[PPT] - Study of Accidental Activity at the Front Barrel of the KOTO PowerPoint Presentation

SLIDE 1

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Study of Accidental Activity at the Front Barrel of the KOTO Detector

Ryota Shiraishi Yamanaka Group Kuno-Yamanaka Group Year-End Presentation 2019

SLIDE 2

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Introduction

2

The KOTO experiment

Purpose : To observe the decay . Signal : 2 photons + “nothing”

KL → π0ν¯ ν

➥ detected at the CsI calorimeter ➥ other veto detectors make sure of no extra hits

γ γ π0 ν¯ ν

KL

CsI

SLIDE 3

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Accidental Signal Loss

3

Accidental hits on veto detectors coincident with the decay could cause signal loss. Major sources…

Other KL decay
Neutron from the J-PARC primary beam line

π0

decay signal @CsI

π0

Accidental hit @veto detector

Discarded (Acceptance loss) Accidental hits need to be reduced.

Veto Window

SLIDE 4

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Purpose of This Study

4

To understand accidental activities at the Front

Barrel of the KOTO detector.

To calculate accidental hit rates by using data

taken in 2019.

To check consistency of accidental hit rates

between physics-triggered data and TMON- triggerd data.

Physics trigger…trigger to collect data TMON trigger…trigger to reproduce accidental hits

KL → π0ν¯ ν

SLIDE 5

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Front Barrel

5

View from the downstream side

Sandwich of lead & plastic

scintillators

2.75m long
Sampled by125MHz FADC
16 modules
32 readout channels

(inner/outer layers are read separately)

Front Barrel

SLIDE 6

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

TMON Trigger

6

TMON trigger is…

A random trigger generated from the signals of the Target

Monitor. The rate is proportional to the beam intensity.

We use this trigger to reproduce accidental activities and

verlay the waveforms on generated waveforms in simulation.

Proton Beam

Au Target 50° 16° KOTO Beam Line Plastic Scintillators

TMON Trigger

SLIDE 7

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Energy Distribution

7

TMON data Energy is distributed up to ~600 MeV. Now, set the energy threshold to 2 MeV. Consider only events with FBAREne > 2 MeV. ➤

FBARModID 5 10 15 20 25 30 FBAREne [MeV] 100 200 300 400 500 600 1 10

2

10

3

10

4

10

FBAREne:FBARModID {ExtTrigType==2}

FBARModID FBAREne [MeV]

h Entries 30082 Mean 2.337 RMS 4.122

5 10 15 20 25 30

2

10

3

10

4

10

h Entries 30082 Mean 2.337 RMS 4.122

FBAREne {FBARModID==0 && ExtTrigType==2 && FBAREne<50}

# of events

FBAREne {FBARModID==0 && ExtTrigType==2}

600

FBAREne:FBARModID {ExtTrigType==2}

104 103 102 2

FBAREne [MeV]

30

Higher counts in inner channels Lower counts in outer channels

➞

SLIDE 8

10 10 20 30 40 50 60 70

Rate [Hz]

FBAR Rate ch0 (E>2.000000MeV)

100 200 300 400 500 600

3

10 ×

FBAR Rate ch0 (E>2.000000MeV)

FBARPTime [clock]

10 − 10 20 30 40 50 60 70

ratio (phys / tmon)

0.5 1 1.5

− : Physics − : TMON

FBARPTime [clock] Rate [Hz] Ratio (phys./tmon) FBAR Rate ch0 (E > 2 MeV)

600

×103

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Comparison between Phys. & TMON data

8

Rate[Hz] per bin(= 1clock=8ns)

Rate = #events / (∆T×#triggered) (∆T = 1clock = 8ns)

Earlier timing region

> consistent

Later timing region

> subtle discrepancy exists

SLIDE 9

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Rates in 10 - 20 clock timing

9

Ratio = Phys./TMON = 1 ~ 1.1

Energy Threshold : 2MeV Rate = #events/(∆T×#triggered) ∆T = ∆T1

10 10 20 30 40 50 60 70

Rate [Hz]

FBAR Rate ch0 (E>2.000000MeV)

100 200 300 400 500 600

3

10 ×

FBAR Rate ch0 (E>2.000000MeV)

FBARPTime [clock]

10 − 10 20 30 40 50 60 70

ratio (phys / tmon)

0.5 1 1.5

∆T1 FBAR Rate ch0 (E>2 MeV)

FBARPTime [clock] Rate [Hz] Ratio (phys./tmon)

− : Physics − : TMON

➞ Good agreement

5 10 15 20 25 30

Rate [Hz]

50 100 150 200 250 300

3

10 ×

(FBARPTime>10.000000 && FBARPTime<20.000000) FBAR Rate E>2.000000MeV

FBARModID

5 10 15 20 25 30

ratio (phys / tmon)

0.9 1 1.1 1.2

E > 2MeV, 10 < FBARPTime < 20

FBARModID Rate [Hz] Ratio (phys./tmon) Outer Channels Inner Channels 300 ×103

⟶ Primary beam line side

SLIDE 10

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

How we will reduce accidental hits

10

Accidental activities by neutrons coming from the J-PARC primary beam line

KOTO detector

To reduce the neutron flux, we installed a 33cm-thick iron wall.

Iron Wall

KOTO Detector

neutron

Primary Beam Line Iron Wall

SLIDE 11

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Summary / To do

11

Confirmed consistency of accidental counting

rates in physics/TMON data.

To reduce neutrons from the primary beam

line, we installed an iron wall and will check the reduction effect.

SLIDE 12

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Backup

SLIDE 13

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Detector

13

View from the downstream side

SLIDE 14

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Waveforms at the Front Barrel

14

Waveform Examples

Physics-triggerd event Energy : 13.8 [MeV] Time : 17.7 [clock=8ns] TMON-triggerd event Energy : 3.1 [MeV] Time : 47.3 [clock=8ns]

Consider an energy threshold and timing distributions.

Iteration$ 10 20 30 40 50 60 70 FBAR.Data 500 600 700 800 900

FBAR.Data:Iteration$ {FBAR.ModID==0 && Entry$==256}

FBAR.Data:Iteration$ {FBAR.ModID==0 && Entry$==256} Time [clock=8ns] ADC counts 20

Iteration$ 10 20 30 40 50 60 70 FBAR.Data 485 490 495 500 505 510 515 520

FBAR.Data:Iteration$ {FBAR.ModID==0 && Entry$==706}

FBAR.Data:Iteration$ {FBAR.ModID==0 && Entry$==706} Time [clock=8ns] ADC counts 40

SLIDE 15

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Time Distribution

15

Take the moving average -> make waveforms smoother Calculate a parabolic curve using three samples around the peak. The parabola time closer to the nominal time (~31 clocks) for the Front Barrel is selected. Tend to have a structure like a broad hill.

➤

htemp Entries 8044 Mean 28.49 RMS 16.34 FBARPTime 10 20 30 40 50 60 50 100 150 200 250 300 350 htemp Entries 8044 Mean 28.49 RMS 16.34

FBARPTime {FBARModID==0 && FBAREne>2 && FBARPTime>-10 && ExtTrigType==2}

FBARPTime [clock]

# of events

TMON

FABRPTime {FBARModID==0 && FBAREne>2 && FBARPTime>-10 && (ScaledTrigBit&0x1)==0x1} 30

htemp Entries 78920 Mean 28.95 RMS 15.4 FBARPTime 10 20 30 40 50 60 500 1000 1500 2000 2500 3000 3500 htemp Entries 78920 Mean 28.95 RMS 15.4

FBARPTime {FBARModID==0 && FBAREne>2 && FBARPTime>-10 && (ScaledTrigBit&0x1)==0x1}

FBARPTime [clock]

# of events

Physics

FABRPTime {FBARModID==0 && FBAREne>2 && FBARPTime>-10 && ExtTrigType==2} 30

Concentrated around the nominal time Dominated by accidental hits Parabola time Parabola curve

SLIDE 16

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Moving Average

16

Calculation Code

Take the average of five consecutive samples. Make waveforms smoother and mitigate local fluctuations.

/sw/koto/e14ana/release/v4.01.10/AnalysisLibrary/UserProjects/ E14ProdLibrary/E14ProdDstConv/src/E14CrateData125MHz.cc

10 20 30 40 50 60 460 480 500 520 540 560 580 600

wfm2

Entries 64 Mean x 31.5 Mean y 503.8 Std Dev x 18.47 Std Dev y 16.24

wfm2

Entries 64 Mean x 31.5 Mean y 503.8 Std Dev x 18.47 Std Dev y 16.24

FBARWfm[0]:Iteration$ {Entry$==153}

10 20 30 40 50 60 460 480 500 520 540 560 580 600

wfm

Entries 60 Mean x 31.5 Mean y 503 Std Dev x 17.32 Std Dev y 15.12

wfm

Entries 60 Mean x 31.5 Mean y 503 Std Dev x 17.32 Std Dev y 15.12

wfm

Averaged Wfm Time [clock] Time [clock] ADC ADC

SLIDE 17

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Parabola Interpolation Method

17

ptime

Moving Average Calculation of ptime

Peak Search

Nominal Time Condition

SLIDE 18

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Rates in 10 - 20 clock timing

18

Ratio = Phys./TMON = 1 ~ 1.1

Energy Threshold FBAREne > 2MeV

10 10 20 30 40 50 60 70

Rate [Hz]

FBAR Rate ch0 (E>2.000000MeV)

100 200 300 400 500 600

3

10 ×

FBAR Rate ch0 (E>2.000000MeV)

FBARPTime [clock]

10 − 10 20 30 40 50 60 70

ratio (phys / tmon)

0.5 1 1.5

∆T1

FBAR Rate ch0 (E>2 MeV)

FBARPTime [clock] Rate [Hz] Ratio (phys./tmon)

− : Physics − : TMON

Rate = #events/(∆T×#triggered) ∆T = ∆T1

➞ Good agreement

5 10 15 20 25 30

Rate [Hz]

50 100 150 200 250 300

3

10 ×

(FBARPTime>10.000000 && FBARPTime<20.000000) FBAR Rate E>2.000000MeV

FBARModID

5 10 15 20 25 30

ratio (phys / tmon)

0.9 1 1.1 1.2

E > 2MeV, 10 < FBARPTime < 20 E > 2MeV, 10 < FBARPTime < 20 FBARModID Rate [Hz] Ratio (phys./tmon) Outer Channels Inner Channels 300 ×103

SLIDE 19

Ryota Shiraishi 2019.12.23 Kuno-Yamanaka Group Year-End Presentation 2019

Rates in 35 - 50 clock timing

19

Energy Threshold FBAREne > 2MeV Rate = #events/(∆T×#triggered) ∆T = ∆T2

10 10 20 30 40 50 60 70

Rate [Hz]

FBAR Rate ch0 (E>2.000000MeV)

100 200 300 400 500 600

3

10 ×

FBAR Rate ch0 (E>2.000000MeV)

FBARPTime [clock]

10 − 10 20 30 40 50 60 70

ratio (phys / tmon)

0.5 1 1.5

∆T2

FBAR Rate ch0 (E>2 MeV)

FBARPTime [clock] Rate [Hz] Ratio (phys./tmon)

Ratio = Phys./TMON = 1.1 ~ 1.2

− : Physics − : TMON

5 10 15 20 25 30

Rate [Hz]

50 100 150 200 250 300

3

10 ×

(FBARPTime>35.000000 && FBARPTime<50.000000) FBAR Rate E>2.000000MeV (FBARPTime>35.000000 && FBARPTime<50.000000) FBAR Rate E>2.000000MeV

FBARModID

5 10 15 20 25 30

ratio (phys / tmon)

0.9 1 1.1 1.2

FBARModID Rate [Hz] Ratio (phys./tmon) E > 2MeV, 35 < FBARPTime < 50 Outer Channels Inner Channels 300 ×103

Study of Accidental Activity at the Front Barrel of the KOTO Detector

Ryota Shiraishi Yamanaka Group Kuno-Yamanaka Group Year-End Presentation 2019

Introduction

The KOTO experiment

Purpose : To observe the decay . Signal : 2 photons + “nothing”

KL → π0ν¯ ν

➥ detected at the CsI calorimeter ➥ other veto detectors make sure of no extra hits

KL

CsI

Accidental Signal Loss

Accidental hits on veto detectors coincident with the decay could cause signal loss. Major sources…

π0

π0

Discarded (Acceptance loss) Accidental hits need to be reduced.

Purpose of This Study

Barrel of the KOTO detector.

taken in 2019.

between physics-triggered data and TMON- triggerd data.

Physics trigger…trigger to collect data TMON trigger…trigger to reproduce accidental hits

KL → π0ν¯ ν

Front Barrel

scintillators

(inner/outer layers are read separately)

TMON Trigger

TMON trigger is…

A random trigger generated from the signals of the Target

We use this trigger to reproduce accidental activities and

Energy Distribution

TMON data Energy is distributed up to ~600 MeV. Now, set the energy threshold to 2 MeV. Consider only events with FBAREne > 2 MeV. ➤

➞

Comparison between Phys. & TMON data

Rate[Hz] per bin(= 1clock=8ns)

Rate = #events / (∆T×#triggered) (∆T = 1clock = 8ns)

Earlier timing region

Later timing region

Rates in 10 - 20 clock timing

Ratio = Phys./TMON = 1 ~ 1.1

− : Physics − : TMON

➞ Good agreement

How we will reduce accidental hits

Accidental activities by neutrons coming from the J-PARC primary beam line

To reduce the neutron flux, we installed a 33cm-thick iron wall.

Summary / To do

rates in physics/TMON data.

line, we installed an iron wall and will check the reduction effect.

Backup

Detector

View from the downstream side

Waveforms at the Front Barrel

Waveform Examples

Consider an energy threshold and timing distributions.

Time Distribution

Take the moving average -> make waveforms smoother Calculate a parabolic curve using three samples around the peak. The parabola time closer to the nominal time (~31 clocks) for the Front Barrel is selected. Tend to have a structure like a broad hill.

➤

Moving Average

Take the average of five consecutive samples. Make waveforms smoother and mitigate local fluctuations.

Parabola Interpolation Method

ptime

Rates in 10 - 20 clock timing

Ratio = Phys./TMON = 1 ~ 1.1

− : Physics − : TMON

➞ Good agreement

Rates in 35 - 50 clock timing

Ratio = Phys./TMON = 1.1 ~ 1.2

− : Physics − : TMON

➞ A little bit worse than earlier timing