"Table 7" of "Measurement of t-tbar production with additional jet activity, including b quark jets, in the dilepton channel using pp collisions at sqrt(s) = 8TeV"

Jet multiplicity distributions in top quark pair (ttbar) events are measured in pp collisions at a centre-of-mass energy of 8 TeV with the CMS detector at the LHC using a data set corresponding to an integrated luminosity of 19.7 inverse-femtobarns. The measurement is performed in the dilepton decay channels (e+ e-, mu+ mu-, and e+/- mu-/+). The absolute and normalized differential cross sections for t-tbar production are measured as a function of the jet multiplicity in the event for different jet transverse momentum thresholds and the kinematic properties of the leading additional jets. The differential t-tbar-b and t-tbar-b-bbar cross sections are presented for the first time as a function of the kinematic properties of the leading additional b jets. Furthermore, the fraction of events without additional jets above a threshold is measured as a function of the transverse momenta of the leading additional jets and the scalar sum of the transverse momenta of all additional jets. The data are compared and found to be consistent with predictions from several perturbative quantum chromodynamics event generators and a next-to-leading order calculation.

本研究利用大型强子对撞机（Large Hadron Collider, LHC）上紧凑缪子线圈探测器（CMS, Compact Muon Solenoid）采集的数据，在质心系能量为8 TeV的质子-质子碰撞中，测量了顶夸克对（top quark pair, ttbar）事件的喷注多重数分布，所用数据集对应的积分亮度为19.7反飞母托靶恩（inverse-femtobarns, fb⁻¹）。

测量针对双轻子衰变道开展，包括e⁺e⁻、μ⁺μ⁻以及e⁺/⁻μ⁻/⁺衰变末态。针对顶夸克对产生过程，本工作以事件中的喷注多重数、不同喷注横向动量阈值以及领头额外喷注的运动学特性为自变量，测量了其绝对微分截面与归一化微分截面。

本工作首次以领头额外b喷注的运动学特性为函数，给出了ttbar-b与ttbar-b-bbar的微分截面。此外，本研究还测量了阈值以上无额外喷注的事件占比，该占比随领头额外喷注横向动量以及所有额外喷注横向动量的标量和的变化关系。

将本次测量数据与多款微扰量子色动力学（perturbative quantum chromodynamics, pQCD）事件产生器的预言以及次领头阶（next-to-leading order, NLO）计算结果进行比对，结果显示二者一致。