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Radiative decay of fully-heavy tetraquark into quarkonium

T0 review · reviewed 2026-06-26 · grok-4.3

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Pith's one-line read Radiative decays of the fully-charm tetraquark to gamma J/psi have widths around 1 MeV and offer a low-background search channel near the J/psi J/psi threshold.

desk verdict NRQCD estimates put T4c radiative widths around 1 MeV but the numbers rest on unmeasured wave-function overlaps that can shift results by factors of several. read the letter →

arxiv 2606.18892 v1 pith:W7VDXFDC submitted 2026-06-17 hep-ph

Hao Yang , Songlin Lyu , Bingwei Long This is my paper · ORCID
classification hep-ph
keywords tetraquarksradiativedecaysfullyheavyquarksNRQCDcharmoniumbottomoniumX(6200)
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

The paper calculates radiative decay widths of fully heavy tetraquarks and mixed heavy-flavor tetraquarks into quarkonium plus photon states using the nonrelativistic QCD factorization framework. Numerical results show that the fully charm tetraquark T4c decays to gamma J/psi or gamma eta_c with widths of order 1 MeV. The gamma J/psi final state receives less experimental background near the J/psi J/psi threshold, making it a practical channel for searching possible tetraquark resonances such as X(6200). The same framework yields much smaller widths for bottom tetraquarks and shows that mixed bc states prefer annihilation into bottomonium over charmonium by several orders of magnitude.

What carries the argument

NRQCD factorization framework applied to radiative transitions of tetraquarks with assumed quantum numbers and wave-function overlaps.

What would settle it

An experimental measurement finding the partial width of T4c to gamma J/psi well below 1 MeV or no resonant signal in the gamma J/psi invariant-mass distribution near the J/psi J/psi threshold despite adequate integrated luminosity.

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Extended reading notes

Core claim

Within the NRQCD factorization framework the decay widths of the fully-charm tetraquark T4c into gamma J/psi (eta_c) are around 1 MeV while the gamma J/psi signal channel receives less experimental background near the J/psi J/psi threshold, providing a compelling way to search for possible tetraquark states X(6200).

Load-bearing premise

The NRQCD factorization framework applies directly to the radiative transitions of these tetraquark states with the assumed quantum numbers and wave-function overlaps used in the calculation.

Editorial extensions

If this is right

  • These radiative decay modes can be measured in future experiments.
  • The modes help distinguish the inner structure of fully heavy tetraquarks.
  • For fully bottom tetraquarks the radiative widths are suppressed to the tens of eV level.
  • Mixed T_bc bbar cbar states decay preferentially to gamma Upsilon over gamma J/psi by three to four orders of magnitude.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Confirmation of the predicted widths would constrain the spatial wave-function overlaps adopted for the tetraquark states.
  • The same NRQCD machinery could be applied to other electromagnetic or hadronic decay channels to test consistency across observables.
  • Non-observation in the gamma J/psi channel would favor alternative interpretations of the X(6200) region over a compact tetraquark.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Circularity Check

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NRQCD factorization yields independent numerical widths; no reduction to inputs by construction

full rationale

The derivation applies standard NRQCD factorization to tetraquark radiative transitions, taking wave-function overlaps and quantum numbers as external model inputs rather than deriving them from the target widths. No quoted equations or self-citations show a fitted parameter being relabeled as a prediction, a self-definitional loop, or a load-bearing uniqueness theorem imported from the same authors. The ~1 MeV result is a direct evaluation within the framework; uncertainty in the overlap affects the output magnitude but does not make the calculation tautological. This is a conventional model calculation whose central content remains independent of its own outputs.

Assumptions & free parameters 0 free parameters · 0 assumptions · 0 invented entities

Abstract-only review yields no explicit free parameters or invented entities; typical NRQCD tetraquark calculations rely on fitted color-octet matrix elements and assumed tetraquark wave functions, but none are listed here.

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Cite this review

Pith. "Pith review of Radiative decay of fully-heavy tetraquark into quarkonium." pith.science (2026). https://pith.science/paper/W7VDXFDC

@misc{pith2026260618892,
  author       = {Pith},
  title        = {Pith review of: Radiative decay of fully-heavy tetraquark into quarkonium},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/W7VDXFDC}},
  note         = {Machine review of arXiv:2606.18892}
}
abstract

We present a comprehensive study of the radiative decays of fully heavy tetraquarks ($T_{4c}$, $T_{4b}$) and mixed heavy-flavor tetraquarks ($T_{bc\bar{b}\bar{c}}$) into charmonium/bottomonium states, within the nonrelativistic QCD factorization framework. Numerical result indicates that the decay widths of fully charm tetraquark $T_{4c}$ into $\gamma J/\psi (\eta_c)$ are around 1 MeV. Crucially, the $\gamma J/\psi$ signal channel receives less experimental background near the $J/\psi J/\psi$ threshold, providing a compelling way to search for the possible tetraquark states X(6200). For $T_{4b}$, the decay width is highly suppressed by the bottom quark mass, just lying in tens eV level. We further find that the decay widths of $T_{bc\bar{b} \bar{c}} \to \gamma \Upsilon$ exceed those to $\gamma J/\psi$ by 3-4 orders of magnitude, indicating preferential $c\bar{c}$-pair annihilation over $b\bar{b}$. These radiative decay modes can be measured in the future experiments, and are helpful to understand the inner structure of the full heavy tetraquark.

Figures

Figures reproduced from arXiv: 2606.18892 by the authors.

Figure 1
Figure 1. FIG. 1: Two representative leading-order Feynman diagrams for the radiative decay [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗

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Works this paper leans on

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