Energy dependence of the differences between the quark and gluon jet fragmentation
Energy dependence of the differences between the quark and gluon jet fragmentation
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DOI：
10.1007/s002880050099
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发表时间：
1996-04-01
期刊：
影响因子：
--
通讯作者：
Zumerle, G
中科院分区：
文献类型：
--
作者：
Abreu, P;Adam, W;Zumerle, G
由 DELPHI 探测器收集的由 Z 贝子衰变引起的三个喷流事件被用来测量夸克和胶子碎裂的差异。通过识别 b 夸克射流来对胶子射流进行反标记。无偏夸克喷流来自两个喷流加一个光子的事件。首次在同一探测器内比较不同能量范围内的夸克和胶子射流特性。还比较了对称三射流事件拓扑中几乎相同能量的夸克和胶子射流。使用三种独立的方法，胶子和夸克喷流的平均带电多重数之比的平均值为[ r ] = 1.241 +/- 0.015（统计）+/- 0.025（系统）。胶子喷流比同等能量的夸克喷流更宽，产生的碎片具有更软的能谱。在完全对称的三射流事件中观察到了弦效应。和 < q (q) 与棒伽马> 样本的喷射间区域中的带电粒子流的测量比率 R(gamma) 与微扰 QCD 期望一致。在光子加 n 射流事件中分析了平均带电多重数对强子质心能量的依赖性。使用 QCD 预测根据这些数据确定的 alpha(s)(M(z)) 值，并在前导和次前导顺序上进行修正，即 alpha(s)(M(z)) = 0.116 +/- 0.003（统计）+/- 0.009（系统）。
Three jet events arising from decays of the Z beson, collected by the DELPHI detector, were used to measure differences in quark and gluon fragmentation. Gluon jets were anti-tagged by identifying b quark jets. Unbiased quark jets came from events with two jets plus one photon. Quark and gluon jet properties in different energy ranges were compared for the first time within the same detector. Quark and gluon jets of nearly the same energy in symmetric three jet event topologies were also compared. Using three independent methods, the average value of the ratio of the mean charged multiplicities of gluon and quark jets is[ r ] = 1.241 +/- 0.015 (stat.) +/- 0.025 (syst.).Gluon jets are broader and produce fragments with a softer energy spectrum than quark jets of equivalent energy. The string effect has been observed in fully symmetric three jet events. The measured ratio R(gamma) of the charged particle flow in the inter-jet region of the and < q (q) over bar gamma> samples agrees with the perturbative QCD expectation. The dependence of the mean charged multiplicity on the hadronic center-of-mass energy was analysed in photon plus n-jet events. The value for alpha(s)(M(z)) determined from these data using a QCD prediction with corrections at leading and next-to-leading order isalpha(s)(M(z)) = 0.116 +/- 0.003 (stat.) +/- 0.009 (syst.).