arXiv subjects

Khanchai Khosonthongkee

Publications and source records attributed to Khanchai Khosonthongkee.

3 recordsLinked to original sources

arXiv2025

Radiative decay of $χ_{c1}$ states in effective Lagrangian approach

The $χ_{c1}(3872)$ state, first observed by the Belle collaboration with its quantum numbers identified as $J^{PC} = 1^{++}$, has been the subject of extensive research due to its intriguing properties. Several theoretical interpretations have been proposed to explain its unique characteristics, including the $χ_{c1}(2P)$ assignment, a molecular $\bar{D}^{*}D/\bar{D}D^{*}$ configuration, a coupled-channel framework incorporating $c\bar{c}$ and di-meson degrees of freedom, and the compact tetraquark hypothesis. However, challenges remain in reconciling its mass coincidence with the threshold and the observed isospin violation within both the pure $c\bar{c}$ and compact tetraquark models. In this study, we examine the radiative decays of the $χ_{c1}(1P)$ and $χ_{c1}(3872)$ states in an effective field theory framework, incorporating triangle loops of $D$ and $D^{*}$ mesons. The model parameters are calibrated based on the observed branching fraction of the radiative decay mode $χ_{c1}(1P) \to J/ψγ$. Utilizing these fixed parameters, we predict the branching fractions $R_{χ_{c1}(3872) \to J/ψγ} \sim 10^{-1}$ and $R_{χ_{c1}(3872) \to ψ(2S) γ} \sim 10^{-2}$, and the relative fraction $\mathcal{R}_{Ψγ} \approx 0.109$. The work supports the argument that the $χ_{c1}(3872)$ is unlikely a $c\bar{c}$ state.

hep-ph↗

arXiv2025

Sterile-neutrino search based on 259 days of KATRIN data

Neutrinos are the most abundant fundamental matter particles in the Universe and play a crucial role in particle physics and cosmology. Neutrino oscillation, discovered about 25 years ago, reveals that the three known species mix with each other. Anomalous results from reactor and radioactive-source experiments suggest a possible fourth neutrino state, the sterile neutrino, which does not interact via the weak force. The KATRIN experiment, primarily designed to measure the neutrino mass via tritium $β$-decay, also searches for sterile neutrinos suggested by these anomalies. A sterile-neutrino signal would appear as a distortion in the $β$-decay energy spectrum, characterized by a discontinuity in curvature (kink) related to the sterile-neutrino mass. This signature, which depends only on the shape of the spectrum rather than its absolute normalization, offers a robust, complementary approach to reactor experiments. KATRIN examined the energy spectrum of 36 million tritium $β$-decay electrons recorded in 259 measurement days within the last 40 electronvolt below the endpoint. The results exclude a substantial part of the parameter space suggested by the gallium anomaly and challenge the Neutrino-4 claim. Together with other neutrino-disappearance experiments, KATRIN probes sterile-to-active mass splittings from a fraction of an electron-volt squared to several hundred electron-volts squared, excluding light sterile neutrinos with mixing angles above a few percent.

hep-ex↗

arXiv2024

Mass spectrum of $1^{--}$ heavy quarkonium

We calculate the masses and leptonic decay widths of the bottomonium $b\bar b$ and charmonium $c\bar c$ states in a constituent quark model where the Cornell-like potential and spin-dependent interaction are employed, with all model parameters predetermined by studying ground and first radial excited states of S- and P-wave heavy quarkonium mesons. By comparing the theoretical predictions for $J^{PC}=1^{--}$ quarkonium states with experimental data and considering possible mixtures of $nS$ and $(n-1)D$ states, we provide tentative assignments for all observed $J^{PC}=1^{--}$ heavy quarkonia. The work suggests that the $Υ$(10860) and $Υ$(11020) are $b\bar b$ $5S-4D$ mixture states, and the $ψ$(4360) and $ψ$(4415) are largely $4S$ and $3D$ $c\bar c$ states respectively. The $ψ$(4260) may not be accommodated with the conventional meson picture in the present work.

hep-ph↗