arXiv subjects

Sang Quang Dinh

Publications and source records attributed to Sang Quang Dinh.

4 recordsLinked to original sources

arXiv2026

Vectorlike lepton imprints at lepton $g-2$ measurements and $e^+e^-$ colliders

A fermion can be chiral or vectorlike with respect to a given symmetry, depending on its coupling to the corresponding gauge boson. Vectorlike fermions have a distinct property that their left-handed and right-handed components behave in the same way under the gauge symmetry. In this paper, we investigate an extension of the standard model with an $SU(2)$ doublet of vectorlike leptons and two complex scalars. The new physics effects on the lepton anomalous magnetic moment, as well as the electron and muon pair production processes at $e^+e^-$ colliders are analyzed. Taking into account the updated measurement results of the electron and muon $g-2$, the LEP and the LHC data, the viable parameter space of the model is identified. We also examine the prospect of testing the model using $μ^+μ^-$ signals from electron-position annihilation at the Future Circular Collider (FCC-ee). The analysis shows that the FCC-ee will be able to exclude a significant part of the parameter space, pinpointing exiguous viable regions to be tested in the future due to its high precision.

hep-ph↗

arXiv2025

Expected statistical uncertainties at future $e^+e^-$ colliders

In future colliders, the frontiers of luminosity and energy are extended to explore the physics of elementary particles at extremely high precision, and to discover new phenomena suggested from current experimental anomalies. In this letter, we present a simple method to estimate the expected statistical uncertainties of scattering cross sections at future colliders using their conceptual design reports. In particular, the expected statistical uncertainties of muon pair production cross section at the Future Circular Collider (FCC-ee) and the Circular Electron-Positron Collider (CEPC) are calculated. The results can be used to set a goal for systematic uncertainty improvement, to determine the standard model parameters accurately, and to identify the viable parameter space of new physics models.

hep-ph↗

arXiv2023

A model with vectorlike fermions and $U(1)_X$ symmetry: CKM unitarity, $b \rightarrow s$ transitions, and prospect at Belle II

The updated analysis of the LHCb Collaboration on the lepton flavor violation suggests that the new physics should couple to muons and electrons with comparable magnitudes, resulting in the anomalies in both rare decay channels, $b \rightarrow s μ^+ μ^-$ and $b \rightarrow s e^+ e^-$. Meanwhile, the recent result of the Muon $g-2$ experiment with higher precision has increased the existing tension with the standard model prediction. In this paper, we consider an extension of the standard model with a new sector consisting of vectorlike fermions and two scalar charged under an extra $U(1)_X$ gauge symmetry. The exotic Yukawa interactions in the this model lead to the quark mixing responsible for the additional contributions to the flavor changing neutral currents in $B$-meson decays, and solve the muon $g-2$ discrepancy. We derive the analytic expression of the new physics contributions to the Wilson coefficient $C_7$ in the effective Hamiltonian, and point out that the CKM unitarity violation can be explained within this context. By calculating the branching ratio of the inclusive radiative $B$ decay, the impact of current experimental data of the $b \rightarrow s γ$ transition on the model and the future prospect at the Belle II experiment are investigated. Taking into account the current data on the muon anomalous magnetic moment, the CKM unitarity violation, the constraints on the flavor observables relevant to the $b \rightarrow s$ transitions, the LHC searches for vectorlike quarks, and the perturbation limits of the couplings, the viable parameter regions of the model are identified.

hep-ph↗

arXiv2021

Muon $g-2$ and semileptonic $B$ decays in Bélanger-Delaunay-Westhoff model with gauge kinetic mixing

In the model proposed by Bélanger, Delaunay and Westhoff (BDW), a new sector consisted of vectorlike fermions and two complex scalars is charged under an extra Abelian symmetry $U(1)_X$. In this paper, we generalize the BDW model by introducing the kinetic mixing between the $U(1)_X$ and the standard model $U(1)_Y$ gauge fields. The new physics contributions to the muon anomalous magnetic moment and the Wilson coefficients $C_{9,10}^{(')}$ are obtained analytically. We have explored the free parameter space of the model, taking into account various constraints on the muon $g-2$ using recent data from the E989 experiment at Fermilab, the lepton universality violation in terms of $R_K$ and $R_{K^*}$, and the branching ratios of the semileptonic decays, $B^+ \rightarrow K^+ μ^+ μ^-$ and $B^0 \rightarrow K^{*0} μ^+ μ^-$, the LEP and LHC searches for sleptons and $Z'$ boson, as well as the perturbative requirement. The viable parameter regions of the model are identified. In the presence of the gauge kinetic mixing term, those regions are enlarged and significantly deformed in comparison to the case with vanishing kinetic mixing. In the near future, the E989 experiment with the projected sensitivity will be able to test significant parts of the currently allowed parameter regions.

hep-ph↗