Development of Electromagnetic Calorimeter for COMET: The ...9th Mar. 2015 @ ELPH Workshop C010, Tohoku University, Japan Kou Oishi / Kyushu University 3.1. INTRODUCTION TO THE COMET

Development of Electromagnetic Calorimeter for COMET:The J-PARC Muon-to-Electron Conversion Search Experiment

J-PARC ��COMET��

大石航 / Kou OishiKyushu University, Japan

9th Mar. 2015 @ ELPH Workshop C010, Tohoku University, Japan

L. EpshteynB, P. EvtoukhovichC, Y. FukaoD, D. GrigorievB, Y. IgarashiD, V. KalinnikovC, K. KawagoeA, B. KriklerE, A. KulikovC, Y. KunoF, T. MibeD, S. MiharaD, A. MoiseenkoC, H. NagashimaA, Y. NakaiA, H. NishiguchiD, N. SaitoD, A. SatoF, J. TojoA, Z. TsamalaidzeC, K. UenoD, H. YamaguchiA, T. YoshiokaG, Y. YudinB, and the COMET Collaboration

Osaka Univ.F

Kyushu Univ.A

KEKDJINRCBINPB Kyushu Univ. RCAPPG

UCLE

Kou Oishi / Kyushu University9th Mar. 2015 @ ELPH Workshop C010, Tohoku University, Japan

Muon-to-Electron (μ-e) Conversion

µ-e Conversion is a very clean probe for the BSM search.

- Charged-Lepton Flavor Violation Process-

µ-e Conversion

Suppressed in the SM (BR ~ O(10-54)).

40-orders gap

(Experimentally Negligible)

nucleus

µ- νµ

µ-νµ

e-

νe

2

Some BSM theories enhance it up to O(10-15).

µ-

e-

muon capture

Decay in Orbit


Muon-to-Electron (μ-e) Conversion

Alµ-

µ-

νµ

muon captureµ-

νµ

e-

νe

Decay in Orbit

e-

3

the DIO electrons is presented in Section 17.2. In this study, the momentum cut of 103.6 MeV/c <Pe < 106.0 MeV/c, where Pe is the momentum of electron, is determined as shown in Fig. 107 [61].According to this study, the contamination from DIO electrons of 0.01 events is expected for a singleevent sensitivity of the µ!N ! e!N conversion of 3.1" 10!15.

Momentum [MeV/c]101.5 102 102.5 103 103.5 104 104.5 105 105.5 106

Coun

ts p

er 0

.1 M

eV/c

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18)-15 10!Signal and DIO (BR=3

Pth [MeV/c]101.5 102 102.5 103 103.5 104 104.5 105 105.5 106

Inte

gral

ove

r Pth

upt

o 10

6.0

MeV

/c

0

0.2

0.4

0.6

0.8

1

1.2

)-15 10!Signal and DIO (BR=3 Signal AcceptanceDIO Contamination 1.0% Contamination 97% Acceptance103.6MeV/c Threshold

Figure 106: Left: Distributions of the reconstructed µ!N ! e!N conversion signals and reconstructed DIOevents. The vertical scale is normalized so that the integrated area of the signal is equal to one event with itsbranching ratio of B(µN ! eN) = 3.1" 10!15. Right: The integrated fractions of the µ!N ! e!N conversionsignals and DIO events as a function of the low side of the integration range and the high side of the integrationrange is 106 MeV/c. The momentum window for signals is selected to be fro 103.6 MeV/c to 106 MeV/c sothat the DIO contamination would be 0.01 events.

16.1.4 Time window for signals

The muons stopped in the muon-stopping target have the lifetime of a muonic atom. The lifetimeof muons in aluminium is about 864 nanoseconds. The µ!N ! e!N conversion electrons can bemeasured between the proton pulses to avoid beam-related background events. However, some beam-related backgrounds would come late after the prompt timing, such as pions in a muon beam. There-fore, the time window for search is chosen to start at some time after the prompt timing. As discussedin Section 16.2, the starting time of time window of measurement of 700 nanoseconds is assumed,although it would be optimized in the future o!ine analysis.

The acceptance due to the time window cut, !time, can be given by,

!time =Ntime

Nall, (9)

Ntime =n!

i=1

" t2+Tsep(i!1)

t1+Tsep(i!1)N(t)dt, (10)

where Nall and Ntime are the number of muons stopped in the target and the number of muons whichcan decay in the window, respectively, Tsep is the time separation between the proton pulses, t1 and t2are the start time and the close time of the measurement time window, respectively, and n indicatesthe window for the nth pulse. The time distribution of the muon decay timing N(t) is obtained byMonte Carlo simulations. In our case, t1 and t2 are 700 nsec and 1100 nsec, respectively and Tsep is1.17 µsec, and !time of 0.3 is obtained.

16.1.5 Net Acceptance of signals

it is assumed that the e"ciencies of trigger, DAQ, and reconstruction e"cacy are about 0.8 for each.From these, the net acceptance for the µ!N ! e!N conversion signal, Aµ-e = 0.043 is obtained. Thebreakdown of the acceptance is shown in Table 24.

98

Signal e-

Monochromatic105 MeV (Aluminum)

Electron Energy (MeV)

Decay in OrbitSignal

105104

High energy resolution is required.• Irreducible background

• Fall down by E-5 below 105 MeV • High rate


COherent Muon Electron Transition

•At J-PARC, Ibaraki, Japan

•The most intense pulsed muon beam line is under construction.

•Two-Staging experimental plan:

Sensitivity (2017) Phase-I 10-15 (2020~) Phase-II 10-17

Current Limit : 7 x 10-13 (SINDRUM-II)

→ Aim at finding signals with 104-improved sensitivity!

COMET Experiment

4

3.1. INTRODUCTION TO THE COMET EXPERIMENT 31

Detector Section

Pion-Decay andMuon-Transport Section

Pion Capture Section

A section to capture pions with a large solid angle under a high solenoidal magnetic field by superconducting maget

A detector to search for muon-to-electron conver-sion processes.

A section to collect muons from decay of pions under a solenoi-dal magnetic field.

Stopping Target

Production Target

Figure 3.1: Schematic layout of the muon beamline and detector for the proposed searchfor µ!!e! conversion, the COMET experiment.

the occurrence of beam-related background events, a pulsed proton beam utilizing abeam extinction system is proposed. Since muons in muonic atoms have lifetimes ofthe order of 1 µsec, a pulsed beam with beam buckets that are short compared withthese lifetimes would allow removal of prompt beam background events by allowingmeasurements to be performed in a delayed time window. As will be discussed below,there are stringent requirements on the beam extinction during the measuring interval.Tuning of the proton beam in the accelerator ring as well as extra extinction devicesneed to be installed to achieve the required level of beam extinction.

• Curved solenoids for charge and momentum selection: The captured pionsdecay to muons, which are transported with high e!ciency through a superconductingsolenoid magnet system. Beam particles with high momenta would produce electronbackground events in the energy region of 100 MeV, and therefore must be eliminatedwith the use of curved solenoids. The curved solenoid causes the centers of the helicalmotion of the electrons to drift perpendicular to the plane in which their paths arecurved, and the magnitude of the drift is proportional to their momentum. By usingthis e"ect and by placing suitable collimators at appropriate locations, beam particlesof high momenta can be eliminated.

ProtonPion production target

Pion decay &muon transportsolenoid magnet

Al TargetSolenoid spectrometer

Detector5 m

Phase-II


COMET Collaboration

5Jan 2015 @ the COMET facility under construction next to the J-PARC Hadron Hall

•Japan• High Energy Accelerator Research Organization (KEK), Tsukuba,

Japan• Institute for Chemical Research, Kyoto University, Kyoto, Japan• Kyoto University Research Reactor Institute, Osaka, Japan• Kyushu University, Fukuoka, Japan• Nagoya University, Nagoya, Japan• Osaka University, Osaka, Japan• Saitama University, Saitama, Japan• Utsunomiya University, Utsunomiya, Japan

•Russia• Institute for Theoretical and Experimental Physics (ITEP),

Moscow, Russia• Joint Institute for Nuclear Research (JINR), Dubna, Russia• Budker Institute of Nuclear Physics (BINP), Novosibirsk, Russia

•Belarus• Belarusian State University (BSU), Minsk, Belarus• National Academy of Sciences of Belarus (NASB), B.I. Stepanov

Institute of Physics, Minsk, Belarus

•Georgia• Institute of High Energy Physics of I.Javakhishvili State

University (HEPI TSU), Tbilisi, Georgia• Ilia State University (ISU), Tbilisi, Georgia

•Czech Republic• Charles University in Prague, Prague, Czech Republic• Czech Technical University in Prague, Prague, Czech Republic

•Korea• Institute for Basic Science & Korea Advanced Institute of Science

and Technology, Deajeon, Korea

•China• Nanjing University, Nanjing, China• North China Electric Power University, Beijing, China

• Institute of High Energy Physics (IHEP), Beijing, China• Joint affiliation with Nanjing University, Nanjing, China• Peking University, Beijing, China

•India• Indian Institute of Technology, Bombay, India

•UK• Imperial College London, London, UK• University of Manchester, UK• University College London, UK• Rutherford Appleton Laboratory (RAL), Didcot, UK

•France• Laboratory of Nuclear and High Energy Physics (LPNHE),

CNRS-IN2P3 and University Pierre and Marie Curie (UPMC), Paris, France

•Malaysia• University of Malaya, Kuala Lumpur, Malaysia

•Vietnam• College of Natural Science, National Vietnam University, Ho Chi

Minh City, Vietnam

•Canada• TRIUMF, Vancouver, Canada


3.1. INTRODUCTION TO THE COMET EXPERIMENT 31

Detector Section

Pion-Decay andMuon-Transport Section

Pion Capture Section

A section to capture pions with a large solid angle under a high solenoidal magnetic field by superconducting maget

A detector to search for muon-to-electron conver-sion processes.

A section to collect muons from decay of pions under a solenoi-dal magnetic field.

Stopping Target

Production Target

Figure 3.1: Schematic layout of the muon beamline and detector for the proposed searchfor µ!!e! conversion, the COMET experiment.

the occurrence of beam-related background events, a pulsed proton beam utilizing abeam extinction system is proposed. Since muons in muonic atoms have lifetimes ofthe order of 1 µsec, a pulsed beam with beam buckets that are short compared withthese lifetimes would allow removal of prompt beam background events by allowingmeasurements to be performed in a delayed time window. As will be discussed below,there are stringent requirements on the beam extinction during the measuring interval.Tuning of the proton beam in the accelerator ring as well as extra extinction devicesneed to be installed to achieve the required level of beam extinction.

• Curved solenoids for charge and momentum selection: The captured pionsdecay to muons, which are transported with high e!ciency through a superconductingsolenoid magnet system. Beam particles with high momenta would produce electronbackground events in the energy region of 100 MeV, and therefore must be eliminatedwith the use of curved solenoids. The curved solenoid causes the centers of the helicalmotion of the electrons to drift perpendicular to the plane in which their paths arecurved, and the magnitude of the drift is proportional to their momentum. By usingthis e"ect and by placing suitable collimators at appropriate locations, beam particlesof high momenta can be eliminated.

COMET Detector Region

6

CHAPTER5.DETECTOR83

calorimetersignalswillbeprocessedlocallybyanFPGAthatwillcutonenergydepositedinshowerclusterswithinthecalorimeter.Attriggerdecisionmustbemadewithin500nsinordertoextractvalidinformationfromthetracker.

5.4.2.5Performance

EnergyresolutionsofthecalorimeterisstudiedusingGeant4withOpticalPhotonPro-cesses.Theresolutiondependsoncrystal,lightguide,photondetector,andtheirgeomet-ricalconfiguration.Inthissection,wediscussdependenceoftheresolutiononthecrystalsunderapossibleconfigurationofthecalorimeter.

Figure5.15:Atypicaleventdisplayofthesimulationstudyofthecalorimeter.Anelectroninjectedtothecalorimeter,thenopticalphotonsfromscintillationprocessesareray-tracedtothephotondetectors.

Figure5.15showsatypicaleventdisplayofthissimulation.Thecalorimeterisacylinder0.8mindiameter,andconsistsof1224rectangularsegments.Thecrystalhassizeof20!20!150mm3asalreadymentioned.Inthissimulationreadoutbyphotomultiplierswithaquantume!ciencydependenceonthewavelengthissupposedforsimplifyinglighttransmissionmodelfromthecrystalendtothephotosensorsurface.

Figure5.16showsphotoelectrondistributionsfor105MeVelectioninjectionstothecalorimeter.Energyresolutionsof5.0%inFWHMforGSO(Ce)and3.6%inFWHMforLYSOareexpected.Notethatthesedoesnotincludethee"ectofelectronenergylossinthemuonstroppingtargetmaterialwhichisestimatedtobelessthan1MeVinFWHM.

KEK/J-PARC-PAC 2012-10

• Measure p and E of incoming particles• Particle ID by using p/E

• Background reduction• ECAL works as the trigger detector.

6.5. ELECTRON TRACKER 103

Figure 6.13: Cut view of COMET detector. Red rings around the curved solenoid sectionare magnet coils, and tilted to produce the compensation field (A field that cancels the driftfor a 105 MeV electron)

understood and controlled.A schematic of the stopping target and detector solenoids is shown in Figure 6.13.

The tracking detector is located downstream of a curved transport solenoid and the muonstopping target. The detector consists of a set of 5 straw planes, 48 cm apart, and placed sothat the axial direction of the straws is transverse to the axis of the solenoid. Each of the5 planes contains a set of 4 straw tube arrays. One array measures position in x, and onemeasures position in y (coordinates rotated by !/2). An identical (x,y) pair is attached tothe first array, but rotated by 45 deg., in order to break hit ambiguities and add redundancy.A hit location is determined by the plane position, the straw position within a plane, andthe drift time. There is presently no second coordinate readout, although charge divisionon a straw anode wire is under consideration. The azimuthal position is obtained fromhits in the rotated coordinate measurements. Both timing and pulse height informationare recorded from one end of each hit wire. Pulse height is used to discriminate betweenelectron and low-energy, heavily ionizing tracks (e.g. protons) which can occur throughatomic muon absorption on nuclei. There are 208 straws in each array for a total of 832straws per plane and 4160 straws in the full 5 planes of the detector. Therefore there are4160 readout channels.

The calorimeter is positioned behind the tracker. Electrons which pass through thetracker are absorbed in the calorimeter and if the deposited energy lies within a small windowaround 105 MeV, a trigger signal is generated. Appropriate signals that were previouslyinserted into in a latency pipeline in the readout electronics of the tracking detector arethen processed by a second level trigger, and the resulting information, including data fromthe calorimeter and cosmic ray shield, are stored as an event for further data analysis. Inthis section, the construction and readout of the tracking detector is mainly addressed.

6.5.2 Design of the electron tracker

The requirement to the tracker system is as follows:

Straw Tube Tracker

Aluminum Stopping Target

Electromagnetic Calorimeter

Electromagnetic Calorimeter (ECAL)　　＆ Straw Tube Tracker


COMET Phase-I

7

Physics Measurement

Trigger Concept (CyDet)

Al Target

CDC

e- Track

Trigger Hodoscope

• Search with a sensitivity of 10-15 before the Phase-II

• Connect the detector region just after the 90° bended solenoid.

• Cylindrical Drift Chamber (CDC),　at the center of which Aluminum sopping targets

• Trigger hodoscopes are installed at each end of inside of CDC.

• For triggering electrons only.


COMET Phase-I

8

Beam Measurement• More important for ECAL in the Phase-I!

• New beam line for the COMET

• now being constructed.

• Hove to understand components in the beam.

• By using ECAL & Straw Tube Tracker,

• Measure the beam itself

• Understand systematics from the beam.

• In addition to the physics measurement in the Phase-II,

• The ECAL (& Straw tube tracker) should satisfy the requirement for this measurement.

Straw Tube Tracker

ECAL

Replace this with..


CHAPTER5.DETECTOR83

calorimetersignalswillbeprocessedlocallybyanFPGAthatwillcutonenergydepositedinshowerclusterswithinthecalorimeter.Attriggerdecisionmustbemadewithin500nsinordertoextractvalidinformationfromthetracker.

5.4.2.5Performance

EnergyresolutionsofthecalorimeterisstudiedusingGeant4withOpticalPhotonPro-cesses.Theresolutiondependsoncrystal,lightguide,photondetector,andtheirgeomet-ricalconfiguration.Inthissection,wediscussdependenceoftheresolutiononthecrystalsunderapossibleconfigurationofthecalorimeter.

Figure5.15:Atypicaleventdisplayofthesimulationstudyofthecalorimeter.Anelectroninjectedtothecalorimeter,thenopticalphotonsfromscintillationprocessesareray-tracedtothephotondetectors.

Figure5.15showsatypicaleventdisplayofthissimulation.Thecalorimeterisacylinder0.8mindiameter,andconsistsof1224rectangularsegments.Thecrystalhassizeof20!20!150mm3asalreadymentioned.Inthissimulationreadoutbyphotomultiplierswithaquantume!ciencydependenceonthewavelengthissupposedforsimplifyinglighttransmissionmodelfromthecrystalendtothephotosensorsurface.

Figure5.16showsphotoelectrondistributionsfor105MeVelectioninjectionstothecalorimeter.Energyresolutionsof5.0%inFWHMforGSO(Ce)and3.6%inFWHMforLYSOareexpected.Notethatthesedoesnotincludethee"ectofelectronenergylossinthemuonstroppingtargetmaterialwhichisestimatedtobelessthan1MeVinFWHM.

KEK/J-PARC-PAC 2012-10

6.5. ELECTRON TRACKER 103

Figure 6.13: Cut view of COMET detector. Red rings around the curved solenoid sectionare magnet coils, and tilted to produce the compensation field (A field that cancels the driftfor a 105 MeV electron)

understood and controlled.A schematic of the stopping target and detector solenoids is shown in Figure 6.13.

The tracking detector is located downstream of a curved transport solenoid and the muonstopping target. The detector consists of a set of 5 straw planes, 48 cm apart, and placed sothat the axial direction of the straws is transverse to the axis of the solenoid. Each of the5 planes contains a set of 4 straw tube arrays. One array measures position in x, and onemeasures position in y (coordinates rotated by !/2). An identical (x,y) pair is attached tothe first array, but rotated by 45 deg., in order to break hit ambiguities and add redundancy.A hit location is determined by the plane position, the straw position within a plane, andthe drift time. There is presently no second coordinate readout, although charge divisionon a straw anode wire is under consideration. The azimuthal position is obtained fromhits in the rotated coordinate measurements. Both timing and pulse height informationare recorded from one end of each hit wire. Pulse height is used to discriminate betweenelectron and low-energy, heavily ionizing tracks (e.g. protons) which can occur throughatomic muon absorption on nuclei. There are 208 straws in each array for a total of 832straws per plane and 4160 straws in the full 5 planes of the detector. Therefore there are4160 readout channels.

The calorimeter is positioned behind the tracker. Electrons which pass through thetracker are absorbed in the calorimeter and if the deposited energy lies within a small windowaround 105 MeV, a trigger signal is generated. Appropriate signals that were previouslyinserted into in a latency pipeline in the readout electronics of the tracking detector arethen processed by a second level trigger, and the resulting information, including data fromthe calorimeter and cosmic ray shield, are stored as an event for further data analysis. Inthis section, the construction and readout of the tracking detector is mainly addressed.

6.5.2 Design of the electron tracker

The requirement to the tracker system is as follows:

9

(1) Energy resolution < 5% @ 105 MeV/cEffectively trigger the signal,suppressing contamination from the decay in orbit

(2) Position resolution < 1 cm @ 105 MeV/cSupport the tracker (momentum measurement)

(3) Response time < 100 nsecFor enough pileup tolerance

(4) Operation in vacuum and 1 T field

the DIO electrons is presented in Section 17.2. In this study, the momentum cut of 103.6 MeV/c <Pe < 106.0 MeV/c, where Pe is the momentum of electron, is determined as shown in Fig. 107 [61].According to this study, the contamination from DIO electrons of 0.01 events is expected for a singleevent sensitivity of the µ!N ! e!N conversion of 3.1" 10!15.

Momentum [MeV/c]101.5 102 102.5 103 103.5 104 104.5 105 105.5 106

Coun

ts p

er 0

.1 M

eV/c

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18)-15 10!Signal and DIO (BR=3

Pth [MeV/c]101.5 102 102.5 103 103.5 104 104.5 105 105.5 106

Inte

gral

ove

r Pth

upt

o 10

6.0

MeV

/c

0

0.2

0.4

0.6

0.8

1

1.2

)-15 10!Signal and DIO (BR=3 Signal AcceptanceDIO Contamination 1.0% Contamination 97% Acceptance103.6MeV/c Threshold

Figure 106: Left: Distributions of the reconstructed µ!N ! e!N conversion signals and reconstructed DIOevents. The vertical scale is normalized so that the integrated area of the signal is equal to one event with itsbranching ratio of B(µN ! eN) = 3.1" 10!15. Right: The integrated fractions of the µ!N ! e!N conversionsignals and DIO events as a function of the low side of the integration range and the high side of the integrationrange is 106 MeV/c. The momentum window for signals is selected to be fro 103.6 MeV/c to 106 MeV/c sothat the DIO contamination would be 0.01 events.

16.1.4 Time window for signals

The muons stopped in the muon-stopping target have the lifetime of a muonic atom. The lifetimeof muons in aluminium is about 864 nanoseconds. The µ!N ! e!N conversion electrons can bemeasured between the proton pulses to avoid beam-related background events. However, some beam-related backgrounds would come late after the prompt timing, such as pions in a muon beam. There-fore, the time window for search is chosen to start at some time after the prompt timing. As discussedin Section 16.2, the starting time of time window of measurement of 700 nanoseconds is assumed,although it would be optimized in the future o!ine analysis.

The acceptance due to the time window cut, !time, can be given by,

!time =Ntime

Nall, (9)

Ntime =n!

i=1

" t2+Tsep(i!1)

t1+Tsep(i!1)N(t)dt, (10)

where Nall and Ntime are the number of muons stopped in the target and the number of muons whichcan decay in the window, respectively, Tsep is the time separation between the proton pulses, t1 and t2are the start time and the close time of the measurement time window, respectively, and n indicatesthe window for the nth pulse. The time distribution of the muon decay timing N(t) is obtained byMonte Carlo simulations. In our case, t1 and t2 are 700 nsec and 1100 nsec, respectively and Tsep is1.17 µsec, and !time of 0.3 is obtained.

16.1.5 Net Acceptance of signals

it is assumed that the e"ciencies of trigger, DAQ, and reconstruction e"cacy are about 0.8 for each.From these, the net acceptance for the µ!N ! e!N conversion signal, Aµ-e = 0.043 is obtained. Thebreakdown of the acceptance is shown in Table 24.

98

Decay in Orbit

Signal

Electromagnetic Calorimeter (ECAL)

Requirements for COMET ECAL

Aluminum Stopping Target

Straw Tube Tracker


ECAL Design(1) Inorganic crystal

• Candidate crystals•GSO (Gd2SiO5)

•LYSO (Lu2-xYxSiO5)

• High light yield

• Short radiation length & Molière radius

• Response time < 100 nsec

• Cost is problem. ( LYSO > GSO )

• Carried out a beam test at the ELPH to compare their performance.

(2) Photo sensor : APD (Avalanche Photo Diode)

• Operational in vacuum and magnetic field.

• A high neutron fluence is estimated in the COMET Facility.

• Carried out a neutron tolerance test at Kyushu University.

(3) Custom-made fast amplifiers and

fast waveform digitizer (DRS4)

• For pileup tolerance

10

Properties (s=slow, f=fast) GSO LYSO PWO CsI(Pure)Light Yield (NaI(Tl)=100) 3s, 30f 83 0.083s, 0.29f 3.6s, 1.1f

Radiation length (cm) 1.38 1.14 0.89 1.86Molière radius (cm) 2.23 2.07 2.00 3.57Decay constant (ns) 600s, 56f 40 30s, 10f 35s, 6f

Density (g/cm3) 6.71 7.40 8.3 4.51Refractive index 1.85 1.82 2.20 1.95Wave length (nm) 430 420 425s, 420f 420s, 310f

GSO

5 mm

Hamamatsu S8664-55

DRS4 Chip (PSI)Prototype preamp

(The fraction of the GSO components; fast : slow = 4 : 1)


Beam Test & Prototype ECAL • Beam test on Mar. 2014 at Tohoku University, Japan.

• e- beam with momenta around 105 MeV/c.

• Developed a prototype ECAL.

• [Purposes]

• To evaluate performance of GSO & LYSO

• Linearity

• Energy resolution

• Position resolution

• To test the prototype amp. and readout chain.

11

Signals

��

Fiber Beam Define Countermeasure the incident position

v1742 WFDWaveform Digitizer CAEN v1742 (DRS4) Finger Counter

Trigger the beam

e− beamPreampsCrystalArray

Front-end amp.

GSO

LYSO

• Hitachi Chemical product• Longitudinal Length

• Central 3x3 : 15 cm (10.9 X0)• Others : 12 cm (8.72 X0)

• Saint-Gobain product• Longitudinal Length

• All : 12 cm (10.5 X0)

7x7 Crystal Array

15 cm

12 cm

12 cm

• Crystal cross section 2x2 cm2 • (Crystal + APD) wrapped by Teflon• 2x2, 2x3, 3x3 matrices gathered

by aluminized mylar

2x2 2x3

3x3


Beam Test & Prototype ECAL

12

Signals

��

Fiber Beam Define Countermeasure the incident position

v1742 WFDWaveform Digitizer CAEN v1742 (DRS4) Finger Counter

Trigger the beam

e− beamPreampsCrystalArray

Front-end amp.

GSO

LYSO

• Hitachi Chemical product• Longitudinal Length

• Central 3x3 : 15 cm (10.9 X0)• Others : 12 cm (8.72 X0)

• Saint-Gobain product• Longitudinal Length

• All : 12 cm (10.5 X0)

7x7 Crystal Array

15 cm

12 cm

12 cm

• Crystal cross section 2x2 cm2 • (Crystal + APD) wrapped by Teflon• 2x2, 2x3, 3x3 matrices gathered

by aluminized mylar

2x2 2x3

3x3

LYSO 7x7 Array


Readout Electronics• Crystal with 5x5 mm2 APD readout.

• Hamamatsu S8664-55.• Differential Preamplifier & Front End Amplifier.

• Total gain ~ 2V / pC• Waveforms were recorded by CAEN V1742 modules (DRS4 chip).

13

Preamp. with differential output

Front End Amp.Crystal APD Preamp. FEnd

Amp.

CAEN V1742(DRS4)


Event Sample (105 MeV/c runs)

14

GSO LYSOBeam

LYSO signal waveform is clearer than that of GSO.(The Amp. gain in the LYSO setup was decreased to 1/4

to accommodate the signals within the digitizer dynamic range)

Dynamic range 1 V Dynamic range 1 V


hgso105sEntries 120355Mean 89.17RMS 9.36

/ ndf 2χ 206.3 / 145Norm. 3.502e+02± 1.211e+05 Energy Norm. 0.000± 1.005 Sigma 0.000± 3.566

MeV0 20 40 60 80 100 120 140

Even

ts /

0.5

MeV

0

500

1000

1500

2000

2500

3000

3500 hgso105sEntries 120355Mean 89.17RMS 9.36


gso105s [nocut]: Energy Spectrum Fitted by The Gaussian-Convoluted MC Spectrum

hlyso105Entries 135131Mean 91.2RMS 10.05


MeV0 20 40 60 80 100 120 140

Even

ts /

0.5

MeV

0

500

1000

1500

2000

2500

3000

3500

4000

4500hlyso105

Entries 135131Mean 91.2RMS 10.05


lyso105 [nocut]: Energy Spectrum Fitted by The Gaussian-Convoluted MC Spectrum

hgso105Entries 40280Mean 89.52RMS 9.576

/ ndf 2χ 48.69 / 45Norm. 4.077e+02± 8.072e+04 Sigma 0.034± 3.673

MeV0 20 40 60 80 100 120 140

Even

ts /

1.0

MeV

0

500

1000

1500

2000

2500

gso105: Energy Spectrum Fitted by The Gaussian-Convoluted MC Spectrum

hgso105Entries 40280Mean 89.52RMS 9.576

/ ndf 2χ 48.69 / 45Norm. 4.077e+02± 8.072e+04 Sigma 0.034± 3.673

gso105: Energy Spectrum Fitted by The Gaussian-Convoluted MC Spectrum

Epeak

50%WH

• Energy deposits are summed up by using a simple clustering method.

• The MC spectra convoluting Gaussian function was fitted to the data.

• Energy resolution was defined as the ratio = (WH/√2ln2) /Epeak.

15

GSO LYSO

Black: Data Red: Fitted MC spectra* Gaussian function@ Pe = 105 MeV/c

Energy Spectra

conversion factor to Gaussian sigma.


70 80 90 100 110 120 130 140

(MeV

)m

ean

E

60708090

100110120130

/ ndf 2χ 425.1 / 4

GSOIntercep 0.04916± -1.637

GSOCoeff 0.000472± 0.9039

/ ndf 2χ 425.1 / 4

GSOIntercep 0.04916± -1.637

GSOCoeff 0.000472± 0.9039

/ ndf 2χ 46.03 / 3

LYSOIntercep 0.04918± -1.42

LYSOCoeff 0.0004391± 0.925

/ ndf 2χ 46.03 / 3

LYSOIntercep 0.04918± -1.42

LYSOCoeff 0.0004391± 0.925

Linearity

(MeV/c)beamP70 80 90 100 110 120 130 140No

n Li

near

ity (%

)

-1.5-1

-0.50

0.51

1.5

GSOLYSO

Linearity

• The difference between GSO and LYSO is due to the shower leakage.• The deviation from the fitted linear functions is within 1%.

16

Epe

ak (M

eV)


(MeV/c)beamP40 60 80 100 120 140 160 180 200

/E (%

)σ

44.5

55.5

66.5

Resolution

GSOLYSO

�

Emean=

sto.⇥Pmean

� const.� noise.Pmean

Requirement

Energy Resolution

• The systematic error was estimated from binning, fitting range, temperature correction, and energy calibration.

• Only LYSO satisfies the requirement.• Noise contribution is under investigation.

17

(MeV/c)beamP40 60 80 100 120 140 160 180 200

/E (%

)σ

4.5

5

5.5

6

6.5

/ ndf 2χ 6.206 / 3 GSOsto 1.648± 42.14

GSOconst 0.1488± 3.569 GSOnoise 366.6± 0.004381

/ ndf 2χ 6.206 / 3 GSOsto 1.648± 42.14

GSOconst 0.1488± 3.569 GSOnoise 366.6± 0.004381

/ ndf 2χ 0.07372 / 2 LYSOsto 16.02± 32.52

LYSOconst 0.7384± 3.535 LYSOnoise 188.9± 128.3

/ ndf 2χ 0.07372 / 2 LYSOsto 16.02± 32.52

LYSOconst 0.7384± 3.535 LYSOnoise 188.9± 128.3

Resolution

GSOLYSO

5.50±0.02(stat)±0.04(syst)%

4.91±0.01(stat)±0.07(syst)%


-30 -20 -10 0 10 20 30-30

-20

-10

0

10

20

30

020406080100120140160180

(MeV/c)beamP60 80 100 120 140 160

(mm

)Rσ

66.5

77.5

88.5

99.510

GSOLYSO

Position Resolution

• The distance between the cluster position and the beam hit position.• The cluster position was reconstructed by the clustering method.• The beam hit position was measured by the fiber BDC.

• Fitted 2D-Gaussian to the distance to extract the position resolution, σR = √(σx2 + σy2)• Both crystals satisfy the requirement.

• We chose LYSO as the crystal of COMET ECAL.18

X (mm)

Y (m

m)

Gaussian’s σ

Position ResolutionGSO 105 MeV/c


BorderCenterCorner

The Central Crystal (20 x 20 mm2)

Beam Incident Dependence• The energy and position resolution depend on the beam incident position.

19

4.50%5.50%6.50%7.50%8.50%9.50%10.50%

40% 90% 140%

Resolu'o

n)(m

m)�

Beam)Momentum)(MeV/c)�

Posi'on)Resolu'on)(GSO))

NO%CUT%

CENTER%

BORDER%

CORNER% 4.50%5.50%6.50%7.50%8.50%9.50%10.50%

40% 90% 140%

Resolu'o

n)(m

m)�


Posi'on)Resolu'on)(LYSO))

NO%CUT%

CENTER%

BORDER%

CORNER%4.50%5.50%6.50%7.50%8.50%9.50%10.50%

40% 90% 140%

Resolu'o

n)(m

m)�



NO%CUT%

CENTER%

BORDER%

CORNER% 4.50%5.50%6.50%7.50%8.50%9.50%10.50%

40% 90% 140%

Resolu'o

n)(m

m)�



NO%CUT%

CENTER%

BORDER%

CORNER%

Energy Resolution

Position Resolution

Beam momentum (MeV/c)

4.50%5.50%6.50%7.50%8.50%9.50%10.50%

40% 90% 140%

Resolu'o

n)(m

m)�



NO%CUT%

CENTER%

BORDER%

CORNER% 4.50%5.50%6.50%7.50%8.50%9.50%10.50%

40% 90% 140%

Resolu'o

n)(m

m)�



NO%CUT%

CENTER%

BORDER%

CORNER%

(MeV/c)beamP40 60 80 100 120 140 160 180 200

/E (%

)σ

3.54

4.55

5.56

6.57

Resolution

(MeV/c)beamP40 60 80 100 120 140 160 180 200

/E (%

)σ

3.54

4.55

5.56

6.57

Resolution

Beam momentum (MeV/c)

GSO LYSO

requirement

NO CUTCENTERBORDERCORNER

requirementGSO LYSO

Posi

tion

Res

olut

ion

(mm

)

10 mm

10 mm


Neutron Tolerance of APD• A high neutron fluence estimation was reported by a

COMET beam line designer.• ~ 1011 n1 MeV eq./cm2 at the detector region

for 100-days experiment of the Phase-I.• Studied neutron tolerance of APD @ the Tandem

Accelerator Lab., Kyushu Univ.

• Three APDs were exposed to neutrons to check deterioration against the neutron fluence.

• 2.2 × 1011, 7.5 × 1011, and 2.2 × 1012 n1 MeV eq./cm2.

• APD is neutron tolerant in condition < 1012 neq. / cm2.• The gain dropped but can be recovered by adjusting

the supplied voltage.• Linearity kept well.• Noise increased but can be compensated by

waveform template fitting.• Energy resolution didn’t change too much.• A bit change in timing resolution but it can be

improved by applying FFT-LPF.20

中性子耐性試験

2015/3/6 第１回九大・佐大高エネルギー物理合同研究会 6

九州大学タンデム加速器施設

2014/10/24-25 (12h)

中性子流量 2.4 ∗ 10 neutrons sr ∗ sec⁄ （ビーム軸上）

全照射量は ~10 neutrons sr⁄

Setup

APD

Neutron distribution

Neutron Fluence in the Phase-I

The Tandem Acceleratorin the Kyushu University.


PMT Fit Charge (ch)0 20 40 60 80 100

310×

S/N

Rat

io

0

50

100

150

200

250

300

5mm: G 25 5mm: G 50 5mm: G 100 5mm: G 150 5mm: G 20010mm: G 2510mm: G 5010mm: G 10010mm: G 15010mm: G 200

APD S/N Ratio: AA5013

4 times improvement as expected

Dark Box

Dark Box

APD Whose Sensitive Area is 5×5 or 10×10 mm2

• New possibility: 10×10 mm2 APD.• Its noise was concerned.

• Compared both and concluded 10×10 mm2 is better.• Noise increased only by 30% in a very clean setup.

• We are going to change the design.

21

��

��

��

��

��

��

��

��

��

��

��

��

��

Run Info σobs σAPD

‘5mm’

‘10mm’

Measurement Box

LEDAPD

Fixture circuitCoaxial cable

LEMO connector

Very short coaxial cable

APD

Black cover

Preamp socket

PreampTo VME

To VME Preamp

Gain Measurement Setup Using LED

Noise Measurement Setup

PMTReference sensor

S/N Ratio

Noise

30% Up


hElectronEntries 704867Mean 16.83RMS 19.89

P (MeV/c)0 20 40 60 80 100120140160180 C

ount

s / I

nitia

l Pro

ton

/ 2 M

eV/c

-810

-710

-610

-510

-410

-310

-210hElectron

Entries 704867Mean 16.83RMS 19.89

hPositronEntries 89083Mean 10.9RMS 8.565

hPositronEntries 89083Mean 10.9RMS 8.565

hMuonEntries 99202Mean 67.11RMS 23.19

hMuonEntries 99202Mean 67.11RMS 23.19

hAntiMuonEntries 2637Mean 38.37RMS 13.07

hAntiMuonEntries 2637Mean 38.37RMS 13.07

hGammaEntries 320088Mean 0.7371RMS 1.392

hGammaEntries 320088Mean 0.7371RMS 1.392

hPiPlusEntries 0Mean 0RMS 0

hPiPlusEntries 0Mean 0RMS 0

hPiMinusEntries 2091Mean 87.65RMS 18.35

hPiMinusEntries 2091Mean 87.65RMS 18.35

hPiZeroEntries 0Mean 0RMS 0

hPiZeroEntries 0Mean 0RMS 0

hKPlusEntries 0Mean 0RMS 0

hKPlusEntries 0Mean 0RMS 0

hKMinusEntries 0Mean 0RMS 0

hKMinusEntries 0Mean 0RMS 0

hKLongEntries 0Mean 0RMS 0

hKLongEntries 0Mean 0RMS 0

hProtonEntries 184Mean 127RMS 37.34

hProtonEntries 184Mean 127RMS 37.34

hAntiProtonEntries 0Mean 0RMS 0

hAntiProtonEntries 0Mean 0RMS 0

hNeutronEntries 881058Mean 23.7RMS 9.514

hNeutronEntries 881058Mean 23.7RMS 9.514

hAntiNeutronEntries 0Mean 0RMS 0

hAntiNeutronEntries 0Mean 0RMS 0

ECAL Momentum Spectra

ElectronPositronMuonAntiMuonGammaPiPlusPiMinusPiZeroKPlusKMinusKLongProtonAntiProtonNeutronAntiNeutron

Simulation Study

22

Protons

Pion Production Target

Momentum Distributions of Each Particle Arriving at ECAL

• Beginning a simulation study for the Phase-I beam measurement• What kind of and how much particle will come?

• To estimate required beam times.


Summary and Prospects• COMET ECAL consists of inorganic crystals readout with the APDs.

• A prototype ECAL was developed and beam-tested in March 2014 at ELPH, Tohoku University.

• GSO and LYSO were the candidates and we chose LYSO.

• Some APD studies:

• APD is neutron tolerant.

• New possibility to change to 10×10 mm2 APD.

• Simulation study is progressing.

• Aiming at achieving much better performance

• Gain calibration method.

• The next prototype of the readout electronics is under development towards the final design.

• The next prototype ECAL with a larger scale and with the (almost) final design will be beam-tested.

23

Documents

Development of Electromagnetic Calorimeter for COMET: The ...9th Mar. 2015 @ ELPH Workshop C010, Tohoku University, Japan Kou Oishi / Kyushu University 3.1. INTRODUCTION TO THE COMET