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arxiv: 2606.11808 · v1 · pith:B77Z7AHUnew · submitted 2026-06-10 · ✦ hep-ph · hep-ex· nucl-ex

Nonexistence of hidden-charm pentaquarks in J/psi photoproduction

Samson Clymton , Sang-Ho Kim , Hyun-Chul Kim This is my paper

Pith reviewed 2026-06-27 09:19 UTC · model grok-4.3

classification ✦ hep-ph hep-exnucl-ex
keywords hidden-charm pentaquarksJ/ψ photoproductioncoupled-channel rescatteringGlueXCLAS12LHCb pentaquarksΣ_c couplings
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The pith

Hidden-charm pentaquarks do not appear in J/ψ photoproduction because Σ_c rescattering is suppressed by an order of magnitude.

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

The paper investigates the absence of pentaquark signals in γp → J/ψp data from GlueX and CLAS12, even though LHCb reports them in other processes. It applies a coupled-channel rescattering model that previously generated the P_c states dynamically and finds that the ar{D}^{(*)}Σ_c intermediate states, which dominate the pentaquark coupling to the J/ψN channel, contribute roughly ten times less than the ar{D}^{(*)}Λ_c states. This difference arises because the relevant coupling constants g_{ar{D}^{(*)}NΣ_c} are about five times smaller than g_{ar{D}^{(*)}NΛ_c}. With only one overall normalization parameter, the calculation reproduces the measured cross sections. The result shows that the null photoproduction result can be consistent with the LHCb observations without requiring the pentaquarks to be absent.

Core claim

Within the coupled-channel framework, the rescattering amplitudes from the ar{D}^{(*)}Σ_c channels are suppressed by roughly one order of magnitude relative to those from ar{D}^{(*)}Λ_c because the couplings g_{ar{D}^{(*)}NΣ_c} are five times smaller; since the P_{car{c}} states reach the J/ψN final state predominantly through the Σ_c intermediates, this suppression removes any visible pentaquark signal from photoproduction while still describing the GlueX and CLAS12 cross sections.

What carries the argument

Coupled-channel rescattering amplitudes whose kernel includes t-channel heavy-meson exchange and u-channel heavy-baryon exchange, with the relative magnitude fixed by the ratio of g_{ar{D}^{(*)}NΣ_c} to g_{ar{D}^{(*)}NΛ_c}.

If this is right

  • The model accounts for the GlueX and CLAS12 cross sections with a single free parameter.
  • P_c resonances reach the J/ψN channel mainly via ar{D}^{(*)}Σ_c intermediates.
  • A null result in photoproduction does not contradict the LHCb pentaquark signals.
  • The relative size of the two sets of rescattering contributions is fixed by the ratio of the two coupling constants.

Where Pith is reading between the lines

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

  • Similar suppression would be expected in other photoproduction or electroproduction channels that proceed through the same Σ_c intermediates.
  • Direct measurement of the ratio g_{ar{D}^{(*)}NΣ_c}/g_{ar{D}^{(*)}NΛ_c} in a different reaction could test the input couplings independently.
  • If the couplings were larger, visible peaks should appear once statistics improve by roughly an order of magnitude.

Load-bearing premise

The coupling constants extracted from an earlier coupled-channel analysis remain valid for the relative strengths of the intermediate-state transitions that appear in photoproduction.

What would settle it

Clear pentaquark peaks appearing in new, higher-statistics J/ψ photoproduction data at the same energies where LHCb reports the states.

Figures

Figures reproduced from arXiv: 2606.11808 by Hyun-Chul Kim, Samson Clymton, Sang-Ho Kim.

Figure 1
Figure 1. Figure 1: FIG. 1. Diagrams for [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. The [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Tree-level diagrams for the subprocess [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Spin-averaged squared transition amplitude to the [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Total cross section for the [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. Total cross section as a function of the total energy. Experimental data are taken from Ref. [ [PITH_FULL_IMAGE:figures/full_fig_p008_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7. Differential cross section as a function of the exchange momentum transfer [PITH_FULL_IMAGE:figures/full_fig_p009_7.png] view at source ↗
read the original abstract

We investigate $J/\psi$ photoproduction off the proton, $\gamma p \to J/\psi p$, to elucidate the nonexistence of hidden-charm pentaquark signals reported by the GlueX and CLAS12 experiments. Within a coupled-channel rescattering mechanism, we employ the transition amplitudes from a previous coupled-channel analysis that dynamically generates the $P_{c\bar{c}}$ states. The kernel amplitudes for the transition to the $J/\psi N$ channel include both $t$-channel heavy-meson exchange and $u$-channel heavy-baryon exchange. We find that the rescattering contributions from the $\bar{D}^{(*)}\Sigma_c$ channels -- indispensable for the formation of the $P_{c\bar{c}}$ resonances -- are about one order of magnitude smaller than those from $\bar{D}^{(*)}\Lambda_c$, since $g_{\bar{D}^{(*)}N\Sigma_c}$ is roughly five times smaller than $g_{\bar{D}^{(*)}N\Lambda_c}$. Since the $P_{c\bar{c}}$ resonances couple to the $J/\psi N$ channel predominantly through the $\bar{D}^{(*)}\Sigma_c$ intermediate states, their suppression prevents the pentaquark signal from appearing in photoproduction. With only a single parameter controlling the overall normalization, the present work describes the GlueX and CLAS12 cross sections well. These results suggest that the null result from photoproduction need not be in conflict with the pentaquark signals observed by the LHCb Collaboration.

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

1 major / 0 minor

Summary. The manuscript claims that hidden-charm pentaquarks do not appear in J/ψ photoproduction because the rescattering contributions from the ar{D}^{(*)}\Sigma_c channels, which are crucial for generating the P_{c\bar{c}} resonances, are suppressed by approximately one order of magnitude relative to the ar{D}^{(*)}\Lambda_c channels. This suppression arises from the coupling constants g_{\bar{D}^{(*)}N\Sigma_c} being roughly five times smaller than g_{\bar{D}^{(*)}N\Lambda_c}, as extracted from a prior coupled-channel analysis. Using these amplitudes in a rescattering mechanism with t- and u-channel exchanges, the model fits the GlueX and CLAS12 cross sections with a single overall normalization parameter, suggesting consistency with the null results from photoproduction experiments despite LHCb observations.

Significance. If the transferability of the coupling ratios to the photoproduction kernels holds, the work offers a parameter-efficient (single overall normalization) explanation for the absence of pentaquark signals in photoproduction while preserving the dynamical generation of P_c states from prior coupled-channel fits. It addresses an apparent tension between LHCb and GlueX/CLAS12 data with minimal additional assumptions.

major comments (1)
  1. [Abstract, paragraph on kernel amplitudes] Abstract, paragraph on kernel amplitudes: the assertion that rescattering contributions from \bar{D}^{(*)}\Sigma_c are ~10 times smaller than from \bar{D}^{(*)}\Lambda_c 'since g_{\bar{D}^{(*)}N\Sigma_c} is roughly five times smaller' assumes the full transition amplitudes (built from t-channel heavy-meson exchange plus u-channel heavy-baryon exchange) scale directly with the coupling ratio. No explicit demonstration is given that kinematic factors, mass differences, isospin, or form-factor cutoffs at GlueX/CLAS12 energies preserve this exact ratio; this assumption is load-bearing for the central claim of pentaquark suppression.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful reading and constructive comment. We address the major point below.

read point-by-point responses

  1. Referee: Abstract, paragraph on kernel amplitudes: the assertion that rescattering contributions from \bar{D}^{(*)}\Sigma_c are ~10 times smaller than from \bar{D}^{(*)}\Lambda_c 'since g_{\bar{D}^{(*)}N\Sigma_c} is roughly five times smaller' assumes the full transition amplitudes (built from t-channel heavy-meson exchange plus u-channel heavy-baryon exchange) scale directly with the coupling ratio. No explicit demonstration is given that kinematic factors, mass differences, isospin, or form-factor cutoffs at GlueX/CLAS12 energies preserve this exact ratio; this assumption is load-bearing for the central claim of pentaquark suppression.

    Authors: The transition amplitudes used for the rescattering are the full kernels taken directly from our prior coupled-channel analysis. These kernels already include the complete t-channel heavy-meson and u-channel heavy-baryon exchanges together with all kinematic factors, mass differences, isospin coefficients, and form-factor cutoffs evaluated at the relevant energies. The numerical evaluation of these amplitudes yields the reported order-of-magnitude suppression, with the factor of ~5 in the couplings g_{\bar{D}^{(*)}N\Sigma_c} being the primary origin. The abstract condenses this numerical result. To remove any potential ambiguity, we will revise the abstract paragraph to state explicitly that the suppression is obtained from the full amplitudes (while still noting the dominant role of the coupling ratio). revision: yes

Circularity Check

1 steps flagged

Central suppression ratio imported unchanged from prior same-author coupled-channel fit

specific steps
  1. self citation load bearing [Abstract]
    "we employ the transition amplitudes from a previous coupled-channel analysis that dynamically generates the P_{c\bar c} states. ... the rescattering contributions from the \bar{D}^{(*)}\Sigma_c channels -- indispensable for the formation of the P_{c\bar c} resonances -- are about one order of magnitude smaller than those from \bar{D}^{(*)}\Lambda_c, since g_{\bar{D}^{(*)}N\Sigma_c} is roughly five times smaller than g_{\bar{D}^{(*)}N\Lambda_c}"

    The decisive numerical factor (factor-of-five coupling ratio and the resulting order-of-magnitude suppression) is imported verbatim from the prior same-author analysis; the photoproduction calculation therefore inherits the nonexistence conclusion by construction once that ratio is accepted.

full rationale

The paper's headline result (no visible P_car c signal in photoproduction) rests on the statement that ar D^{(*)}\Sigma_c rescattering is ~10 times weaker than ar D^{(*)}\Lambda_c because the couplings satisfy g_{\bar D^{(*)}N\Sigma_c} \approx (1/5) g_{\bar D^{(*)}N\Lambda_c}. This ratio and the full transition amplitudes are taken directly from the authors' earlier coupled-channel work that generated the poles; the present kernels (t-channel meson + u-channel baryon exchange) do not re-derive or correct the ratio for the new kinematics, masses, or form factors. The single overall normalization parameter is then fitted to GlueX/CLAS12 data. This satisfies the self-citation load-bearing pattern: the nonexistence conclusion is a direct consequence of quantities fixed in the prior analysis rather than independently obtained here.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The model rests on the validity of prior coupled-channel amplitudes and the extracted coupling constants; no new entities are postulated.

free parameters (1)
  • overall normalization parameter
    Single free parameter used to scale the calculated cross sections to the measured data.
axioms (1)
  • domain assumption Transition amplitudes from the previous coupled-channel analysis correctly generate the P_{car{c}} states and supply the kernels for the J/ψ N channel.
    Invoked to justify the rescattering mechanism and the relative channel strengths.

pith-pipeline@v0.9.1-grok · 5821 in / 1342 out tokens · 23896 ms · 2026-06-27T09:19:14.996639+00:00 · methodology

discussion (0)

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Reference graph

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