1. 20/Feb/2004K.Ozone1 TERAS analysis update 1.Compton Spectrum estimation 2.Energy resolution 3.Summary

2. 20/Feb/2004K.Ozone2 Why so broad? It is not consistent with the result (FWHM~4.5% for 55MeV) estimated in CEX beam test. The absorption length is long enough and PMT outputs were stable during the test. We can guess something was wrong with the incident beam spectrum. FWHM=11.8% In terms of energy resolution at the Compton edge (approx. 40MeV monochro.), we obtain an energy resolution of 11.8% in FWHM.

3. 20/Feb/2004K.Ozone3 Parameters in LCS beam - Most of parameters are measured and estimated. - Electron bunch size is not determined. - We may have located collimator(s) apart from the beam axis.

4. 20/Feb/2004K.Ozone4 Compton spectrum estimation Horizontal bunch size 1.55 mm 1.88 mm 2.2 mm The most sensitive factor is displacement. It was possible that collimators were shifted for some reasons. Actually the resolution would be too bad unless a certain displacement was assumed. These are not so difference. This time this parameter is fixed at 1.88mm.

5. 20/Feb/2004K.Ozone5 Fit to estimate it The fitting function is a convolution of a response function with various Compton spectra. Response functionCompton spectrum Fitting result in MC Monochromatic 40MeV gamma - Bunch size is fixed. - The displacement of collimator ranges from 0.0 mm to 3.6 mm. Gamma-ray Energy [MeV] 0.0mm 2.0mm 3.0mm 3.6mm

6. 20/Feb/2004K.Ozone6 Compton spectrum estimation Dspl =3.3mm FWHM=2.8(=1.8+1.0)% Chi2/ndf=1.03 Dspl =2.4mm FWHM=5.8(=4.8+1.0)% Chi2/ndf=1.99 Dspl =3.4mm FWHM=2.5(=1.6+0.9)% Chi2/ndf=1.44 Dspl =0.0mm FWHM=11.8(=10.3+1.5) % Chi2/ndf=2.52 Dspl:=displacement Dspl =3.6mm FWHM=3.2(=2.2+1.0)% Chi2/ndf=6.67 When the displacement becomes a few mm (right figures), chi2/ndf becomes smaller. However the others wasn’t fitted well (see below). Right-side widths are almost same ~1%.

7. 20/Feb/2004K.Ozone7 Compton spectrum estimation ndf = 25 Error bar: fitting error Displacement in X/Y was between 0.0 mm to 3.4 mm. That is, the upper limit is 3.4 mm.

8. 20/Feb/2004K.Ozone8 Energy resolution Energy resolution is estimated, assuming the displacement is less than 3.4 mm conservatively. It requires Chi2/ndf < 2.0. Center of the front face Center of the PMT - 10 points - Compton (<40MeV) events Event selection 5432154321 5 slice cuts by sigma2(D)

9. 20/Feb/2004K.Ozone9 Result (slice cut) Dspl=2.2~2.8mm Dspl=1.8~2.4mm Dspl=2.4~2.8mmDspl=1.8~2.6mm Dspl=1.8~2.2mmDspl=1.4~2.2mm Dspl=2.2~2.8mm Dspl=1.8~2.6mm Dspl=2.2~3.2mm In every cases, right widths are 3% down to 1% as below.

10. 20/Feb/2004K.Ozone10 Error evaluation 1.Collimator displacement: error bars shown in figures. 2.Electron bunch size: 0.3% 3.Gain determination: <3% 4.QE: Not corrected. 5.Total noise(pedestal): <1% against 30,000 p.e. Fitting results include 3., 4., and 5. The most dominant factor is uncertainty of the collimator displacement.

11. 20/Feb/2004K.Ozone11 Summary It is reasonable to suppose that collimators were shifted by a few mm. However it was not realistic because we by measuring counting rate. The 1 st collimator may have been shifted a bit. The energy resolution (FWHM) is expected to be less than 4% if D>45. It is almost the same as results in CEX beam test. In this analysis energy resolutions are estimated. It is found that higher tail of the spectrum is sharp enough.