K2K 実験 SciBar 前置ニュートリノ検出器

久野研　　田窪　洋介

読み出しシステムと時間情報の較正

Contents

• K2K experiment

• SciBar detector & readout system

• Cosmic ray trigger system

• Timing calibration

• Conclusion

K2K　 Experiment

Super-Kamiokande

KEK 12GeV PS

Near Detectors

L = 250kmPure 　 νμ

SciBar detector1kt water cherenkov detector

MRD(Muon Range Detector)

SciFi detector

νμ

K2K experiment uses neutrinos made by the accelerator

Pure νμ beam whose Flux and energy are well known, can be obtained .

Neutrino Oscillation

OscillationProbability =

Mixing angleNeutrino energy (GeV)

Square mass difference(eV2) Flight length (km)

Data

Best Fit0.6 GeV

No oscillation

E

Δm2 = 2.8×10 － 3(eV2)

sin22Θ= 1.0

Best fit

K2K current status

Neutrino interaction

• Assuming Charged Current Quasi-Elastic interaction– Dominant process around

1GeV neutrinos.

• Oscillation maximum ~0.6GeV

• Non-QE interactions are backgrounds for E measurement

proton

p

n

cos

2/2

PEm

mEm

n

n

recE

CC-QE Interaction

nucleon

Npion

CC-nonQE Interaction

SciBar detector• Extruded scintillator with WLS

fiber readout

• Neutrino target is scintillator itself

• 2.5 x 1.3 x 300 cm3 cell

• ~15000 channels

• Light yield

7~20p.e./MIP/cm (2 MeV)

• Detect 10 cm track

• Distinguish proton from pion by using dE/dx

High 2-track CC-QE efficiency

Low non-QE backgrounds

Extrudedscintillator(15t)

Multi-anodePMT (64 ch.)

Wave-lengthshifting fiber

EM calorimeter

1.7m

3m

3m

Just constructed in this summer!

Detector Components

DAQ board

64ch MAPMT

Front-end board

Scintillator & WLS Fiber

• Kuraray

– Y11(200)MS 1.5mmφ

– Multi-clad

• Attenuation length ~3.6m• Absorption peak ~430nm• Emission peak ~476nm

Charged particle

Wave-length Shifting Fiber

Scintillator

• Size : 1.3×2.5×300 cm3

• Peak of emission spectrum : 420 nm

• TiO2 reflector (white) : 0.25 mm thick2.5cm

1.3 cm

300 cm1.8 mmφ

Multi-anode PMT• Hamamatsu H7546 type 64-channel PMT

– 2 x 2 mm2 pixel– Bialkali photo-cathode– Compact– Low power : < 1000V, < 0.5mA– Typical gain : 6 x 105

– Cross talk : ~3%– Gain uniformity : ~20% (RMS)– Linearity : ~200 p.e. @ 6 x 105

Top view

Readout Electronics

mu

ltip

lexer

sample&holdslow shaper

preamp.

fast shaper discri.

CH1

CH2

CH32

VA serial output

TA (32ch OR)

hold

PMTsignal

∝ charge

1.2s

VA/TA chip

VATA Chip

Front-end board

DAQ board• Control of VA readout sequence• Setting of VA trigger threshold• A/D conversion of VA serial output by FADC• 8 front-end board (8 MAPMT) are connected to

one DAQ board.

8 fr

ont-

end

boar

ds(8

×64

ch）

16ch

×2

TA

sig

nal

Scintillator Installation

64 X and 64 Y layers

X and Y planes were glued

WLS Fiber and PMT installation

Logic Diagram for Cosmic Ray Trigger

Master trigger board

TRGTiming Distributor

Top

Trigger Board

Identification of hit track Make coincident with two trigger signals

Distribute signals made from the trigger signal to other modules

7 DAQ Board

Side56 MAPMT

56 Front-end Board

Trigger Board

7 DAQ Board

56 MAPMT

56 Front-end Board

112 TA

112 TA

We use half of the TA channels (224ch/448ch) for cosmic ray trigger.

Top view Side view

Trigger Board

• Front panel : input 128 (16×8) ch LVDS/ECL

• Back plane : output 16ch LVDS/ECL

• VME 9U module

inp

ut

: 12

8 ch

(16

×8)

Ou

tpu

t :

16 c

h

FPGA decide to make trigger signal.

Output : 1ch

• Using FPGA, trigger logic can be easily implemented for any combinations of 128 inputs.

Timing Distributor

• VME 6U module to distribute timing signals made by trigger system to DAQ backend boards

• 4ch NIM I/O on main board + 2 daughter boards

16ch NIM I/O

Daughter board

Daughter board

FPGA

16c h

NIM

I/O

16×

2ch

LV

DS

/EC

L I

np

ut

16×2 ch LVDS/ECL Input

8ch

LV

DS

I/O

• Flexible data processing is realized using FPGA.

Requirement for Cosmic Ray Trigger

• Horizontally through-going muons are taken for calibration effectively.

• Distribution of cosmic ray hits is uniform.

• Decision time is less than 100 ns (due to the cable length of electron catcher)

• 32ch OR’ed signals from TA*1 (fast-triggering ASIC) are trigger board input signals.

Trigger Design

Zenith angle > 45 degree Zenith angle < 45 degree

Preparing hit patterns, track pattern matching them is selected.

• Track which is less than 45 degree of zenith angle is taken.

• Pre-scale factor can be set on the hit pattern to make hit distribution uniformly.

•Trigger is generated, based on the hit pattern identification.

Achieved Performance & Current Status

• Decision time is 100 nsec.

• Single rate of one TA is about 100 Hz.

•Trigger rate is about 100 Hz.

• Data acquisition rate is about 20 Hz.

Achieved performance

We now use a trigger logic for the commissioning. We make “or” signals of every other layer, and make coincident with those of the top and side separately. We make “and” signal of the top and side.

Current Status

Angle distribution of cosmic ray event

Azimuth angle (degree)

Zen

ith

angl

e(de

gree

)

Horizontal line

taken by commissioning trigger

-80 0 80

-60

0

60

Hit distribution of cosmic ray event

Z(cm)

Hor

izon

tal p

osit

ion(

cm)

Z(cm)

Ver

tica

l pos

itio

n(cm

)

taken by commissioning trigger

0 80 160 0 80 160

150

250

150

250

ν ν

Event display of cosmic ray event

Top View Side View

μ

μ

TQ Distribution

ΔT = T(X12Z1) – T(X12Z2)

ADC ADC

ΔT

(nse

c)

ΔT

(nse

c)

Correction function : ΔT = A/(ADC ＋ B) + C A,B,C : const

0 300 600 0 300 600

-5

10

25

ΔT = 1719.8/(ADC ＋ 65.5 ）－5.6

-5

10

25

Time ResolutionΔT = T(X12Z1) – T(X12Z2)

ΔT(nsec)

coun

t

After TQ correction Before TQ correction

ΔT(nsec)

coun

t

Time resolution

σ/√2 = 2.83 nsec

Time resolution

σ/√2 = 1.70 nsec

Light velocity in the fiber

0.05847E － 01 ±0.8594E － 03

y15z8

Light velocity in a fiber = 17.2 nsec/cm

Δx(cm) Δx(cm)

ΔT

(nse

c)

ΔT

(nse

c)

Conclusion & Next step

• Cosmic ray data is taken by commissioning trigger and useful for timing and energy calibration, and so on.

• Timing correction was done by cosmic ray data.• Timing resolution is 1.70 nsec.

• Light velocity in a fiber is 17.2 nsec.

Ability of direction ID by using TOF will be estimated.

Next step

CC-QE candidate• Area of circle is proportional to ADC• Hits along the proton track are larger

Top view Side view

μμ

p

p

3-Track Event

Top view Side view

1

12

23 3

Neutral Current 0 Candidate

Top view Side view

Vertex!

π0

e

e

e

eγ

γ

π0 γ