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Analysis of Pion beam test

Analysis of Pion beam test. R.Sawada 20/Jan/2004 on VRVS. Q.E. estimation Energy Resolution Timing Resolution. Absorption. distance dependence of number of photoelectrons at each PMT normalized with MC. Xenon was very pure !. Q.E. estimation.

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Analysis of Pion beam test

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  1. Analysis of Pion beam test • R.Sawada • 20/Jan/2004 • on VRVS Q.E. estimation Energy Resolution Timing Resolution

  2. Absorption distance dependence of number of photoelectrons at each PMT normalized with MC. Xenon was very pure !

  3. Q.E. estimation We have ever used gas data for Q.E. estimation. But now we can also use liquid data because Xe is pure. gas alpha in gas TERAS in 2003 gain ~ 5e6 liquid alpha in liquid PSI in 2003 gain ~ 1e6 beam on (FSH52 =125) Q.E. (liquid ~ -105℃) ~ 0.74 * Q.E. (gas ~ -85℃)

  4. Comparison between data and MC Q.E. estimated from liquid alpha data was used in MC. MC data data MC alpha Pi0->2gamma The peak position is well reproduced by this MC code.

  5. Energy Resolution

  6. with paraffin shield Collimator size Xenon 9.5 cm NaI 11.5 cm FSH52 DAC value (beam intensity) 125 PMT gain 1e6 Data Condition

  7. cut & correction MC rejected Nfpmt(0.5)>4 accepted Nfpmt(0.5) is used as depth parameter for correction and cut. sigma2<90 is also applied to remove very deep events. Nfpmt : number of PMTs which occupy the half of Qfront.

  8. Energy Resolution • Depth cut and correction. • 55 MeV gamma is selected by NaI energy cut. • Impinging position cut is also applied • (sqrt(x_average^2 + y_average^2)< 1.5cm) FWHM = 4.5 ± 0.3 (left:2.7 + right:1.8) % (sigma of the right part is 1.53%)

  9. Position dependence of resolution center of F14 center of F20 center of the detector There is no positioin dependence of resolution. center of F15 center of F21 FWHM [%]

  10. Depth dependence of resolution Resolution is estimated with slicing with depth parameter. Correspondence of depth parameter and the depth is calculated from MC. FWHM is constant if depth > ~4cm

  11. Masking effect Some PMTs are masked to simulate the curved shape of the final detector. Curved shape is corresponding between 1and 3(it depends on how to put PMTs). 4 mask: edge of front top,bottom right,left 2 mask: edge of front gamma 3 mask: edge of front top,bottom 1 without masking

  12. Timing Resolution

  13. without Amplifier Collimator size Xenon 9.5 cm NaI 11.5 cm FSH52 DAC value (beam intensity) 125 PMT gain ~5e6 Data Condition

  14. Timing Counter (TC) • 2 × 5cm × 5cm × 1cm BC404 • 4 × 1-inch finemesh type PMTs • 5cm × 5cm × 0.6 cm lead target • Time walk correction. • virtex correction with Nphe(light)/Nphe(right) Timing resolution of the timing counter is 60 psec

  15. Algorithm TDC’(i) = TDC(i) - TDC(TC) • Timing correction of each PMT • time walk • vertex (x_average,y_average,sigma2) Timing of each PMT is shifted so that mean become 0. • Taking the average with • software threshold : 20 nphe • weight : sqrt(ADC)

  16. Timing resolution (right - left) Compared the timing of each part after dividing the detector to right and left. • Depth cut is the same as energy analysis. • No impinging point cut is applied. • Energy cut for selecting 55MeV gamma is applied. Resolution is 75 ± 4 psec (5e6 gain) (fluctuation from the first conversion depth distribution is not included in this resolution)

  17. Timing resolution (Xe - TC) Time resolution is also estimated from the difference between the Xenon and the timing counter. Resolution is sqrt(128^2-60^2) = 113 psec (5e6 gain) Timing has no correlation with depth because it is corrected for each PMTs before taking the average. If we don’t correct depth correlation, it is like the right figure. The difference from the analysis(right-left) can be the resolution of depth reconstruction (~70psec).

  18. Timing resolution with 1e6 gain + Amplifier Time resolution using 8 PMTs which is applied amplifiers. Amplifier improve the resolution at 1e6 gain.

  19. Summary • Q.E. is estimated from liquid data to take into account the decrement of it under backgrounds. • Energy resolution is estimated as 4.5 ± 0.3 %. There is no strong dependence on impinging position or depth. (if depth > ~4cm) • Energy resolution is estimated with masking some PMTs to simulate curved shape. The effect must not be so large. • Timing resolution of (right -left) is 75 psec • Timing resolution of (Xe - TC) is 113 psec. We need more sophisticated way to reconstruct the depth. • Amplifier will improve timing resolution at 1e6 PMT gain.

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