"Table 2" of "Event shapes and azimuthal correlations in Z + jets events in pp collisions at sqrt(s) =7 TeV"

CERN-LHC. Measurements of event shapes and azimuthal correlations are presented for events where a Z boson is produced in association with jets in proton-proton collisions. The data collected with the CMS detector at the CERN LHC at sqrt(s) = 7 TeV correspond to an integrated luminosity of 5.0 inverse femtobarns. The analysis provides a test of predictions from perturbative QCD for a process that represents a substantial background to many physics channels. Results are presented as a function of jet multiplicity, for inclusive Z boson production and for Z bosons with transverse momenta greater than 150 GeV, and compared to predictions from Monte Carlo event generators that include leading-order multiparton matrix-element (with up to four hard partons in the final state) and next-to-leading-order simulations of Z + 1-jet events. The experimental results are corrected for detector effects, and can be compared directly with other QCD models For $Z/\gamma^{*}$ plus jets events we select: - two same flavour opposite sign leptons with $p_{T} > 20$ GeV and $|\eta| < 2.4$ and $71 < M_{\ell\ell} < 111 $ GeV - leptons are "dressed" with all photons in a cone of radius $\Delta R = 0.1$ - at least one jet, jet selection $p_{T} > 30$ GeV and $|\eta| < 2.4$, we remove jets within a radius of $\Delta R < 0.4$ with respect to the axes of each lepton - for the ratio plots a cut on Z rapidity |y|<1.4 is also applied The event shape variable is defined as $\tau_{\perp}\equiv 1-\max_{\vec{n}_{T}}\frac{\sum_{i}\left|\vec{p}_{\perp,i}\cdot \vec{n}_{T} \right|}{\sum_{i}p_{\perp,i}}$.

CERN-LHC合作组：本数据集报道了质子-质子碰撞中伴随喷注产生Z玻色子的事件的事件形状与方位角关联测量结果。在欧洲核子研究中心（CERN）大型强子对撞机（Large Hadron Collider, LHC）上，采用CMS探测器（Compact Muon Solenoid）在质心系能量√s=7 TeV条件下采集的数据，其积分亮度为5.0 逆飞靶（fb⁻¹）。本分析为微扰量子色动力学（Quantum Chromodynamics, QCD）针对该过程的理论预言提供了检验依据，该过程是诸多物理道的重要本底。测量结果以喷注多重数为函数形式给出，涵盖全域Z玻色子产生过程以及横向动量（transverse momentum, p_T）大于150 GeV的Z玻色子产生过程，并与包含领头阶多部分子矩阵元（末态最多含4个硬部分子）的蒙特卡洛事件发生器预言，以及Z+1喷注过程的次领头阶模拟结果进行对比。实验结果已针对探测器效应进行校正，可直接与其他量子色动力学模型比对。
针对Z/γ*伴随喷注事件，我们的选择标准如下：
- 一对同味异号轻子，需满足横向动量p_T>20 GeV、赝快度（pseudorapidity, η）|η|<2.4，且双轻子不变质量71 GeV < M_ll < 111 GeV；
- 轻子需进行“穿衣”校正：在半径ΔR=0.1的锥区内的所有光子均被纳入轻子的动量重建过程；
- 事件至少包含一个喷注，喷注选择标准为p_T>30 GeV、|η|<2.4，且需剔除与任意轻子轴间距ΔR<0.4的喷注；
- 对于比值绘图，还需施加Z玻色子快度（rapidity, y）|y|<1.4的截断条件。
事件形状变量定义为：$ au_{perp}equiv 1-max_{vec{n}_{T}}frac{sum_{i}left|vec{p}_{perp,i}cdot vec{n}_{T}
ight|}{sum_{i}p_{perp,i}}$。