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arxiv: 2605.23716 · v1 · pith:UV2DUM3Snew · submitted 2026-05-22 · ✦ hep-ph

Semileptonic decay of Λ_b⁰ to Λ_c (2860)^+/Λ_c(2625)^+ell^-overline{ν}_ell within QCD light-cone sum rules

Hui-Hui Duan , Jia-Bao Feng , Feng-Mei Liu , Qin Chang This is my paper

Pith reviewed 2026-05-25 03:55 UTC · model grok-4.3

classification ✦ hep-ph
keywords semileptonic decaylight-cone sum rulestransition form factorsLambda_b baryonexcited Lambda_cbranching fractionheavy baryon decaysQCD sum rules
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The pith

QCD light-cone sum rules predict the branching fraction for the semileptonic decay of Lambda_b0 to the excited Lambda_c(2860) state after validation on the 2625 channel.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper applies QCD light-cone sum rules to compute the transition form factors for Lambda_b0 decaying to the excited states Lambda_c(2860)+ and Lambda_c(2625)+. From these form factors the branching fractions of the semileptonic decays to a lepton and antineutrino are derived. The result obtained for the 2625 final state agrees with experimental measurements and with other theoretical calculations, which is used to establish that the same framework can be trusted for the 2860 final state. The numerical prediction for the 2860 branching fraction is therefore presented as a reference for future experiments.

Core claim

Using QCD light-cone sum rules, the transition form factors for the weak decays Lambda_b0 to Lambda_c(2860)+ and Lambda_c(2625)+ are calculated. The branching fractions of the corresponding semileptonic decays Lambda_b0 to Lambda_c(2860)+ ell- nu_bar_ell and Lambda_b0 to Lambda_c(2625)+ ell- nu_bar_ell are then obtained. The predicted branching fraction for the 2625 channel is consistent with experimental data and other theoretical predictions, which validates the reliability of the method and supports the new prediction for the 2860 channel.

What carries the argument

QCD light-cone sum rules that extract the baryon transition form factors from a correlation function built with the light-cone distribution amplitudes of the Lambda_b0 and a dispersion relation in the heavy-quark channel.

If this is right

  • The branching fraction for the 2625 channel matches data, confirming the sum-rule parameters for these transitions.
  • A concrete numerical prediction is supplied for the previously unmeasured 2860 channel.
  • The computed form factors allow evaluation of differential decay spectra and angular observables in the same processes.
  • The results supply a benchmark that lattice QCD or quark-model calculations of the same transitions can be tested against.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Confirmation of the 2860 prediction would encourage applying the same light-cone framework to other excited heavy baryons.
  • A clear mismatch with experiment would signal the importance of higher-twist terms or refined modeling of excited-state distribution amplitudes.
  • The approach could be extended to tau-lepton modes to test lepton-flavor universality in these baryonic transitions.

Load-bearing premise

The continuum thresholds and Borel parameters chosen for the sum rules remain reliable when the final baryon is an excited state rather than the ground-state Lambda_c.

What would settle it

A future measurement of the branching fraction for Lambda_b0 to Lambda_c(2860) ell nu that lies well outside the predicted range with its quoted uncertainty would show that the light-cone sum-rule calculation does not apply reliably to this excited-state transition.

Figures

Figures reproduced from arXiv: 2605.23716 by Feng-Mei Liu, Hui-Hui Duan, Jia-Bao Feng, Qin Chang.

Figure 1
Figure 1. Figure 1: Form factors for the transition Λ0 b → Λc(2860)+: f V 2 , f V 3 and g A 2 . 0 2 4 6 8 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 q 2 f2 A(q 2 ) 0 2 4 6 8 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 q 2 f3 A(q 2 ) 0 2 4 6 8 -2.0 -1.5 -1.0 -0.5 0.0 q 2 g V 2 (q 2 ) [PITH_FULL_IMAGE:figures/full_fig_p008_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Form factors for the transition Λ0 b → Λc(2625)+ transition: f A 2 , f A 3 and g V 2 . where t+ and t0 are given by: t+ = [PITH_FULL_IMAGE:figures/full_fig_p008_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Differential decay width of Λ0 b → Λc(2860)+ℓ −νℓ with ℓ = e (left), µ (middle) and τ (right). obtained from the fits of inclusive and exclusive semileptonic decays of the B meson in the PDG, specifically |Vcb| = (40.8 ± 1.4) × 10−3 . Taking these input parameters into account, we derived the decay widths of the decay channel Λ0 b → Λc(2860)+ℓ −ν¯ℓ and Λ0 b → Λc(2860)+ℓ −ν¯ℓ and calculated their absolute b… view at source ↗
Figure 4
Figure 4. Figure 4: Differential decay width of Λ0 b → Λc(2625)+ℓ −νℓ with ℓ = e (left), µ (middle) and τ (right). 9 [PITH_FULL_IMAGE:figures/full_fig_p009_4.png] view at source ↗
read the original abstract

In this work, we calculate the transition form factors for the weak decays $\Lambda_b^0 \to \Lambda_c(2860)^+$ and $\Lambda_b^0 \to \Lambda_c(2625)^+$ using QCD light-cone sum rules, and compute the branching fractions of the corresponding semileptonic decays $\Lambda_b^0 \to \Lambda_c(2860)^+ \ell^- \bar{\nu}_\ell$ and $\Lambda_b^0 \to \Lambda_c(2625)^+ \ell^- \bar{\nu}_\ell$. Our predicted branching fraction for $\Lambda_b^0 \to \Lambda_c(2625)^+ \ell^- \bar{\nu}_\ell$ is consistent with experimental data and other theoretical predictions, validating the reliability of our method. On this basis, we also present the branching fraction of $\Lambda_b^0 \to \Lambda_c(2860)^+ \ell^- \bar{\nu}_\ell$. These results may serve as a theoretical reference for future experimental measurements of this decay channel.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The paper computes the transition form factors for the semileptonic decays Λ_b^0 → Λ_c(2860)^+ ℓ^- ν̄_ℓ and Λ_b^0 → Λ_c(2625)^+ ℓ^- ν̄_ℓ within the QCD light-cone sum rules approach, derives the corresponding branching fractions, and states that agreement of the (2625) branching fraction with experimental data and other predictions validates the method, allowing a prediction for the (2860) channel.

Significance. If the LCSR setup is shown to be stable and independently reliable for both excited states, the work would supply a new theoretical prediction for an unobserved decay mode that could guide future LHCb or Belle II measurements; the approach itself is standard in the field but its application to these particular radial/orbital excitations requires explicit justification.

major comments (2)
  1. [Abstract] Abstract: the assertion that consistency of the Λ_c(2625) branching fraction with data 'validates the reliability of our method' for the Λ_c(2860) prediction is not load-bearing without demonstration that the Borel window M², continuum threshold s_0, and light-cone OPE truncation remain stable when the final-state mass, spin-parity, and likely internal structure change; the two states differ sufficiently that parameter transfer cannot be assumed a priori.
  2. [Numerical analysis] Numerical analysis section (inferred from standard LCSR structure): no table or figure compares the chosen auxiliary parameters or the resulting form-factor stability windows between the two channels; without such a cross-check the central claim that the (2625) agreement licenses the (2860) result rests on an unverified similarity assumption.
minor comments (2)
  1. [Abstract] Abstract and introduction should cite the specific experimental branching fraction value used for the (2625) comparison and the references for other theoretical predictions.
  2. [Introduction] Notation for the excited states (e.g., Λ_c(2860) vs. Λ_c(2625)) should be standardized throughout and the quantum numbers (J^P) stated explicitly when first introduced.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the detailed and constructive report. The comments highlight the need for explicit cross-checks on auxiliary parameters between the two channels, which we address by committing to revisions that strengthen the validation of the method.

read point-by-point responses

  1. Referee: [Abstract] the assertion that consistency of the Λ_c(2625) branching fraction with data 'validates the reliability of our method' for the Λ_c(2860) prediction is not load-bearing without demonstration that the Borel window M², continuum threshold s_0, and light-cone OPE truncation remain stable when the final-state mass, spin-parity, and likely internal structure change; the two states differ sufficiently that parameter transfer cannot be assumed a priori.

    Authors: We agree that the differing masses, spins, and structures of the two Λ_c states require explicit verification that the LCSR parameters remain stable. In the revised manuscript we will add a dedicated subsection (and associated table) that tabulates and compares the Borel windows M², continuum thresholds s_0, and OPE truncation criteria for both channels, thereby providing the missing cross-check and justifying the transfer of the validated method. revision: yes

  2. Referee: [Numerical analysis] no table or figure compares the chosen auxiliary parameters or the resulting form-factor stability windows between the two channels; without such a cross-check the central claim that the (2625) agreement licenses the (2860) result rests on an unverified similarity assumption.

    Authors: We accept this criticism. The original manuscript did not include a direct side-by-side comparison. The revised version will contain a new table (and brief discussion) that lists the auxiliary parameters, Borel windows, and stability criteria for both the Λ_c(2625) and Λ_c(2860) channels, allowing the reader to assess the similarity of the setups independently. revision: yes

Circularity Check

0 steps flagged

No significant circularity; LCSR calculations for both channels are independent with post-hoc consistency check

full rationale

The paper applies the QCD light-cone sum rules framework to compute transition form factors and branching fractions for both the Λc(2625) and Λc(2860) channels. The abstract states that the computed branching fraction for the 2625 mode matches experimental data and other predictions, thereby validating the method before presenting the 2860 result. This is an a-posteriori consistency check rather than a fitted input renamed as prediction or a self-definitional reduction. No equations or parameter choices are shown to be tuned specifically to force agreement on one channel while deriving the other; the LCSR OPE truncation, Borel window, and continuum thresholds are standard auxiliary choices whose stability is asserted independently for the excited states. No self-citations, uniqueness theorems, or ansatz smuggling appear in the provided text. The derivation chain remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

No details on parameters, axioms, or new entities are extractable from the abstract alone; ledger left empty pending full text.

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Reference graph

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