The matrix element method (MEM) has been extensively used for the analysis of
top-quark and W-boson physics at the Tevatron, but in general without dedicated
treatment of initial state QCD radiation. At the LHC, the increased center of
mass energy leads to a significant increase in the amount of QCD radiation,
which makes it mandatory to carefully account for its effects. We here present
several methods for inclusion of QCD radiation effects in the MEM, and apply
them to mass determination in the presence of multiple invisible particles in
the final state. We demonstrate significantly improved results compared to the
standard treatment.

本研究针对 LHC 中 QCD 辐射的效应和多重不可见粒子的存在，提出了几种用于纳入 QCD 辐射效应的矩阵元方法，相比标准方法，本文方法在质量测量方面得到了显著改善。

矩阵元方法与量子色动力学辐射

The Matrix Element Method and QCD Radiation

We clarify the relation between the variable MT2 and the method of kinematic
constraints, both of which can be used for mass determination in events with
two missing (dark matter) particles at hadron colliders. We identify a set of
minimal kinematic constraints, including the mass shell conditions for the
missing particles and their mother particles, as well as the constraint from
the measured missing transverse momentum. We show that MT2 is the boundary of
the mass region consistent with the minimal constraints. From this point of
view, we also obtained a more efficient algorithm for calculating MT2. When
more constraints are available in the events, we can develop more sophisticated
mass determination methods starting from the MT2 constraint. In particular, we
discuss cases when each decay chain contains two visible particles.

我们研究了在亏失两个（暗物质）粒子的轨迹下用于质量测量的变量 MT2 和动力学约束的关系，识别出一组最小的动力学约束，并证明了 MT2 是最小动力学约束下的一致质量区间的边界。