We consider the electroweak production of a top quark in association with a photon at the LHC to probe the electroweak top quark couplings (t$\bar{\text{t}}γ$) as well as the triple gauge boson couplings (WW$γ$). The study is based on the modifications of the t$\bar{\text{t}}γ$ and WW$γ$ interactions via heavy degrees of freedom in the form of dimension-six operators which we add to the standard model Lagrangian. A binned angular asymmetry in single top quark plus photon events and cross section ratio are proposed to probe the anomalous
t$\bar{\text{t}}γ$ and WW$γ$ couplings. It is shown that the proposed angular asymmetry can distinguish anomalous t$\bar{\text{t}}γ$, WW$γ$ couplings from the standard model prediction and yield a great sensitivity.
We calculate the spinor helicity amplitudes of anomalous $H\to ZZ \to 4\ell$ decay. After embedding these analytic formulas into the $\texttt{MCFM}$ package, we study the interference effects between the anomalous $gg\to H\to ZZ \to 4\ell$ process and the SM processes, which are indispensable in the Higgs off-shell region. Subsequently, the constraints on the anomalous couplings are estimated using LHC experimental data.
Anomalous quartic ZZgammagamma couplings in gamma-proton collision at the LHC
我们通过LHC的过程$p p\to pγp\to p γq Z X$研究了反常四次$ZZγγ$耦合的约束。考虑到各种前向探测器的接受度和集成LHC的光度，我们发现95%的置信水平上的异常耦合参数的界限。我们表明，这些耦合的界限是在$10^{-6}GeV^{-2}$的顺序，这是约四个数量级的限制，相对于目前的实验界限。
A new process with the lepton flavor violation (LFV) is presented in the setup for LHC. The LFV is induced by the one-loop effect through Higgs bosons in the framework of the type-III two Higgs doublet model. It is demonstrated that the vast of parameter space in the Yukawa sector could be accessed by current and future LHC experiments.
We show how the $W$ boson polarization in the process of associated $W^{\pm}H$ production at the Large Hadron Collider (LHC) can be used to constrain anomalous $WWH$ couplings. We first calculate the spin density matrix for the $W$ to linear order in the anomalous couplings, which are assumed to be small. We then evaluate angular asymmetries in the decay distributions of leptons produced in the decay of the $W$ and show how they can be used to measure the individual elements of the polarization tensor. We estimate the limits that can be placed on the anomalous $WWH$ couplings at a future run o…
We estimate model-independent bounds that could be obtained on the anomalous $ZZH$ vertex using polarization parameters of the $Z$ boson produced in the Higgstrahlung process at the LHC. We calculate the eight independent polarization parameters from the spin density matrix elements of the $Z$, which can probe underlying new physics contributions to $ZH$ production. By using the approach that connects these polarization observables to the coefficients in the angular distribution of the decay products of the $Z$, we estimate the limits on the anomalous $ZZH$ coupling that can be obtained at the…
We make a careful analysis of $W^\pmγ$ production at the LHC, identifying the $W^\pm$ through leptonic decays, with a view to exploring the sensitivity of the machine to anomalous $CP$-conserving $WWγ$ interactions. All the available kinematic variables are used, but we find that the most useful one is the opening angle in the transverse plane between the decay products of the $W^\pm$. It is shown that even a simple-minded analysis using this variable can lead to a much greater sensitivity at the LHC than the current constraints on the relevant parameters.
Dimension-six anomalous $tqγ$ couplings in $γγ$ collision at the LHC
在LHC上，通过考虑不同的前向探测器接受度，研究了通过$pp\to pγγp\to p t\bar{q}p$过程的六维反常$tqγ$（$q=u,c$）耦合的味变顶夸克物理.在本文中，我们考虑并研究了顶夸克衰变的影响。在有效拉格朗日方法的$95\%$置信水平下，得到了异常耦合和$t\to qγ$分支比的灵敏度界限。此外，我们还研究了反常耦合对单顶夸克自旋不对称性的影响。
We perform an exclusive study of the anomalous $Wtb$ interaction in the context of LHC. The limits on $Wtb$ anomalous couplings have been estimated via the measurements of the top-quark decay width and cross-section as well as production asymmetries in case the CP is violated. Our investigations reveal that the upper bounds on $(|C_L|, |C_R|)$ would be of about (1.82, 0.03) $\times 10^{-4}$ at $2.5 σ$ C.L., for the already collected data at the LHC with $\sqrt{S} = 13$ TeV for an integrated luminosity of 139 fb$^{-1}$. The corresponding limits for future hadron colliders, namely, High Luminosi…
In this study, we investigate the potential of the process $pp\rightarrow pγ^{*} p\rightarrow p τ\barν_τq^{\prime} X$ at the LHC to examine the anomalous electromagnetic moments of the tau lepton. We obtain $95\%$ confidence level bounds on the anomalous coupling parameters with various values of the integrated luminosity and center-of-mass energy. The improved bounds have been obtained on the anomalous coupling parameters of electric and magnetic moments of the tau lepton $a_τ$ and $\vert$$d_τ$$\vert$ compared to the current experimental sensitivity bounds. The $γp$ mode of photon reactions a…
The determination of the electromagnetic dipole moments of the top quark is one of the most important goals of the top quark physics program in the collider experiments. For this reason, the top quark pair production to investigate the sensitivity on the electric and magnetic dipole moments of the top quark via the process $pp\rightarrow p γp \rightarrow p t \bar{t} X$ at the Large Hadron Collider (LHC), the High-Luminosity Large Hadron Collider (HL-LHC) and High-Energy Large Hadron Collider (HE-LHC) is discussed. We apply pure leptonic and semileptonic decays for top quark pair production in …
Production and decay of up-type and down-type new heavy quarks through anomalous interactions at the LHC
We study the process pp->QVX (where Q=t,b and V=g,gamma,Z) through the anomalous interactions of the new heavy quarks at the LHC. Considering the present limits on the masses and mixings, the signatures of the heavy quark anomalous interactions are discussed and analysed at the LHC for the center of mass energy of 13 TeV. An important sensitivity to anomalous couplings kappa_{g} ^{t'}/Lambda=0.10 TeV^{-1}, kappa_γ^{t'}/Lambda=0.14 TeV^{-1}, kappa_{Z} ^{t'}/Lambda=0.19 TeV^{-1} and kappa_{g} ^{b'}/Lambda=0.15 TeV^{-1}, kappa_{Z} ^{b'}/Lambda=0.19 TeV $^{-1}, kappa_γ^{b'}/Lambda=0.30 TeV$ ^{-1} …
Effect of Anomalous Couplings on the Associated Production of a Single Top Quark and a Higgs Boson at the LHC
我们考虑在大型强子对撞机上产生一个顶夸克和一个希格斯玻色子。特别是，我们计算的横截面过程$ p p \to t h j$，$t h b$，$t h W$，$t h j j$，$t h j b$，$t h W j$，$t h W b$中存在的异常$Wtb, WWh$和$tth$耦合。我们发现，反常的$Wtb$和$tth$耦合可以显着提高截面。我们还分析了一些签名，并表明，如果这些耦合确实是异常的，那么有足够的数据，人们应该能够观察到的希格斯玻色子的生产与单顶夸克。
We investigate the prospects for discovering the Flavour Changing Neutral Current (FCNC) $tqZ$ couplings via two production processes yielding trilepton signals: top quark pair production $pp\to t\bar{t}$ with one top decaying to the $Z$ boson and one light jet and the anomalous single top plus $Z$ boson production process $pp\to tZ$. We study these channels at various successors of the Large Hadron Collider~(LHC), i.e., the approved High-Luminosity LHC (HL-LHC) as well as the proposed High-Energy LHC~(HE-LHC) and Future Circular Collider in hadron-hadron mode (FCC-hh). We perform a full simul…
本文计算了LHC上的顶夸克对产生反应pp -> b u anti-d anti-b mu- anti-nu_mu中的μ ~-分布，并在反常Wtb耦合的情况下得到了最高阶的结果。在实验室坐标系中，反常Wtb耦合对束流的横动量、快度和μ角的余弦分布以及在静止坐标系中对b夸克的反动量的分布的影响都比较小。用整组首阶费曼图计算的分布实际上与用t反t生产图计算的分布没有区别，具有典型的接受截点。这表明非共振背景贡献的影响非常小。
We study the sensitivity of certain observables to the anomalous right tensorial coupling in single top production at the LHC at $\sqrt{s}=13 \text{ TeV}$. The observables consist of asymmetries constructed from the energy and angles of the decay products of the top quark produced in single top production through $t$-channel. The computation is done at Leading Order (LO) and Next-to-Leading Order (NLO) in the strong coupling in the $5$ flavor scheme. We have estimated projected limits on the anomalous coupling, both at the parton level without cuts and at the particle level with cuts. We find …
