KL Æ π0νν experiment at KEK
12-GeV PS
Mitsuhiro YAMAGAE391a group, KEKMar. 4-5, 2003
@ 科研費特定領域研究会

Golden channel in K decays
KL→π0νν physics


Flavor-changing neutral current
Direct CP violation (∆s=1)
Clean measurement of Im(Vtd) ~ ηπ0νν) = 6κ1(Im(VtdV*ts))2X2(xt)~ 1.94x10-10η2A4X2Theoretical uncertainty is very small.
Br(KLSensitive to the New Physics

Goal of the experiment
BR(KLJπoνν)

Present experimental Limit-7¾ Br ~ 5.7 x 10 E391a First dedicated experiment Last experiment at KEK
12-GeV PS-10 of sensitivity.
 ~ 3 x 10
 Pilot experiment for next step
(50GeV PS)
 50-GeV PS-13 of sensitivity,¾ < 10¾ Standard model events > 100¾ ∆η/η < 5%


L. Littenberg
E731
E799
KTeV

SM Expectation

E391a
KOPIO
50GeV PSYearCollaboration
High Energy Accelerator Research Organization, KEK
Faculty of Science and Engineering, Saga University
Department of Physics, Yamagata University
Department of Physics, Osaka University
Research Center for Nuclear Physics, Osaka University
National Defense Academy of Japan
Joint Institute for Nuclear Research (Dubna) Russia
Department of Physics, University of Chicago
Fermi National Accelerator Laboratory
Department of Physics, Pusan National University
10 Institutes from 4 countries, over 50 collaborators.

KEK PS-E391a experiment

Experimental apparatus
Compact detector system
K0 beam linez

Pencil beam.
zDetector with complete veto system.



zz

Narrow and clean beam.

4π coverage.
Double decay chamber.
Highly evacuated decay region.

High PT selection for π0.
Wide acceptance.

E391a detector

Background rejection
2 photons + nothing
pure CsI

Hermetic Calorimeter

Consider KL→2π0(4γ) as the main BG source.
Very-high γ detection efficiency
required (~10-4 inefficiency).
Could be achieved.
1 MeV threshold required.
~1mV threshold for discriminator.
Extremely low-noise operation.
γ inefficiency of CsI(ES147,ES171)

Schedule
Front barrel
DesignFront barrel
Construction

Assembling
Upstream section

Main barrel
Construction

Central barrel
DesignVacuumCsI&Assembling

Cosmic Test

Beam survey

Assembling
Detector setup

Engineering Run
Cosmic RunJan.

Apr.

Jul.

2001

Oct.

Jan.

Apr.

Jul.

2002

Oct.

Data Taking

Cosmic RunJan.

Apr.

Jul.

2003

Oct.

Jan.

Apr.

Jul.

2004

Oct.

Beam survey
First survey … April 2000
 γ and neutron … Dec. 2000
 KL flux … Nov. 2001
Energy Spectrum

Beam profile

Detector construction
Going smoothly on schedule.

DAQ system
Network distributed system with MIDAS software.


Scalability, stability, ...

Recycle of the present equipment as much as possible.
FASTBUS-ADC (High-resolution), TKO-TDC, ...
 Cost reduction

Low threshold, low noise.
Clustering module

1mV threshold

Noise reduction
Stable Ground Shield-roomGround and Shield-room

Engineering RunOct. 30 ~ Dec. 17, 2002 （49 days）
 Calibration of the calorimeters.


Muon from upstream of the beam line, cosmic rays,π0 from the fixed target, KL→2π0,3π0.

Overall check of the DAQ system.


70% of readout channels.
Noise test

Performance:
 DAQ was quite stable.
 No serious noise problem for the detector calibration.
→ Proved to be excellent.

In Preparation
Upstream section being ready to assemble.


Vacuum-vessel
Feb. 2003.
Lead-scinti calorimeterDec. 2002
Collar counter~ Apr. 2003.

Assembling work ~ June 2003.

In Preparation (cont.)
Middle section (5m-long Lead-scinti calorimeters)
 R&D finished for production.


1 modules/week → 32 weeks (8 months)
March ~ Oct. 2003.

Vacuum-vessel construction until Oct. 2003.

Installation will finish in Dec. 2003.
Evacuation in Jan. 2004.
Beam time from Feb. 2004.

Summary
Golden channel to access CP violation .
 Pilot experiment to establish the method.


Search at KEK 12-GeV PS.
Measurement at 50-GeV PS.

Detector and DAQ construction on schedule.
 Beam survey, engineering-run.
Good understanding for our system.
 Achieved excellent performance.
→ Significant step to the success of the experiment.
Physics run will start from Feb. 2004.