arXiv subjects

Dongqi Yu

Publications and source records attributed to Dongqi Yu.

6 recordsLinked to original sources

arXiv2004

Neutral top-pion and the rare top decays $t\to c l_{i} l_{j}$

We study the rare top decays $t\to c l_{i} l_{j}(l=τ,μ,or e)$ in the framework of topcolor-assisted technicolor($TC2$) models. We find that the neutral top-pion $π_{t}^{0}$ can produce significant contributions to these processes via the flavor changing couplings $π_{t}^{0} \bar{t} c$ and $π_{t}^{0} l_{i} l_{j}$. For the $π_{t}^{0}$ mass $m_{π_{t}}=150 GeV$ and the parameter $ε=0.08$, the branching ratio $Br$(t$\to c ττ)$ can reach $7.1\times10^{-7}$. Taking into account the constraints of the present experimental limit of the process $μ\to e γ$ on the free parameters of $TC2$ models, we find that the value of $Br$($t\to c τμ$)$\approx$$Br$($t\to c τe$) is in the range of 1.8$\times10^{-10}\sim1.7\times10^{-8}$.

hep-ph↗

arXiv2004

Neutral top-pion and $tγ(z)$ production at the HERA and THERA colliders

In the context of top-color assisted technicolor ($TC2$) models, we calculate the contributions of the neutral top-pion $ π_{t}^{0}$ to $tγ$ and $tz$ production via the processes $ ep\to γc \to tγ$ and $ ep\to γc \to tz$ at the $HERA$ and $THERA$ colliders. Our results show that the cross sections $σ_{tγ}(s)$ and $σ_{tz}(s)$ are very small at the $HERA$ collider with $\sqrt{s}=320GeV $. However, in most of the parameter space, $σ_{tγ}(s)$ or $σ_{tz}(s)$ is in the range of about $0.1pb \sim 1 pb$ at the $THERA$ collider with $\sqrt{s}=1000GeV$.

hep-ph↗

arXiv2004

Detecting the non-universal gauge boson $Z^{'}$ at high-energy $e^{+}e^{-}$ collider

In the context of topcolor-assisted techicolor($TC2$) models, we investigate the feasibility of detecting the non-universal gauge boson $Z^{'}$ in the future high-energy linear $e^{+}e^{-}$ collider($LC$) experiments by performing $χ^{2}$ analysis via studying its virtual effects on the processes $e^{+}e^{-}\to f\bar{f}$ with $f=τ$, $μ$, b, and c. We find that the non-universal gauge boson $Z^{'}$ is most sensitive to the process $e^{+}e^{-}\to τ\barτ$. Discovery limits of the $Z^{'}$ mass $M_{Z^{'}}$ can be enhanced by the suitably polarized beams. If we assume that polarization of electron beam and positron beam are 80% and 60%, the $LC$ experiment with $\sqrt{s}=500GeV$ and $£_{int}=340fb^{-1}$ can explore $M_{Z^{'}}$ up to 8$TeV$ for the coupling parameter $K_{1}\leq$0.8 at 95% $CL$.

hep-ph↗

arXiv2004

Neutral top-pion and lepton flavor violating processes

In the context of topcolor-assisted techicolor(TC2) models, we study the contributions of the neutral top-pion $π^{0}_{t}$ to the lepton flavor violating(LFV) processes $l_{i}\to l_{j}γ$ and $l_{i}\to l_{j}l_{k}l_{l}$. We find that the present experimental bound on $μ\to eγ$ gives severe constraints on the free parameters of $TC2$ models. Taking into account these constraints, we consider the processes $l_{i}\to l_{j}l_{k}l_{l}$ generated by top-pion exchange at the tree-level and the one loop level, and obtain $Br(μ\to 3e)\simeq 2.87\times 10^{-14}$, $1.1\times 10^{-15}\leq Br(τ\to 3e)\simeq Br(τ\to 2eμ)\leq 4.4 \times 10^{-15} $, $3.1\times 10^{-15} \leq Br(τ\to 2μe)\simeq Br(τ\to 3μ)\leq 1.5 \times 10^{-14}$ in most of the parameter space.

hep-ph↗

arXiv2003

Littlest Higgs model and associated ZH production at high energy $e^{+}e^{-}$ collider

In the context of the littlest Higgs (LH) model, we consider the Higgs strahlung process $e^{+}e^{-}\to ZH $. We find that the correction effects on this process mainly come from the heavy photon $B'$. If we take the mixing angle parameter $c$ in the range of 0.75 - 1, the contributions of the heavy gauge boson $W_{3}'$ is larger than 6%. In most of the parameter space, the deviation of the total production cross section $σ^{tot}$ from its SM value is larger than 5%, which may be detected in the future high energy $e^{+}e^{-}$ collider (LC) experiments. The future LC experiments could test the LH model by measuring the cross section of the process $e^{+}e^{-}\to ZH $.

hep-ph↗

arXiv2003

Detecting the neutral top-pion at future muon colliders

The signals of the neutral top-pion $π^{0}_{t}$ at the first muon collider (FMC) are discussed by calculating its contributions to the processes $μ^{+}μ^{-}\longrightarrow b\bar{b}$ and $μ^{+}μ^{-}\longrightarrow \bar{t}c$. We find that the contributions to the process $μ^{+}μ^{-}\longrightarrow b\bar{b}$ are very small and the ratio of signal over square root of the background ($S/\sqrt{B})$ is smaller than 0.2. However, in most of the parameter space, the $π^{0}_{t}$ can generate 36 and up to 649 observable $\bar{t}c$ events at the FMC. The signals of the neutral top-pion $π^{0}_{t}$ may be detected via the process $μ^{+}μ^{-}\longrightarrow \bar{t}c$ at the FMC.

hep-ph↗