Exclusive semileptonic and nonleptonic J/ψ decays

Only the abstract is in front of us, so this is a thin read. The one thing to know is that Galkin and Sukhanov apply their existing relativistic quasipotential quark model to exclusive semileptonic and nonleptonic J/ψ weak decays and report branching fractions of order 10⁻⁹–10⁻¹². That is the load-bearing claim.

What is new is the set of numerical rates for specific channels, obtained from form factors written as wave-function overlaps with full relativistic kinematics, evaluated over the whole kinematic range. The model itself is not new; it is a standard extension of their long-running program. They do the honest comparison to earlier predictions and to existing experimental upper bounds, which is useful for BESIII-scale searches. Semileptonic modes (e and μ) rest only on the form factors; nonleptonic modes add factorization at Nc→∞, which they state explicitly.

Soft spots are real but proportionate. Without the full text we cannot inspect the wave functions, potential parameters, or the numerical integrals, so the rates are uncheckable from what we have. Factorization at the few-GeV charmonium scale is the usual modeling assumption and is the weakest link for the nonleptonic numbers; if it fails, those BRs move even if the form factors are fine. Circularity is the ordinary phenomenological kind: parameters fixed on other spectra and decays. None of that is a smoking gun; it is just the normal limitation of this class of calculation.

This paper is for people who need order-of-magnitude guidance on rare charmonium weak modes or who already work inside the quasipotential framework. It will not reorganize heavy-flavor theory. I would not bring it to reading group unless someone is actively hunting these channels, and I would not cite it myself without the full tables. Still, it is a legitimate, limited-scope prediction paper that deserves a serious referee rather than a desk reject — send it out if the full manuscript arrives with the form-factor expressions and comparisons intact.

The paper’s load-bearing claim is the set of exclusive branching fractions of order 10^{-9}–10^{-12} obtained from relativistic form factors written as meson wave-function overlaps in the quasipotential approach. Because only the abstract is available, those form factors, the wave functions, the kinematic integrals, and the numerical tables are all inaccessible. Consequently the single most load-bearing concern is simply that the numerical results cannot be verified or reproduced from the given material. The factorization approximation at Nc o∞ (explicitly flagged for nonleptonic modes) is a genuine modeling assumption whose failure would invalidate the nonleptonic rates even if the form factors themselves are correct, yet that assumption also cannot be examined without the full calculation. No independent support (code, data, machine-checked steps) is supplied. The concern is therefore informational rather than an identified internal inconsistency.

The Reader correctly identifies that an abstract-only review of a standard phenomenological calculation cannot support a firm verdict; the factorization premise is the most fragile stated assumption, but the deeper obstacle is the absence of any checkable content. My stress-test therefore finds no new technical flaw that would move the verdict away from UNVERDICTED. The concrete test simply restores the missing information and verifies one number; until that is done the claim remains untestable. Agreement with the Reader is complete on both the weakest assumption and the overall posture.

Rare weak decays of J/ψ probe factorization and heavy-quark dynamics at the few-GeV scale and are of experimental interest at high-luminosity facilities (BESIII, LHCb, etc.). If the form-factor calculation and the quoted rates hold, the work supplies a coherent set of exclusive predictions in a standard phenomenological framework that includes relativistic effects over the full kinematic range. The explicit use of wave-function overlap integrals and the comparison with prior theory and experimental bounds are useful contributions; the nonleptonic results, however, inherit the well-known limitations of large-Nc factorization.

This paper calculates exclusive weak decays of the J/ψ meson—both semileptonic modes with an electron or muon and nonleptonic modes that produce only hadrons. The authors work in a relativistic quark model based on the quasipotential approach of QCD, express the weak form factors as overlap integrals of meson wave functions, and evaluate them over the full kinematic range with all relativistic effects kept. From those form factors they obtain branching fractions of order 10⁻⁹ to 10⁻¹². Nonleptonic rates are obtained under the factorization approximation taken in the large-Nc limit. The numbers are compared with earlier theoretical estimates and with existing experimental upper bounds, providing a concrete target for future high-luminosity measurements of rare charmonium decays.

What carries the argument. Relativistic form factors of the weak current, expressed as overlap integrals of meson wave functions in the quasipotential approach and evaluated over the entire kinematic range with full relativistic effects retained.

Core claim. Exclusive semileptonic and nonleptonic J/ψ branching fractions, obtained from relativistic form factors written as meson wave-function overlap integrals, lie in the range 10⁻⁹ ∼ 10⁻¹².

The premise it rests on. Nonleptonic rates rest on the factorization approximation taken in the limit of infinitely many colors; if that approximation fails at the few-GeV charmonium scale the quoted branching fractions are unreliable even when the form factors themselves are correct.

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