标题： SM和MSSM对电弱精确数据的更新全局拟合 显示英文标题

标题： Updated Global Fits of the SM and MSSM to Electroweak Precision Data

摘要： 具有轻量级顶夸克、带电微子或赝标希格斯玻色子的最小超对称标准模型（MSSM）被认为可以解释$Z^0$玻色子衰变为$b$夸克的分支比过高问题（$R_b$异常）。 一个包括所有辐射修正的程序，其在MSSM中的精度与标准模型（SM）的辐射修正相同，已被开发并用于对LEP、SLC和Tevatron的所有弱电数据以及CLEO的辐射b->sgamma衰变进行全局拟合。 最近在1996年夏季华沙会议上提出的弱电数据更新，将R_b异常从3.2\sigma 降低到1.8\sigma ，这使得标准模型中的概率从8%提高到24%。 尽管MSSM可以完全解释R_b与标准模型值之间的剩余偏差，但由于自由参数数量更多，其概率并不更好。 在{MS}色规范方案中，M_Z 标度下强耦合常数的最佳拟合值为 SM 的 0.120\pm 0.003 和 MSSM 的 0.116\pm 0.005 (0.119\pm 0.005)，对应 tan beta 的低（高）值。 导出量\sin ^2\theta _{微软}等于 0.2317\pm 0.0004 (0.2315\pm 0.0004) 对于 SM (MSSM)。 显示英文摘要

摘要： The Minimal supersymmetric extension of the Standard Model (MSSM) with light stops, charginos or pseudoscalar Higgs bosons has been suggested as an explanation of the too high value of the branching ratio of the $Z^0$ boson into $b$ quarks ($R_b$ anomaly). A program including all radiative corrections to the MSSM at the same level as the radiative corrections to the SM has been developed and used to perform global fits to all electroweak data from LEP, SLC and the Tevatron and the radiative b->sgamma decay from CLEO. Recent updates on electroweak data, which have been presented at the Warsaw Conference in summer 1996, reduce the R_b anomaly from a 3.2 \sigma to a 1.8 \sigma effect, which improves the probability in the SM from 8% to 24%. Although the MSSM can fully explain the remaining deviation of R_b from the SM value, its probability is not better because of the larger number of free parameters. The best fitted value of the strong coupling constant at the M_Z scale in the {MS} renormalization scheme is 0.120\pm0.003 for the SM and 0.116\pm0.005 (0.119\pm0.005) for the MSSM with low (high) values of tan beta. The derived quantity \sin^2\theta_{MS} equals 0.2317\pm0.0004 (0.2315\pm0.0004) for the SM (MSSM).