arXiv subjects

Ling-Xiao Xu

Publications and source records attributed to Ling-Xiao Xu.

24 records · Page 2Linked to original sources

arXiv2020

Determining the Shape of Higgs Potential at Future Colliders

Although the Higgs boson has been discovered, its self-couplings are poorly constrained. This leaves the nature of the Higgs boson undetermined. Motivated by different Higgs potential scenarios other than the Landau-Ginzburg type in the standard model, we systematically organize various new physics scenarios -- elementary Higgs, Nambu-Goldstone Higgs, Coleman-Weinberg Higgs, and Tadpole-induced Higgs, etc. We find that double-Higgs production at the 27 TeV high energy LHC can be used to discriminate different Higgs potential scenarios, while it is necessary to use triple-Higgs production at a future 100 TeV proton-proton collider to fully determine the shape of the Higgs potential.

hep-ph↗

arXiv2019

Holographic Completion of Minimal Neutral Naturalness Model and Deconstruction

We previously presented the minimal neutral naturalness model, in which neutral naturalness is realized with the minimal coset and the minimal field content in the color-neutral sector. To fully eliminating the cutoff dependence in the Higgs potential, its ultraviolet completion was laid out. In this work, we investigate in details the holographic realization in warped five-dimensional framework. Using the holographic method, we obtain the effective action on the UV brane and derive the finite Higgs potential, with the Higgs being a pseudo Nambu-Goldstone boson. The Higgs potential is fully radiatively generated and vacuum misalignment is naturally realized through only the fermionic contribution. To illustrate general features of the lowest Kaluza-Klein states, we construct the corresponding deconstructed two-site composite model.

hep-ph↗

arXiv2019

EFTs meet Higgs Nonlinearity, Compositeness and (Neutral) Naturalness

Composite Higgs and neutral-naturalness models are popular scenarios in which the Higgs boson is a pseudo Nambu-Goldstone boson, and naturalness problem is addressed by composite top partners. Since the standard model effective field theory (SMEFT) with dimension-six operators cannot fully retain the information of Higgs nonlinearity due to its PNGB nature, we systematically construct low energy Lagrangian in which the information of compositeness and Higgs nonlinearity are encoded in the form factors, the two-point functions in the top sector. We classify naturalness conditions in various scenarios, and first present these form factors in composite neutral naturalness models. After extracting out Higgs effective couplings from these form factors and performing the global fit, we find the value of Higgs top coupling could still be larger than the standard model one if the top quark is embedded in the higher dimensional representations. Also we find the impact of Higgs nonlinearity is enhanced by the large mass splitting between composite states. In this case, pattern of the correlation between the $t\bar{t}h$ and $t\bar{t}hh$ couplings is quite different for the linear and nonlinear Higgs descriptions.

hep-ph↗

arXiv2019

Resolving the degeneracy in top quark Yukawa coupling with Higgs pair production

The top quark Yukawa coupling ($y_t$) can be modified by two dimension-six operators $\mathcal{O}_H$ and $\mathcal{O}_y$ with the corresponding Wilson coefficients $c_H$ and $c_y$, whose individual contribution cannot be distinguished by measuring $y_t$ alone. However, such a degeneracy can be resolved with Higgs boson pair production. In this work we explore the potential of resolving the degeneracy of the unknown Wilson coefficients $c_H$ and $c_y$ at the 14~TeV LHC and the 100~TeV hadron colliders. Combining the information of the single Higgs production, $t\bar{t}h$ associated production and Higgs pair production, the individual contribution of $c_H$ and $c_y$ to $y_t$ can be separated. Regardless of the value of $c_H$, the Higgs pair production can give a strong constraint on $c_y$ at the 100 TeV hadron collider. We further show that it is possible to differentiate various $c_y$ and $c_t$ values predicted in several benchmark models.

hep-ph↗

arXiv2018

Signature of Pseudo Nambu-Goldstone Higgs boson in its Decay

If the Higgs boson is a pseudo Nambu-Goldstone boson (PNGB), the $hZγ$ contact interaction induced by the $\mathcal{O}(p^4)$ invariants of the non-linear sigma model is free from its nonlinearity effects. The process $h\rightarrow Zγ$ can be used to eliminate the universal effects of heavy particles, which can fake the nonlinearity effects of the PNGB Higgs boson in the process $h\rightarrow V^*V$ ($V=W^\pm$,\ $Z$). We demonstrate that the ratio of the signal strength of $h\rightarrow Zγ$ and $h\rightarrow V^*V$ is good to distinguish the signature of the PNGB Higgs boson from Higgs coupling deviations.

hep-ph↗

arXiv2018

Minimal Neutral Naturalness Model

We build a minimal neutral naturalness model in which the top partners are not charged under QCD, with a pseudo Goldstone Higgs arising from $SO(5)/SO(4)$ breaking. The color-neutral top partners generate the Higgs potential radiatively without quadratic divergence. The misalignment between the electroweak scale and global symmetry breaking scale is naturally obtained from suppression of the Higgs quadratic term, due to cancellation between singlet and doublet top partner contributions. This model can be embedded into ultraviolet holographic setup in composite Higgs framework, which even realizes finite Higgs potential.

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