arXiv subjects

Xiao-Fang Han

Publications and source records attributed to Xiao-Fang Han.

At least 19 recordsLinked to original sources

arXiv2025

95 GeV Higgs boson and nano-Hertz gravitational waves from domain walls in the N2HDM

We explore the diphoton and $b\bar{b}$ excesses at 95.4 GeV, as well as nano-Hertz gravitational waves originating from domain walls, within the framework of the next-to-two-Higgs-doublet model (N2HDM), which extends the two-Higgs-doublet model by introducing a real singlet scalar subject to a discrete $Z_2$ symmetry. The $Z_2$ symmetry is spontaneously broken by the non-zero vacuum expectation value of the singlet scalar, $v_s$, which leads to the formation of domain walls. We discuss two different scenarios: in scenario A, the 95.4 GeV Higgs boson predominantly originates from the singlet field, while in scenario B, it arises mainly from the CP-even components of the Higgs doublets. Taking into account relevant theoretical and experimental constraints, we find that scenario A can fully account for both the diphoton and $b\bar{b}$ excesses at 95.4 GeV within the $1\sigma$ range. Moreover, the peak amplitude of the gravitational wave spectrum at a peak frequency of $10^{-9}$ Hz can reach $2 \times 10^{-12}$ for $v_s = 100$ TeV. Scenario B only marginally accounts for the diphoton and $b\bar{b}$ excesses at the $1\sigma$ level, but the peak amplitude of the gravitational wave spectrum at the peak frequency of $10^{-9}$ Hz can reach $6\times 10^{-8}$ for $v_s=100$ TeV. The nano-Hertz gravitational wave signals predicted in both scenarios can be tested by the current and future pulsar timing array projects.

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arXiv2024

Revisiting wrong sign Yukawa coupling of type II two-Higgs-doublet model in light of the recent LHC data

In light of the recent LHC Higgs data, we examine the parameter space of type II two-Higgs-doublet model in which the 125 GeV Higgs has the wrong sign Yukawa couplings. Combining related theoretical and experimental limits, we find that the LHC Higgs data exclude most of the parameter space of the wrong sign Yukawa coupling. For $m_H=$ 600 GeV, the allowed samples are mainly distributed in several corners and narrow bands of m_A<20 GeV, 30 GeV<m_A<120 GeV, 240 GeV<m_A<300 GeV, 380 GeV <m_A<430 GeV, and 480 GeV<m_A<550 GeV. For m_A=600 GeV, m_H is required to be less than 470 GeV. The light pseudo-scalar with a mass of 20 GeV is still allowed in case of the wrong sign Yukawa coupling of 125 GeV Higgs.

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arXiv2024

The $U(1)_{L_μ-L_τ}$ breaking phase transition, muon $g-2$, dark matter, collider and gravitational wave

Combining the dark matter and muon $g-2$ anomaly, we study the $U(1)_{L_μ-L_τ}$ breaking phase transition, gravitational wave spectra, and the direct detection at the LHC in an extra $U(1)_{L_μ-L_τ}$ gauge symmetry extension of the standard model. The new fields includes vector-like leptons ($E_1,~ E_2,~ N$), $U(1)_{L_μ-L_τ}$ breaking scalar $S$ and gauge boson $Z'$, as well as the dark matter candidate $X_I$ and its heavy partner $X_R$. A joint explanation of the dark matter relic density and muon $g-2$ anomaly excludes the region where both $min(m_{E_1},m_{E_2},m_N,m_{X_R})$ and $min(m_{Z'},m_S)$ are much larger than $m_{X_I}$. In the parameter space accommodating the DM relic density and muon $g-2$ anomaly, the model can achieve a first order $U(1)_{L_μ-L_τ}$ breaking phase transition, whose strength is sensitive to the parameters of Higgs potential. The corresponding gravitational wave spectra can reach the sensitivity of U-DECIGO. In addition, the direct searches at the LHC impose stringent bound on the mass spectra of the vector-like leptons and dark matter.

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arXiv2022

A joint explanation of W-mass and muon g-2 in 2HDM

Since both $W$-mass and muon $g-2$ can be affected by the mass splittings among extra Higgs bosons $(H,~A,~H^\pm)$ in a 2HDM, we take a model with $μ$-$τ$ LFV interactions to examine the two anomalies reported respectively by CDF II and FNAL. We obtain the following observations: (i) Combined with theoretical constraints, the CDF $W$-mass measurement disfavors $H$ or $A$ to degenerate in mass with $H^\pm$, but allows $H$ and $A$ to degenerate. The mass splitting between $H^\pm$ and $H/A$ is required to be larger than 10 GeV. The $m_{H^\pm}$ and $m_{A}$ are favored to be smaller than 650 GeV for $m_H<120$ GeV, and allowed to have more large values with increasing of $m_H$. (ii) After imposing other relevant experimental constraints, there are parameter spaces that simultaneously satisfy (at $2σ$ level) the CDF $W$-mass, the FNAL muon $g-2$ and the data of lepton universality in $τ$ decays, but the mass splittings among extra Higgs bosons are strictly constrained.

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arXiv2022

The CDF W-mass, muon g-2, and dark matter in a $U(1)_{L_μ-L_τ}$ model with vector-like leptons

We study the CDF $W$-mass, muon $g-2$, and dark matter observables in a local $U(1)_{L_μ-L_τ}$ model in which the new particles include three vector-like leptons ($E_1,~ E_2,~ N$), a new gauge boson $Z'$, a scalar $S$ (breaking $U(1)_{L_μ-L_τ}$), a scalar dark matter $X_I$ and its partner $X_R$. We find that the CDF $W$-mass disfavors $m_{E_1}= m_{E_2}={m_N}$ or $s_L=s_R=0$ where $s_{L(R)}$ is mixing parameter of left (right)-handed fields of vector-like leptons. A large mass splitting between $E_1$ and $E_2$ is favored when the differences between $s_L$ and $s_R$ becomes small. The muon $g-2$ anomaly can be simultaneously explained for appropriate difference between $s_L$ $(m_{E_1})$ and $s_R$ $(m_{E_2})$, and some regions are excluded by the diphoton signal data of the 125 GeV Higgs. Combined with the CDF $W$-mass, muon $g-2$ anomaly and other relevant constraints, the correct dark matter relic density is mainly obtained in two different scenarios: (i) $X_IX_I\to Z'Z',~ SS$ for $m_{Z'}(m_S)<m_{X_I}$ and (ii) the co-annihilation processes for $min(m_{E_1},m_{E_2},m_N,m_{X_R})$ closed to $m_{X_I}$. Finally, we use the direct searches for $2\ell+E_T^{miss}$ event at the LHC to constrain the model, and show the allowed mass ranges of the vector-like leptons and dark matter.

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arXiv2021

Lepton-specific inert two-Higgs-doublet model confronted with the new results for muon and electron g-2 anomalies and multi-lepton searches at the LHC

Combining the multi-lepton searches at the LHC, we study the possibilities of accommodating the new data of muon and electron $g-2$ anomalies in the lepton-specific inert two-Higgs-doublet model. We take the heavy CP-even Higgs as the 125 GeV Higgs, and find the muon and electron $g-2$ anomalies can be explained simultaneously in the region of 5 GeV $< m_h<60$ GeV, 200 GeV $<m_A< 620$ GeV, 190 GeV $<m_{H^\pm}< 620$ GeV for appropriate Yukawa couplings between leptons and inert Higgs. Meanwhile, the model can give a better fit to the data of lepton universality in $τ$ decays than the SM. Further, the multi-lepton event searches at the LHC impose a stringent upper bound on $m_h$, $m_h<$ 35 GeV.

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arXiv2020

Dark matter, electroweak phase transition and gravitational wave in the type-II two-Higgs-doublet model with a singlet scalar field

In the framework of type-II two-Higgs-doublet model with a singlet scalar dark matter $S$, we study the dark matter observables, the electroweak phase transition, and the gravitational wave signals by such strongly first order phase transition after imposing the constraints of the LHC Higgs data. We take the heavy CP-even Higgs $H$ as the only portal between the dark matter and SM sectors, and find the LHC Higgs data and dark matter observables require $m_S$ and $m_H$ to be larger than 130 GeV and 360 GeV for $m_A=600$ GeV in the case of the 125 GeV Higgs with the SM-like coupling. Next, we carve out some parameter space where a strongly first order electroweak phase transition can be achieved, and find benchmark points for which the amplitudes of gravitational wave spectra reach the sensitivities of the future gravitational wave detectors.

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arXiv2019

The simple interpretations of lepton anomalies in the lepton-specific inert two-Higgs-doublet model

There exist about $3.7σ$ positive and $2.4σ$ negative deviations in the muon and electron anomalous magnetic moments ($g-2$). Also, some ratios for lepton universality in $τ$ decays have almost $2σ$ deviations from the Standard Model. In this paper, we propose a lepton-specific inert two-Higgs-doublet model. After imposing all the relevant theoretical and experimental constraints, we show that these lepton anomalies can be explained simultaneously in many parameter spaces with $m_H > 200$ GeV and $m_A~(m_{H^\pm})> 500$ GeV for appropriate Yukawa couplings between leptons and inert Higgs. The key point is that these Yukawa couplings for $μ$ and $τ$/$e$ have opposite sign.

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arXiv2018

A light scalar dark matter extension of the type-II two-Higgs-doublet model

We examine the type-II two-Higgs-doublet model with a light scalar dark matter ($S$) after imposing the constraints from the Higgs searches at the LHC and dark matter experiments. We first assume that both two CP-even Higgses ($h$ and $H$) are portals between the DM and SM sectors, and the CP-odd Higgs ($A$) and $H$ are heavier than 130 GeV. We find that the DM with a mass of $10\sim 50$ GeV is disfavored by the joint constraints of the 125 GeV Higgs signal data, the relic density, XENON1T (2017), PandaX-II (2017) and the Fermi-LAT. Next, we consider a special scenario in which the heavy CP-even Higgs is taken as the 125 GeV Higgs. The light CP-even Higgs is the only portal between the DM and SM sectors, and the DM mass is slightly below Higgs resonance. We find that the signal data of the 125 GeV Higgs restrict $\tanβ$ to be in the range of $1\sim 1.5$ for $m_h<$ 62 GeV. The $gg\to A\to hZ$ and $b\bar{b}\to h \to τ^+τ^-$ channels at the LHC can impose lower limits and upper limits on $\tanβ$, respectively. For appropriate values of $\tanβ$, $λ_h$ and $m_h$, the DM with a mass of $10\sim 50$ GeV is allowed by the constraints of the Higgs searches at the LHC and dark matter experiments. For example, $\tanβ$ is restricted to be in the range of $1.0\sim1.5$ for 10 GeV $ $ 1.125 is excluded for 30 GeV $<m_S<$ 50 GeV.

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arXiv2017

Wrong sign Yukawa coupling of the 2HDM plus a singlet scalar dark matter confronted with dark matter and Higgs data

In the framework of type-II two-Higgs-doublet model with a scalar dark matter ($S$), we examine the wrong sign Yukawa coupling of the 125 GeV Higgs which is the only portal between the dark matter and SM sectors. After imposing the constraints from the Higgs searches at the LHC and dark matter experiments, we obtain some interesting observables: (i) The theory, oblique parameters, and the Higgs searches at the LHC can impose stringent constraints on $\tanβ$ in the case of the wrong sign Yukawa coupling of the 125 GeV Higgs. For example, for $m_H=600$ GeV and 140 GeV $ -0.82$. (iv) The Fermi-LAT limits exclude most of samples in the range of 62.5 GeV $<m_S <65$ GeV, including the samples with $f^n/f^p\sim -0.7$.

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arXiv2017

$h\toμτ$ and muon g-2 in the alignment limit of two-Higgs-doublet model

We examine the $h\to μτ$ and muon g-2 in the exact alignment limit of two-Higgs-doublet model. In this case, the couplings of the SM-like Higgs to the SM particles are the same as the Higgs couplings in the SM at the tree level, and the tree-level lepton-flavor-violating coupling $hμτ$ is absent. We assume the lepton-flavor-violating $μτ$ excess observed by CMS to be respectively from the other neutral Higgses, $H$ and $A$, which almost degenerates with the SM-like Higgs at the 125 GeV. After imposing the relevant theoretical constraints and experimental constraints from the precision electroweak data, $B$-meson decays, $τ$ decays and Higgs searches, we find that the muon g-2 anomaly and $μτ$ excess favor the small lepton Yukawa coupling and top Yukawa coupling of the non-SM-like Higgs around 125 GeV, and the lepton-flavor-violating coupling is sensitive to another heavy neutral Higgs mass. In addition, if the $μτ$ excess is from $H$ around 125 GeV, the experimental data of the heavy Higgs decaying into $μτ$ favor $m_A>230$ GeV for a relatively large $H\bar{t}t$ coupling.

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arXiv2017

Two-Higgs-doublet model of type-II confronted with the LHC run-I and run-II data

We examine the parameter space of two-Higgs-doublet model of type-II after imposing the relevant theoretical and experimental constraints from the precision electroweak data, $B$-meson decays, the LHC run-I and run-II data. We find that the searches for Higgs via the $τ\barτ,~WW,~ZZ,γγ,~hh,~hZ,~HZ,~AZ$ channels can give strong constraints on the CP-odd Higgs $A$ and heavy CP-even Higgs $H$, and the parameter space excluded by each channel is respectively carved out in detail. The surviving samples are discussed in two different of regions: (i) In the SM-like coupling region of the 125 GeV Higgs, $m_A$ is allowed to be as low as 350 GeV, and $\tanβ$ is imposed a strong upper limit. $m_H$ is allowed to be as low as 200 GeV for the proper $\tanβ$, $\sin(β-α)$ and $m_A$, but is required to be larger than 300 GeV for $m_A=700$ GeV. (ii) In the wrong sign Yukawa coupling of the 125 GeV, $\tanβ$ and $\sin(β-α)$ can be imposed upper limits by $b\bar{b}\to A/H\to τ\barτ$ channel and lower limits by the $A\to hZ$ channel. $m_A$ and $m_H$ are respectively allowed to be as low as 60 GeV and 200 GeV, but 320 GeV $< m_A<$ 500 GeV is excluded for $m_H=$ 700 GeV.

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arXiv2016

Explaining 750 GeV diphoton excess from top/bottom partner cascade decay in two-Higgs-doublet model extension

In this paper, we interpret the 750 GeV diphoton excess in the Zee-Babu extension of the two-Higgs-doublet model by introducing a top partner ($T$)/bottom partner ($B$). In the alignment limit, the 750 GeV resonance is identified as the heavy CP-even Higgs boson ($H$), which can be sizably produced via the QCD process $pp \to T\bar{T}$ or $pp \to B\bar{B}$ followed by the decay $T\to Ht$ or $B \to Hb$. The diphoton decay rate of $H$ is greatly enhanced by the charged singlet scalars predicted in the Zee-Babu extension and the total width of $H$ can be as large as 7 GeV. Under the current LHC constraints, we scan the parameter space and find that such an extension can account for the observed diphoton excess.

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arXiv2016

Implication of the 750 GeV diphoton resonance on two-Higgs-doublet model and its extensions with Higgs field

We examine the implication of the 750 GeV diphoton resonance on the two-Higgs-doublet model imposing various theoretical and experimental constraints. The production rate of two-Higgs-doublet model is smaller than the cross section observed at the LHC by two order magnitude. In order to accommodate the 750 GeV diphoton resonance, we extend the two-Higgs-doublet model by introducing additional Higgs fields, and focus on two different extensions, an inert complex Higgs triplet and a real scalar septuplet. With the 125 GeV Higgs being agreement with the observed data, the production rate for the 750 GeV diphoton resonance can be enhanced to 0.6 fb for the former and 4.5 fb for the latter. The results of the latter are well consistent with the 750 GeV diphoton excess at the LHC.

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arXiv2016

An extension of two-Higgs-doublet model and the excesses of 750 GeV diphoton, muon g-2 and $h\toμτ$

In this paper we simultaneously explain the excesses of the 750 GeV diphoton, muon g-2 and $h\to μτ$ in an extension of the two-Higgs-doublet model (2HDM) with additional vector-like fermions and a CP-odd scalar singlet ($P$) which is identified as the 750 GeV resonance. This 750 GeV resonance has a mixing with the CP-odd scalar ($A$) in 2HDM, which leads to a coupling between $P$ and the SM particles as well as a coupling between $A$ and the vector-like fermions. Such a mixing and couplings are strongly constrained by $τ\toμγ$, muon g-2 and the 750 GeV diphoton data. We scan over the parameter space and find that such an extension can simultaneously account for the observed excesses of 750 GeV diphoton, muon g-2 and $h\to μτ$. The 750 GeV resonance decays in exotic modes, such as $P\to hA$, $P\to HZ$, $P\to HA$ and $P\to W^\pm H^\mp$, and its width can be dozens of GeV and is sensitive to the mixing angle.

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arXiv2015

Higgs pair signal enhanced in the 2HDM with two degenerate 125 GeV Higgs bosons

We discuss a scenario of the type-II 2HDM in which the $b\bar{b}γγ$ rate of the Higgs pair production is enhanced due to the two nearly degenerate 125 GeV Higgs bosons ($h$, $H$). Considering various theoretical and experimental constraints, we figure out the allowed ranges of the trilinear couplings of these two Higgs bosons and calculate the signal rate of $b\bar{b}γγ$ from the productions of Higgs pairs ($hh$, $hH$, $HH$) at the LHC. We find that in the allowed parameter space some trilinear Higgs couplings can be larger than the SM value by an order and the production rate of $b\bar{b}γγ$ can be greatly enhanced. We also consider a "decoupling" benchmark point where the light CP-even Higgs has a SM-like cubic self-coupling while other trilinear couplings are very small. With a detailed simulation on the $b\bar{b}γγ$ signal and backgrounds, we find that in such a "decoupling" scenario the $hh$ and $hH$ channels can jointly enhance the statistical significance to 5$σ$ at 14 TeV LHC with an integrated luminosity of 3000 fb$^{-1}$.

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arXiv2015

A light pseudoscalar of 2HDM confronted with muon g-2 and experimental constraints

A light pseudoscalar of the lepton-specific 2HDM can enhance the muon g-2, but suffer from various constraints easily, such as the 125.5 GeV Higgs signals, non-observation of additional Higgs at the collider and even $B_s\to μ^+μ^-$. In this paper, we take the light CP-even Higgs as the 125.5 GeV Higgs, and examine the implications of those observables on a pseudoscalar with the mass below the half of 125.5 GeV. Also the other relevant theoretical and experimental constraints are considered. We find that the pseudoscalar can be allowed to be as low as 10 GeV, but the corresponding $\tanβ$, $\sin(β-α)$ and the mass of charged Higgs are strongly constrained. In addition, the surviving samples favor the wrong-sign Yukawa coupling region, namely that the 125.5 GeV Higgs couplings to leptons have opposite sign to the couplings to gauge bosons and quarks.

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arXiv2015

A simplified 2HDM with a scalar dark matter and the galactic center gamma-ray excess

Due to the strong constrain from the LUX experiment, the scalar portal dark matter can not generally explain a gamma-ray excess in the galactic center by the annihilation of dark matter into $b\bar{b}$. With the motivation of eliminating the tension, we add a scalar dark matter to the aligned two-Higgs-doublet model, and focus on a simplified scenario, which has two main characteristics: (i) The heavy CP-even Higgs is the discovered 125 GeV Higgs boson, which has the same couplings to the gauge bosons and fermions as the SM Higgs. (ii) Only the light CP-even Higgs mediates the dark matter interactions with SM particles, which has no couplings to $WW$ and $ZZ$, but the independent couplings to the up-type quarks, down-type quarks and charged leptons. We find that the tension between $<σv>_{SS\to b\bar{b}}$ and the constraint from LUX induced by the scalar portal dark matter can go away for the isospin-violating dark matter-nucleon coupling with $-1.0< f^n/f^p<0.7$, and the constraints from the Higgs search experiments and the relic density of Planck are also satisfied.

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