Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
Phys Rev Lett. 2013 May 24;110(21):212001. doi: 10.1103/PhysRevLett.110.212001. Epub 2013 May 21.
Knowing the charge of the parton initiating a light-quark jet could be extremely useful both for testing aspects of the standard model and for characterizing potential beyond-the-standard-model signals. We show that despite the complications of hadronization and out-of-jet radiation such as pileup, a weighted sum of the charges of a jet's constituents can be used at the LHC to distinguish among jets with different charges. Potential applications include measuring electroweak quantum numbers of hadronically decaying resonances or supersymmetric particles, as well as standard model tests, such as jet charge in dijet events or in hadronically decaying W bosons in tt[over ¯] events. We develop a systematically improvable method to calculate moments of these charge distributions by combining multihadron fragmentation functions with perturbative jet functions and pertubative evolution equations. We show that the dependence on energy and jet size for the average and width of the jet charge can be calculated despite the large experimental uncertainty on fragmentation functions. These calculations can provide a validation tool for data independent of Monte Carlo fragmentation models.
了解引发轻夸克喷注的部分子荷电量可能对测试标准模型的各个方面以及对潜在的超越标准模型信号进行特征化都非常有用。我们表明，尽管夸克化和喷注外的辐射（如堆积）等复杂情况，在 LHC 上仍可以使用喷注成分的荷电量的加权和来区分具有不同荷电量的喷注。潜在的应用包括测量强子衰变共振或超对称粒子的电弱量子数，以及标准模型测试，如双喷注事件中的喷注荷电或 tt[over ¯]事件中强子衰变的 W 玻色子的喷注荷电。我们通过将多强子碎裂函数与微扰喷注函数和微扰演化方程相结合，开发了一种可系统改进的方法来计算这些荷电分布的矩。我们表明，尽管强子碎裂函数的实验不确定性很大，但仍可以计算喷注荷电的平均值和宽度的能量和喷注尺寸依赖性。这些计算可以为不依赖于蒙特卡罗碎裂模型的数据提供验证工具。
