Status Report for KEK-PS E391a KEK IPNS G.Y.Lim 14 April 2003

E391a experiment  Measurement of BR( K L    ) 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 Joint Institute for Nuclear Research (Dubna) Russia Department of Physics, University of Chicago, USA Fermi National Accelerator Laboratory, USA Department of Physics, Pusan National University, KOREA New KEK member Department of Physics, Kyoto University Data taking from Feb  Engineering run  Preparation of detector components  Two-step program (KEK-PS  JPARC)  From the E391a Establish measurement principle Search for near SM expectation

E391a Detector Upstream section Downstream section Middle Section Engineering Run on last winter

Engineering Run  Fabricate on last summer  KL decay data – same format of real run Develop on-line/off-line software  DAQ using self-trigger of CsI Same scheme of real run Tuning / feed-back  CsI calibration Cosmic test in vacuum chamber Cosmic test during stacking Punch-through muon Two gammas from single  0 Multi-gamma decay (Kpi2, Kpi3) Significant step to the successful experiment

DAQ with low noise level  Distributed and parallel processing  LeCroy 1885N FASTBUS ADC  TKO HR-TDC  Operation with tiny noise 1mV threshold for TDC ( 1 MeV) 50 fC ADC pedestal (0.1 MeV)

Calibration using cosmic/punch-through muon Using cosmic rays pQ pQ/cm Using punch-through muons CsI ID MeV/pQ Good agreement between two gain factors !

Calibration using  0 -production n  Before correction After correction Reconstructed position(cm) Incident position (cm) Two  invariant mass (MeV/c 2 )  m : 5.4 MeV/c  3.7 MeV/c  22

Study using Kpi3 decay Calibration method in real run How to get correct energy scale Background free without veto system Comparison with M.C. Detailed study is going on Radial hit distribution of gamma Vertex along the beam direction - Good agreement

 Short spill beam (1X10 12 ppp/ 200 ms) Single counting rates (10 mV Thres.) Response at the high Intensity PMT gain (Xe monitoring system) KTeV CsI CC03 Counts / SEC Outer CsI Inner CsI 7.0 X / 2s 1.4 X /2s 1.0 X / 0.2s ADC channels Xe signal of the 1 st CsI module Normalize counts On spillOff spill Peak=1437  /Mean=1.6% Ratio of on/off spill for Xe-peak CsI ID Same performance under the high beam intensity

Detector fabrication – Upstream Modules/vacuum chamber done Cosmic test is going on No. of p.e. / MeV Distance from the PMT (cm) Assembling on June -July Assembling jigs are being fabricated - KEK machine shop

Detector fabrication – Middle Fabrication of 3 modules ー Finished 1 module/1 week  End of Oct. (32 modules) Design of assembling jigs – final stage Assembling Nov. – Dec. Vacuum Chamber : Start bidding process  arrive at the end of Oct.

Schedule Data Taking Assembling Detector setup Vacuum & Cosmic Test Assembling Front barrel Construction Main barrel Construction Cosmic Run Beam surveyEngineering Run Jan. Apr. Jul. Oct. CsI Cosmic Run Assembling Upstream section Front barrel Design Central barrel Design Up-dated on April, 2003 Evacuating Test

Summary  E391a is aiming for measuring the BR( K L    ) Realizing Step-by-step  Engineering run Stable data taking using same triggering scheme of real run CsI calibration – cosmic ray data is very nice input No problem at high beam intensity Good agreement with M.C. Detailed study is going on  E391a is preparing almost on schedule Downstream section is polishing stage Upstream/middle section – being fabricated smoothly Prompt start at the real run (Feb. – June, 2004) Prompt start at the real run (Feb. – June, 2004) - Full beam acceptable