Rare Kaon Decays, KEK experiment E391 and E14 at the Japan Physics and Accelerator Research Complex (J-PARC)

Wah, Yau Wai¹ 

[1] University of Chicago

关键词: Rare kaon decays;    CP violation;    experimental particle physics;    DAQ system;    waveform digitizer;    CKM matrix;    physics beyond Standard Model;   

DOI  :  10.2172/1089558
RP-ID  :  DOE/FP044046-1
PID  :  OSTI ID: 1089558

学科分类：物理（综合）

美国|英语

来源: SciTech Connect

【 摘 要 】

The goal of the J-PARC neutral kaon experiment (E14/KOTO) is to discover and measure the rate of the kaon rare decay to pi-zero and two neutrinos. This flavor changing neutral current decay proceeds through second-order weak interactions. Other, as yet undiscovered particles, which can mediate the decay could provide an enhancement (or depletion) to the branching ratio which in the Standard Model is accurately predicted within a few percent to be 2.8x10-11. The experiment is designed to observe more than 100 events at the Standard Model branching. It is a follow-up of the KEK E391a experiment and has stage-2 approval by J-PARC PAC in 2007. E14/KOTO has collaborators from Japan (Kyoto, Osaka, Yamagata, Saga), US (Arizona State, Chicago, Michigan Ann Arbor), Taiwan (National Taiwan), Korea, and Russia (Dubna). The experiment exploits the 300kW 30-50 GeV proton delivery of the J-PARC accelerator with a hermetic high acceptance detector with a fine grained Cesium Iodide (CsI) crystal calorimeter, and state of the art electronic front end and data acquisition system. With the recovery of the tsunami disaster on March 11th 2011, E14 is scheduled to start collecting data in December 2012. During the detector construction phase, Chicago focuses on the front end electronics readout of the entire detector system, particularly the CsI calorimeter. The CsI crystals together with its photomultipliers were previously used at the Fermilab KTeV experiment (E832/E799), and were loaned to E14 via this Chicago DOE support. The new readout electronics includes an innovative 10-pole pulse-shaping technique coupled with high speed digitization (14-bit 125MHz and 12-bit 500MHz). This new instrument enables us to measure both energy and timing, particularly with timing resolution better than 100 psec. Besides the cost saving by elimination of the standard time to digital converters, it is now possible to measure the momenta of the final state photons for additional background suppression. Chicago also designed and built several technically difficult hardware items including the vacuum cable feed-through (for a total of 3500 channels); special 50 ohm single-ended signal to 100 ohm differential signal converters; and last but not least, the recommendations on the selection of the differential signal cables for all detector elements to eliminate ground loops while maintaining signal fidelity.