1. Kyoto University H. Nanjo1
DPF/JPS 2006

2. Collaboration J-PARC E14 Experiment
to measure Br(KL p0nn) at J-PARC
Stage1 approval at J-PARC PAC on Jun 2006
Based on E391 collaboration.
New members are joining.
Arizona State Univ.
Chicago Univ.
JINR
KEK
Kyoto Univ.
Michigan Univ.
National Defense Academy
National Taiwan Univ.
Osaka Univ.
Pusan National Univ.
Saga Univ.
Tbilisi State Univ.
TRIUMF
Yamagata Univ.
We aim to measure Br(KL p0nn) with basically the same method used in E391. 2
DPF/JPS 2006

3. Motivation Rare FCNC process Direct CP violation
Sensitive to new physics
SM : Br(KLp0nn)=(2.8  0.4)  10-11
Direct CP violation
Br(KLp0nn)  h2
Unitary triangle by K
Small theoretical uncertainty
2% in (Br h)
Br in 10 % accuracy
Golden mode 3
DPF/JPS 2006

4. Current Status Such topics will be presented here. E391
Sensitivity
Understanding of BG source
Kp2 is main K-origin BG
Halo neutron
Toward J-PARC K exp. (2010-)
Detector upgrade and new beam line are designed
Sensitivity is evaluated with Fast MC
New upper limit 2.1 10-7
(PRD 74:051105, 2006)
S.E.S
Run1 1week
9.1 10-8
Run2 Full
1.1510-8
Full
<5 10-9 expected
The box will be opened in a few months
2 order to SM 3 10-11
Tentative Final plot
(E391 Run2 1/3)
Such topics will be presented here. 4
DPF/JPS 2006

5. Strategy 100 times higher intensity at J-PARC
E391 detector with necessary modifications
Two-step approach
Step1: First observation in
Step2: Measure Br with over 100 KLp0nn events
Step1
Construct new beam line
E391 detector upgrade
New electronics 5
DPF/JPS 2006

6. J-PARC Japan Proton Accelerator Research Complex
World’s highest intensity proton beam
Construction at Tokai First beam in 2008
MR(50GeV PS)
perimeter~1.6km
30 GeV for slow ext.
21014 ppp 0.3MW
0.7s spill/3.3s repe.
E391 det. at 16 deg line
Exp Hall
20m neutral beamline
proton
T1 Ni Target 6
DPF/JPS 2006

7. Neutral beam 16 deg. Extraction from Target 20m Beamline
30 times more intense KL than E391
Softer n spectrum
Better n/K=9(42 for E391)
Reduce n-induced BG
20m Beamline
E391:halo-n/core=10-5
scatter at the collimator surface
J-PARC design to reduce it KL
8.1106/spill
Step1
E391
Core neutron
6.9107/spill 7
DPF/JPS 2006

8. E391 Detector upgrade CC02 : move to upstream
To reduce halo neutron BG
MB : increase the thickness
To reduce the inefficiency
CsI 7730cm2.52.550cm
Reduce inefficiency, improve energy resolution, discrimination of g fusion
BA : single is ~1MHz impossible
 totally different detector, BHPV (described after) 8
DPF/JPS 2006

9. BHPV Photon veto detector at beam hole Lead-Aerogel “sparse” sandwich
Coincidence of 3 consecutive layers
g efficiency is 99.9% for (Eg>1 GeV)
neutron efficiency < 10-3 for En=1 GeV
Operation under 0.5 GHz n/0.6 GHz g
Single rate is ~1 MHz (beam g)
Inefficient to backward-going g
Reduce back-splash to upstream
Performance has already been tested
in beam test and E391 Run3.
25 layer = 8.9X0 9
DPF/JPS 2006

10. CsI Improve w/o fusion cut w/ E391 fusion cut w/ KTeV CsI
7cm7cm  30cm
2.5cm  2.5cm  50cm
Improve
Energy resolution
Inefficiency
Fusion rejection
w/o fusion cut
w/ E391 fusion cut
w/ KTeV CsI
Due to photonuclear effect 10
DPF/JPS 2006

11. Things to consider Rate Inefficiency Halo neutron
Extrapolate E391 accidental rate
(reproduced with MC within a factor 1-3)
Highest single rate is ~1MHz for BHCV, BHPV at J-PARC
Detector operation
Signal acceptance loss due to false veto
Inefficiency due to masking
Inefficiency
Kp2 with 2 missing g (even/odd pair)
Kp2 with 1 missing g and fusion
Photonuclear effect and charge exchange interaction of p are also considered.
Halo neutron
CC02 position
Better n/K and halo-n suppression in beamline 11
DPF/JPS 2006

12. Sensitivity@Step1 S.E.S.=810-12 with 3 Snowmass years
Decay probability=3.6%, acceptance=9.4%
Acceptance loss = 50% mainly due to accidental loss with 10ns resolving time for veto.
3.5 SM events assuming Br = 2.810-11
2.6 BG events are expected mainly from even pair of Kp2 (similar kinematics) S/N=1.4
p0nn
Kp2 even
Kp2 odd 12
DPF/JPS 2006

13. Recent studies Beamline study DAQ and trigger
Performance check and optimization toward construction by 2008 is underway.
DAQ and trigger
Full simulation of J-PARC K detector
To design electronics and develop trigger system.
Single rate from KL decay at J-PARC
CC02 : 220kHz (Eth=1MeV)
CsI : 60kHz (Eth=1MeV)
CV : 220kHz (Eth=0.1MeV) 13
DPF/JPS 2006

14. Recent Studies (contd.)
CsI readout
2576ch with 1ns timing resolution
7-pole Bessel filter with 125 MHz waveform digitizer
(passive quasi-Gaussian shaper)
Veto counters’ readout with waveform digitizer
Single rate is ~1 MHz for BHCV (core n) and BHPV (beam g)
2ns timing resolution (for 10 ns veto window) 0.2% acc.loss
10ns double pulse resolution 1% inefficiency
500MHz waveform digitizer 14
DPF/JPS 2006

15. Schedule 2006 2007 2008 2009 2010 Beamline design New readout design
CsI readout test with prototype is planned.
Move KTeV CsI
Detector upgrade
2008
Build and test K0 beamline
Assemble detector
2009
Beam survey
Detector tuning
2010
Start physics run 15
DPF/JPS 2006

16. Summary and prospects J-PARC E14 experiment to measure Br(KL p0nn)
Neutral beam at J-PARC is being studied.
Detector upgrade is being designed.
Sensitivity has been studied.
S.E.S. = 810-12 with 50% acceptance loss
3.5 SM events with 2.6 background is expected in 3 years at Step1 (Br = 2.810-11 is assumed.)
Further studies on beamline, DAQ, and trigger system are in progress toward real construction or production. 16
DPF/JPS 2006

17. Backup slides 17
DPF/JPS 2006

18. New Physics Higgs mediated decay, for example Predict ~10% higher Br.
hep-ph/061094
MSSM with large tan b and general flavour mixing 18
DPF/JPS 2006

19. Step by Step 19
DPF/JPS 2006

20. J-PARC Plan 2006/12 : LINAC commissioning start
2007/ 9 : RCS(3-GeV PS) commissioning
2008/ 5 : MR(50-GeV PS) commissioning
Experiments at hadron experimental area
will be started in FY 2008
Before that, beamline for J-PARC K
should be installed. 20
DPF/JPS 2006

21. E391 beamline 21
DPF/JPS 2006

22. Inefficiency
CsI MB 22
DPF/JPS 2006

23. Fusion Probability 23
DPF/JPS 2006

24. BHPV Inefficiency 24
DPF/JPS 2006

25. E391 Rate Study Counting rate by accidental trigger (TMON)
Accidental trigger rate CSI:1.7 kHz
CC | |
BHCV | |
BHPV | | ~ 600 incl. beam photon  good agreement 25
DPF/JPS 2006

26. 26
DPF/JPS 2006

27. 7-pole Bessel Filter Used for ATLAS Tile-Calorimeter
NIM A 551 (2005) 27
DPF/JPS 2006

28. Cut list Eg cut Veto Calorimeter fiducial Vertex(300-500cm)
(2 g>0.1GeV,no >1MeV)
Veto
(photon 1MeV, charged 100keV)
Calorimeter fiducial
( cm)
Vertex( cm)
Pt( GeV/c)
Collinearity angle<150deg
E-q cut
E-ratio>0.2
E-total>0.5GeV 28
DPF/JPS 2006

29. Background 29
DPF/JPS 2006

30. Background from KL 30
DPF/JPS 2006

31. Cost Total $3.7M Beamline $0.6M CsI $1.1M Main Barrel $0.3M
Vacuum System
$0.25M
Beam Hole Photon Veto
Collar Counter
$0.2M
Trigger & DAQ
$0.55M
Transportation
$0.5M
Detector assembly 31
DPF/JPS 2006