At the Large Hadron Collider, the identification of jets originating from b
quarks is important for searches for new physics and for measurements of
standard model processes. A variety of algorithms has been developed by CMS to
select b-quark jets based on variables such as the impact parameters of
charged-particle tracks, the properties of reconstructed decay vertices, and
the presence or absence of a lepton, or combinations thereof. The performance
of these algorithms has been measured using data from proton-proton collisions
at the LHC and compared with expectations based on simulation. The data used in
this study were recorded in 2011 at sqrt(s) = 7 TeV for a total integrated
luminosity of 5.0 inverse femtobarns. The efficiency for tagging b-quark jets
has been measured in events from multijet and t-quark pair production. CMS has
achieved a b-jet tagging efficiency of 85% for a light-parton misidentification
probability of 10% in multijet events. For analyses requiring higher purity, a
misidentification probability of only 1.5% has been achieved, for a 70% b-jet
tagging efficiency.

本文讨论了 CMS 在大型强子对撞机上使用多种算法通过诸如荷电粒子轨迹的冲击参数、重构衰变顶点的属性和存在或不存在只有电子，或两者结合的变量来选择起源于 b 夸克的喷注。

CMS 实验中的 b 强子喷注鉴别

Identification of b-quark jets with the CMS experiment

The most precise measurements of the top quark mass are based on the Matrix
Element method. We present a detailed description of this analysis method,
taking the measurements of the top quark mass in final states with one and two
charged leptons as concrete examples. In addition, we show how the Matrix
Element method is suitable to reduce the dominant systematic uncertainties
related to detector effects, by treating the absolute energy scales for b-quark
and light-quark jets independently as free parameters in a simultaneous fit
together with the top quark mass. While the determination of the light-quark
jet energy scale has already been applied in several recent measurements, the
separate determination of the absolute b-quark jet energy scale is a novel
technique with the prospect of reducing the overall uncertainty on the top
quark mass in the final measurements at the Tevatron and in analyses at the LHC
experiments. The procedure is tested on Monte Carlo generated events with a
realistic detector resolution.

本文介绍了基于 Matrix Element 方法的研究分析方式，并以一个带电粒子正负电子的最终状态下的顶夸克质量测量作为具体例子。同时，本文还展示了 Matrix Element 方法如何适用于减少与探测器效应相关的主要系统误差，通过将 b - 夸克和轻夸克喷注的绝对能量尺度视为独立的自由参数，与顶夸克质量一起进行同时拟合。此方法通过对模拟实验数据测试，有望降低在 Tevatron 和 LHC 实验中测量出的顶夸克质量的总体不确定性。