (see 05_28_06 below) are shown below. SIMC with radiation, eloss, etc turned on is shown in blue. The data are the green and red histograms, which should overlap.

Q2=0.633 GeV2
Q2=4.51 GeV2
Q2=6.1 GeV2
Q2=7.47 GeV2

Normalized yields

Elastic cuts

Cointime cuts

The graphical cointime cut was used
Large Q2

Small Q2

Data cuts
PID and missing mass cuts
(scer_npe>1.35.and.Em<0.025.and.abs(W-0.94)<0.1)
Acceptance
abs(hsyptar)<0.04.and.abs(hsxptar)<0.07.and.abs(hsdelta)<8.0
      (abs(ssyptar)<0.07.and.abs(ssxptar)<0.04.and.abs(ssdelta-2.5)<12.5)
Jochen's cut (Pg 80 of his thesis)
       (ssyptar>-125.0+4.25*ssdelta+64.0*ssytar-1.7*ssdelta*ssytar)
     (ssyptar<125.0-4.25*ssdelta+64.0*ssytar-1.7*ssdelta*ssytar)
Coincidence blocking and sync cuts (values from the database)
       hsrawct>[myblockcut].and.(hsrawct+ssrawct)>[mysynccut]
Angle cointime cuts (protons in the SOS)
       abs((cointime)-[a])<[b].and.(ssbeta)>[b1min].and.(ssbeta)<[b1max]
       (ssbeta)>[b2min].and.(ssbeta)<[b2max]
   (cointime)-[a]>-[b]+[m]*(-0.5)*((ssbeta)-[c]-abs((ssbeta)-[c]))
       (cointime)-[a]<[b]+[m]*(-0.5)*((ssbeta)-[c]-abs((ssbeta)-[c]))

SIMC cuts
      Em<0.025.and.abs(W-0.94)<0.1
abs(hsyptar)<0.04.and.abs(hsxptar)<0.07.and.abs(hsdelta)<8.0
abs(ssyptar)<0.07.and.abs(ssxptar)<0.04.and.abs(ssdelta-2.5)<12.5
   (ssyptar>-125.0+4.25*ssdelta+64.0*ssytar-1.7*ssdelta*ssytar)
     (ssyptar<125.0-4.25*ssdelta+64.0*ssytar-1.7*ssdelta*ssytar)

NB the HMS acceptance cut was reduced at the highest Q2 point, where the HMS momentum was 4.864 GeV. The edges of the acceptance were removed in both SIMC and the data, according to the cuts
     abs(hsyptar)<0.03.and.abs(hsxptar)<0.015.and.abs(hsdelta)<6.0

Data and SIMC distributions

Q2=4.51 GeV2
Q2=6.1 GeV2
Q2=7.47 GeV2

Systematic uncertainty

The significant contributions are:
Proton absorption: 0.5% random and 2.0% scale
HMS fid effic: 1% random and 1.0% scale
SOS fid effic: 0.5% random and 0.5% scale
Radiative corrections: 0.5% random and 1.0% scale
Acceptance: 2.0% scale
Total systematic uncertainty: 1.3% random and 3.2% scale

Model dependence: 2-3% at the lowest Q2 and 3-4% at the other two data points.

Extra plots
W plot
p corsi