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arXiv 0804.3883hep-ex
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用LEP的DELPHI探测器研究多喷流拓扑中的b夸克质量效应

Study of b-quark mass effects in multijet topologies with the DELPHI detector at LEP

The DELPHI Collaboration, J. Abdallah

摘要:

利用DELPHI实验1994年和1995年在Z峰收集的LEP数据,研究了重b夸克质量对两喷注、三喷注和四喷注速率的影响。用CAMBRIDGE喷注成团算法,用双标记技术测量了n = 2,3,4喷注事例中b夸克喷注和轻夸克喷注(l = uds)的速率,以及b夸克与轻夸克的二喷注和四喷注速率之比R_n^bl。强子化阶段后,实验结果和理论(矩阵元素或Monte Carlo事件发生器,如PYTHIA,HERWIG和ARIADNE)之间的比较。使用四喷注可观测的R_4^bl,通过质量领先级计算得到b夸克质量的测量结果:m_b(M_Z)= 3.76 +/- 0.32(stat)+/- 0.17(syst)+/- 0.22(had)+/- 0.90(theo)GeV/c^2。这一结果与以前在M_Z能量尺度下的三喷流测量和用QCD重整化群方程演化到M_Z尺度的低能质量测量是一致的。

英文摘要:

The effect of the heavy b-quark mass on the two, three and four-jet rates is studied using LEP data collected by the DELPHI experiment at the Z peak in 1994 and 1995. The rates of b-quark jets and light quark jets (l = uds) in events with n = 2, 3, and 4 jets, together with the ratio of two and four-jet rates of b-quarks with respect to light-quarks, R_n^bl, have been measured with a double-tag technique using the CAMBRIDGE jet-clustering algorithm. A comparison between experimental results and theory (matrix element or Monte Carlo event generators such as PYTHIA, HERWIG and ARIADNE) is done after the hadronisation phase. Using the four-jet observable R_4^bl, a measurement of the b-quark mass using massive leading-order calculations gives: m_b(M_Z) = 3.76 +/- 0.32 (stat) +/- 0.17 (syst) +/- 0.22 (had) +/- 0.90 (theo) GeV/c^2 . This result is compatible with previous three-jet determinations at the M_Z energy scale and with low energy mass measurements evolved to the M_Z scale using QCD Renormalisation Group Equations.

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