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arxiv: 2604.23078 · v1 · submitted 2026-04-25 · ✦ hep-ph

Recognition: unknown

Dbar{D}^ast-π J/psi scatterings of coupled channels for Z_c(3900) channel

Yukihiro Abe , Yasuhiro Yamaguchi , Atsushi Hosaka
Authors on Pith no claims yet

Pith reviewed 2026-05-08 07:59 UTC · model grok-4.3

classification ✦ hep-ph
keywords Zc(3900)coupled channelsquark exchangemeson exchangeD Dbar*J/psi piscattering amplitudesexotic charmonium
0
0 comments X

The pith

Quark-exchange interactions at short distances dominate the scattering amplitudes for the Zc(3900) channel.

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

The paper performs a coupled-channel analysis of D Dbar*, J/psi pi and related meson pairs using an effective model that includes both meson-exchange potentials and quark-exchange terms. Meson exchanges such as one-pion and D(*) exchanges turn out to be weak, while the off-diagonal quark exchanges between D Dbar* and J/psi pi are strong and drive the amplitudes. This result is presented as consistent with lattice simulations from the HALQCD group. A sympathetic reader would care because it points to short-range quark dynamics as the key mechanism behind this exotic charmonium-like state rather than long-range meson forces.

Core claim

In the effective hadron-quark model the meson-exchange potentials are small, while the off-diagonal interactions by the quark exchanges at short distances, particularly for transitions between D Dbar* and J/psi pi, are strong and play the main role for the scattering amplitudes in the Zc(3900) channel.

What carries the argument

Coupled-channel effective model combining meson-exchange potentials (one-pion and D(*) exchanges) with quark-exchange potentials, where the latter supply the dominant off-diagonal transitions.

If this is right

  • The Zc(3900) arises mainly from short-distance quark dynamics rather than molecular meson-exchange binding.
  • Scattering amplitudes match lattice results without additional data-driven tuning for this channel.
  • The model predicts measurable effects in related open-charm and hidden-charm channels.
  • Similar quark-exchange dominance may appear in other near-threshold exotic states.

Where Pith is reading between the lines

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

  • Models of other XYZ states that omit quark-exchange terms may systematically underestimate transition strengths between open- and hidden-charm channels.
  • Higher-resolution lattice studies focused on sub-femtometer distances could directly test the claimed strength of these off-diagonal transitions.
  • If quark exchanges dominate, the Zc(3900) likely contains significant compact four-quark components alongside any molecular component.

Load-bearing premise

The chosen meson-exchange and quark-exchange potentials in the effective model accurately capture the short-distance dynamics of the coupled channels without needing full non-perturbative QCD or extra parameters tuned to Zc(3900) data.

What would settle it

A lattice calculation or scattering measurement that finds the D Dbar* to J/psi pi transition amplitudes dominated by meson exchanges rather than quark exchanges would falsify the central claim.

Figures

Figures reproduced from arXiv: 2604.23078 by Atsushi Hosaka, Yasuhiro Yamaguchi, Yukihiro Abe.

Figure 1
Figure 1. Figure 1: FIG. 1. Meson exchange diagrams view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Phase shifts obtained by using the meson exchange view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Six types of quark exchange diagrams. view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Definition of various momenta for the process Trans view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Important potentials for off-diagonal channels, view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. The other potentials generated by quark exchanges, view at source ↗
Figure 8
Figure 8. Figure 8: We argue that the line shapes of the ampli view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7. Various scattering amplitudes of the four channels, view at source ↗
Figure 8
Figure 8. Figure 8: FIG. 8. Various amplitude in a toy model. view at source ↗
read the original abstract

We perform coupled channel analysis for $D \bar D^*$, $J/\psi \pi$ and related meson pairs for the $Z_c(3900)$ channel in an effective model of hadrons and quarks. The model incorporates meson exchange potential such as one pion and $D^{(*)}$ meson exchanges, and quark exchanges. It turns out that the meson exchange potential is small, while the off-diagonal interactions by the quark exchanges at short distances, particularly for transitions between $D\bar D^*$-$J/\psi \pi$ are strong, which plays a main role for the scattering amplitudes for the $Z_c(3900)$ channel, in consistent with the results of the lattice simulations of the HALQCD group.

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.

Circularity Check

0 steps flagged

No significant circularity in the model-based derivation

full rationale

The paper defines an effective coupled-channel model that includes explicit meson-exchange potentials (one-pion and D(*) exchanges) plus quark-exchange terms at short distances, solves the resulting scattering equations for the D D-bar* – J/ψ π system, and reports the numerical outcome that quark-exchange off-diagonal potentials dominate while meson exchanges remain small. This dominance is presented as a computed result of the model dynamics and is then compared for consistency with independent HALQCD lattice phase shifts. No equation or step reduces by construction to a fitted parameter renamed as prediction, a self-definitional loop, or a load-bearing self-citation; the central claim is an output of the explicit solution rather than presupposed by the inputs.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The central claim rests on an effective model whose potentials are not derived from QCD but introduced phenomenologically; without the full text the exact number of free parameters cannot be counted.

free parameters (1)
  • quark-exchange coupling strengths
    Short-distance quark-exchange amplitudes are introduced in the model and likely adjusted to produce the reported dominance.
axioms (1)
  • domain assumption Meson-exchange potentials can be reliably computed from known meson couplings while quark exchanges are modeled by a separate short-range operator.
    Invoked to separate the two interaction mechanisms and conclude meson exchanges are small.

pith-pipeline@v0.9.0 · 5434 in / 1412 out tokens · 23311 ms · 2026-05-08T07:59:55.151614+00:00 · methodology

discussion (0)

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Reference graph

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