arXiv subjects

Kai-Ge Kang

Publications and source records attributed to Kai-Ge Kang.

4 recordsLinked to original sources

arXiv2026

Studies of low energy $l+p\to l+p+γ$ process in covariant chiral perturbation theory

This study presents a tree-level calculation of the scattering amplitude for the $lp\to lpγ$ (with a hard photon) process within the framework of Chiral Perturbation Theory. Our calculations, based on the $O(p^2)$ and $O(p^3)$ nucleon-pion Lagrangians, aim to provide a theoretical prediction for the differential cross-section. The result shows that explicit inclusion of the nonzero lepton mass significantly influences the low energy differential cross section for $μp\to μp γ$ process. The kinematic region of the present experimental data is beyond the validity domain of the $χ$PT and is therefore not suitable for determining the low-energy constants (LECs). By comparing our results with future experimental data, we expect to determine the values of the LECs as a further test of $χ$PT as an effective low-energy theory of QCD. The process is of significant interest as it can help to determine the generalized polarizabilities of the nucleon.

hep-ph↗

arXiv2025

Studies on quark-mass dependence of the $N^*(920)$ pole from $πN$ $χ$PT amplitudes

The quark-mass dependence of the $N^*(920)$ pole is analyzed using $K$-matrix method, with the $πN$ scattering amplitude calculated up to $O(p^3)$ order in chiral perturbation theory. As the quark mass increases, the $N^*(920)$ pole gradually approaches the real axis in the complex $w$-plane (where $w=\sqrt{s}$). Eventually, in the $O(p^2)$ case, it crosses the $u$-cut on the real axis and enters the adjacent Riemann sheet when the pion mass reaches $526~{\rm MeV}$. At order $O(p^3)$, the rate at which it approaches the real axis slows down; however, we argue that it will ultimately cross the $u$-cut and enter the adjacent Riemann sheet as well. Additionally, the trajectory of the $N^*(920)$ pole is in qualitative agreement with the results from the linear $σ$ model calculation.

hep-ph↗

arXiv2025

Double pion photoproduction off nucleons in covariant chiral perturbation theory

The double pion photoproduction off nucleons near threshold is analyzed in a covariant baryon chiral perturbation theory up to next to leading order, where the $Δ(1232)$, $N^*(1400)$ and $ρ(770)$ resonances are included as explicit degrees of freedom. For the process $γp \to π^+ π^0 n$, the chiral results of total cross sections, invariant-mass distributions and beam-helicity asymmetry are in good agreement with the experimental data within uncertainties. For the process $γp \to π^0 π^0 p$, the prediction of total cross section deviates from the existing experimental data. Once the final-state interaction of $ππ$ in the isoscalar S-wave channel is taken into account, a good description of the cross section is achieved. The effect of the Roper resonance always turns out be negligible, and hence can be thrown away in future study of this process.

hep-ph↗

arXiv2023

The $X(6900)$ peak could be a molecular state

The analyses of the LHCb data on $X(6900)$ found in di-$J/ψ$ and $J/ψψ(3686)$ systems are performed using a momentum-dependent {Flatté}-like parameterization. The use of the pole counting rule and spectral density function sum rule give consistent conclusions that $X(6900)$ may not be a molecule of $J/ψψ(3686)$. Nevertheless it is still possible that $X(6900)$ be a molecule of higher states, such as $J/ψψ(3770)$, $χ_{c0}χ_{c2}$, etc.

hep-ph↗