1. New Developments of Flavor Physics 2009 1 Kyoto University H. Nanjo for E391a and K O TO collaboration

2. New Developments of Flavor Physics 2009 KEK-PS E391a –The first dedicated experiment for K L  . J-PARC E14 to measure Br(K L   ) at J-PARC –K O TO (K0 at Tokai) Japan-USA-Russia-Taiwan-Korea –5 countries and 15 institutes. Based on E391a collaboration. New members are joining. We aim to discover K L   with the similar method used in the E391a. Collaboration 2 KEK Kyoto NDA Osaka Saga Yamagata Arizona State Chicago Michigan JINR National Taiwan Pusan National Seoul CheonBuk National Jeju National

3. New Developments of Flavor Physics 2009 Flavor Physics –Direct CP violation. –Br(K L  0 )    :Complex phase in CKM (Height of unitary triangle) Beyond the SM –Rare FCNC process (highly suppressed in SM). Br(K L  0 )=(2.8  0.4)  10 -11 –Very Sensitive to new physics(TeV-Scale Physics). Small theoretical uncertainty –Short distance physics (>99% due to t quark) –  2% uncertainty in (Br  )  Golden mode. Motivation 3

4. New Developments of Flavor Physics 2009 K O TO Physics Run 2011  2014 E391a New Physics Status and Room for New Physics 4 Chance to reach TeV-scale New Physics using Kaon  Next-Generation World-Wide Kaon Physics –KEK-PS E391 Run2 –Run3 analysis  K O TO –Grossman-Nir bound –model independent (can be violated if LFV) –indirect limit from K +    BNL E797/E949  CERN NA62 European Rare-decays Experiments with Kaons, FNAL Project-X

5. New Developments of Flavor Physics 2009 Concept of Experiment K L beam (proton  target) –neutral beam line »Long beam line  Kill particles with shorter lifetime »Charged particle sweeping magnet. »Pb photon absorber  reduce beam photons »Collimator  shaping (  source of beam halo) –Core : K L, photon, neutron –Halo : neutron scattering on the surface of collimator Detector –   (  ) and nothing Photon calorimeter and hermetic vetos 5

6. New Developments of Flavor Physics 2009 Concept of Experiment How to make KL beam? –Proton beam  Target  K L 6 proton target KL

7. New Developments of Flavor Physics 2009 Concept of Experiment How to make KL beam? –Proton beam  Target  K L »Charged particles »neutral short-lived particles »photon »neutron 7 proton target photon neutron charged particle KL Short Lived

8. New Developments of Flavor Physics 2009 Concept of Experiment How to make KL beam? –Proton beam  Target  K L  Shaping Collimator »Charged particles »neutral short-lived particles »photon »neutron 8 proton target photon neutron charged particle collimator KL Short Lived

9. New Developments of Flavor Physics 2009 Concept of Experiment How to make KL beam? –Proton beam  Target  K L  Shaping Collimator »Charged particles  sweeping magnet »neutral short-lived particles  long beam line »photon  Pb absorber (kill  but pass KL) »neutron 9 B proton target photon neutron charged particle collimator Pb KL Short Lived c  K L 15000mm   87mm   79mm K S 27mm

10. New Developments of Flavor Physics 2009 Concept of Experiment How to make KL beam? –Proton beam  Target  K L  Shaping Collimator –core : neutron, photon –halo : neutron (scattering at Pb /on the surface of collimator) 10 B proton target neutron collimator Pb KL halo neutron core photon, neutron

11. New Developments of Flavor Physics 2009 Concept of Experiment How to detect K L  0 ? –   (  ) and nothing Photon calorimeter 11 B proton target collimator Pb KL 00   halo neutron core photon, neutron

12. New Developments of Flavor Physics 2009 Concept of Experiment How to detect K L  0 ? –   (  ) and nothing Photon calorimeter and hermetic vetos –for photons 12 B proton target collimator Pb KL 00   halo neutron core photon, neutron 00  

13. New Developments of Flavor Physics 2009 Concept of Experiment How to detect K L  0 ? –   (  ) and nothing Photon calorimeter and hermetic vetos –for photons and charged particles 13 B proton target collimator Pb KL 00   halo neutron core photon, neutron -- ++

14. New Developments of Flavor Physics 2009 Concept of Experiment How to detect K L  0 ? –   (  ) and nothing Photon calorimeter and hermetic vetos –for photons and charged particles Beam hole veto under huge core  /n flux  Weaker veto. 14 B proton target collimator Pb KL 00   halo neutron core photon, neutron

15. New Developments of Flavor Physics 2009 Concept of Experiment How to detect K L  0 ? –   (  ) and nothing Photon calorimeter and hermetic vetos –for photons and charged particles Beam hole veto under huge core  /n flux  Weaker veto. Make beam hole small!  Pencil Beam 15 B proton target collimator Pb KL 00   halo neutron core photon, neutron

16. New Developments of Flavor Physics 2009 Concept of Experiment How to detect K L  0 ? –   (  ) and nothing Photon calorimeter and hermetic vetos –for photons and charged particles Beam hole veto under huge core  /n flux  Weaker veto. Make beam hole small! 16 B proton target collimator Pb KL 00   halo neutron core photon, neutron Pencil Beam

17. New Developments of Flavor Physics 2009 Concept of Experiment 17 proton target Pb KL 00   halo neutron core photon, neutron How to reconstruct K L  0 ? –  in Calorimeter and nothing –Energy and Position. –Reconstruct   –assuming KL vertex in the beam line thanks to the pencil beam. –Decide Z vtx with  0 invariant mass.   0 full reconstruction

18. New Developments of Flavor Physics 2009 Concept of Experiment 18 proton target Pb KL 00   halo neutron core photon, neutron How to reconstruct K L  0 ? –  in Calorimeter and nothing –Energy and Position. –Reconstruct   –assuming KL vertex in the beam line thanks to the pencil beam. –Decide Z vtx with  0 invariant mass.   0 full reconstruction  E1 E2

19. New Developments of Flavor Physics 2009 Concept of Experiment Kinematics of K L   –  0 P T -Z vtx Plane (Kinematics and Fiducial) – Higher P T distribution of  0 –Max 231 MeV/c (V-A theory) – Kaon-orign background Veto and Kinematics 19 Z Z K L →2γ PTPT PTPT K L →2π 0 signal region K L →π + π - π 0  0  0  0 (even) +-0+-0 Signal Region

20. New Developments of Flavor Physics 2009 Concept of Experiment 20 B proton target collimator Pb   0 /  0 production halo neutron  Halo neutron background –halo neutron  interact with detector component  create  0 /  0  decay to 2  –Vertex position  shift due to Energy mis-measurement –photonuclear, neutron-contami  0 mass

21. New Developments of Flavor Physics 2009 halo-n background in P T -Z vtx Plane – Contamination into the signal box Point –Suppress halo-n –Lower halo-n momentum –Reduce material –Place it far from signal region –Veto at  0 production Concept of Experiment 21 Z Z halo-n CV-  PTPT PTPT halo-n CC02 π 0 signal region halo-n CV-  0

22. New Developments of Flavor Physics 2009 KLKL E391a Experiment K L production with KEK 12GeV PS –2 x 10 12 protons on target (POT) per 2sec spill, 4sec cycle –production angle: 4°, K L peak momentum 2GeV/c, n/K L ratio: ~40  0 and nothing. –Pure CsI Calorimeter –Hermetic Vetos Physics runs –Run I: February to July of 2004 “Express” analysis with 10% data published in PRD (2006) –Run II: February to April of 2005 (~ 32 days without break) published in PRL(2007) –Run III: October - December of 2005 Analysis  Expect to be finished in 2009 22

23. New Developments of Flavor Physics 2009 E391 Detector a 23 Decay region –High vacuum: 10 -5 Pa to suppress the background from interactions w/ residual gas Detector components –Set in the vacuum: 0.1 Pa separating the decay region from the detector region with “membrane”: 0.2mmt film

24. New Developments of Flavor Physics 2009 E391a Status K L   –Run2 Published Phys.Rev.Lett.100,201802(2008) No event observed. (BG estimate 0.41) –Run3 Analysis ~ 2 times higher sensitivity  expect to be finished in 2009 –3 order to SM sensitivity  K O TO K L     X (X  light pseudoscalar particle X –Published with Run2 data Phys.Rev.Lett.102,051802(2009) K L     X (X  –Analysis in final stage with Run3 data. 24

25. New Developments of Flavor Physics 2009 25 Strategy from E391a to K O TO High intensity beam New beam line (halo-n surpress) Detector upgrade (background) MR(50GeV PS) perimeter~1.6km 30 GeV for slow ext. 2  10 14 ppp 0.3MW 0.7s spill/3.3s repe. T1 Ni Target E391 det. at 16 deg line proton Exp Hall 20m neutral beamline

26. New Developments of Flavor Physics 2009 26 High intensity beam Flux x RunTime x Acceptance  ~2.8 SM event KOTOE391a (Run2) Proton energy30 GeV12 GeV Proton intensity2e142.5e12 Spill/cycle0.7/3.3sec2/4sec Extraction Angle 16 deg4 deg Solid Angle 9  Str12.6  Str KL yield/spill7.1e132.4e11 x30 /sec Run Time3 s.m. years =12 months. 1 month x10 Decay Prob.4%2% x 2 Acceptance3.6% * 0.67% x5 KOTO E391a * without Back splash loss

27. New Developments of Flavor Physics 2009 New Beamline 27 Jan/2009 Collimator Fabrication We fixed the beamline design and fabrication is on-going.

28. New Developments of Flavor Physics 2009 halo-n surpression E391 : core  tail : 10 -3 level KOTO : : 10 -4 level –softer neutron momentum. –beamline design  Next talk by Shimogawa. 28

29. New Developments of Flavor Physics 2009 29 Detector Upgrade NCC Increase Veto Performance Reduce halo-n affection Cope with high rate NCC : move to upstream, full active pure-CsI, WLS fiber readout. –To reduce halo neutron BG and monitor halo-n itself in stew. CsI 7  7  30cm  2.5  2.5  50cm –Reduce inefficiency, improve energy resolution, discrimination of  fusion –CW base with amp. to reduce heat and increase gain. CV : 2-layer design Scintillator + WLS fiber + MPPC (light, space, cost) BHPV : Pb converter + Aerogel Cerenkov radiator + winstone cone light collection. (single rate@E391 is ~1MHz  ~40MHz @J-PARC  impossible  totally different.) MB : increase the thickness  To reduce the inefficiency

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36. New Developments of Flavor Physics 2009 36 Summary and prospects KOTO experiment to measure Br(K L   ) Neutral beamline design is fixed and fabrication is on-going and delivery and construction in this FY. Beamline survey in ~Oct. 2009 with the BL. Detector upgrade is being designed and prototype is made and tested toward Engineering run in 2010 and Physics run in 2011.