"Table 99" of "Measurement of distributions sensitive to the underlying event in inclusive Z-boson production in $pp$ collisions at $\sqrt{s}=7$ TeV with the ATLAS detector"

CERN-LHC. A measurement of charged-particle distributions sensitive to the properties of the underlying event is presented for an inclusive sample of events containing a Z-boson, decaying to an electron or muon pair. The measurement is based on data collected using the ATLAS detector at the LHC in proton--proton collisions at a centre-of-mass energy of 7 TeV with an integrated luminosity of 4.6/fb. Distributions of the charged particle (excluding the two leptons from Z decay) multiplicity and of the charged particle transverse momentum are measured in regions of azimuthal angle delta(phi) = |phi - phi(Z)| defined with respect to the Z-boson direction: - the toward region: |delta(phi)| < 60 degrees - the transverse region: 60 < |delta(phi)| < 120 degrees - the away region: |delta(phi)| > 120 degrees - the trans-max region: one of the two transverse sectors having a maximum scalar sum of transverse momenta of charged particles on event-by-event basis - the trans-min region: one of the two transverse sectors having a minimum scalar sum of transverse momenta of charged particles on event-by-event basis The fiducial volume is defined as follows: - the two oppositely charged leptons from Z decay are required to have pT > 20 GeV, |eta| < 2.4 and 66 < M(ll) < 116 GeV - charged particles are required to have a proper lifetime tau > 0.3*10**-10 sec, be primary (i.e. produced directly in pp interaction or being decay products of prompt particles with the lifetime less than tau), have pT > 0.5 GeV and |eta| < 2.5 The observables: - pT(Z): transverse momentum of the Z-boson - N(ch)/delta(eta)/delta(delta(phi)): number of stable charged particles per eta-phi unit, averaged over eta-phi range, where -2.5 mu+ mu-, e+ e- identification efficiency and Z momentum resolution; background from pileup and final states yielding the same experimental signature as the Z -> mu+ mu-, e+ e- signal. - Published distributions can be directly compared to a particle level MC generator output with the two definitions of Z -> lepton+ lepton- final state (as indicated in the tables): - Born approximation: Z momentum is defined as the sum of leptons' and FSR photons' momenta, in neglect of interference between photon radiation off the leptons and other charged legs in the process. The particle level fiducial volume can be viewed as the one obtained in an imaginary experiment without FSR, e.g., with Z -> nu nubar final state where both leptons have pT>20 GeV and |eta|<2.5. - Dressed leptons: dressed lepton momentum is defined as a sum of the lepton's momentum and the momenta of all photons of non-hadronic origin within DeltaR<0.1 cone around the direction of the lepton. The particle level fiducial volume is defined using dressed lepton momenta. Material referenced as `auxiliary' in the tables is available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2011-42/.

欧洲核子研究组织大型强子对撞机（CERN-LHC）数据集：本研究针对包含Z玻色子（Z-boson）且衰变为电子对或μ子对的全域事件样本，报告了对 underlying事件（underlying event）性质敏感的带电粒子分布测量结果。本次测量基于大型强子对撞机（LHC）上的ATLAS探测器（ATLAS detector）采集的数据，数据来自质心系能量为7 TeV的质子-质子碰撞，积分亮度为4.6 fb⁻¹。

本次测量了扣除Z玻色子衰变产生的两个轻子后的带电粒子多重数分布，以及带电粒子横向动量分布，测量区域由相对于Z玻色子方向定义的方位角差Δφ = |φ - φ_Z| 划分为以下区域：
- 向前区域（toward region）：|Δφ| < 60°
- 横向区域（transverse region）：60° < |Δφ| < 120°
- 背向区域（away region）：|Δφ| > 120°
- 最大横向扇区（trans-max region）：按事件逐个统计的两个横向扇区中，带电粒子横向动量标量和最大的扇区
- 最小横向扇区（trans-min region）：按事件逐个统计的两个横向扇区中，带电粒子横向动量标量和最小的扇区

有效接收体积（fiducial volume）定义如下：
- Z玻色子衰变产生的两个异号轻子需满足：横向动量p_T > 20 GeV，赝快度|η| < 2.4，双轻子不变质量M(ll) 满足66 GeV < M(ll) < 116 GeV
- 带电粒子需满足：固有寿命τ > 0.3×10⁻¹⁰ s，为原初粒子（即直接产生于质子-质子碰撞，或是寿命小于τ的瞬态粒子的衰变产物），横向动量p_T > 0.5 GeV，赝快度|η| < 2.5

观测量包括：
- p_T(Z)：Z玻色子的横向动量
- N_ch/Δη/Δφ：单位η-φ空间内的稳定带电粒子数目，在η范围-2.5 < η < 2.5、|Δφ| < 180°内取平均，该观测量已针对电子/μ子识别效率以及Z玻色子动量分辨率进行校正；本测量同时考虑了堆迹（pileup）以及与Z→μ⁺μ⁻、e⁺e⁻信号具有相同实验特征的末态带来的本底。

已发表的分布可直接与粒子级蒙特卡洛（Monte Carlo, MC）发生器输出结果进行对比，对比时采用两种Z→轻子对末态的定义（如表中所示）：
- 玻恩近似（Born approximation）：Z玻色子动量定义为轻子与末态辐射光子（Final State Radiation, FSR）的动量之和，忽略轻子与过程中其他带电粒子线的光子辐射干涉效应。粒子级有效接收体积可视为在不存在FSR的假想实验中得到的体积，例如Z→中微子对（νar{ν}）末态，且两个轻子的p_T>20 GeV、|η|<2.5。
- 缀饰轻子（Dressed leptons）：缀饰轻子动量定义为轻子自身动量，与轻子方向周围ΔR<0.1锥区内所有非强起源光子的动量之和。粒子级有效接收体积采用缀饰轻子动量进行定义。

表格中标记为‘辅助材料’的内容可通过以下链接获取：https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2011-42/。