K2K Near Detector !2"
SciBar Detector
Masashi Yokoyama !Kyoto"
Nov.10 NBI03 @ KEKIntroduction

K2K result indicates∆m2≈2.8x10–3for νµ ντ oscillation

EventsMotivation
12108Oscillation maximum atEν≈0.6GeV

6for 250km of baseline

4Study of neutrino
interaction at low energy isimportant to maximize
sensitivity

2001Construct new detector

2345EνrecRequirements
Clean reconstruction of vertex
High efficiency for all particles
Low momentum threshold for tracks (esp. protons)
Full active detector
Fine segmentationµ/p/π separation
Range+dE/dx
EM calorimetry for study of νe/π0Full-active tracker with Scintillator Bars!!

K2K Front Detector
SciFi/Water target

SciBar detector
Muon chamberν beam

1kt
Water Cherenkov
Detector

To Super-KamiokandeDetector design

SciBar detector overview
3x3x1.8m3 (Tot. mass ~15t)~300 interactions/day,~40,000 int./3x1019 POT
expected if fid. mass=10t
Full active, fine grained
1.3x2.5cm2, 64 layers
High efficiency for allparticles from vertex
Threshold for protons~350MeVe/π0 ID capability w/ EMcalorimeter

Precise study of ν interaction!

Scintillator and fiber
Scintillator
2.5x1.3x300cm3
MINOS-type extruded
scintillator (made at FNAL)
64 layers (X+Y)
14336 channels in total
Wave length shifting fiber
1.5mmΦ x 360mm Kuraray Y11
Attenuation length: ~360cm(all fibers measured before installation)
Light yield: 20p.e./cm for MIP after 40cm of fiber

Multi-Anode PMT
Hamamatsu H8804
2
64ch w/ 2x2mm pixel size

Alignment w/ fiber better than 300µm
Cross-talk to adjacent channel: ≤3%All channels calibrated
before installation
Gain~5x105

Fibers w/ cookie
after polishingLarge number of channels (~15,000)
VA frontend LSI: Multiplex analog
DAQ Board x28
signalFrontend Board
FIFO
FADC
FADC
FADC
FADC
FADC
FADC
FADC
FADC
FADC
FADC
FADC
Readout 64ch with
FADC
FADC
FADC
FADC
(FEB)
x224
a signal line
VA/TA
VA/TA&timing
Low noise: ~0.3p.e.
VA/TA
Controller(MIP=10-20p.e.)
64ch
VME-IF
MA-PMT
Large dynamic range
Linear up to 300p.e.
TDC (64ch)
low energy proton
Linux PC
Trigger module
Fast trigger/timing signal
spill info
Timing Distributor
TA LSI chip at frontend
VME-PCI BRIDGE
32-ch ORed output

VME-bus

Readout electronics

4x4cm2 cell read out fromboth ends
30 horiz. + 32 vert. modules(11X0) placed just downstreamof SciBar main detector
Expected resolution: 14%√ELinearity: better than 10%cm

ν Beam8 cm

Modules from CHORUS“spaghetti” calorimeter
1mm diameter fibers in thegrooves of lead foils

26
2Electron Catcher

4 cm

Readout CellbνmaePhoto Gallery

Main SciBar E-catcher

PMT (backside)
WLS fibers

VA/TA chipJust Completed!

Aug. 22, 2003

Data taking started on Oct.7...
Extensive calibration workongoing

Arbitrary unit

400

Gain, timing, alignment...

So far, SciBar looks working
as expected(=excellent performance!!)

300

imle

250
200r
P

150
100

020

8220
3092
19.07
8.641

Light yield for MIP(Cosmic-ray µ)@40cm from PMT

50

40

60

80

100p.e./cm

Timing of first hit in beam event
after tracking
Events (arb. unit)

Software development(traking, MC simulationtuning) startedyrani

3500ID
Entries
MeanRMS803604 5 67891240
200–0.500.5

1.0

1.5
2.0time(µs)

Event Gallery

Neutrino event (1)Top view

ν beamSide view
MRDADCTDC (in-time)

MRDNeutrino event (2)Top view

Side view

ν beamADC
TDC (in-time)Neutrino event (3)NC pi0 cand.

Top view

Side view
vertex!

Neutrino event(4) ν candidate
eTop view

Side view

E-catcherE-catcherSummary
SciBar is
Full-active (15t total volume)Fine-grained (1.3x2.5cm)
detector for precise studies of ν interaction
Stably working for one month, data quality
looks excellent
Still lots of work (and fun) to be done, but
making rapid progress towards physicsresults

Backup Slides

Extruded Scintillator• Mix poly-stylene with PPO 1%, POPOP 0.3%
– Maximum of emission spectrum : 420nm• 1.3 x 2.6 x 300 cm3• 1.8mm diameter hole at the center• TiO2 coating (t0.25mm)
300cm– As a reflector– Extruded together
1.3cm
2.5cm

Light yield uniformity <5%Wavelength Shifting
FiberCharged particle• Kuraray
Y11(200)MS 1.5mm diam.

• Attenuation length : 3.6mScintillation

Secondaryemission• Absorption peak
– 430nm• Emission peak
– 476nm
400

500

600

Gain monitoring w/ LED(4)(564)

pedestal(count)

Pedestal(Main Part) Page1
2040
2038

view0:layer0:strip0

2036
2034
2032
2030
2028
2026
2024
2022
5020

5040

5060

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5100

5120

5140

5160

pedestal(count)

run
2030
2028

view0:layer0:strip1

2026
2024
2022
2020
2018
2016
2014
2012
5020

5040

5060

5080

5100

5120

5140

5160

run

Gain(ADC/PIN)

Stability of gain
0.17
view1:layer8:strip46
0.165

+2%

0.16
0.155

-2%

0.15
0.145
50205040

5060

5080

5100

5120

5140

run

VA/TA readout chipsample&holdpreamp.
slow shaper

VA serial output

CH1

fast shaper
CH2discri.

multiplexer（energy information）

CH32~1µs

TA (32ch OR)（trigger,timing information）

p.e./layer

Proton ID w/ dE/dx
Beam test w/
prototype,1 cell only

Protonp (GeV/c)p/pi separationw/ <10% mis-ID
below 1.2GeV/c
possible by more
sampling points

Proton momentum w/ dE/dx

10% precision w/ dE/dx only