μ和τ的辐射轻子衰变（英文）

Radiative μ and τ leptonic decays

τ的辐射轻子衰变的精确数据为探测τ的电磁性质提供了机会,而且可能允许确定其除了标准模型精确预言从来没有测量过的反常磁矩.最近,BaBar合作组测量了τ辐射轻子衰变的分支比(τ→lννγ,以l=e,μ).这些约3%的相对误差的精确测量必须在次领头阶上与QED预言的分支比一致.实际上,对l=e,辐射修正预计在10%量级,对于l=μ大约在3%.这里给出了μ和τ辐射轻子衰变微分衰变率和分支比的标准模型到次领头阶的预测,并与BaBar实验结果比较.此外,给出了在Belle和Belle II测量τ反常磁矩的可行性研究.

Precise data on radiative leptonicτ decays offer the opportunity to probe the electromagnetic properties of theτand may allow to determine its anomalous magnetic moment which,in spite of its precise Standard Model prediction,has never been measured.Recently,the branching fractions of the radiative leptonicτdecays(τ→lννγ,with l=e,μ)were measured by the Babar Collaboration.These precise measurements,with a relative error of about 3%,must be compared with the branching ratios at the next-to-leading order in QED.Indeed the radiative corrections are expected to be of order 10%,for l=e,and 3%,for l=μ.Here,we present the prediction of the differential decay rates and branching ratios of the radiativeμandτleptonic decays in the Standard Model at the next-to-leading order and we compare them with the recent Babar measurements.Moreover,we report on a dedicated feasibility study for the measurements of theτanomalous magnetic moment at Belle and Belle Ⅱ.