"Table 2" of "Measurement of four-jet production in proton-proton collisions at sqrt(s)=7 TeV"

CERN-LHC. Measurements of the differential cross sections for the production of exactly four jets in proton-proton collisions are presented as a function of the transverse momentum pT and pseudorapidity eta, together with the correlations in azimuthal angle and the pT balance among the jets. The data sample was collected in 2010 at a center-of-mass energy of 7 TeV with the CMS detector at the LHC, with an integrated luminosity of 36 pb-1. The cross section for exactly four jets, with two hard jets of pT>50 GeV each, together with two jets of pT>20 GeV each, within |eta|<4.7 is measured to be sigma=330+-5(stat.)+-45(syst.) nb. It is found that fixed-order matrix element calculations including parton showers describe the measured differential cross sections in some regions of phase space only, and that adding contributions from double parton scattering brings the Monte Carlo predictions closer to the data. The four-jet fiducial region is defined as: - exactly four jets in the final state in |eta|<4.7. - Two jets are required with pT > 50 GeV - Two additional jets are required with pT > 20 GeV.

欧洲核子研究中心大型强子对撞机（CERN-LHC）实验团队报道了质子-质子碰撞（proton-proton collisions）中严格四喷注产生的微分截面（differential cross section）测量结果，该测量以横向动量（transverse momentum, $p_ ext{T}$）和赝快度（pseudorapidity, $eta$）为函数形式呈现，同时给出了喷注间的方位角（azimuthal angle）关联与横向动量平衡特性。该数据样本于2010年在质心系能量7 TeV下通过紧凑型μ子螺线管探测器（Compact Muon Solenoid, CMS）于大型强子对撞机（Large Hadron Collider, LHC）上采集，积分亮度（integrated luminosity）为36 pb⁻¹。针对$|eta|<4.7$范围内、包含两个横向动量大于50 GeV的硬喷注（hard jets）以及两个横向动量大于20 GeV喷注的严格四喷注过程，其截面测量结果为$sigma=330pm5( ext{统计误差})pm45( ext{系统误差})$ nb（纳靶恩）。研究表明，包含部分子阵雨（parton showers）的固定阶矩阵元（fixed-order matrix element）计算仅能在部分相空间区域内复现测得的微分截面；而引入双部分子散射（double parton scattering）的贡献后，蒙特卡洛（Monte Carlo）模拟的预言值与实验数据的吻合程度得到显著提升。四喷注 fiducial接收域（fiducial region）定义如下：- 末态存在严格四个喷注且满足$|eta|<4.7$；- 其中两个喷注的横向动量需大于50 GeV；- 另外两个喷注的横向动量需大于20 GeV。