"Cross section ($pp \rightarrow \ X\phi) [pb]$" 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）的自旋0玻色子（spin-0 boson）φ的搜寻工作，该粒子衰变至电子（electron）对、μ子（muon）对或τ轻子（tau lepton）对。本次搜寻针对该类玻色子与W玻色子（W boson）、Z玻色子（Z boson）或顶夸克-反夸克对（top quark-antiquark pair）的联合产生过程，选取包含3个或4个带电轻子（包括强衰变τ轻子）的事例进行分析。本分析所用的质子-质子碰撞（proton-proton collision）数据集，采集于大型强子对撞机（Large Hadron Collider, LHC）的紧凑型μ子螺线管（Compact Muon Solenoid, CMS）实验，采集时段为2016至2018年，质心系能量为13 TeV，对应的积分亮度为138 fb⁻¹。观测结果与标准模型过程的预期一致。我们在95%置信水平（confidence level）下，对这类具有标量（scalar）、赝标量（pseudoscalar）或类希格斯（Higgs-like）耦合的新粒子的产生截面（cross section）与分支比（branching fraction）的乘积，以及耦合参数（coupling parameter）与分支比的乘积设置了上限。这是此类产生与衰变模式下，针对标准模型扩充引入标量或赝标量粒子的最严格直接限制。本研究还给出了若干依赖于模型的排除范围。对于类希格斯φ模型，我们对希格斯玻色子与φ玻色子的混合角（mixing angle）设置了限制；对于φ玻色子与顶夸克-反夸克对的联合产生过程，我们对其与顶夸克的耦合强度设置了限制。最后，我们首次对费米亲和类dilaton模型（fermiophilic dilaton-like model）以及具有赝标量耦合的类轴子模型（axion-like model）设置了限制。