Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Phys Rev Lett. 2010 Aug 27;105(9):092002. doi: 10.1103/PhysRevLett.105.092002. Epub 2010 Aug 25.
Jet vetoes are essential in many analyses at the LHC and Tevatron. Typical signals have a specific number of hard jets or leptons, while backgrounds have additional jets. Vetoing undesired jets efficiently discriminates signal and background. For a sample with ≥N jets, the veto to give N energetic jets defines an "exclusive" N-jet cross section. This strongly restricts the phase space and causes large double logarithms in perturbation theory that must be summed. Jet vetoes are typically implemented using jet algorithms, yielding complicated phase-space restrictions, and reliance on leading-log parton-shower Monte Carlo simulations. We introduce a global event shape "N jettiness" τN, which is defined for events with N signal jets. Requiring τN≪1 constrains radiation between the signal jets and provides a theoretically well-controlled jet veto. N jettiness yields a factorization formula with inclusive jet and beam functions.
喷注抑制在 LHC 和 Tevatron 的许多分析中是必不可少的。典型的信号具有特定数量的硬喷注或轻子，而背景则有额外的喷注。有效地抑制不需要的喷注可以区分信号和背景。对于具有≥N 个喷注的样本，将 N 个高能喷注抑制定义为“排他性”N 个喷注截面。这强烈限制了相空间，并在微扰理论中产生了必须求和的大的双对数。喷注抑制通常使用喷注算法来实现，产生复杂的相空间限制，并依赖于领头阶部分子 shower Monte Carlo 模拟。我们引入了一个全局事件形状“N 度偏离”τN，它是为具有 N 个信号喷注的事件定义的。要求 τN≪1 限制了信号喷注之间的辐射，并提供了一个理论上控制良好的喷注抑制。N 度偏离给出了一个具有包含喷注和束流函数的因子化公式。
