Analysis of PSI beam test R.Sawada 09/Feb/2004 MEG collaboration R.Sawada 09/Feb/2004 MEG collaboration

Energy Resolution

3 Data Condition #6628-#6671with paraffin shield Collimator size Xenon 9.5 cm NaI 11.5 cm FSH52 DAC value (beam intensity) 125 PMT gain1e6

4 Event Selection and Q.E. correction Q.E. estimated from liquid data was used for each PMT. & (NaI sum)<105 This cut is not important, because resolution doesn’t change with this cut.

5 5th step (depth correction) 3077 events (2059 events Qsum>25000) 3077 events (2059 events Qsum>25000) FWHM = 4.5 ± 0.4 %

6 Masking effect ➀ without masking ➁ mask: edge of front ➂ mask: edge of front top,bottom ➂ mask: edge of front top,bottom ➃ mask: edge of front top,bottom right,left ➃ mask: edge of front top,bottom right,left gamma Some PMTs are masked to simulate the curved shape of the final detector. Curved shape is corresponding between ➀ and ➂ (it depends on how to put PMTs). FWHM sigma(right) FWHM sigma(right)

7 Masking effect 2 mask ➄ mask ➅ mask ➄ mask ➅ Is symmetry important?

8 Energy resolution (83,129 MeV) #689[6-7], trigger:S1*Xe FWHM: 4.5 ± 1.8 % σ(right): 1.0 ± 0.2 % FWHM: 4.5 ± 1.8 % σ(right): 1.0 ± 0.2 % FWHM: 5.0 ± 0.6 % σ(right): 1.16 ± 0.06 % FWHM: 5.0 ± 0.6 % σ(right): 1.16 ± 0.06 % What are these 2 events? 83MeV 129MeV

9 High energy events Cosmic Ray? Miss reconstructed position ? (due to using simple average) Miss reconstructed position ? (due to using simple average)

10 Energy and Resolution PSI 2003 TERAS 2003 alpha PSI 2003 TERAS 2003 alpha Resolution(right) becomes better as a function of gamma energy. * Error bar shows only fitting error.

Timing Resolution

12 Data Condition #699[4-6],7045without Amplifier Collimator size Xenon 9.5 cm NaI 11.5 cm FSH52 DAC value (beam intensity) 125 PMT gain~5e6 added

13 Algorithm Timing correction of each PMT ☀ time walk ☀ vertex (x_average,y_average,sigma2) 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 : 50 nphe ☀ weight : sqrt(ADC) ☀ masked if (TDC - mean) > 10nsec Taking the average with ☀ software threshold : 50 nphe ☀ weight : sqrt(ADC) ☀ masked if (TDC - mean) > 10nsec TDC’(i) = TDC(i) - TDC(TC) added

14 Timing resolution (right - left) Resolution is 65 ± 2 psec (5e6 gain) ☀ Depth cut : Nfpmt(0.5)>4 ☀ No impinging point cut is applied. ☀ Xe energy cut for selecting 55MeV gamma is applied. ☀ Depth cut : Nfpmt(0.5)>4 ☀ No impinging point cut is applied. ☀ Xe energy cut for selecting 55MeV gamma is applied. # of eventsresolution (σ) 55 MeV w/ depth cut psec 55 MeV w/o depth cut psec 83 MeV w/ depth cut psec 83 MeV w/o depth cut psec

15 Timing resolution (Xe - TC) 3:00 9:00 4:00 12:00 cut# of eventsresolution (σ) w/ Nfpmt(0.5>4 w/ sigma2< psec w/ Nfpmt(0.5)> psec w/o depth cut psec Resolution includes ☀ resolution of TC ~ 60psec ☀ target size ~ 60 psec but it is still worse than “r-l analysis”. Resolution includes ☀ resolution of TC ~ 60psec ☀ target size ~ 60 psec but it is still worse than “r-l analysis”. due to temperature of delay cable ? Time difference is shifting. corrected with linear function.

16 Masking effect (Timing) gamma # of photo- electrons w/ depth cut (R-L) w/o depth cut (R-L) w/o mask30,00065 psec73 psec mask: L,R18,83075 psec86 psec mask: L,R,T,BT 7, psec152 psec mask: ADC#>127 23,02473 psec80 psec

Summary Energy resolution of 83,129MeV gamma is estimated. Resolution becomes better as a function of gamma energy. Timing resolution is estimated with more statistics. Depth cut which I applied is strict. I will search optimum depth cut for sensitivity. Energy resolution of 83,129MeV gamma is estimated. Resolution becomes better as a function of gamma energy. Timing resolution is estimated with more statistics. Depth cut which I applied is strict. I will search optimum depth cut for sensitivity.

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19 Number of Events # of events (Qsum>25000) FWHM [%] all367k step1 Mainly,removal pedestal events. 267k step2removal 83 MeV82k(34k)8.5 ± 0.3 step3x-y selection7160(4223)7.9 ± 0.9 step4depth cut3077(2059)4.9 ± 0.4 step5depth correctionsame4.5 ± 0.4

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

21 Position dependence of resolution FWHM [%] center of the detector center of F14 center of F21 center of F20 center of F15 There is no positioin dependence of resolution. 4.3±1.04.8±0.44.6± ±0.64.5±0.34.5± ±0.95.0±0.55.0±1.6

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

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

24 Timing resolution with 1e6 gain + Amplifier gain beam intensity (FSH52 DAC) time resolution (right - left) [psec] time resolution (Xenon - tc) [psec] w/o Amp1e ± ± 11 w/ Yuri’s Amp1e ± 6295 ± 6 w/ Lecce Amp1e ± 6300 ± 7 w/o Amp5e ± 6256 ± 7 Time resolution using 8 PMTs which is applied amplifiers. Amplifier improve the resolution at 1e6 gain.

25 1st Step (remove pedestal events) 367k events 267k events Mainly, subtraction of pedestal events.

26 2nd Step (83 MeV gamma rejection) 82k events (34k events Qsum>25000) 82k events (34k events Qsum>25000) FWHM = 8.5 ± 0.3 % & (NaI sum)<105

27 3rd step (position selection) 7160 events (4223 events Qsum>25000) 7160 events (4223 events Qsum>25000) FWHM = 7.9 ± 0.9 %

28 4th step (depth selection) FWHM = 4.9 ± 0.4 % 3077 events (2059 events Qsum>25000) 3077 events (2059 events Qsum>25000)