Rare decay of the Higgs boson is a powerful tool to probe new physics beyond the standard model. The rare decays occur through quantum loops in which the standard model and new physics contributions might cancel each other out. We consider a faked-no-new-physics scenario that the new physics contributions are about minus two times the standard model contribution such that partial widths of Higgs boson rare decays are the same as the standard model predictions. We propose to measure the $HZγ$ and $Hγγ$ anomalous couplings in the process of $e^+ e^- \to Hγ$ that is strongly correlated to Higgs boson rare decays. We show that the faked-no-new-physics scenario can be fully probed at a high energy electron-positron collider.
We analyze the possibility of probing anomalous Higgs couplings in the rare decays $H \to Z V$, $V$ being a vector quarkonium state. These rare decays involve both gauge as well as the Yukawa sectors and either of them can potentially be anomalous. We show that the branching fractions for $H \to Z V$ decays in Standard Model are small, making it a sensitive probe for anomalous Higgs couplings originating from physics beyond Standard Model. Moreover, as both $V$ and $Z$ can decay into pair of charged leptons, they provide experimentally clean channels and future LHC runs should observe such dec…
We propose a new scenario of using the dark axion portal at one-loop level to explain the recently observed muon anomalous magnetic moment by the Fermilab Muon g-2 experiment. Both axion/axion-like particle (ALP) and dark photon are involved in the same vertex with photon. Although ALP or dark photon alone cannot explain muon $g-2$, since the former provides only negative contribution while the latter has very much constrained parameter space, dark axion portal can save the situation and significantly extend the allowed parameter space. The observed muon anomalous magnetic moment provides a ro…
We have estimated the sensitivity to the anomalous couplings of the $γγγZ$ vertex in the $γγ\rightarrowγZ$ scattering of the Compton backscattered photons at the CLIC. Both polarized and unpolarized collisions at the $e^+e^-$ energies 1500 GeV and 3000 GeV are addressed, and anomalous contributions to helicity amplitudes are derived. The differential and total cross sections are calculated. We have obtained 95\% C.L. exclusion limits on the anomalous quartic gauge couplings (QGCs). They are compared with corresponding bounds derived for the $γγγZ$ couplings via $γZ$ production at the LHC. The …
Probing anomalous tWb interactions with rare B decays
顶夸克性质的精确研究目前正在LHC和Tevatron对撞机上进行，并有望探测异常的t-W-b相互作用。同时，最近关于B_{d,s}-\bar{B}_{d,s}振荡观测量的实验结果，分支比B_s-> μ ^+ μ ^-，以及B-> K \starl^+ l ^-中的前后不对称性，以及在SM中得到的对相关观测量的精确理论预言，激发了在存在反常t-W-b顶点的情况下对这些观测量的联合研究。我们研究了这种反常耦合对B-> X_s l ^+ l ^-衰变模的贡献，并将它们与B_{d,s}-\bar{B}_d，s，B-> X_s γ观测量的修正相结合，确定了反常t-W-b相互作用实部和虚部的间接界.我们发现这些是最优于目前的直接约束来自顶级衰变和生产测量在LHC和Tevatron。最后，我们预测了B_s-> μ ^+ μ ^-和B-> K ^{（*）} v \bar v的分支比的允许效应，以及B-> K ^* l ^+ l ^-的前后向不对称性。我们发现，在未来这些可观的知识的改进可能会进一步限制一些异常的tWb相互作用。
We study the anomalous $W^+W^-V$ ($V=γ,Z$) couplings in $e^+e^-\to W^+W^-$ using the complete set of polarization observables of $W$ boson with longitudinally polarized electron ($e^-$) and positron ($e^+$) beams. For the effective $W^+W^-V$ couplings, we use the most general Lorentz invariant form factor parametrization as well as $SU(2)\times U(1)$ invariant dimension-$6$ effective operators. We estimate simultaneous limits on the anomalous couplings using the Markov-Chain--Monte-Carlo (MCMC) method for an $e^+e^-$ collider running at center of mass energy of $\sqrt{s}=500$ GeV and the integ…
The anomalous quartic neutral couplings of the $γγγγ$ vertex in a polarized light-by-light scattering of the Compton backscattered photons at the CLIC are examined. Both differential and total cross sections are calculated for $e^+e^-$ collision energies 1500 GeV and 3000 GeV. The helicity of the initial electron beams is taken to be $\pm\,0.8$. The unpolarized and SM cross sections for the same values of helicities are also estimated. The 95\% C.L. exclusion limits on two anomalous photon couplings $ζ_1$ and $ζ_2$ are calculated. The best bounds on these couplings are found to be $6.85 \times…
Probing anomalous right--handed current in Z b bbar vertex
由于LEP数据中$Z \to b \bar{b}$衰变的前向-后向不对称性，$-2 σ$偏离了标准模型的预测，我们通过引入$A_{FB}^b$扩展的电弱精度检验来探索$Z b \bar{b}$顶点的异常耦合.我们引入一个新的变量$ε'_b$来测量$Z b \bar{b}$顶点的反常右手耦合。我们的分析对非普适接触相互作用的影响进行了研究，左-右模型也被认为是异常右手耦合的可能起源。
Probing Weak Anomalous Top Quark Couplings with Final State Gluons at the NLC
过程$e^+e^- \to t\bar tg$的速率和相应的胶子喷流能量分布对顶部与光子和产生顶点处的$Z$的异常偶极耦合的存在敏感。对于这种类型的相当大的反常耦合，很可能与标准模型的预期有很大的偏差。我们探讨的能力的NLC发现或放置这些类型的顶夸克耦合的界限。由此产生的限制被发现是相当互补的那些所产生的直接探针的顶夸克生产顶点。[To出现在{ \it Physics and Technology of the Next Linear Collider}，eds. D. Burke和M. Peskin，1996年提交给Snowmass的报告。
We propose to utilize the exclusive $Z$-boson rare decays $Z\to Υ(ns)+γ$ to constrain the $Zb\bar{b}$ couplings at the HL-LHC and 100 TeV proton-proton collider. We demonstrate that the event yield of the proposed processes is sensitive to the axial-vector component of the $Zb\bar{b}$ coupling and can provide complementary information to the jet-charge weighted single-spin asymmetry measurement at the EIC and the $gg\to Zh$ production rate measurement at the LHC. By applying the NRQCD factorization formalism, we calculate the partial decay width of $Z\to Υ(ns)+γ$ to the NLO accuracy in strong …
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 …
We study possible new physics interactions in the $ZZH$ vertex contributing to the Higgsstrahlung process $e^+ e^- \to ZH$ at proposed future $e^+e^-$ colliders using the polarization of the $Z$ as a probe. We calculate the spin density matrix of the $Z$ for the process and determine the eight independent polarization parameters of the $Z$ boson which have the potential to constrain the anomalous couplings. We study angular asymmetries using the decay leptons from the $Z$ boson which are simply related to the polarization observables. We also estimate the limits that can be placed on the anoma…
We study the anomalous FCNC $tqγ$ and $tqg$ couplings via $pp\to Wbγ+X$ signal process including realistic detector effects for both leptonic and hadronic decay channels of the W boson at 100 TeV FCC-hh. The relevant background are considered in the cut based analysis to obtain not only limits on the anomalous $λ$ and $ζ$ couplings but also branching ratios of $t\to qγ$ and $t\to qg$ decay channels. We find that the sensitivity to the branching ratio of $t \to q γ$ channel is three order better than the available LHC experimental limits, and it is comparable for the branching ratio of the $t\t…
The sensitivities to the anomalous quartic gauge boson coupling $γγγZ$ are estimated via $γZ$ production with intact protons in the forward region at the LHC. Proton tagging proves to be a powerful tool to suppress the background, which allows consideration of the hadronic decays of the $Z$ boson in addition to the leptonic ones. We discuss the discovery potential for an integrated luminosity of $300\,\mathrm{fb}^{-1}$ and $3000\,\mathrm{fb}^{-1}$. The sensitivity we obtain at $300\,\mathrm{fb}^{-1}$ goes beyond the one expected from LHC bounds on the $Z\rightarrow γγγ$ decay by about three or…
Role of polarization in probing anomalous gauge interactions of the Higgs boson
我们探索使用偏振$e^+/e^-$光束和/或末态衰变轻子偏振的信息来探测希格斯玻色子与一对矢量玻色子的相互作用。通过构造在离散对称变换下具有相同性质的观测量作为不同的单个反常相互作用，对过程$e^+ e^- \to f \bar f H$（其中$f$是任意的轻费米子）进行了与模型无关的分析.这使我们能够独立于其他项来探测单个异常项。我们发现初始态光束偏振可以显著提高$Z$玻色子与希格斯玻色子（$ZZH$）CP奇耦合的灵敏度。此外，以甚至40%的效率分离具有特定$τ$螺旋度的事件的能力可以将对某些$ZZH$偶联的灵敏度提高多达3倍。此外，在三线性$W$（$WWH$）耦合的测量中，来自$ZZH$顶点贡献的污染可以通过使用偏振光束在很大程度上减少。初始状态辐射（ISR）和beamstrahlung，这可能是相关的更高的值的光束能量的影响也包括在分析中。
Probing anomalous $Wtb$ couplings through $bW$ spin correlations in top-quark pair production at the HL-LHC
School of Physics, Beihang University（北京航空航天大学物理学院）；School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University（北京大学物理学院与核物理及技术国家重点实验室）；Center for High Energy Physics, Peking University（北京大学高能物理中心）
We investigate the anomalous flavour changing neutral current (FCNC) interactions of top quark through the process $e^{-}p\to e^{-}W^{\pm}q+X$. We calculate the signal and background cross sections in electron proton collisions at Large Hadron electron Collider (LHeC) with a 7 TeV proton beam from the LHC and a new 60 GeV electron beam from energy recovery linac (ERL). We study the relevant background processes including one electron and three jets in the final state. The distributions of the invariant mass of two jets and an additional jet tagged as $b$-jet are used to account signal and back…
We study the prospects of probing the anomalous $tHq$~($q= u, c$) couplings via SS2L or 3L signatures at the High Luminosity (HL-LHC) run of the 14 TeV CERN collider. We focus on signals of the $tH$ associated production followed by the decay modes $t\to b\ell^{+}ν_{\ell}$ and $H\to WW^{\ast}$, and $t\bar{t}$ production followed by the decay modes $t\to b\ell^{+}ν_{\ell}$ and $\bar{t}\to H(\to WW^{\ast})\bar{q}$, where $\ell=e, μ$. Based on two types of $H\to WW^{\ast}$ decay topologies, one assuming the semileptonic decay mode $H\to WW^{\ast}\to \ell^{+}νjj $ and the other the fully leptonic …
A proposed high energy Future Circular Hadron-Electron Collider would provide sufficient energy in a clean environment to probe di-Higgs production. Using this channel we show that the azimuthal angle correlation between the missing transverse energy and the forward jet is a very good probe for the non-standard $hhh$ and $hhWW$ couplings. We give the exclusion limits on these couplings as a function of integrated luminosity at a $95$\% C.L. using the fiducial cross sections. With appropriate error fitting methodology we find that the Higgs boson self coupling could be measured to be $g^{(1)}_{…
We propose a novel idea for probing the Higgs boson couplings through the measurement of hadronic event shape distributions in the decay of the Higgs boson at lepton colliders. The method provides a unique test of the Higgs boson couplings and of QCD effects in the decay of the Higgs boson. It can be used to probe the Yukawa couplings of the light quarks and to further test the mechanism of electroweak symmetry breaking. From a case study for the proposed Circular Electron-Positron Collider, assuming a hypothesis of SM-like theory, light-quark couplings with a strength greater than 9% of the b…
