arXiv subjects

Tai-Fu Feng

Publications and source records attributed to Tai-Fu Feng.

At least 109 records · Page 6Linked to original sources

arXiv2019

The QCD NLO fragmentation functions for $c$ or $\bar{b}$ quark to $B_c$ or $B_c^*$ meson and their application

The fragmentation functions for $c$ or $\bar{b}$ quark to $B_c$ or $B_c^*$ meson are derived up to QCD next-to-leading order (NLO). They are further computed numerically and presented in figures precisely. In order to reach a higher accuracy, we have also tried properly to apply them to estimating the $B_c$ and $B_c^*$ production at a $Z$-factory (an $e^+e^-$ collider running at the energy of the $Z$-boson pole).

hep-ph↗

arXiv2019

The two-loop corrections to lepton MDMs and EDMs in the EBLMSSM

Extending BLMSSM with exotic Higgs superfields $(Φ_{NL},φ_{NL})$ and superfields ($Y,Y^\prime$), one obtains the new model called as EBLMSSM, where exotic leptons are heavy and have tree level couplings with SM lepton. In this model, some new parameters with CP-violating phases are considered, so there are new contributions to lepton anomalous magnetic dipole moments (MDMs) and electric dipole moments (EDMs). Therefore, we study the one-loop, two-loop Barr-Zee and two-loop Rainbow type corrections to lepton MDMs and EDMs in the EBLMSSM. Considering the constraints from the lightest CP-even Higgs mass and decays, we calculate the corresponding numerical results. In our used parameter space, the new physics contributions to lepton MDMs are large, which can remedy the deviation between the SM prediction and experimental result well. New introduced CP-violating phases also affect the lepton EDMs in a certain degree.

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arXiv2019

Study of dark matter in the extended BLMSSM

There are strong evidences for existence of dark matter in some experiments at present. However, the question is that we do not have a reasonable explanation for dark matter in the framework of the Standard Model(SM) of particle physics. It is necessary to extend the SM in order to explain the dark matter. According to the current possible existence conditions of dark matter, we choose $χ^0_L$ and $\tilde{Y}$ as candidates for dark matter in the EBLMSSM. We study the dominant annihilation processes in detail, including $\barχ^0_Lχ^0_L(\bar{\tilde{Y}}\tilde{Y})\rightarrow \bar{l}^Il^I$ and $\barχ^0_Lχ^0_L(\bar{\tilde{Y}}\tilde{Y})\rightarrow \barν^Iν^I$. And we calculate their annihilation cross section $σ$ and relic density $Ω_D h^2$. Then we analyze the limitations of dark matter relic density on the parameters of the EBLMSSM.

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arXiv2019

The system of partial differential equations for the $C_{_0}$ function

We present an approach to analyze the scalar integrals of any Feynman diagrams in detail here. This method not only completely recovers some well-known results in the literature, but also produces some brand new results on the $C_{_0}$ function. The approach can be employed to evaluate the coefficient of arbitrary power of $\varepsilon$ in the expansion of a scalar integral, where $D=4-2\varepsilon$ denotes the time-space dimension.

hep-th↗

arXiv2019

Charged lepton flavor violation in extended BLMSSM

Within the extended BLMSSM, the exotic Higgs superfields $(Φ_{NL},φ_{NL})$ are added to make the exotic leptons heavy, and the superfields ($Y$,$Y^\prime$) are also introduced to make exotic leptons unstable. This new model is named as the EBLMSSM. We study some charged lepton flavor violating (CLFV) processes in detail in the EBLMSSM, including $l_j\rightarrow l_i γ$, muon conversion to electron in nuclei, the $τ$ decays and $h^0\rightarrow l_i l_j$. Being different from BLMSSM, some particles are redefined in this new model, such as slepton, sneutrino, exotic lepton (neutrino), exotic slepton (sneutrino) and lepton neutralino. We also introduce the mass matrices of superfields $Y$ and spinor $\tilde{Y}$ in the EBLMSSM. All of these lead to new contributions to the CLFV processes. In the suitable parameter space, we obtain the reasonable numerical results. The results of this work will encourage physicists to explore new physics beyond the SM.

hep-ph↗

arXiv2019

Lepton-flavor violation and two loop electroweak corrections to $(g-2)_μ$ in the B-L symmetry SSM

Charged lepton flavor violating processes are forbidden in the standard model (SM), hence the observation of charged lepton flavor transitions would represent a clear signal of new physics beyond the standard Model. In this work, we investigate some lepton flavor violating processes in the minimal supersymmetric extension of the SM with local $B-L$ gauge symmetry (B-LSSM). And including the corrections from some two loop diagrams to the anomalous dipole moments (MDM) of muon, we discuss the corresponding constraint on the relevant parameter space of the model. Considering the constraints from updated experimental data, the numerical results show that, new contributions in the B-LSSM enhance the MSSM predictions on the rates of $l_j-l_i$ transitions about one order of magnitude, and also enhance the MSSM prediction on the muon MDM. In addition, two loop electroweak corrections can make important contributions to the muon MDM in the B-LSSM.

hep-ph↗

arXiv2018

Corrections to $R_{D}$ and $R_{D^{*}}$ in the BLMSSM

The deviation of the measurement of $R_{D}$ ($R_{D^{*}}$) from the Standard Model (SM) expectation is $2.3σ$ ($3.1σ$). $R_{D}$ ($R_{D^{*}}$) is the ratio of the branching fraction of $\overline{B} \rightarrow Dτ\overlineν_τ$ ($\overline{B} \rightarrow D^{*}τ\overlineν_τ$) to that of $\overline{B} \rightarrow Dl\overlineν_{l}$ ($\overline{B} \rightarrow D^{*}l\overlineν_{l}$), where $l = e$ or $μ$. This anomaly may imply the existence of new physics (NP). In this paper, we restudy this problem in the supersymmetric extension of the Standard Model with local gauged baryon and lepton numbers (BLMSSM), and give one-loop corrections to $R_{D}$ ($R_{D^{*}}$).

hep-ph↗

arXiv2018

Muon conversion to electron in nuclei within the BLMSSM

In a supersymmetric extension of the standard model with local gauged baryon and lepton numbers (BLMSSM), there are new sources for lepton flavor violation, because the right-handed neutrinos, new gauginos and Higgs are introduced. We investigate muon conversion to electron in nuclei within the BLMSSM in detail. The numerical results indicate that the $μ\rightarrow e $ conversion rates in nuclei within the BLMSSM can reach the experimental upper bound, which may be detected in the future experiments.

hep-ph↗

arXiv2018

Two loop electroweak corrections to $\bar B\rightarrow X_sγ$ and $B_s^0\rightarrow μ^+μ^-$ in the B-LSSM

The rare decays $\bar B\rightarrow X_sγ$ and $B_s^0\rightarrow μ^+μ^-$ are important to research new physics beyond standard model. In this work, we investigate two loop electroweak corrections to $\bar B\rightarrow X_sγ$ and $B_s^0\rightarrow μ^+μ^-$ in the minimal supersymmetric extension of the SM with local $B-L$ gauge symmetry (B-LSSM), under a minimal flavor violating assumption for the soft breaking terms. In this framework, new particles and new definition of squarks can affect the theoretical predictions of these two processes, with respect to the MSSM. Considering the constraints from updated experimental data, the numerical results show that the B-LSSM can fit the experimental data for the branching ratios of $\bar B\rightarrow X_sγ$ and $B_s^0\rightarrow μ^+μ^-$. The results of the rare decays also further constrain the parameter space of the B-LSSM.

hep-ph↗

arXiv2018

Top quark decays with flavor violation in the B-LSSM

The decays of top quark $t\rightarrow cγ,\;t\rightarrow cg,\;t\rightarrow cZ,\;t\rightarrow ch$ are extremely rare processes in the standard model (SM). The predictions on the corresponding branching ratios in the SM are too small to be detected in the future, hence any measurable signal for the processes at the LHC is a smoking gun for new physics. In the extension of minimal supersymmetric standard model with an additional local $U(1)_{B-L}$ gauge symmetry (B-LSSM), new gauge interaction and new flavor changing interaction affect the theoretical evaluations on corresponding branching ratios of those processes. In this work, we analyze those processes in the B-LSSM, under a minimal flavor violating assumption for the soft breaking terms. Considering the constraints from updated experimental data, the numerical results imply $Br(t\rightarrow cγ)\sim5\times10^{-7}$, $Br(t\rightarrow cg)\sim2\times10^{-6}$, $Br(t\rightarrow cZ)\sim4\times10^{-7}$ and $Br(t\rightarrow ch)\sim3\times10^{-9}$ in our chosen parameter space. Simultaneously, new gauge coupling constants $g_{_B},\;g_{_{YB}}$ in the B-LSSM can also affect the numerical results of $Br(t\rightarrow cγ,\;cg,\;cZ,\;ch)$.

hep-ph↗

arXiv2018

Higgs boson decay $h^0\rightarrow m_VZ$ in the BLMSSM

In the framework of BLMSSM, the Higgs decays $h^0\rightarrow Zγ$ and $h^0\rightarrow m_VZ$ are studied where $m_V$ represents a vector meson($ρ, ω, ϕ, J/ψ, Υ$ etc.). Corrections to the CP-even and CP-odd $h^0γZ$ couplings occur via loop diagrams where new particles are involved. Actually both of them obviously influence the decay rates of $h^0\rightarrow Zγ$ and $h^0\rightarrow m_VZ$. Concretely, our obtained numerical result shows that the decay width of $h^0\rightarrow Zγ$ can be 1.3 times larger than the prediction of the Standard Model(SM). For the light mesons ($ρ,ω$), the corrections to $h^0\rightarrow m_VZ$ are within $15\%\sim 20\%$ still consistent with the SM results. The results of this work would encourage a detection on $h^0\rightarrow Zγ$ at LHC for exploring new physics beyond SM.

hep-ph↗

arXiv2018

Neutrino masses in the minimal gauged $(B-L)$ supersymmetry

We present the radiative corrections to neutrino masses in a minimal supersymmetric extension of the standard model with local $U(1)_{B-L}$ symmetry. At tree level, three tiny active neutrinos and two nearly massless sterile neutrinos can be obtained through the seesaw mechanism. Considering the one-loop corrections to the neutrino masses, the numerical results indicate that two sterile neutrinos obtain ${\rm KeV}$ masses and the small active-sterile neutrino mixing angles. The lighter sterile neutrino is a very interesting dark matter candidate in cosmology. Meanwhile the active neutrinos mixing angles and mass squared differences agree with present experimental data.

hep-ph↗

arXiv2018

The extended BLMSSM with a 125 GeV Higgs boson and dark matter

To extend the BLMSSM, we not only add exotic Higgs superfields $(Φ_{NL},φ_{NL})$ to make the exotic lepton heavy, but also introduce the superfields($Y$,$Y^\prime$) having couplings with lepton and exotic lepton at tree level. The obtained model is called as EBLMSSM, which has difference from BLMSSM especially for the exotic slepton(lepton) and exotic sneutrino(neutrino). We deduce the mass matrices and the needed couplings in this model. To confine the parameter space, the Higgs boson mass $m_{h^0}$ and the processes $h^0\rightarrow γγ$, $h^0\rightarrow VV, V=(Z,W)$ are studied in the EBLMSSM. With the assumed parameter space, we obtain reasonable numerical results according to data on Higgs from ATLAS and CMS. As a cold dark mater candidate, the relic density for the lightest mass eigenstate of $Y$ and $Y'$ mixing is also studied.

hep-ph↗

arXiv2018

Evaluating Feynman integrals by the hypergeometry

The hypergeometric function method naturally provides the analytic expressions of scalar integrals from concerned Feynman diagrams in some connected regions of independent kinematic variables, also presents the systems of homogeneous linear partial differential equations satisfied by the corresponding scalar integrals. Taking examples of the one-loop $B_{_0}$ and massless $C_{_0}$ functions, as well as the scalar integrals of two-loop vacuum and sunset diagrams, we verify our expressions coinciding with the well-known results of literatures. Based on the multiple hypergeometric functions of independent kinematic variables, the systems of homogeneous linear partial differential equations satisfied by the mentioned scalar integrals are established. Using the calculus of variations, one recognizes the system of linear partial differential equations as stationary conditions of a functional under some given restrictions, which is the cornerstone to perform the continuation of the scalar integrals to whole kinematic domains numerically with the finite element methods. In principle this method can be used to evaluate the scalar integrals of any Feynman diagrams.

hep-ph↗

arXiv2017

Search for charged lepton flavor violation of vector mesons in BLMSSM model

We analyze the charged lepton flavor violating (CLFV) decays of vector mesons $V\rightarrow l_i^{\pm}l_j^{\mp}$ with $V\in\{ϕ, J/Ψ, Υ, ρ^0, ω\}$ in BLMSSM model. This new model is introduced as an supersymmetric extension of Standard Model (SM), where local gauged baryon number B and lepton number L are considered. The numerical results indicate BLMSSM model can produce significant contributions to such two-body CLFV decays. And the branching ratios for these CLFV processes can easily reach the present experimental upper bounds. Therefore, searching for CLFV processes of vector mesons may be an effective channels to study new physics.

hep-ph↗

arXiv2017

The NLO QCD corrections to $B_c$($B_c^*$) production around $Z$ pole at an $e^+e^-$ collider

Production of the $B_c$ and $B_c^*$ mesons at $Z$-factory (an $e^+e^-$ collider running at energies around $Z$ pole) is calculated up-to the next-to-leading order (NLO) QCD corrections. The results show that the dependence of the total cross sections on the renormalization scale $μ$ is reduced by the corrections, and the NLO corrections enhance the production cross section by $52\%$($33\%$) when the renormalization scale is taken at $μ=2m_b$. For experimental observations of the $B_c$ and $B_c^*$ mesons, the differential cross sections for the production are also analyzed up-to the NLO accuracy.

hep-ph↗

arXiv2017

$Z\rightarrow l_i^{\pm}l_j^{\mp}$ processes in the BLMSSM

In a supersymmetric extension of the Standard Model(SM) where baryon and lepton numbers are local gauge symmetries (BLMSSM), we investigate the charged lepton flavor violating (CLFV) processes $Z\rightarrow l_i^{\pm}l_j^{\mp}$ after introducing the new gauginos and the right-handed neutrinos. In this model, the branching ratios of $Z\rightarrow l_i^{\pm}l_j^{\mp}$ are around ($10^{-8}\sim10^{-10}$), which approach the present experimental upper bounds. We hope that the branching ratios for these CLFV processes can be detected in the near future.

hep-ph↗

arXiv2017

Higgs boson mass corrections in the $μν$SSM with effective potential methods

To solve the $μ$ problem of the MSSM, the $μ$ from $ν$ Supersymmetric Standard Model ($μν$SSM) introduces three singlet right-handed neutrino superfields $\hatν_i^c$, which lead to the mixing of the neutral components of the Higgs doublets with the sneutrinos, producing a relatively large CP-even neutral scalar mass matrix. In this work, we analytically diagonalize the CP-even neutral scalar mass matrix and analyze in detail how the mixing impacts the lightest Higgs boson mass. We also give an approximate expression for the lightest Higgs boson mass. Simultaneously, we consider the radiative corrections to the Higgs boson masses with effective potential methods.

hep-ph↗