arXiv subjects

Chao-Qiang Geng

Publications and source records attributed to Chao-Qiang Geng.

At least 19 recordsLinked to original sources

arXiv2026

Weak Decays of the $Λ_{b}$ Baryon in Light-Front Dynamics

We investigate the exclusive semileptonic and nonleptonic $Λ_{b} \to Λ_{c}(p)$ decays within the Standard Model by using the light-front quark model. To determine the behavior of the $Λ_{b} \to Λ_{c}(p)$ transition form factors, we employ the Bethe-Salpeter formalism in the timelike region, effectively accounting for both valence and nonvalence contributions. Using these form factors, including nonvalence contributions, we obtain branching fractions of $Λ_b \to Λ_c\,\ell\,\barν_{\ell}$, $Λ_b \to Λ_c\,τ\,\barν_τ$, $Λ_b \to p\,\ell\,\barν_{\ell}$ and $Λ_b \to p\,τ\,\barν_τ$~($\ell=e$ or $μ$) are found to be around $5.39\%$, $1.41\%$, $3.33\times 10^{-4}$ and $2.08\times 10^{-4}$, respectively, which are consistent with the experimental measurements. The ratios of $R^{\ellτ}(Λ_{c})=\frac{{\cal B}({Λ_b}\to {Λ_c}\,τ\,\barν_τ)} {{\cal B}({Λ_b}\to {Λ_c}\,\ell\,\barν_l)}$ and $R^{\ellτ}(p)=\frac{{\cal B}({Λ_b}\to p\,τ\,\barν_τ)} {{\cal B}({Λ_b}\to p\,\ell\,\barν_l)}$, are given by $0.261^{+0.097}_{-0.117}$ and $0.624^{+0.119}_{-0.129}$, respectively. The forward-backward asymmetries in the above semilepton decays are also examined. Our results indicate that, within the light-front framework, the nonvalence contributions to the asymmetries are negligible compared to the $β$-induced uncertainties. In addition, we calculate the branching ratios for the nonleptonic decays of $Λ_{b}\to Λ_{c}(p)\,M$ with $M$ being the pseudo scalar and vector mesons with the results found to be consistent with the current experimental data.

hep-ph↗

arXiv2026

Geodesic Focusing Conditions in $f(Q)$ Gravity

We study the geodesic deviation equation in symmetric teleparallel geometry (STG), where the relative acceleration is defined with respect to the STG connection. We analyze the modified Raychaudhuri equation along a geodesic congruence in $f(Q)$ gravity under the Weyl-type ansatz, together with an additional assumption under which the metric variation term along the congruence is converted into a disformation-induced acceleration term. In contrast to the purely geometrical Raychaudhuri equation obtained in general metric-affine settings, the equation derived here contains matter-source contributions through the trace equation of $f(Q)$ gravity. Different from general relativity, focusing in $f(Q)$ gravity is not automatic, and one must impose an appropriate focusing condition. We collect the model-dependent terms in the modified Raychaudhuri equation into an effective energy-momentum trace $T_{\text{eff}}$, so that the focusing condition can be written as the inequality $T\leq T_{\text{eff}}$, where $T$ is the trace of the matter energy-momentum tensor. We also apply this condition to the flat Friedmann--Lemaître--Robertson--Walker (FLRW) background. The homogeneous and isotropic STG connection admits three branches, each characterized by a single connection function $γ_i$, with $i=1,2,3$. Only the first branch with the coincident gauge is compatible with the Weyl-type ansatz. We obtain the resulting effective trace $T_{\text{eff}}=T$ for any form of $f(Q)$ satisfying $f_Q>0$ in the flat FLRW universe. The focusing inequality is saturated and imposes no additional constraint on the matter content.

gr-qc↗

arXiv2026

New $CP$ sum rules from exact $U$-spin degeneracy

We propose a new class of $CP$ sum rules in the $U$-spin limit, based on the observation that the weak phase in the Standard Model can be removed in the degenerate limit $m_d=m_s$. Unlike previous $U$-spin analyses formulated at the amplitude level, our sum rules are expressed directly in terms of decay widths. They apply to matched partial waves, spin observables, and angular moments and include nonpairwise cases beyond the usual single-insertion $d\leftrightarrow s$ relation.

hep-ph↗

arXiv2026

Strange Quark Electric Dipole Moment withTopological Anomalies

We introduce an anomaly-based framework to probe quark electric dipole moments in exclusive hadronic final states produced in $e^+e^-$ annihilation. Chern-Simons-induced anomalous couplings yield a clean T-odd asymmetry $A_T$ from interference between the Standard-Model amplitude and dipole-moment contributions. As an application, $γ^\ast\to K^+K^-π^0$ provides direct sensitivity to the strange-quark EDM $d_s$ in the chiral limit. The precision on $d_s$ can reach $\mathcal{O}(10^{-16})\,e\cdot\mathrm{cm}$ with existing CMD--3 data and $\mathcal{O}(10^{-18})\,e\cdot\mathrm{cm}$ using current $J/ψ$ samples at BESIII, improving the current direct constraint from hyperon EDM by two to three orders.

hep-ph↗

arXiv2026

Puzzles in charmed baryon semileptonic decays with $SU(3)_F$ flavor symmetry and lattice inputs

Recent measurements of charmed-baryon semileptonic decays signal large tensions between experiment and theory, including $SU(3)_F$ analyses and lattice-quantum chromodynamics simulations. Possible sources of the discrepancy include the experimental normalization mode $Ξ_c^0 \to Ξ^- π^+$. Using lattice-QCD inputs in an $SU(3)_F$ analysis including first-order symmetry breaking, we predict ${\cal B}( Ξ_c^+ \to Σ^0 \ell^+ ν_\ell ) / {\cal B}( Ξ_c^+ \to Ξ^0 \ell^+ ν_\ell )=(2.6\pm0.3)\%, $ and ${\cal B}( Ξ_c^+ \to Λ\ell^+ ν_\ell )/{\cal B}( Ξ_c^+ \to Ξ^0 \ell^+ ν_\ell )=(1.1\pm0.1)\%, $ with $\ell^+=(e^+,μ^+)$. These ratios provide normalization-independent tests and may help clarify the origin of the present tension.

hep-ph↗

arXiv2026

The Negative-$Σ\barΣ$ Angular-Parameter Puzzle in $J/ψ$ and $ψ(2S)$ Decays

Experimental measurements of $J/ψ$ and $ψ(2S)$ decays to octet baryon pairs reveal a negative-$Σ\barΣ$ puzzle in the angular distributions: $α_Σ^{J/ψ}<0$, whereas the other measured $J/ψ$ octet channels and the corresponding $ψ(2S)$ channels have positive angular parameters. We show that an $\mathrm{SU}(3)_F$-exact singlet description is strongly disfavored in a $χ^2$ fit, giving $χ^2\simeq 10^5$. By contrast, a reduced scenario in which a common final-state interaction mixes the $\mathrm{S}$- and $\mathrm{D}$-wave amplitudes, with an antisymmetric direct octet and a full diagonal $\mathrm{S}$-$\mathrm{D}$ rescattering block, gives $χ^2=4.21$ for two nominal degrees of freedom. The negative $Σ\barΣ$ angular parameter is traced to the pattern of the rescattered $\mathrm{S}$- and $\mathrm{D}$-wave amplitudes. The apparent large $\mathrm{SU}(3)_F$-breaking effect is decomposed into three ingredients: the fitted $\mathrm{D}$-wave source is much larger than the $\mathrm{S}$-wave source, the breaking remains modest when normalized to the $\mathrm{D}$ wave, and $\mathrm{D}\to\mathrm{S}$ rescattering transfers the $\mathrm{SU}(3)_F$-breaking effect from the $\mathrm{D}$ wave into the small $\mathrm{S}$-wave baseline, where it appears large. The largest remaining pull comes from the $ψ(2S)\to N\bar{N}$ angular input, motivating a renewed experimental check of $ψ(2S)\to n\bar{n}$.

hep-ph↗

arXiv2026

Strong decays and effective spin-symmetry-breaking corrections in excited charm-strange mesons

We study two-body pseudoscalar-emission decays of excited charm-strange mesons in heavy meson effective field theory, where phenomenological $1/m_c$ corrections are encoded as effective relative shifts between $DP$ and $D^*P$ amplitudes, referred to here as effective spin-symmetry-breaking corrections. Using $D_{s2}^*(2573)$ data to calibrate the $T(3/2^+)$ doublet, we obtain $h'=0.407\pm0.034$ and $ε_T=-0.207\pm0.109$, indicating a natural effective correction of order $20\%$. Applying this input to the $D_{s1}(2460)$ and $D_{s1}(2536)$ system, the Belle and LHCb partial-wave data constrain the mixing angle to $0^\circ<θ_P\lesssim22.0^\circ$ and $0^\circ<θ_P\lesssim14.6^\circ$, respectively, confirming that $D_{s1}(2536)$ is dominantly a $T(3/2^+)$ state with only a small $S(1/2^+)$ admixture. In the radial sector, the pure-$2S$ assignment gives $R_{2700}^{\rm LO}=0.919$, consistent with the observed $D^{*0}K^+/D^0K^+$ ratio of $D_{s1}^*(2700)$, but predicts only $Γ_{\rm ps}[D_{s0}(2590)]\simeq20$ MeV. Allowing mixing between $D_{s1}^*(2700)$ and $D_{s1}^*(2860)$, together with a relative strong phase and effective spin-symmetry-breaking corrections, substantially increases this width while preserving agreement with the vector-state widths and $R_{2700}$. This scenario further gives $R_{1,2860}=0.911$, far from the pure-$X$ leading-order value $R_{1,2860}^{\rm pure\,X}=0.242$, so the spin-one $D^*K/DK$ ratio near $2.86$ GeV offers a clear discriminator between the mixed and unmixed assignments. Overall, this scenario reduces but does not remove the $D_{s0}(2590)$ width tension, leaving room for non-pseudoscalar channels, threshold effects, or coupled-channel dynamics. Reference decay patterns for $D_{s3}^*(2860)$, $D_{s1}(2933)$, and $D_{sJ}(3040)$ are also given.

hep-ph↗

arXiv2026

Semileptonic Decays of $Λ\to p \ell^{-} \barν_{\ell}$ in the Light-Front Dynamics

We investigate the exclusive semileptonic decays of $Λ\to p \ell^{-} \barν_{\ell}~(\ell=e,μ)$ within the Standard Model using the light-front quark model. The transition form factor behaviors of $Λ\to p$ are obtained from the effective treatment of nonvalence contributions in addition to the valence ones in the Drell-Yan-West frame due to the Bethe-Salpeter formalism. Based on these form factors, we obtain that the branching ratios of $Λ\to p e^{-} \barν_{e}$ and $p μ^{-} \barν_μ$, including nonvalence contributions, are around $8.32\times 10^{-4}$ and $1.31\times 10^{-4}$, which are consistent with the latest measurements from the BESIII Collaboration, respectively. Our results indicate that nonvalence contributions can play a non-negligible role in the semileptonic baryon decays within the light-front framework.

hep-ph↗

arXiv2026

Time-like electromagnetic form factors of $Λ,~Σ$ and $Ξ^{+}$ in a light-front quark model

We use the light front quark model to investigate the form factors in the $e^{+}e^{-} \to B\bar{B}$ collision proceses with $B=Λ,~Σ$ and $Ξ$. These form factor behaviors are calculated based on the Bethe-Salpeter formalism with $q^{+} > 0$ to effectively account for non-valence contributions. We show that our results of the $q^2$-dependent form factors closely match the BESIII data. In particalar, we obtain that $|G_{eff}| = (0.921,~0.098,~0.189$) and $R =|$$G_E\over G_M$$|= (0.97,~0.89$,~$0.936$) for $e^{+} e^{-}\to Λ\barΛ$,~$Σ^{+} Σ^{-},~Ξ^{+} Ξ^{+})$ which $q^2 = (5.74,~6.0,~7.0)$ GeV$^2$.

hep-ph↗

arXiv2026

Spin-flavor entanglement in $Λ_b \to ΛD$ and weak phase extraction

We identify a new spin-flavor entanglement structure in $Λ_b\toΛD$ decays, formed by the correlation between the $Λ$ spin and the $D$ flavor states ($D=D^0,\overline D^0,D_1,D_2$). The entanglement information is encoded in the decay rates and Lee-Yang parameters of the four neutral-$D$ modes. We then show that the same spin-flavor structure provides a new method to determine the weak phase $γ$, a key angle of the Cabibbo-Kobayashi-Maskawa unitarity triangle. We find that the experimental uncertainty scales as $σ_γ\propto 1/{\cal C}$, where ${\cal C}$ is the Wootters concurrence, thereby quantitatively relating the precision of the weak-phase extraction to the amount of spin-flavor entanglement.

hep-ph↗

arXiv2026

Topological quantization of vector meson anomalous couplings

We identify an overlooked Wess--Zumino--Witten structure in the hidden-local-symmetry~(HLS) formulation of vector mesons. The newly identified term generically leads to the topological quantization of the vector-meson anomalous couplings. If confirmed experimentally, this structure would expose the gauge nature of vector mesons in the anomalous sector and single out HLS over matter-field descriptions. The observed success of vector-meson dominance in anomalous interactions can then be explained by topological-action saturation of the odd-intrinsic-parity processes. Precision measurements of $η^{(\prime)}\toπ^+π^-γ^*$ form factors at BESIII and the Super $τ$-Charm Facility can directly test this saturation picture.

hep-ph↗

arXiv2026

Purely Baryonic Weak Decays of Heavy Baryons in Skyrme Model

Purely baryonic weak decays of heavy baryons are investigated within the framework of the Skyrme model. These decays belong to a new class of unobserved decay channels, which would help us to test the standard model, particularly potential sources of CP violation in the baryonic sector. By interpreting the heavy baryon as a bound state of a heavy meson and a baryon (Skyrmion), a direct calculation of the decay process $Λ_b \to p\,\bar p\,n$ is performed. The resulting branching fraction is of $\mathcal{O}(10^{-6})$, in agreement with previous estimates.

hep-ph↗

arXiv2025

Regularization of Gauss-Bonnet Gravity in Riemann-Cartan Geometry

We extend the conformal dimensional-derivative regularization of four-dimensional Gauss- Bonnet gravity to Riemann-Cartan geometry, obtaining a regularized action whose torsionless limit equals the well-known regularized four-dimensional Einstein-Gauss-Bonnet model. Varying independently with respect to the scalar, tetrad, and spin connection yields field equations that remain strictly second order in covariant derivatives, thereby avoiding Ostrogradsky-type instabil- ities. Within this framework we obtain static, spherically symmetric black holes carrying torsion hair, showing that the regularized Gauss-Bonnet interaction can support long-range torsion hair without invoking extra dimensions.

gr-qc↗

arXiv2025

Potential of discovering $Ξ_{cc}^+$ in $Λ_b $ decays

We propose to search for $Ξ_{cc}^+$ in the decay $Λ_b \to Ξ_{cc}^+ D^-$, which serves as a tagged and reconstructible source of $Ξ_{cc}^+$, providing an experimentally clean environment for its discovery. A possible fully charged final state is $[(pK^- K^- π^+)_{Ξ^0_c} π^ + ]_{Ξ_{cc}^+} \,(K^+ π^- π^-)_{D^-}$, where the subscripts indicate the parent hadron in the decay chain. We estimate the branching fraction to be ${\cal B}(Λ_b \to Ξ_{cc}^+ D^-) = ( 5.1 \pm 3.9) \times 10^{-4}$, while the fully charged final state corresponds to an effective branching fraction of order $10^{-8}$. These results indicate that LHCb has the potential to discover the $Ξ_{cc}^+$. The prospects for observing $Ω_{cc}^+$ are also briefly discussed.

hep-ph↗

arXiv2025

Semileptonic decays of $Λ^{+}_{c}$ in light-front quark model with nonvalence contributions

We investigate the exclusive semilpetonic decays of $Λ^{+}_{c}\to (Λ/n) \ell^{+} ν_{\ell}~(\ell=e,μ)$ within the standard model by using the light-front quark model (LFQM). The form factor behaviors are obtained from the effective treatment of nonvalence contributions in addition to the valence ones in the Drell-Yan-West frame due to the Bethe-Salpeter formalism. Based on these form factors, we find that the decay branching ratios of $Λ^{+}_{c}\to (Λe^{+} ν_{e},\,Λμ^{+} ν_{e} ,\, n e^{+} ν_{e},\, n μ^{+} ν_{e})$ are about $ (3.39,\,3.21,\,0.36,\,0.35)\%$ with the non-valence contributions, which are consistent with the recent experimental measurements at BESIII. Furthermore, we use the experimental data to fit the $β$ parameters in the baryonic distribution amplitudes under the LFQM, resulting in ($β_{Λ_{c}},β_Λ, β_{n})= (0.58\pm0.08, 0.52\pm0.08,0.44\pm0.04)$.

hep-ph↗

arXiv2025

A radiative lepton model in a non-invertible fusion rule

We propose a new mechanism in which electron and muon masses are induced at one-loop level after dynamically violating the symmetry of the Ising fusion rule. In the neutrino sector, while the neutrino mass is generated at one-loop level, the Ising fusion rule plays a role in stabilizing the particles inside the loop. As a result, the symmetry works like a $Z_2$ symmetry that is not broken at any loop order. Subsequently, we discuss the lepton flavor violating processes, muon anomalous magnetic dipole moment, and relic density of dark matter, where we specify our dark matter candidate to be a singlet boson and briefly analyze the relic density by estimating the DM annihilation cross section. Finally, we present results for both the DM cross section and the muon $g-2$, satisfying the neutrino oscillation data as well as the constraints of lepton flavor violations.

hep-ph↗

arXiv2025

Large CP Asymmetries from Final-State Interactions in Charmful Baryonic Decays of $B^0 \to Ξ_c^+ \overlineΞ_c^-$ and $B_s^0 \to Λ_c^+ \overlineΛ_c^-$

We study the direct CP asymmetries in the decays of $B^0 \to Ξ_c^+ \overlineΞ_c^-$ and $B_s^0 \to Λ_c^+ \overlineΛ_c^-$, emphasizing the critical role of final-state interactions (FSIs). In these channels, the small energy release and annihilation topology suppress short-distance contributions while enhancing long-distance effects. By separating the decay amplitudes into S and P waves, we show that the P-wave component, carrying only a single weak phase, contributes negligibly to CP asymmetries. In contrast, the S-wave amplitude, strongly modified by FSIs, acquires a substantial strong phase that enables interference among multiple weak phases, producing large CP-violating effects. Numerically, we find sizable asymmetries of $a_{CP}^{\text{dir}} = 0.88 \pm 0.05 \pm 0.10$ for $B^0 \to Ξ_c^+ \overlineΞ_c^-$ and $a_{CP}^{\text{dir}} = -0.106 \pm 0.019 \pm 0.010$ for $B_s^0 \to Λ_c^+ \overlineΛ_c^-$, where the first and second uncertainties stem from the poorly known hadron couplings and the omission of the $B^0 \to K^+ K^- \to Ξ_c^+ \overlineΞ_c^-$ rescattering process. For practical feasibility, we restrict our analysis to intermediate states involving pseudoscalar mesons, which yield tractable loop integrals. Excited intermediate states, such as $D^{(*)} \overline{D}^{(*)}$, are omitted because their inclusion would require handling non-renormalizable interactions, introducing substantial ambiguity. These results, combined with the relatively large branching fractions, make these modes prime targets for experimental searches at LHCb and Belle II, potentially offering new insights into strong dynamics and nonperturbative QCD in heavy-hadron decays.

hep-ph↗

arXiv2025

Identify hadron anomalous couplings at colliders

We investigate the identification of the Wess-Zumino-Witten (WZW) Lagrangian at colliders such as BESIII and the Super-$τ$-Charm Facility. Our analysis concentrates on the radiative decays of $η$ and $η'$ mesons, including $η^{(\prime)} \to γγ$, $η^{(\prime)} \to γ\ell^+ \ell^-$, $η^{(\prime)} \to π^+π^-γ$, and $η^{(\prime)} \to π^+π^-\ell^+\ell^-$, as well as semileptonic kaon decays such as $K^+ \to π^+π^- e^+ ν_e$. Employing the hidden local symmetry framework to incorporate vector meson contributions, we compute the decay amplitudes and form factors. For the decay $η\to π^+π^-γ$, the box anomaly dominates, and we find that the anomalous coupling can be experimentally determined to percent-level precision at BESIII. In contrast, vector meson contributions are significant in the decay $η' \to π^+π^-γ$. Using experimental data for $η' \to π^+π^-γ$, we obtain ${\cal B}_{\mathrm{box}}^{\text{exp}} = (1.70 \pm 0.05)\%$, which is approximately ten times larger than previously expected experimentally. We observe good agreement between our calculated anomalous couplings and experimental results. In kaon decays, WZW terms uniquely contribute to the form factor $H$, which can be extracted from parity-conserving decay distributions. While predictions at the chiral point closely match experimental values (e.g., $H^+ = -2.31$ versus $-2.27 \pm 0.10$), we find that intermediate vector meson states introduce substantial corrections, potentially as large as 25%. We strongly advocate for revisiting these experiments to achieve improved precision in form factor extractions.

hep-ph↗