03 Aug NP041 KOPIO Experiment Measurement of K L    Hideki Morii (Kyoto Univ.) for the KOPIO collaborations Contents Physics Motivation of KOPIO Experimental Concept KOPIO Detector Prospects of KOPIO

03 Aug NP042 Physics Motivation of KOPIO KOPIO BNL –K L    measurement Measures CP parameter  –B(K L    ) |Im (V ts * V td )| 2 One of the “gold-plated” modes –Hadronic matrix elements (K  ) from K  e –Negligible long distance effects –Top quark dominance  small theoretical uncertainty ~ 2-3%

03 Aug NP043 CP violation in K L    B(K +    ) | V ts * V td | 2 E949 B(K L    ) |Im (V ts * V td )| 2 KOPIO Jarlskog invariant |J CP | = 2 A  = |Im(V ts * V td )|   

03 Aug NP044 K L    Experiments B(K L    ) KTeV (FNAL) Result : < 5.9 x E391a (KEK) goal : – KOPIO (BNL) goal : (~40 events S/N 2) K +    and isospin limit (Grossman-Nir limit from E949) : < 1.4 x SM prediction : ( ) x

03 Aug NP045 K L    Beyond Standard Model Enhanced EW penguins B(K L    ) = (3 1) x (hep-ph/ ) 12 New prediction by Buras et al.

03 Aug NP046 KOPIO Concept Detect   and nothing    veto Measures as much as possible K L TOF : to work in K L CMS –microbunched p beam –2  detection timing Reconstruct  0 decay from  –Measure  directions in PR –Measure  energy in CAL Veto : cover 4  solid angle –Photon veto –Charged particle veto

03 Aug NP047 Kinematic Rejection of K L  0  0 BG  0  0 even both  from same  0 –Kinematic cut : E  *  0  0 odd  from different  0 –Kinematic cut : M        

03 Aug NP048 Kinematic Rejection of K L   BG K L   0  0  0 –easy to veto (have 4 extra  ) K L   +    0 –Kinematic cut : E  *, E MISS

03 Aug NP049 Signal and Background Estimates Signal ~ 40 events (at SM rate) Background ~ 20 events S/N ~ 2  B/B ~ 20%  /  ~ 10%

03 Aug NP0410 Beam Proton Beam –100 Tp / Spill –2.7 s spill 2.3 s interspill period –25 MHz micro-bunching frequency –Bunch width 200 ps –Interbunch extinction Neutral Beam –Large take-off angle ~ 45degree –Soft momentum : 0.5 – 1.5 GeV/c –3 x 10 8 KL / spill, 12% decay –3.5 x neutrons / spill K L spectrum

03 Aug NP0411 KOPIO Detector Preradiator measures direction of  Beam Catcher in-beam  veto Shashlyk Calorimeter measures energy of 

03 Aug NP0412 Preradiator Measures the position and angle of  Radiation length : 2X 0 (70% converts) Consists of –Cu converter –drift chamber –plastic scintillator TRIUMF

03 Aug NP0413 Preradiator

03 Aug NP0414 Preradiator – Angle Resolution Angle resolution of 25 mr at 250 MeV Angular distribution resolution ~ MeV  Measured 

03 Aug NP0415 Shashlyk Calorimeter Measures energy of  Consists of –Pb converter –Plastic scintillator –penetrating WLS fiber Shashlyk type calorimeter Yale

03 Aug NP0416 Shashlyk Energy Resolution Required resolution : 3.5 % / (GeV) Estimated (Combined with PR) : ~2.7 % / (GeV) Energy Resolution

03 Aug NP0417 Charged Veto Plastic scintillator Inefficiency (1 GeV/c): e + : ( ) x  + : < 1.6 x e - : < 1.3 x  - : ( ) x 10 -4

03 Aug NP0418 Beam Catcher Photon veto which covers beam core region under high neutron rate Need to be… –efficient to  rays –insensitive to neutrons Aerogel Cherenkov + distributed geometry –suppress neutron sensitivity Catcher Module Japan

03 Aug NP0419 Beam Catcher – MC Event Display Event Display for  Event Display for neutron Top View Side View Secondary particles are created isotropically  Can distinguish  from neutron using geometry Shower spreads forward

03 Aug NP0420 Beam Catcher – Expected Performance Simulation :  energy (GeV) efficiency efficiency for  efficiency for neutron efficiency neutron kinetic energy (GeV)

03 Aug NP0421 Beam Catcher – Prototype Test Light yield – using  + Neutron inefficiency - using proton in place of neutrons Prototype Module Light Yield Proton Efficiency Data agree MC very well

03 Aug NP0422 Prospects of KOPIO Approved by NSF(2003), construction start in M$ RSVP on 2005 presidental budget KOPIO schedule –2004 Detector R&D –2005 – 2006 Construction of beam line Mass production of detectors –2007 – 2008 Installation of detectors –2009 ~ Engineering run Physics run

03 Aug NP0423 Summary KOPIO experiment measures K L    Gold-plated mode –small theoretical uncertainty –measures CP parameter  R&D is concluding successfully Advanced planning for the construction is undergoing

03 Aug NP0424 Extras

03 Aug NP0425 Kinematic Constraint

03 Aug NP0426 Production Target Pt? 10cm long

03 Aug NP0427 Photon Veto

03 Aug NP0428 Vacuum Very high vacuum (~10 -7 Torr) is needed to reduce interaction with residual gas Vacuum vessel –thickness ~ a few % of X 0

03 Aug NP0429 Requirement for Catcher Energy Distribution of   after kinematic cut 