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Investigating Rare Process with J-PARC

Collaborative research aims to measure rare process Br(KL ➞ p0nn) at J-PARC with high intensity proton beams, enhancing detection techniques to improve sensitivity and accuracy.

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Investigating Rare Process with J-PARC

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  1. Kyoto University H. Nanjo 1

  2. 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. 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. We aim to measure Br(KL p0nn) with basically the same method used in E391. 2

  3. Motivation • Rare FCNC process • 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

  4. Current Status • 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) 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

  5. Strategy • 100 times higher intensity at J-PARC • E391 detector with necessary modifications • Two-step approach • Step1: First observation in 2010-2013 • Step2: Measure Br with over 100 KLp0nn events • Step1 • Construct new beam line • E391 detector upgrade • New electronics 5

  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 T1 Ni Target proton 6

  7. Neutral beam • 16 deg. Extraction from Target • 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 8.1106/spill KL Step1 E391 Core neutron 6.9107/spill 7

  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 rate@E391 is ~1MHz ~40MHz @J-PARC impossible  totally different detector, BHPV (described after) 8

  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

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

  11. Things to consider • Rate • 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

  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 odd Kp2 even 12

  13. Recent studies • Beamline study • 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

  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

  15. Schedule • 2006 • Beamline design • New readout design • 2007 • 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

  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

  17. Backup slides 17

  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

  19. Step by Step 19

  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

  21. E391 beamline 21

  22. Inefficiency CsI MB 22

  23. Fusion Probability 23

  24. BHPV Inefficiency 24

  25. E391 Rate Study Counting rate by accidental trigger (TMON) Accidental trigger rate CSI:1.7 kHz CC07 | 125 | 130 BHCV | 50 | 25 BHPV | 600 | ~ 600 incl. beam photon  good agreement 25

  26. 26

  27. 7-pole Bessel Filter • Used for ATLAS Tile-Calorimeter • NIM A 551 (2005) 460-476 27

  28. Cut list • Eg cut • (2 g>0.1GeV,no >1MeV) • Veto • (photon 1MeV, charged 100keV) • Calorimeter fiducial • (17.5-85cm) • Vertex(300-500cm) • Pt(0.12-0.25 GeV/c) • Collinearity angle<150deg • E-q cut • E-ratio>0.2 • E-total>0.5GeV 28

  29. Background 29

  30. Background from KL 30

  31. Cost • Total $3.7M 31

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