arXiv subjects

Shi-Ping He

Publications and source records attributed to Shi-Ping He.

14 recordsLinked to original sources

arXiv2025

Scalar leptoquark contributions to the $gg\rightarrow Zh$ process

In this manuscript, we study the general scalar leptoquark contributions to the $gg\rightarrow Zh$ process at one-loop level. We find that the contributions only show up for the off-diagonal Higgs and $Z$ boson interactions with scalar leptoquarks, which can lead to new tensor structures different from the standard model. In the one-field and two-field models, the contributions vanish exactly; thus, the contributions are possible at least in the three-field models. We exemplify the contributions in the $S_1+\widetilde{R}_2+S_3$ model, which can appear in the presence of scalar leptoquark mass splittings and $CP$ violation. In view of the heavy scalar leptoquark mass suppression, the leading contributions are typically small and difficult to observe at hadron colliders. However, this work offers a quantitative and systematic investigation of scalar leptoquark contributions, also making it valuable for the new physics studies in other models.

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arXiv2024

Hybrid Type-II and Type-III seesaw model for the muon $g-2$ anomaly

In this work we investigate the muon anomalous magnetic dipole moment $a_\mu$ in a model that extends the Standard Model with a scalar triplet and a lepton triplet. Different from previous studies, we find that there is still viable parameter space in this model to explain the discrepancy $\Delta a_\mu=a_{\mu}(\mathrm{Exp})-a_{\mu}(\mathrm{SM})$. While being consistent with the current data of neutrino mass, electroweak precision measurements and the perturbativity of couplings, our model can provide new physics contribution $a_\mu^\textrm{NP}$ to cover the central region of $\Delta a_\mu$ with new scalar and lepton mass as low as around TeV. This mass scale is allowed by the current collider searches for doubly charged scalars and the lepton triplet, and they can be tested at future high energy and/or high luminosity colliders.

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arXiv2023

Charting the new physics through one-loop effects in the muon magnetic dipole moment

Since the announcement of the muon $g-2$ measurements, numerous studies have been devoted to exploring the new physics through this precision probe. In specific models, the new physics contributions depend on the couplings and mass scales. Approximate formulae are widely adopted when determining the new physics contributions. This manuscript is dedicated to comprehensive analytical results and approximations for the canonical interactions at one-loop level, which is universal for the spin-half fermions and can serve as a useful reference for the magnetic dipole moment calculations. We present the analytic and approximate expressions for the scalar and vector mediator cases, supplemented by explicit examples in specific models to illustrate their applications. For given muon interactions, we can estimate both the sign and magnitude of the contributions conveniently. Furthermore, we investigate the broader physical implications of these results, offering insights into potential new physics.

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arXiv2023

Scalar leptoquark and vector-like quark extended models as the explanation of the muon $g-2$ anomaly: bottom partner chiral enhancement case

Leptoquark (LQ) models are well motivated solutions to the $(g-2)_μ$ anomaly. In the minimal LQ models, only specific representations can lead to the chiral enhancements. For the scalar LQs, the $R_2$ and $S_1$ can lead to the top quark chiral enhancement. For the vector LQs, the $V_2$ and $U_1$ can lead to the bottom quark chiral enhancement. When we consider the LQ and vector-like quark (VLQ) simultaneously, there can be more scenarios. In our previous work, we considered the scalar LQ and VLQ extended models with up-type quark chiral enhancement. Here, we study the scalar LQ and VLQ extended models with down-type quark chiral enhancement. We find two new models with $B$ quark chiral enhancement, which originate from the bottom and bottom partner mixing. Then, we propose new LQ and VLQ search channels under the constraints of $(g-2)_μ$.

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arXiv2023

A leptoquark and vector-like quark extended model for the simultaneous explanation of the $W$ boson mass and muon $g-2$ anomalies

The CDF collaboration recently announced a new measurement result of the $W$ boson mass, and it is in tension with the standard model (SM) prediction. In this paper, we explain this anomaly in the vector-like quark (VLQ) $(X,T,B)_{L,R}$ and leptoquark (LQ) $S_3$ extended model. In this model, both the VLQ and LQ have positive corrections to the $W$ boson mass. Moreover, it can also be a solution to the $(g-2)_μ$ anomaly because of the chiral enhancements from top, $T$, and $B$ quarks.

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arXiv2022

Leptoquark and vectorlike quark extended models as the explanation of $(g-2)_μ$ anomaly

In minimal leptoquark (LQ) models, the $R_2$ and $S_1$ can be the solution to the $(g-2)_μ$ anomaly because of the chiral enhancements. Here, we study the LQ and vectorlike quark (VLQ) extended models. In the one LQ and one VLQ extended models, the $(g-2)_μ$ can receive the contributions from top and top partner $T$ because of the $t-T$ mixing. Besides the traditional $R_2$ and $S_1$ representations, we find that the $S_3$ LQ can also explain the anomaly when including the $(X,T,B)_{L,R}$ triplet at the same time. Moreover, we find that the LQ has the new decay channel $Tμ$ in these models.

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arXiv2022

Leptoquark and vector-like quark extended models as the explanation of the muon $g-2$ anomaly

Leptoquark (LQ) models can be the solution to the $(g-2)_μ$ anomaly because of the chiral enhancements. In this work, we consider the models extended by the LQ and vector-like quark (VLQ) simultaneously, which can be used to explain the anomaly because of the top quark and top partner (denoted as $T$) mixing. For the one LQ and one VLQ extended models, there are contributions from the top and $T$ quark. In the minimal LQ models, only the $R_2$ and $S_1$ representations can lead to the chiral enhancements. Here, we find one new $S_3$ solution to the anomaly in the presence of $(X,T,B)_{L,R}$ triplet. We also consider the one LQ and two VLQ extended models, which can solve the anomaly even in the absence of top interactions and mixings. Then, we propose new LQ search channels under the constraints of $(g-2)_μ$. Besides the traditional $tμ$ decay channel, the LQ can also decay into $Tμ$ final states, which will lead to the characteristic multi-top and multi-muon signals at hadron colliders.

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arXiv2020

Di-Higgs production as a probe of flavor changing neutral Yukawa couplings

Top partners are well motivated in many new physics models. Usually, vector like quarks $T_{L,R}$ are introduced to avoid the quantum anomaly. It is crucial to probe their interactions with the standard model particles. However, flavor changing neutral couplings are always difficult to detect directly in the current and future experiments. In this paper, we will show how to constrain the flavor changing neutral Yukawa coupling $Tth$ through the di-Higgs production indirectly. We consider the simplified model including a pair of gauge singlet $T_{L,R}$. Under the perturbative unitarity and experimental constraints, we choose $m_T=400~\mathrm{GeV},s_L=0.2$ and $m_T=800~\mathrm{GeV},s_L=0.1$ as benchmark points. After the analysis of amplitude and evaluation of the numerical cross sections, we find that the present constraints from di-Higgs production have already surpassed the unitarity bound because of the $(y_{L,R}^{tT})^4$ behavior. For the case of $m_T=400~\mathrm{GeV}$ and $s_L=0.2$, $\mathrm{Re}y_{L,R}^{tT}$ and $\mathrm{Im}y_{L,R}^{tT}$ can be bounded optimally in the range $(-0.4, 0.4)$ at HL-LHC with $2σ$ CL. For the case of $m_T=800~\mathrm{GeV}$ and $s_L=0.1$, $\mathrm{Re}y_{L,R}^{tT}$ and $\mathrm{Im}y_{L,R}^{tT}$ can be bounded optimally in the range $(-0.5, 0.5)$ at HL-LHC with $2σ$ CL. The anomalous triple Higgs coupling $δ_{hhh}$ can also affect the constraints on $y_{L,R}^{tT}$. Finally, we find that the top quark electric dipole moment can give stronger bounds of $y_{L,R}^{tT}$ in the off-axis regions for some scenarios.

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arXiv2020

Higgs boson to $γZ$ decay as a probe of flavour changing neutral Yukawa couplings

With the deeper study of Higgs particle, Higgs precision measurements can be served to probe new physics indirectly. In many new physics models, vector-like quarks $T_L,~T_R$ occur naturally. It is important to probe their couplings with standard model particles. In this work, we consider the singlet $T_L,~T_R$ extended models and show how to constrain the $Tth$ couplings through the $h\rightarrowγZ$ decay at high-luminosity LHC. Firstly, we derive the perturbative unitarity bounds on $|y_{L,~R}^{tT}|$ with other couplings set to be zeros simply. To optimize the situation, we take $m_T$ = 400 GeV and $s_L$ = 0.2 considering the experimental constraints. Under this benchmark point, we find that the future bounds from $h\rightarrowγZ$ decay can limit the real parts of $y_{L,~R}^{tT}$ in the positive direction to be O(1) because of the double enhancement. For the real parts of $y_{L,~R}^{tT}$ in the negative direction, it is always surpassed by the perturbative unitarity. Moreover, we find that the top quark electric dipole moment can give stronger bounds (especially the imaginary parts of $y_{L,~R}^{tT}$) than the perturbative unitarity and $h\rightarrowγZ$ decay in the off-axis regions for some scenarios.

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arXiv2019

One-Loop Radiative Correction to the Triple Higgs Coupling in the Higgs Singlet Model

Though the 125 GeV Higgs boson is consistent with the standard model (SM) prediction until now, the triple Higgs coupling can deviate from the SM value in the physics beyond the SM (BSM). In this paper, the radiative correction to the triple Higgs coupling is investigated in the minimal extension of the SM by adding a real gauge singlet scalar. In this model there are two scalars $h$ and $H$, and both of them are mixing states of the doublet and singlet. Provided that the mixing angle is set to be zero, namely the SM limit, $h$ is the pure left-over of the doublet and its behaviour is the same as that of the SM at the tree level. However the loop corrections can alter $h$-related couplings. In this SM limit case, the effect of the singlet $H$ may show up in the $h$-related couplings, especially the triple $h$ coupling. Our numerical results show that the deviation is sizable. For $λ_{Φ{S}}=1$ (see the text for definition), the deviation $δ_{hhh}^{(1)}$ around threshold can be more than $20\%$ if mass of the new scalar is light. For $λ_{Φ{S}}=1.5,3$, the deviation $δ_{hhh}^{(1)}$ can reach above $30\%$ in the vicinity of threshold. For $λ_{Φ{S}}=-1$, $m_H$ can be light. The deviation $δ_{hhh}^{(1)}$ is negative in this case and can be even $-50\%$ in the threshold enhanced region. The radiative correction for the $hZZ$ coupling is from the counter-term, which is universal in this model and always with negative sign. $δ_{hZZ}^{(1)}$ is independent of the sign of $λ_{Φ{S}}$ and its typical size is $-0.2\%\sim-2\%$. When combining $hhh$ and $hZZ$ precision measurements together, parameter space of this model can be probed well including the sign and size of $λ_{Φ{S}}$.

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arXiv2019

Phenomenology of A Little Higgs Pseudo-Axion

In models where the Higgs is realized as a pseudo-Nambu-Goldstone boson (pNGB) of some global symmetry breaking, there are often remaining pNGBs of some $U(1)$ groups (called `pseudo-axions'), which could lead to smoking gun signatures of such scenarios and provide important clues on the electroweak symmetry breaking mechanism. As a concrete example, we investigate the phenomenology of the pseudo-axion in the anomaly-free Simplest Little Higgs (SLH) model. After clarifying a subtle issue related to the effect of symmetric vector-scalar-scalar (VSS) vertices (e.g. $Z_μ(H\partial^μη+η\partial^μH)$), we show that for natural region in the parameter space, the SLH pseudo-axion is top-philic, decaying almost exclusively to a pair of top quarks. The direct and indirect (i.e. via heavy particle decay) production of such a pseudo-axion at the $14\,\mbox{TeV}$ (HL-)LHC turn out to suffer from either large backgrounds or small rates, making its detection quite challenging. A $pp$ collider with higher energy and luminosity, such as the $27\,\mbox{TeV}$ HE-LHC, or even the $100\,\mbox{TeV}$ FCC-hh or SppC, is therefore motivated to capture the trace of such a pNGB.

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arXiv2018

Simplest Little Higgs Revisited: Hidden Mass Relation, Unitarity and Naturalness

We analyze the scalar potential of the Simplest Little Higgs (SLH) model in an approach consistent with the spirit of continuum effective field theory (CEFT). By requiring correct electroweak symmetry breaking (EWSB) with the $125\,\text{GeV}$ Higgs boson, we are able to derive a relation between the pseudo-axion mass $m_η$ and the heavy top mass $m_T$, which serves as a crucial test of the SLH mechanism. By requiring $m_η^2>0$ an upper bound on $m_T$ can be obtained for any fixed SLH global symmetry breaking scale $f$. We also point out that an absolute upper bound on $f$ can be obtained by imposing partial wave unitarity constraint, which in turn leads to absolute upper bounds of $m_T\lesssim 19\,\text{TeV}, m_η\lesssim 1.5\,\text{TeV}$ and $m_{Z'}\lesssim 48\,\text{TeV}$. We present the allowed region in the three-dimensional parameter space characterized by $f,t_β,m_T$, taking into account the requirement of valid EWSB and the constraint from perturbative unitarity. We also propose a strategy of analyzing the fine-tuning problem consistent with the spirit of CEFT and apply it to the SLH. We suggest that the scalar potential and fine-tuning analysis strategies adopted here should also be applicable to a wide class of Little Higgs and Twin Higgs models, which may reveal interesting relations as crucial tests of the related EWSB mechanism and provide a new perspective on assessing their degree of fine-tuning.

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arXiv2018

$ZHη$-vertex: EFT Analysis and the Behavior in the SLH Model

We re-analyze the $ZHη$-vertex with the form $Z_μ(η\partial^μH-H\partial^μη)$, where $H$ is the 125 GeV Higgs boson and $η$ is an exotic pseudo-axion, based on the effective field theory (EFT) analysis and choose the simplest little Higgs (SLH) model as an example. For a pure gauge singlet pseudoscalar $η$, after carefully removing all off-diagonal two-point transitions, we show that its coefficient $c_{ZHη}$ cannot appear before $\mathcal{O}(ξ^3)$ level, where $ξ$ is the ratio between the electro-weak scale $v$ and a high scale $f$. The same behavior arises in the simplest little Higgs (SLH) model, which is quite different from the result that has already existed for a long time.

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arXiv2018

On the $ZHη$ vertex in the simplest Little Higgs Model

The issue of deriving $ZHη$ vertex in the simplest Little Higgs (SLH) model is revisited. Special attention is paid to the treatment of non-canonically-normalized scalar kinetic matrix and vector-scalar two-point transitions. We elucidate a general procedure to diagonalize a general vector-scalar system in gauge theories and apply it to the case of SLH. The resultant $ZHη$ vertex is found to be different from those which have already existed in the literature for a long time. We also present an understanding of this issue from an effective field theory viewpoint.

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