Measurement of KL p0nn decay G.Y.Lim IPNS,KEK
Why KL→p0nn ? Flavor Changing Neutral Current Br(KL g p o n n ) = 6 k1 ・Im(VtdVts)2X2(xt) = 1.94・10-10h2A4X2 Strong Interaction : Factorized by Ke3 Decay * Negligible Charm contribution Very Small Theoretical Uncertainty
In JHF era h r Unitarity Triangle vertices Beyond Standard Models K+ p+nn KL p0nn E391a DMBd/DMBs ACP(BJ/YKS) r G. Buchalla hep-ph/0110313 L.Littenberg HEPAP(2001)
Search for the decay KL p0nn po gg po e+e- g BR(KLgponn) L. Littenberg E731 E799 KTeV Phys. Rev. D61 (2000) po gg SM Prediction Year Phys. Lett. B447(1999)
KL Decay Modes Decay Mode Branching Ratio Additional Particles popopo p+p-po p+m-n p+e-n gg ggg pogg pop+e-n p+e-ng p+m-ng p+p-g popog m+m-g e+e-g e+eｰgg 21.13 % 12.55 % 27.18 % 38.78 % 5.86・10-4 <2.4 ・10-7 1.68・10-6 5.18・10-5 3.62・10-3 5.7 ・10-4 4.61・10-5 <5.6 ・10-6 3.25・10-7 10.0 ・10-7 6.9 ・10-7 4g 2Ch 1g 2g 3g 2Ch Decay Mode Branching Ratio Additional Particles poge+e- p+p- popo m+m- e+e- p+p-e+e- m+m-e+e- e+e-e+e- pom+m- poe+e- ponn e+m- e+e-m+m- pom+e- <7.1 ・10-7 2.06・10-3 9.27・10-4 7.15・10-9 9 ・10-12 3.5 ・10-7 2.9 ・10-9 4.1 ・10-8 <5.1 ・10-9 <4.3 ・10-9 <5.9 ・10-7 <4.7 ・10-12 <6.1 ・10-9 <6.2 ・10-9 1g 2Ch 2Ch 2g 4Ch
Detector Inefficiency Inefficiency of g detection Inefficiency for charged particles NIM A359 p478 (1995) B.G. from KLgp-e+n Decay Separating charged veto
Fermi National Accelerator Laboratory E391a Collaboration 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
KEK-PS E391a First dedicated experiment 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
How far we have to go ? BR(KLg po nn) New Physics (?) Ke3, Kp3, Km3 KTeV d Current Exp. Limit hep-ph/9908399 hep-ph/9804412 hep-ph/9808487 Limit from K+ g p+nn (PRL 84, 3768 (2000)) E391a New Physics (?) S. M. Prediction JHF KOPIO(BNL)
E391a Detector Setup KL po n n gg Nothing pure CsI calorimeter 4p veto system
Pencil Beam
Beam Profile
Layout of Beam survey H. Watanabe (2002) : Revised B.G. estimation 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
Schedule 2001 2002 2003 2004 CsI Front barrel Construction Beam Test Main barrel Construction Vacuum & Cosmic Test CsI Assembling Assembling Detector setup Beam survey Engineering Run Data Taking Data Taking Cosmic Run Jan. Apr. Jul. Oct. Jan. Apr. Jul. Oct. Jan. Apr. Jul. Oct. Jan. Apr. Jul. Oct. 2001 2002 2003 2004
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
JHF 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 p0nn Measurement Experiment at the first stage of JHF Flexible approach
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)
In future ・・・ BR(KLgponn) E391a SM Expectation KOPIO JHF Year
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 !