2001 Fiscal Year Final Research Report Summary
Study of time reversal invariance in K decays
| Project/Area Number |
11694101
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | High Energy Accelerator Research Organization |
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Principal Investigator |
IMAZATO Jun KEK, IPNS, High Energy Accelerator Research Organization, Professor, 素粒子原子核研究所, 教授 (40107686)
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| Co-Investigator(Kenkyū-buntansha) |
IGARASHI Yoichi KEK, IPNS, High Energy Accelerator Research Organization, Assistant, 素粒子原子核研究所, 助手 (50311121)
AOKI Masaharu Osaka Univ., Associate Professor, 理, 助教授 (80290849)
KUNO Yoshitaka Osaka Univ., Professor, 理, 教授 (30170020)
ASANO Yuzo Univ. of Tsukuba, Professor (80100808)
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| Project Period (FY) |
1999 – 2001
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| Keywords | Kaon decay / K_<μ3> decay / Muon transverse polarization / Time reversal inveriance / Toroidal spectrometer / KEK-PS / 対称性の破れ |
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| Research Abstract |
The research consisted of the KEK-PS experiments E246 and E470. The E246 experiment was searching for T-violating muon polarization (P_γ) in K^+→π^0μ^+νdecay (K_<μ3> using the superconducting toroidal spectrometer setup in conjunction with a stopped K^+ beam. It was aimed to carry out a measurement with small systematic errors. We performed data taking in 1999 and 2000 using 1600 hours of beam time. In 2001 we continued data analysis and obtained a result of P_T= -0.0033±0.0117(stat)±0.003(syst) combined with our previous result and reported in a conference. The systematic errors of the 1998 results were further studied carefully. The data from the 1999 and 2000 runs were also analyzed and a preliminary result of P_T was obtained.
One of the byproduct physics from this stopped K^+ experiment is the branching ratio measurement of the direct emission in K^+→π^+π^0γ decay. For an optimized trigger condition run, a new experiment was approved as E470 and it ran in the fall of 2001 for 960 hours. The data taking was successful and the branching ratio of the order of magnitude of 10^<-5> is expected to be determined with an accuracy of about 10 %. As another byproduct channel of E246, K^+→π^0e^+νdecay (K_<e3> was studied further to constrain the exotic scalar and tensor couplings. The values of f_R/f_+(0)=0.0040±0.0160(stat)±0.0067(syst) and f_T/f_+(0)=0.019±0.080(stat)±0.038(syst) were obtained. The decay width ratio of the two channels, Γ(K_<e3>)/Γ(K_<μ3>), was also analyzed and determined the q^2-dependent coefficient of f_0 form factor of the K_</3> decay to be λ_0 =0.019±0.005(stat)±0.004 (syst).
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Research Products
(13 results)
