"Table 95" 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/.

CERN-LHC。针对包含衰变为电子或μ子对的Z玻色子的全域事件样本，本研究给出了对本底事件（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ATLAS探测器（ATLAS）在质心系能量7 TeV的质子-质子对撞中采集的数据，积分亮度为4.6 fb⁻¹。

本次测量的对象为排除Z衰变产生的两个轻子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：
- 前向区域：|Δφ| < 60°
- 横向区域：60° < |Δφ| < 120°
- 对向区域：|Δφ| > 120°
- 横向极大区域：逐个事件选取两个横向扇区中，带电粒子横向动量标量和最大的扇区
- 横向极小区域：逐个事件选取两个横向扇区中，带电粒子横向动量标量和最小的扇区

fiducial体积（fiducial volume）定义如下：
- 要求Z衰变产生的两个带异号电荷的轻子满足横向动量p_T > 20 GeV、赝快度|η| < 2.4，且不变质量66 GeV < M(ll) < 116 GeV
- 要求带电粒子的固有寿命τ > 0.3×10⁻¹⁰ s，且为原初粒子（即直接产生于质子-质子相互作用，或是寿命小于τ的瞬态粒子的衰变产物），同时满足p_T > 0.5 GeV、|η| < 2.5

可观测物理量包括：
- p_T(Z)：Z玻色子的横向动量
- N_ch/Δη/Δ(Δφ)：单位η-φ区间内的稳定带电粒子数目，在-2.5 < η < 2.5且φ覆盖全部2π区间的范围内取平均
- 本次测量的修正项包括电子与μ子的识别效率、Z玻色子动量分辨率，以及来自堆迹（pileup）和与Z→μ⁺μ⁻、e⁺e⁻信号具有相同实验特征的末态背景。

已发布的分布可直接与两种Z→轻子+轻子⁻末态定义的粒子级蒙特卡洛（Monte Carlo, MC）发生器输出进行比较，两种定义如表中所述：
- 玻恩近似（Born approximation）：Z的动量定义为轻子与末态辐射光子（final state radiation, FSR）的动量之和，忽略轻子辐射的光子与过程中其他带电外线之间的干涉。粒子级 fiducial体积可视为不存在末态辐射的假想实验中得到的体积，例如Z→νν̅末态且两个轻子满足p_T>20 GeV、|η|<2.5的场景。
- 缀饰轻子（dressed leptons）：缀饰轻子的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 fiducial体积采用缀饰轻子动量进行定义。

表格中标记为“辅助（auxiliary）”的材料可通过链接https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2011-42/ 获取。