REVIEW
Charmed baryon semileptonic decays in a relativistic three-quark model
High Energy Physics - Phenomenology · Submitted 9 Sep 2026 · 81 references
Pith's verdict: Solid quark-model calculation with a clear systematic limitation: the harmonic oscillator truncation is unchecked for the transverse form factor that drives the Xi_c rate puzzle.
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The paper
The paper claims
A parameter-free relativistic three-quark model predicts charmed baryon semileptonic branching fractions and polarizations, revealing a large discrepancy between theory and experiment for Xi_c^0 decays.
The reading
Extended reading notes
Core claim
For Xi_c^0 -> Xi^- e^+ nu_e, the model obtains B_e about 4.0 percent, which is consistent with recent LQCD calculations but lies well above the current experimental average (1.05 +/- 0.20 percent). The paper asserts that this discrepancy cannot be explained by the small Xi_c-Xi'_c mixing angle (2.03 degrees) determined from the mass spectrum.
Load-bearing premise
The harmonic oscillator basis truncation at N_osc <= 2 with L=0 for the baryon wave functions is relied upon to compute the q^2 dependence of form factors over the full kinematic range. The adequacy of this truncation for the recoil-sensitive f_2 and g_2 form factors has not been independently validated for these specific decays, and the smaller f_2 values compared to LQCD suggest that higher radial or orbital excitations might modify the transverse response.
Original abstract
We study the spin-$1/2\to1/2$ semileptonic decays of singly charmed baryons ($\Lambda_c^+$, $\Xi_c^{0,+}$, and $\Omega_c^0$) into the light baryon octet within a relativistic three-quark model. The constituent quark masses and spatial wave functions are determined by the baryon mass spectrum. For the physical $\Xi_c$ states, the light flavor $\mathrm{SU}(3)$ breaking ($m_s > m_{u,d}$) naturally induces a coherent mixing between the flavor antitriplet and flavor sextet configurations, which is completely fixed by the mass eigenstates. Consequently, no adjustable parameters are introduced in calculating the weak transition amplitudes. Using these wave functions, we calculate the $c\to s,d$ helicity amplitudes with the Bakamjian--Thomas boost, including the spatial Jacobian and the Wigner rotations of the constituent spins. The branching fractions, $q^2$ distributions, longitudinal polarizations, and form factors are then obtained from these amplitudes. For the $\Lambda_c^+\to\Lambda\ell^+\nu_\ell$ and $\Lambda_c^+\to n\ell^+\nu_\ell$ modes, our branching fractions and form factors are in good agreement with the experimental data and Lattice QCD results. For $\Xi_c^0\to\Xi^-e^+\nu_e$, we obtain branch ratio $\mathcal B_{\ell} \simeq 4.0~\%$, which is consistent with recent Lattice QCD calculations but lies well above the current experimental average. Clarifying the origin of this discrepancy calls for further dedicated efforts from both experimental and theoretical sides. For the $\Omega_c^0\to\Xi^-\ell^+\nu_\ell$ decay, the spin-$1$ $ss$ spectator yields a positive longitudinal polarization of the final $\Xi^-$, in contrast to the negative polarizations in the predominantly antitriplet decay modes. Our predictions for the $q^2$ spectra, angular asymmetries, and final baryon polarizations may provide useful references for future measurements of singly charmed baryon semileptonic decays.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
We study the spin-$1/2\to1/2$ semileptonic decays of singly charmed baryons ($\Lambda_c^+$, $\Xi_c^{0,+}$, and $\Omega_c^0$) into the light baryon octet within a relativistic three-quark model. The constituent quark masses and spatial wave functions are determined by the baryon mass spectrum. For the physical $\Xi_c$ states, the light flavor $\mathrm{SU}(3)$ breaking ($m_s > m_{u,d}$) naturally induces a coherent mixing between the flavor antitriplet and flavor sextet configurations, which is completely fixed by the mass eigenstates. Consequently, no adjustable parameters are introduced in calculating the weak transition amplitudes. Using these wave functions, we calculate the $c\to s,d$ helicity amplitudes with the Bakamjian--Thomas boost, including the spatial Jacobian and the Wigner rotations of the constituent spins. The branching fractions, $q^2$ distributions, longitudinal polarizations, and form factors are then obtained from these amplitudes. For the $\Lambda_c^+\to\Lambda\ell^+\nu_\ell$ and $\Lambda_c^+\to n\ell^+\nu_\ell$ modes, our branching fractions and form factors are in good agreement with the experimental data and Lattice QCD results. For $\Xi_c^0\to\Xi^-e^+\nu_e$, we obtain branch ratio $\mathcal B_{\ell} \simeq 4.0~\%$, which is consistent with recent Lattice QCD calculations but lies well above the current experimental average. Clarifying the origin of this discrepancy calls for further dedicated efforts from both experimental and theoretical sides. For the $\Omega_c^0\to\Xi^-\ell^+\nu_\ell$ decay, the spin-$1$ $ss$ spectator yields a positive longitudinal polarization of the final $\Xi^-$, in contrast to the negative polarizations in the predominantly antitriplet decay modes. Our predictions for the $q^2$ spectra, angular asymmetries, and final baryon polarizations may provide useful references for future measurements of singly charmed baryon semileptonic decays.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We study the spin-$1/2\to1/2$ semileptonic decays of singly charmed baryons ($\Lambda_c^+$, $\Xi_c^{0,+}$, and $\Omega_c^0$) into the light baryon octet within a relativistic three-quark model. | contribution 1.00 | 0.92 | 0.06 | asserted 0.97 |
| s1 | The constituent quark masses and spatial wave functions are determined by the baryon mass spectrum. | method 1.00 | 0.72 | 0.02 | asserted 1.00 |
| s2 | For the physical $\Xi_c$ states, the light flavor $\mathrm{SU}(3)$ breaking ($m_s > m_{u,d}$) naturally induces a coherent mixing between the flavor antitriplet and flavor sextet configurations, which is completely fixed by the mass eigenstates. | method 0.80 | 0.68 | 0.07 | asserted 1.00 |
| s3 | Consequently, no adjustable parameters are introduced in calculating the weak transition amplitudes. | method 0.69 | 0.77 | 0.07 | asserted 1.00 |
| s4 | Using these wave functions, we calculate the $c\to s,d$ helicity amplitudes with the Bakamjian--Thomas boost, including the spatial Jacobian and the Wigner rotations of the constituent spins. | method 1.00 | 0.94 | 0.03 | asserted 0.99 |
| s5 | The branching fractions, $q^2$ distributions, longitudinal polarizations, and form factors are then obtained from these amplitudes. | method 0.92 | 0.94 | 0.05 | asserted 1.00 |
| s6 | For the $\Lambda_c^+\to\Lambda\ell^+\nu_\ell$ and $\Lambda_c^+\to n\ell^+\nu_\ell$ modes, our branching fractions and form factors are in good agreement with the experimental data and Lattice QCD results. | result 0.96 | 0.94 | 0.20 | asserted 0.97 |
| s7 | For $\Xi_c^0\to\Xi^-e^+\nu_e$, we obtain branch ratio $\mathcal B_{\ell} \simeq 4.0~\%$, which is consistent with recent Lattice QCD calculations but lies well above the current experimental average. | result 1.00 | 0.96 | 0.12 | asserted 0.91 |
| s8 | Clarifying the origin of this discrepancy calls for further dedicated efforts from both experimental and theoretical sides. | future work 0.99 | 0.07 | 0.06 | hedged possibility 0.44 |
| s9 | For the $\Omega_c^0\to\Xi^-\ell^+\nu_\ell$ decay, the spin-$1$ $ss$ spectator yields a positive longitudinal polarization of the final $\Xi^-$, in contrast to the negative polarizations in the predominantly antitriplet decay modes. | result 0.99 | 0.92 | 0.12 | asserted 1.00 |
| s10 | Our predictions for the $q^2$ spectra, angular asymmetries, and final baryon polarizations may provide useful references for future measurements of singly charmed baryon semileptonic decays. | future work 0.68 | 0.71 | 0.22 | hedged possibility 1.00 |
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