Precision measurement of the ratio

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• 作者：NA48/1 Collaboration ; J.R. Batley ; G.E. Kalmus ; C. Lazzeroni ; D.J. Munday ; M. Patel ; M.W. Slater ; S.A. Wotton ; R. Arcidiacono ; G. Bocquet ; A. Ceccucci ; D. Cundy ; N. Doble ; V. Falaleev ; L. Gatignon ; A.
• 关键词：Neutral kaon radiative decay ; Kaon rare decay ; CP-violating asymmetry ; Inner bremsstrahlung ; Direct emission
• 刊名：Physics Letters B
• 出版年：2011
• 出版时间：3 January 2011
• 年：2011
• 卷：694
• 期：4-5
• 页码：301-309
• 全文大小：484 K

文摘

The K_S→π⁺π⁻e⁺e⁻ decay mode was investigated using the data collected in 2002 by the NA48/1 Collaboration. With about 23 k K_S→π⁺π⁻e⁺e⁻ events and 59 k normalization decays, the K_S→π⁺π⁻e⁺e⁻ branching ratio relative to the one was determined to be . This result was used to set the upper limit g_E1/g_BR<3.0 at 90 % CL on the presence, in the decay amplitude, of an E1 direct emission (g_E1) term relative to the dominant inner bremsstrahlung (g_BR) term. The CP-violating asymmetry in the distribution of K_S→π⁺π⁻e⁺e⁻ events, where is the angle between the π⁺π⁻ and the e⁺e⁻ decay planes in the kaon centre of mass, was found to be , consistent with zero. These results are in good agreement with a description of the K_S→π⁺π⁻e⁺e⁻ decay amplitude dominated by the CP-even inner bremsstrahlung process.