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arxiv: 2606.19991 · v1 · pith:JQNYAVP7new · submitted 2026-06-18 · ✦ hep-ph · hep-ex

Xi_(cc)⁺⁺-Xi_(cc)⁺ Transitions as a Two-Charm-Selective Portal to Ultra-Low-Q Charged Currents

Yong Du This is my paper

Pith reviewed 2026-06-26 17:11 UTC · model grok-4.3

classification ✦ hep-ph hep-ex
keywords doubly charmed baryonscharged current new physicsLHCbportal interactionsultra-low Q transitionseffective operatorsbaryon matrix elements
0
0 comments X

The pith

Transitions between doubly charmed baryons can probe a charged-current new physics portal that evades other constraints.

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

The paper shows that the LHCb observation of the Ξcc+ baryon makes the ultra-low energy transition to Ξcc++ a practical null test for new charged-current interactions. Analyses of two- and three-body decays indicate that this channel can reach effective baryon-level couplings of order 10^{-6} to 10^{-7} at MeV-scale momenta. A universal light charged scalar is ruled out by existing electroweak and beta-decay bounds, yet the authors construct a two-charm-selective portal whose leading operator affects only doubly charmed baryons. In models realizing this portal the Ξcc transition therefore supplies the leading direct probe because the operator vanishes at leading order in pions, nucleons, nuclei, and singly charmed mesons.

Core claim

The central claim is that Ξcc++→Ξcc+ transitions provide the leading direct probe of a two-charm-selective charged-current portal; the portal's leading operator has a nonzero matrix element in doubly charmed baryons while vanishing at leading order in pions, nucleons, nuclei, and singly charmed mesons, so that in this class of models the transition is not superseded by other searches.

What carries the argument

The two-charm-selective charged-current portal, an effective operator whose leading term couples only to states containing two charm quarks.

If this is right

  • The transition reaches sensitivity to baryon-level couplings of O(10^{-6}–10^{-7}) at MeV recoil momenta.
  • It functions as a null test for charged-current new physics in this selective class of models.
  • Existing electroweak-precision and beta-decay constraints remain parametrically stronger for any universal light charged scalar.
  • The portal operator produces no leading-order effects in pions, nucleons, nuclei, or singly charmed mesons.

Where Pith is reading between the lines

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

  • Dedicated LHCb analyses of the Ξcc++→Ξcc+ channel could set the first direct limits on such selective portals.
  • The same selectivity logic may apply to other multi-heavy-flavor systems where ordinary-matter constraints are absent.
  • Theoretical work on the precise matrix element in the doubly charmed baryons would sharpen the projected reach.

Load-bearing premise

The leading operator of the two-charm-selective portal has a nonzero matrix element in doubly charmed baryons but vanishes at leading order in pions, nucleons, nuclei, and singly charmed mesons.

What would settle it

An experimental bound on the Ξcc++→Ξcc+ rate that is stronger than the projected 10^{-6}–10^{-7} coupling sensitivity while beta-decay and electroweak observables remain consistent with the standard model would support the portal's selectivity; a comparable signal appearing first in ordinary beta decay would falsify it.

Figures

Figures reproduced from arXiv: 2606.19991 by Yong Du.

Figure 2
Figure 2. Figure 2: For the two-body benchmark QΞ = 1.77 MeV, mX = 1.0 MeV, our simulation gives ϵ fd rel(X+) = 0.571, ϵvis rel(X+) = 2.00 × 10−3 , ftrk(X+) = 2.99 × 10−4 , (17) where ϵ fd rel is the feed-down efficiency relative to the nor￾malization mode, ϵ vis rel is the efficiency after imposing a visible-recoil trackability proxy, and ftrk is the fraction of recoils satisfying p(X+) > 1.5 GeV. The correspond￾ing expected… view at source ↗
Figure 1
Figure 1. Figure 1: FIG. 1. Left: projected LHCb sensitivity to the two-body coupling [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Fast-simulation projection, based on standalone [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. One-sided 95% C.L. profile-likelihood limit on [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Dominance plane at [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Tree-level matching topology for the two-charm [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. Representative fast-simulation diagnostics. Panels (a) and (b) show the two-body [PITH_FULL_IMAGE:figures/full_fig_p009_6.png] view at source ↗
read the original abstract

The recent LHCb observation of $\Xi_{cc}^{+}$ opens the ultra-low-$Q$ transition $\Xi_{cc}^{++}\to\Xi_{cc}^{+}$ as an experimentally motivated null test of charged-current new physics. Our two- and three-body analyses show sensitivity to effective baryon-level couplings of $\mathcal{O}(10^{-6}-10^{-7})$ for MeV-scale recoil momenta. We establish a practical no-go result for a universal light charged scalar $\phi^+$: with a first-generation $\phi^+\bar u d$ coupling, existing electroweak-precision and beta-decay constraints are parametrically stronger than the projected LHCb sensitivity. We then identify a two-charm-selective charged-current portal whose leading operator has a nonzero matrix element in doubly charmed baryons but vanishes at leading order in pions, nucleons, nuclei, and singly charmed mesons. In this class of models, $\Xi_{cc}^{++}\to\Xi_{cc}^{+}$ transitions can provide the leading direct probe of the portal interaction.

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

0 major / 2 minor

Summary. The manuscript proposes the ultra-low-Q transition Ξcc++ → Ξcc+ as a null test for charged-current new physics. It reports that two- and three-body analyses yield sensitivity to effective baryon-level couplings of O(10^{-6}–10^{-7}), derives a parametric no-go for a universal light charged scalar from electroweak-precision and beta-decay bounds, and constructs a class of two-charm-selective portals in which the leading operator has a nonzero matrix element between doubly charmed baryons while vanishing at leading order in pions, nucleons, nuclei, and singly charmed mesons; in this class the Ξcc transition supplies the leading direct probe.

Significance. If the results hold, the work identifies a targeted experimental channel for charged-current new physics that is automatically selective to doubly charmed systems and therefore evades standard constraints from lighter hadrons. The explicit construction of the selective operator class, the parametric no-go for the universal scalar, and the sensitivity projections grounded in existing LHCb observations constitute the main strengths.

minor comments (2)
  1. [Abstract] Abstract: the statement that 'two- and three-body analyses show sensitivity' is not accompanied by a reference to the section or equation containing the matrix elements or error estimates; adding such a pointer would improve traceability.
  2. The explicit form of the two-charm-selective operator and its leading-order matrix elements between Ξcc states versus the listed lighter systems are asserted but not displayed; placing the operator definition and the leading-order vanishing argument in a dedicated subsection would strengthen the presentation.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for the positive assessment of our manuscript, including the summary of the proposed Ξcc++ → Ξcc+ transition as a two-charm-selective null test for charged-current new physics, the significance of the selective operator class and parametric no-go result, and the recommendation for minor revision. No specific major comments were raised in the report.

Circularity Check

0 steps flagged

No significant circularity identified

full rationale

The paper constructs a specific class of models featuring a two-charm-selective charged-current portal by design, then demonstrates that the leading operator has a nonzero matrix element between Ξcc states while vanishing at leading order for pions, nucleons, nuclei, and singly charmed mesons. It derives a parametric no-go for the universal light scalar from existing electroweak-precision and beta-decay constraints (external to this work) and projects LHCb sensitivity to the selective case. No load-bearing step reduces by construction to a fitted parameter from the same data, a self-citation chain, or a self-definitional loop; the central claim remains conditional on the deliberately constructed model class but is independent of the result itself.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 1 invented entities

The central claim rests on standard effective-field-theory assumptions for charged-current operators plus the existence of a new selective interaction whose matrix elements are computed but not shown. No free parameters are fitted in the abstract; the O(10^{-6}-10^{-7}) range is a projected sensitivity, not a fit. The invented entity is the two-charm-selective portal itself.

axioms (2)
  • domain assumption Effective baryon-level operators can be matched to quark-level charged-current interactions in the low-energy regime.
    Invoked to translate the portal into observable transition rates (abstract).
  • ad hoc to paper Matrix elements of the selective operator vanish at leading order in pions, nucleons, nuclei, and singly charmed mesons.
    This is the defining property of the portal that makes the Ξcc transition the leading probe.
invented entities (1)
  • two-charm-selective charged-current portal no independent evidence
    purpose: New interaction that couples only to doubly charmed baryons at leading order while vanishing elsewhere.
    Introduced to evade electroweak and beta-decay bounds while remaining visible in the target transition.

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discussion (0)

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Reference graph

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