"Limit on $\Lambda^{-2} B$, $W\phi (ee)$ Scalar" of "Search for a scalar or pseudoscalar dilepton resonance produced in association with a massive vector boson or top quark-antiquark pair in multilepton events at $\sqrt{s}$ = 13 TeV"

A search for beyond the standard model spin-0 bosons, $\phi$, that decay into pairs of electrons, muons, or tau leptons is presented. The search targets the associated production of such bosons with a $\mathrm{W}$ boson, a $\mathrm{Z}$ boson, or a top quark-antiquark pair, and uses events with three or four charged leptons, including hadronically decaying tau leptons. The proton-proton collision dataset used in the analysis was collected by the CMS experiment at the LHC in 2016-2018 at a center-of-mass energy of $13\,\mathrm{TeV}$, and corresponds to an integrated luminosity of $138\,\mathrm{fb}^{-1}$. The observations are consistent with the expectations from standard model processes. Upper limits at $95\%$ confidence level are placed on the product of the cross sections and branching fractions of such new particles with scalar, pseudoscalar, or Higgs-like couplings, as well as the product of coupling parameters and branching fractions. These are the most restrictive direct limits in these production and decay modes on an extension of the standard model with scalar or pseudoscalar particles. Several model-dependent exclusions are also presented. For a Higgs-like $\phi$ model, limits are set on the mixing angle of the Higgs boson with the $\phi$ boson. For the associated production of a $\phi$ boson with a top quark-antiquark pair, limits are set on the coupling to top quarks. Finally, limits are set for the first time on a fermiophilic dilaton-like model with scalar couplings and an axion-like model with pseudoscalar couplings.

本研究开展了针对超出标准模型（Standard Model）自旋为0的玻色子$phi$的搜寻工作，该玻色子会衰变至电子对、μ子对或τ轻子对。本次搜寻针对该类玻色子与$mathrm{W}$玻色子、$mathrm{Z}$玻色子或顶夸克-反夸克对的联合产生过程，分析对象包含带有3或4个带电轻子（包括强衰变τ轻子）的事例。本分析使用的质子-质子对撞数据集，由大型强子对撞机（Large Hadron Collider, LHC）上的紧凑μ子线圈（Compact Muon Solenoid, CMS）实验于2016至2018年间采集，质心系能量为$13,mathrm{TeV}$，积分亮度为$138,mathrm{fb}^{-1}$。观测结果与标准模型过程的理论预期相符。针对这类带有标量、赝标量或类希格斯耦合的新粒子，我们给出了其产生截面与分支比乘积的95%置信度上限，同时也给出了耦合参数与分支比乘积的相应上限。在基于标量或赝标量粒子的标准模型扩充理论中，上述结果是此类产生与衰变道目前最严格的直接探测上限。本研究同时给出了若干依赖于具体模型的排除范围。针对类$phi$希格斯模型，我们给出了希格斯玻色子与$phi$玻色子混合角的约束上限。针对$phi$玻色子与顶夸克-反夸克对的联合产生过程，我们给出了其与顶夸克耦合强度的约束上限。最后，本研究首次针对带有标量耦合的费米嗜性类膨胀子模型，以及带有赝标量耦合的类轴子模型给出了约束上限。