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Measurement of KL→p0nn: Flavor-Changing Neutral Current in Beyond Standard Models

This experiment aims to measure the KL→p0nn decay in order to study flavor-changing neutral currents in the context of beyond standard models. It also explores potential new physics and contributes to the understanding of CP violation and the unitary triangle in the K-system. The E391a collaboration at KEK-PS is conducting this pilot experiment as a precursor to future measurements at JHF.

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Measurement of KL→p0nn: Flavor-Changing Neutral Current in Beyond Standard Models

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  1. Measurement of KL p0nn decay G.Y.Lim IPNS,KEK

  2. Why KL→p0nn ? • Flavor Changing Neutral Current • Br(KL gp on n ) = 6 k1 ・Im(VtdVts)2X2(xt) • 　 = 1.94・10-10h2A4X2 Strong Interaction : Factorized by Ke3 Decay * Negligible Charm contribution Very Small Theoretical Uncertainty

  3. Unitarity Triangle vertices Beyond Standard Models In JHF era h K+ p+nn KL p0nn E391a DMBd/DMBs ACP(BJ/YKS) r G. Buchalla hep-ph/0110313 L.Littenberg HEPAP(2001)

  4. KL p0nn Search for the decay po e+e-g L. Littenberg BR(KLgponn) E731 E799 KTeV Phys. Rev. D61 (2000) po gg SM Prediction Year Phys. Lett. B447(1999)

  5. KL Decay Modes

  6. B.G. from KLgp-e+n Decay Separating charged veto Detector Inefficiency Inefficiency of g detection Inefficiency for charged particles NIM A359 p478 (1995)

  7. High Energy Accelerator Research Organization, KEK Faculty of Science and Engineering, Saga University Department of Physics, Yamagata University Department of Physics, Osaka University Research Center for Nuclear Physics, Osaka University National Defense Academy of Japan Department of Physics, Ibaraki University Joint Institute for Nuclear Research (Dubna) Russia Department of Physics, University of Chicago Fermi National Accelerator Laboratory Department of Physics, Pusan National University http://psux1.kek.jp/~e391/index.html E391a Collaboration

  8. KEK-PS E391a • First dedicatedexperiment • Pilot experiment for next step (JHF) • Figure out sources of background • Developing method of rejection/estimation • Realizing detector setup in high vacuum system • Compact detector system • High acceptance • Pencil beam • Double decay chamber • Highly evacuated decay region • High PT selection

  9. How far we have to go ? Ke3, Kp3, Km3 BR(KLgponn) KTeV d Current Exp. Limit hep-ph/9908399 hep-ph/9804412 hep-ph/9808487 Limit from K+gp+nn (PRL 84, 3768 (2000)) New Physics (?) E391a S. M. Prediction JHF KOPIO(BNL)

  10. E391a Detector Setup • KLpo n n • ggNothing • pure CsI calorimeter4pveto system

  11. Pencil Beam

  12. Beam Profile

  13. Layout of Beam survey Thermal Neutron Detectors (LiI, Li glass) Hodoscopes (15x15) Profile detectors KL monitoring using regeneration Cerberus BGO KL monitor Liquid Scin. CsI Copper Lead glass n/g detector (SLSD) Moving Rail H. Watanabe (2002) : Revised B.G. estimation

  14. Schedule Front barrel Construction Main barrel Construction Beam Test Vacuum & Cosmic Test CsI Assembling Assembling Detector setup Data Taking Beam survey Engineering Run Data Taking Cosmic Run Jan. Apr. Jul. Oct. Jan. Apr. Jul. Oct. Jan. Apr. Jul. Oct. Jan. Apr. Jul. Oct. 2001 2002 2003 2004

  15. Search a Measurement • High flux of KL • Large acceptance • Suppression of the Background • Standard model event • B.G. linear to beam intensity  Same S/N ratio (~3) • New physics • Newly designed detectors system • Physical motivation • Following talk

  16. Large Number of KL Decay Three orders larger KL flux Beam will be given from 2007 Two stages of construction Limited beam lines Many experimental programs KL p0nnMeasurement Experiment at the first stage of JHF Flexible approach JHF

  17. E391a at JHF • Experience at KEK-PS • Same veto system • Low cost, earlier starting • New calorimeter • resolution, clustering, efficiency • Fast DAQ • High counting rates • Optimization of beam line • KL/n/g ratio, L production T.Inagaki　CP Violation in K Dec. (1998)

  18. In future ・・・ BR(KLgponn) E391a SM Expectation KOPIO JHF Year

  19. Summary • Golden channel to access CP violation (KL  p0nn) • KEK-PS E391a • Pilot experiment for JHF • The first high sensitivity experiment • Plan for data taking on 2003 • JHF • Real measurement of branching ratio • Most clean measurement of CPV parameter • Unitary triangle in K-system • Potential to access the New Physics LOI within 2002 !

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