Beam test report Energy resolution of calorimeter for

Beam test report Energy resolution of calorimeter for beam test at Tohoku Univ. 20/Dec/2010 End Year Meeting Kuno group M 1 Takahiro Hiasa

Outline ○Introduction ・COMET experiment ・EM calorimeter ○EM calorimeter R&D ・outline of beam test at Tohoku Univ. this year ・install of detector ・how to analyze energy resolution of EM calorimeter ○Summary and feedback 2 COMET collaboration

Proton beam from MR Introduction　 <COMET experiment> <physics> Charge Lepton Flavor Violation (c. LFV) pion PAC in J-PARC approved Stage 1 muon : 1011個/sec μ‐ hit the Al or Ti ~~ μ-e conversion ~~ Measurement is impossible by Standard Model　(BR<10 -54) ~ Introduction of Super Symmetry ~ Grand Unified Theory・see-saw Theory shows the possibility to discover the phenomenon, μ-e conversion. ↓ Discovery of new physics Detection of electron which energy is 105 Me. V Detectors SINDRUM Ⅱ(present) at PSI BR(μ−Ti→e−Ti<6. 1× 10− 13) COMET experiment 　at J-PARC BR(μ−Ti→e−Ti<10− 16)

EM calorimeter size 直径： 1 m 長さ： 11 X 0 <calorimeter’s role> ○To make event trigger ○To distinguish particles （to remove background particle） ○To confirm the momentum which Tracker measure. ・measurement of momentum ・specification of some accidental event < demand for calorimeter > ○time response < 100 nsec （which is decided by hit rate） ○work in solenoidal magnet （magnetic field： 1 T） ○energy resolution(<5%@105 Me. V)

Energy resolution of EM calorimeter Energy distribution of incident electron threshold Background Electron from μ-e conversion A broken line: Energy distribution by calorimeter 105 Me. V End point of background ＜making event trigger＞ When threshold is decided, energy resolution of EM calorimeter effects a rate of background for event rate of μ-e conversion. End point of background by calorimeter It is important how shape of right tale become slender. 5 COMET collaboration

Energy resolution of EM calorimeter Energy resolution (right tail) simulation experiment : energy resolution : fluctuation of energy deposit in crystal : fluctuation of photon equivalent : fluctuation of noise We can estimate the fluctuation of photon equivalent and noise by 105 Me. V electron beam. We experimented by 105 Me. V electron beam 6 COMET collaboration (22 nd~27 th/Nov/2010

Outline of beam test by 105 Me. V/c electron beam ○Purpose To achieve energy resolution dσ/d. E < 5% ○geometry of beam test calorimeter (188 mm by 188 mm) Si-strip detector (30 mm by 30 mm) (position sensitive detector) Electron beam Trigger counter (for cosmic ray) ○beam condition (electron beam) Beam energy : 75 Me. V/c, 105 Me. V/c, 125 Me. V/c Beam expansion : RMS ~ 5 cm Trigger counter (for beam) (100 mm by 100 mm, thickness: 6 mm) ~~~ We used GSO as crystal and MPPC as photo detector ~~~

Equipment Si-pixel detector (position detector) GSO with LAPD Trigger counter (with MPPC) electron beam calorimeter Trigger counter (for cosmic) Trigger counter (for beam) • ○Equipment • Calorimeter (188 mm by 188 mm) 　　　 → energy resolution • Si-pixel detector(30 mm by 30 mm) → decision of position • Trigger counter (for beam)(100 mm by 100 mm) → trigger for beam • Trigger counter (for cosmic) → trigger for cosmic • Trigger counter (readout : MPPC) → trigger and time resolution of MPPC (100 mm× 10 mm　thickness: 3 mm) • GSO with Large APD(LAPD) 　 → comparison with MPPC

Crystal and MPPC < GSO crystal> (2 plane is polished) 20 mm× 120 mm The key is how this slow component of GSO effects the energy resolution. < MPPC > ・Good photo counting ・Workable in magnetic field ・ High gain (~106) ・Low bias voltage ・Good time resolution ☆We use S 10362 -33 -050 C (hamamatsu photonics co. ) ・Effective area : 3 cm by 3 cm ・Number of pixel : 3600 pixel (pixel size : 50 micron)

Drive circuit of MPPC • • High path filter and Low path filter We put LED on the circuit. LED is to correct output of MPPCs and monitor the gain of MPPCs. LED GSO Drive circuit MPPC 18 mm

Geometry of EM calorimeter Wrapping of crystal: Teflon sheet and tape Back plate : Teflon sheet and Aluminum plate Front plane : Aluminized PVC plate Taflon tape zone Center of beam Radius=3*RM Because we used 50 segments, we needed to calibrate them.

Back of calorimeter LED GSO crystal MPPC Al plate screw spring

Signal of oscilloscope

How to analyze energy resolution • 1. calibration of each segment by MIP peak of cosmic ray • ↓problem • There is the possibility which MPPCs are saturated for cosmic ray. • → to estimate energy of calorimeter for cosmic ray to include the effect of saturation. • Reset of energy scale • Fitting with simulation for MIP peak and getting the fitting parameter. • Calibration of the energy for each segment with beam run on offline.

• • 2. Cut of position by Si-strip detector ↓problem the center of calorimeter is not that of Si-strip detector → to estimate the center of calorimeter for Si-strip detector 　with offline • From 2 D histogram, ADC distribution for 4 segments as center of calorimeter VS position for Si-strip detector, I should estimate position of center, cut around 2 cm by 2 cm for each histogram of segment and sum histograms of 50 segments.

• 3. Fitting ↓problem • There is also the possibility with MPPCs are saturated for beam. • I need to fit by using the value of energy deposit of simulation for beam and estimate the number of photon for calorimeter. ~~Results of analysis have been not yet finished~~

Summary • EM calorimeter has most important role as event trigger. • Energy resolution effect rate of background for event rate. • This year we experiment with 50 GSO crystals and 50 MPPCs at Tohoku Univ. • We use 105 Me. V electron beam whose expansion is 10 cm. • We need to consider with the saturation of MPPC for cosmic ray and beam to analysis. • Analysis is coming soon

Back up

Equipment Si-strip detector (position sensitive detector) calorimeter Trigger counter (for cosmic ray) Electron beam Trigger counter (for beam) ○Equipment Calorimeter　　　 → energy resolution Si-strip detector → decision of position Trigger counter (for beam) → trigger for beam Trigger counter (for cosmic) → trigger for cosmic Trigger counter (readout : MPPC) → trigger and time resolution of MPPC GSO with Large APD(LAPD) 　 → comparison with MPPC

μ-e conversion

Hit rate of calorimeter

Introduction • μ-e conversion

How to currect bias voltage • Calibration of PDE of 50 MPPCs by LED. 1. We put LED on each diver circuit of MPPCs. 2. We subtract ADC count of pedestal from that of LED and made gain curve for each MPPC by LED 3. We re-supplied new value of bias voltage to calibrate PDE of MPPCs. ☆We set bias voltage such as ADC count of peak with 105 Me. V/c electron beam is near 2000 ADC count. LED 18 mm GSO MPPC Drive circuit

How to calibrate ② • Calibration of 50 segments by cosmic ray in offline analysis. 1. We took 242, 120 events on cosmic run. (trigger rate ~ 3 Hz) 2. We calculated the calibration factor for each segment and calibrate each ADC distribution of beam run in offline.

Analysis for energy resolution

Calibration of position by Si-pixel detector and energy resolution by cutting with position

Estimation of number of photon