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Kyoto University H. Nanjo for E391a and K O TO collaboration

Kyoto University H. Nanjo for E391a and K O TO collaboration. Collaboration. KEK-PS E391a The first dedicated experiment for K L  p 0 nn . J-PARC E14 to measure Br(K L  p 0 nn ) at J-PARC K O TO (K0 at Tokai) Japan-USA-Russia-Taiwan-Korea 5 countries and 15 institutes.

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Kyoto University H. Nanjo for E391a and K O TO collaboration

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  1. Kyoto University H. Nanjo for E391a and KOTO collaboration 1

  2. Collaboration • KEK-PS E391a • The first dedicated experiment for KL p0nn . • J-PARC E14 • to measure Br(KL p0nn) at J-PARC • KOTO (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 KL p0nn with the similar method used in the E391a. • KEK • Kyoto • NDA • Osaka • Saga • Yamagata • Arizona State • Chicago • Michigan • JINR • National Taiwan • Pusan National • Seoul • CheonBuk National • Jeju National 2

  3. Motivation • Flavor Physics • Direct CP violation. • Br(KLp0nn)  h2 • h:Complex phase in CKM (Height of unitary triangle) • Beyond the SM • Rare FCNC process (highly suppressed in SM). • Br(KLp0nn)=(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 h) Golden mode. 3

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

  5. Concept of Experiment • KL 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 : KL, photon, neutron • Halo : neutron scattering on the surface of collimator • Detector • p0 (gg) and nothing • Photon calorimeter and hermetic vetos 5

  6. Concept of Experiment • How to make KL beam? • Proton beam  Target  KL proton KL target 6

  7. Concept of Experiment • How to make KL beam? • Proton beam  Target  KL • Charged particles • neutral short-lived particles • photon • neutron photon Short Lived proton KL target charged particle neutron 7

  8. Concept of Experiment • How to make KL beam? • Proton beam  Target  KLShaping Collimator • Charged particles • neutral short-lived particles • photon • neutron photon Short Lived proton KL target collimator charged particle neutron 8

  9. Concept of Experiment • How to make KL beam? • Proton beam  Target  KLShaping Collimator • Charged particles  sweeping magnet • neutral short-lived particles  long beam line • photon  Pb absorber (kill g but pass KL) • neutron c t KL 15000mm X087mm L079mm KS27mm photon Pb Short Lived proton KL B target collimator charged particle neutron 9

  10. Concept of Experiment • How to make KL beam? • Proton beam  Target  KLShaping Collimator • core : neutron, photon • halo : neutron (scattering at Pb /on the surface of collimator) core photon, neutron Pb proton KL B target collimator halo neutron neutron 10

  11. Concept of Experiment • How to detect KLp0nn? • p0 (gg) and nothing • Photon calorimeter core photon, neutron g Pb proton KL p0 B target g collimator halo neutron 11

  12. Concept of Experiment • How to detect KLp0nn? • p0 (gg) and nothing • Photon calorimeter and hermetic vetos • for photons g core photon, neutron g Pb proton KL p0 g p0 B target g collimator halo neutron 12

  13. Concept of Experiment • How to detect KLp0nn? • p0 (gg) and nothing • Photon calorimeter and hermetic vetos • for photons and charged particles core photon, neutron p- g Pb proton KL p+ p0 B target g collimator halo neutron 13

  14. Concept of Experiment • How to detect KLp0nn? • p0 (gg) and nothing • Photon calorimeter and hermetic vetos • for photons and charged particles • Beam hole veto under huge core g/n flux  Weaker veto. core photon, neutron g Pb proton KL p0 B target g collimator halo neutron 14

  15. Concept of Experiment • How to detect KLp0nn? • p0 (gg) and nothing • Photon calorimeter and hermetic vetos • for photons and charged particles • Beam hole veto under huge core g/n flux  Weaker veto. • Make beam hole small! Pencil Beam core photon, neutron g Pb proton KL p0 B target g collimator halo neutron 15

  16. Concept of Experiment • How to detect KLp0nn? • p0 (gg) and nothing • Photon calorimeter and hermetic vetos • for photons and charged particles • Beam hole veto under huge core g/n flux  Weaker veto. • Make beam hole small! core photon, neutron Pencil Beam g Pb proton KL p0 B target g collimator halo neutron 16

  17. Concept of Experiment • How to reconstruct KLp0nn? • 2g in Calorimeter and nothing • Energy and Position. • Reconstruct p0 • assuming KL vertex in the beam line thanks to the pencil beam. • Decide Zvtx with p0 invariant mass .  p0 full reconstruction core photon, neutron g Pb proton KL p0 target g halo neutron 17

  18. Concept of Experiment • How to reconstruct KLp0nn? • 2g in Calorimeter and nothing • Energy and Position. • Reconstruct p0 • assuming KL vertex in the beam line thanks to the pencil beam. • Decide Zvtx with p0 invariant mass .  p0 full reconstruction core photon, neutron E1 g Pb proton KL q p0 target g E2 halo neutron 18

  19. Concept of Experiment • Kinematics of KLp0nn • p0 PT-Zvtx Plane (Kinematics and Fiducial) • Higher PT distribution of p0 • Max 231 MeV/c (V-A theory) • Kaon-orign background • Veto and Kinematics PT signal region p0p0 (even) p+p-p0 KL→2π0 p0nn KL→π+π-π0 Z Signal Region KL→2γ 19

  20. Concept of Experiment • Halo neutron background • halo neutron  interact with detector component  create p0 /h0 decay to 2 g • Vertex position  shift due to • Energy mis-measurement • photonuclear, neutron-contami • h0 mass p0 /h0 production g Pb proton g B target collimator halo neutron 20

  21. Concept of Experiment • halo-n background in PT-Zvtx Plane • Contamination into the signal box • Point • Suppress halo-n • Lower halo-n momentum • Reduce material • Place it far from signal region • Veto at p0 production halo-n CC02 π0 halo-n CV-p0 PT signal region Z halo-n CV-h 21

  22. KL E391a Experiment • KL production with KEK 12GeV PS • 2 x 1012 protons on target (POT) per 2sec spill, 4sec cycle • production angle: 4°, KL peak momentum 2GeV/c, n/KL ratio: ~40 • p0 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. E391 Detector • a • Decay region • High vacuum: 10-5 Pa • to suppress the backgroundfrom interactions w/ residual gas • Detector components • Set in the vacuum: 0.1 Pa • separating the decay regionfrom the detector regionwith “membrane”: 0.2mmt film 23

  24. E391a Status • KL p0nn • 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  KOTO • KL p0p0X (X gg) light pseudoscalar particle X • Published with Run2 data Phys.Rev.Lett.102,051802(2009) • KL p0p0X (X mm) • Analysis in final stage with Run3 data. 24

  25. Strategy from E391a to KOTO • High intensity beam • New beam line (halo-n surpress) • Detector upgrade (background) 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 T1 Ni Target proton 25

  26. High intensity beam • Flux x RunTime x Acceptance  ~2.8 SM event KOTO E391a *without Back splash loss 26

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

  28. halo-n surpression • E391 : core  tail : 10-3 level • KOTO : : 10-4 level • softer neutron momentum. • beamline design •  Next talk by Shimogawa. 28

  29. Detector Upgrade NCC • 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 g 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 Increase Veto Performance Reduce halo-n affection Cope with high rate 29

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  36. Summary and prospects • KOTO experiment to measure Br(KL p0nn) • 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. 36

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