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K L  p 0 nn experiment at J-PARC

K L  p 0 nn experiment at J-PARC. Hiroaki Watanabe (KEK) for the J-PARC-E14 collaboration. J-PARC E14 Collaboration. Arizona State Univ. Univ. of Chicago JINR KEK Kyoto Univ. Univ. of Michigan, Ann Arbor National Defense Academy National Taiwan Univ. Osaka Univ.

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K L  p 0 nn experiment at J-PARC

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  1. KLp0nn experiment at J-PARC Hiroaki Watanabe (KEK) for the J-PARC-E14 collaboration

  2. J-PARC E14 Collaboration • Arizona State Univ. • Univ. of Chicago • JINR • KEK • Kyoto Univ. • Univ. of Michigan, Ann Arbor • National Defense Academy • National Taiwan Univ. • Osaka Univ. • Pusan National Univ. • Saga Univ. • Tbilisi State Univ. • TRIUMF • Yamagata Univ. • 16 Institutes from 7 countries • Newly Joined • Univ. of Seoul • ChonBuk National Univ.

  3. Vtd Measurement of Br(KL p0nn) Amplitude of CP-violation in Quark Sector. • The most clean process : 1-2 % theoretical uncertainty • Sensitive to New Physics.

  4. F. Mescia @CKM2006 It gives us strong motivation!

  5. Strategy • Step by Step approach. • E391  Close to GN limit. • J-PARC Step-1 (E14)  First observation. Search for Big enhancement by New Physics. • J-PARC Step-2  > 100 evts • Dedicated beam-line. ( not common target.)

  6. Hadron Experimental Facility Material-life science ５００ｍ！ Ｔ２Ｋ（ν） 3GeV Synchrotron（25Hz,1MW） 50GeV Synchrotron （0.75MW) J-PARC (Japan Proton Accelerator Research Complex) Linac (350m,180MeV) Stage-1: 2x1014 protons on target/spill(=3.7sec), 30GeV

  7. Nov, 2006 Pacific Ocean

  8. Beam Line at step-1 30GeV proton KL First slow beam extraction is scheduled on Dec., 2008.

  9. May 18th, 2007 K+1.8 KL K+1.1/0.8 T1 Target

  10. ○ 54mm-thick pure-Nickel. It divided in to 5 disks 21.7, 11.2, 8.3, 6.9, 5.9 ○Beam Energy: up to 50 GeV. ○Beam Size : sX~sY~1.3mm。 ○　Target is cooled by water in 1 atm. T1 Common target Beam

  11. Parameters of beam • Item J-PARC E14 KEK E391a • Primary proton energy 30 GeV 12 GeV • Proton intensity(/spill) 2x1014 2.5x1012 • Spill-length/repetition 0.7s / 3.3s 2s / 4s • Production target Common “T1” Pt rod • Extraction angle 16 degree 4 deg. • KL yield 8.1x106 3.3x105 • Average PKL 2.1 GeV/c 2.6 GeV/c

  12. ` Top view of new KL beamline Detail engineering design is in progress.

  13. Detection Principle ・　Detection of 2 photons from p0 using high-efficiency hermetic calorimeters with well collimated KL beam. • Current upper limit (E391a-Run-I): <2.1x10-7 (90%C.L.) • E14 aims at First Observation(~3.5evts) at J-PARC. • Upgraded E391a-Detector. γ γ

  14. Key issues: • Halo Neutron. • KLp0p0 Background. • Acceptance loss by accidental hits.

  15. Preliminary E391a 2-clusters data （Run-II 1/3 data) Halo neutron is Main Background Source。 PT(GeV/c) Zvtx(cm) Halo neutron

  16. Target simulation : KL/core-n yield KL8×106/spill Momentum of neutron Momentum of KL • softer neutron • n/K=9(42 for E391) •  reduce n-induced BG E14 E391a E391 E14

  17. Optimization of Collimator Shapes • Inner f100mm : Tungsten alloy(17.9g/cm3) ・Outer : Iron ・In Vacuum Simple MC Simulation Model ±9mm

  18. scattering at 1st collimator scattering at 2nd collimator E14-proposal #33 ~10-5 halo/core Further optimization is in progress.

  19. Control of halo-neutron events by detector side. 1 .Thicker Calorimeter: E391a: 16X0-CsI  E14: 27X0-CsI (loan from KTeV) • Less shower leakage. • Better vertex resolution. + moving to upstream side. In total, ~4x10-5 reduction is expected. 2. Full Active Collar Counter(CC02) E391a: Lead/Scintillator sampling type  E14: CsI crystal. • Full active: higher efficiency of secondary particles detection in the neutron interaction. • Shorter X0/cm: • Most g’s interact before going out CC02. A factor of ~20 reduction Is expected. 3. Careful configuration of detector position. Reconstruction-Vertex distribution. E391a-CC02

  20. Key issues: • Halo Neutron. • Beam-line optimization. • Thicker calorimeter. • Full active heavy crystal for CC02.  Enough reduction is succeeded. • KLp0p0 Background. • Acceptance loss by accidental hits.

  21. KEK-E391a KLp0p0 B.G. • KLp0p0 is major B.G. in E14. • 2g missing (inefficiency/fusion) (1) Fine segmentation: • 7x7cm2 2.5x2.5cm2 • ( x~8 KLp0p0 B.G. reduction) • (2) Thicker veto to suppress • punch-through inefficiency. w/o fusion cuts J-PARC E14(loan from KTeV) w/E391a fusion cut w/KTeV CsI

  22. Proposed Detector Upgrade. J-PARC E14(loan from KTeV) KEK-E391a γ γ Lead/plastic-scintillator  CsI crystal.

  23. Key issues: • Halo Neutron. • Beam-line optimization. • Thicker calorimeter. • Full active heavy crystal for CC02. • KLp0p0 Background. • Fine segmented CsI’s. • Thicker Veto (CsI, Main barrel.) • Acceptance loss by accidental hits.

  24. Proposed Detector Upgrade( cont’d) Acceptance loss by BHPV due to accidental hit : 30~40 %(E391a 2E+12ppp)  2 % (E14, 2E+14ppp) 99.9% Lead / Aerogel Cerenkov radiator

  25. Assuming 3 snowmass years(=3months-beam/year) • =1.8x1021 protons on target • 3.5 p0nn events are expected • if Br.=standard model prediction. • 2.5 background events are expected. • S/B~1.4. • B.G. source No. of B.G events. • Other KL decay • KLp0p01.8 • KLp+p-p0 0.4 • KLp-e+n 0.005 • KLgg negligible • KLp0p0p0 negligible • Neutron Interaction • With Residual gas 0.04 • At the CC02 0.01 • At the C.V. negligible • Accidental coin. 0.10 MC: KLp0nn

  26. Schedule & Summary • J-PARC E14 experiment aims at First Observation of KLp0nn decay. • Upgrade of KEK-E391a detector are planed. • E14 submitted a proposal to PAC (program advisory committee).  1st-stage scientific approval.  2nd stage process is in progress. • Schedule • 2007: • All engineering design of beam-line will be completed. • KTeV CsI’s will be started to move to J-PARC. • Many R&D’s are in progress. • 2008: beam-line construction will be scheduled. • Dec, 2008~: First commissioning of slow beam extraction is scheduled. • Beam survey : measuring the beam-line performances. • 2008~2009: Assembling of Detector system. • 2010~:First Engineering Run or/and Physics Run.

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