arxiv: 2604.10405 · v1 · submitted 2026-04-12 · ✦ hep-ex

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Search for dark sector and rare decays at BESIII

Zhi-Jun Li , Zheng-Yun You (on behalf of BESIII)

Authors on Pith no claims yet

Pith reviewed 2026-05-10 16:42 UTC · model grok-4.3

classification ✦ hep-ex

keywords BESIIIdark sectorsub-GeV dark matterinvisible decaysrare decayslepton number violationcharmoniumhyperon decays

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The pith

BESIII reports searches for sub-GeV dark matter and rare decays in charmonium and hyperon data.

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

The paper presents recent results from the BESIII experiment on searches for dark sector particles and rare processes using large data samples of charmonium, charm mesons, and hyperons. It covers searches for invisible particles that could indicate sub-GeV dark matter in channels such as eta to pi-zero plus missing energy and J/psi to phi plus invisible, as well as dark baryons in Xi-minus to pi-minus plus invisible. Additional analyses look for light vector bosons produced in chi_cJ decays and decaying to electron-positron pairs. The work also includes searches for rare decays like psi to electron-muon and processes that violate baryon or lepton number. These searches aim to constrain new physics models by testing for signals beyond standard model expectations in accessible low-energy regimes.

Core claim

BESIII has analyzed its charmonium and hyperon datasets to search for sub-GeV dark matter via invisible final states in eta, J/psi, and Xi decays, for light vector bosons via dilepton pairs in chi_cJ to J/psi transitions, and for rare decays including lepton flavor violation in psi decays plus baryon and lepton number violating processes.

What carries the argument

Missing-mass reconstruction in two-body decays to identify invisible particles together with dilepton invariant mass analysis for light vector boson candidates.

If this is right

Upper limits on branching fractions for invisible decays constrain the production rates of sub-GeV dark matter and dark baryons.
Limits on light vector boson production in charmonium transitions bound the couplings of such bosons to charm quarks.
Searches for lepton flavor violation and number-violating decays set bounds on the rates of these forbidden processes.

Where Pith is reading between the lines

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

These limits from low-energy decays can be combined with direct detection results to narrow dark matter model parameter spaces.
Future increases in BESIII luminosity would tighten the constraints on lighter or more weakly coupled dark particles.
The missing-mass techniques used here could extend to other exotic searches at similar energy colliders.

Load-bearing premise

That backgrounds from known processes and detector inefficiencies are correctly accounted for so that any excess would point to new physics.

What would settle it

A statistically significant excess above expected backgrounds in the missing-mass spectrum for one of the invisible decay channels or a resonant peak in the dilepton mass distribution.

read the original abstract

The BESIII experiment has collected a large data sample of charmonium, charm mesons, hyperons, and other light mesons. These data provide a unique opportunity to explore the dark sector and rare decays. We present recent dark sector results from the BESIII experiment, including searches for sub-GeV dark matter in $\eta \to \pi^0 + \text{invisible}$ and $J/\psi \to \phi + \text{invisible}$, searches for dark baryon particles in $\Xi^- \to \pi^- +\rm{invisible}$, and searches for light vector bosons in $\chi_{cJ} \to J/\psi X$, where $X \to e^+ e^-$. In addition, we also present the recent rare decay searches, including a search for $\psi \to e \mu$, as well as searches for several baryon number and lepton number violation processes, and searches for various charmonium weak decays.

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.

Desk Editor's Note private letter to a colleague

BESIII summary reports new upper limits on invisible decays and rare processes from their data, all null results using standard methods.

read the letter

This paper is a concise summary of recent BESIII searches for sub-GeV dark sector particles and rare or forbidden decays. The main points are updated limits on invisible final states in eta to pi0, J/psi to phi, and Xi to pi invisible, plus light vector boson searches in chi_cJ decays and a few lepton or baryon number violating modes, all with no signals observed in the current data sample. These are new results because they draw on the latest statistics collected at the tau-charm factory. The work does well by pulling together several motivated channels in one place and showing how the clean e+e- environment helps with missing-energy and low-mass resonance searches. The collaboration has experience with these techniques, so the null outcomes line up with expectations from prior BESIII papers. Soft spots are minor and expected for this format. It reads like a conference proceedings overview, so background modeling, efficiency curves, and full systematic breakdowns are referenced rather than shown in detail. That makes independent verification harder from this text alone, but the claims do not rely on any unusual assumptions or circular fits. The results rest on established procedures. This is useful for experimentalists and model builders who need a quick update on current bounds in the light dark sector or rare decay space. A reader who wants the precise numbers or plans to incorporate the limits into a model would get value here, though they would likely cross-check the individual analysis papers. It deserves serious referee time because the results are fresh experimental constraints from a running facility, even if the paper itself is more report than deep methodological advance. I would send it for peer review rather than desk reject.

Referee Report

0 major / 3 minor

Summary. The manuscript summarizes recent BESIII results on dark sector searches and rare decays using charmonium, charm, and hyperon data samples. It reports upper limits from null searches for sub-GeV dark matter via invisible decays (η → π⁰ + invisible, J/ψ → φ + invisible, Ξ⁻ → π⁻ + invisible), light vector bosons (χcJ → J/ψ X with X → e⁺e⁻), lepton-flavor violation (ψ → eμ), and baryon/lepton-number violating processes, along with charmonium weak decays.

Significance. If the reported limits hold, the results tighten constraints on sub-GeV dark matter and light vector boson models in a mass range complementary to other experiments, while the rare-decay searches test Standard Model conservation laws at the 10^{-6}–10^{-8} level. The use of existing high-statistics BESIII samples provides competitive bounds without requiring new data taking.

minor comments (3)

The abstract and introduction list multiple searches but do not include a summary table of all branching-fraction upper limits; adding such a table (with references to the corresponding sections) would improve readability and allow direct comparison with results from Belle II or LHCb.
Several figures are mentioned (e.g., invariant-mass distributions or efficiency curves for the invisible-decay channels) but lack explicit labels for background components or systematic uncertainty bands; clarifying these would strengthen the presentation of the null results.
The text refers to 'recent' results without specifying the data sample sizes (e.g., number of J/ψ or η events) or integrated luminosities used in each analysis; including these numbers explicitly in the relevant sections would aid reproducibility.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for the careful review and positive recommendation of minor revision. The report highlights the relevance of our BESIII results on sub-GeV dark matter searches and rare decays. No specific major comments were provided in the report, so we have performed a thorough internal review and incorporated minor clarifications and updates to the text, figures, and references as appropriate for the final version.

Circularity Check

0 steps flagged

No significant circularity detected

full rationale

This is a concise experimental summary paper reporting null results and upper limits from BESIII searches for dark sector signals and rare decays. No derivations, theoretical models, parameter fits, or ansatzes are introduced; the claims rest on standard data analysis, background subtraction, and efficiency corrections already validated externally. No load-bearing step reduces by construction to self-citation, fitted inputs renamed as predictions, or self-definitional loops. The paper is self-contained against external benchmarks with no internal reduction of results to its own inputs.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

No theoretical derivations; the paper reports experimental limits on standard dark-sector and rare-decay hypotheses. No free parameters, axioms, or invented entities are introduced by the authors.

pith-pipeline@v0.9.0 · 5462 in / 1073 out tokens · 49369 ms · 2026-05-10T16:42:17.278911+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

22 extracted references · 22 canonical work pages · 2 internal anchors

[1]

Design and Construction of the BESIII Detector

M. Ablikimet al.[BESIII], Nucl. Instrum. Meth. A 614 (2010), 345-399 [arXiv:0911.4960 [physics.ins-det]]

work page Pith review arXiv 2010
[2]

Yuet al.doi:10.18429/JACoW-IPAC2016-TUYA01

C. Yuet al.doi:10.18429/JACoW-IPAC2016-TUYA01

work page doi:10.18429/jacow-ipac2016-tuya01
[3]

Z. J. Liet al.Front. Phys. (Beijing) 19 (2024) no.6, 64201 [arXiv:2404.07951 [physics.data- an]]

work page arXiv 2024
[4]

Batell, A

B. Batellet al.Phys. Rev. D 100 (2019) no.9, 095020 [arXiv:1812.05103 [hep-ph]]

work page arXiv 2019
[5]

Search for sub-GeV dark particles in $\eta\to\pi^0+\rm{invisible}$ decay

M. Ablikimet al.[BESIII], [arXiv:2601.10597 [hep-ex]]

work page internal anchor Pith review Pith/arXiv arXiv
[6]

Ninget al.[PandaX], Phys

X. Ninget al.[PandaX], Phys. Rev. Lett. 131 (2023) no.4, 041001 doi:10.1103/PhysRevLett.131.041001 [arXiv:2301.03010 [hep-ex]]

work page doi:10.1103/physrevlett.131.041001 2023
[7]

Cortina Gilet al.[NA62], JHEP 11 (2025), 143 [arXiv:2507.17286 [hep-ex]]

E. Cortina Gilet al.[NA62], JHEP 11 (2025), 143 [arXiv:2507.17286 [hep-ex]]

work page arXiv 2025
[8]

A. V. Artamonovet al.[BNL-E949], Phys. Rev. D 79 (2009), 092004 [arXiv:0903.0030 [hep-ex]]

work page arXiv 2009
[9]

Cortina Gilet al.[NA62], JHEP 02 (2021), 201 [arXiv:2010.07644 [hep-ex]]

E. Cortina Gilet al.[NA62], JHEP 02 (2021), 201 [arXiv:2010.07644 [hep-ex]]

work page arXiv 2021
[10]

Ablikimet al.[BESIII], Phys.Rev.Lett

M. Ablikimet al.[BESIII], Phys.Rev.Lett. 135 (2025), 151804 [arXiv:2506.10316 [hep-ex]]

work page arXiv 2025
[11]

Alonso- ´Alvarez, G

G. Alonso- ´Alvarezet al.Phys. Rev. D 105 (2022) no.11, 115005 [arXiv:2111.12712 [hep- ph]]

work page arXiv 2022
[12]

Ablikimet al.[BESIII], Phys.Lett.B 872 (2026) 140099 [arXiv:2505.22140 [hep-ex]]

M. Ablikimet al.[BESIII], Phys.Lett.B 872 (2026) 140099 [arXiv:2505.22140 [hep-ex]]

work page arXiv 2026
[13]

Ablikimet al.) (10 2025),arXiv:2510.16531 [hep-ex]

M. Ablikimet al.[BESIII], Phys.Rev.D 113 (2026) 3, 032009 [arXiv:2510.16531 [hep-ex]]

work page arXiv 2026
[14]

Ablikimet al.[BESIII], [arXiv:2507.10331 [hep-ex]]

M. Ablikimet al.[BESIII], [arXiv:2507.10331 [hep-ex]]

work page arXiv
[15]

Ablikimet al.[BESIII], Phys.Rev.D 111 (2025), 112010 [arXiv:2504.07817 [hep-ex]]

M. Ablikimet al.[BESIII], Phys.Rev.D 111 (2025), 112010 [arXiv:2504.07817 [hep-ex]]

work page arXiv 2025
[16]

Ablikimet al.[BESIII], [arXiv:2507.06872 [hep-ex]]

M. Ablikimet al.[BESIII], [arXiv:2507.06872 [hep-ex]]

work page arXiv
[17]

Ablikimet al.(BESIII), Search for the lepton number violating decayη→π +π+e−e−+c.c

M. Ablikimet al.[BESIII], Phys.Rev.D 112 (2025), 112021 [arXiv:2509.21921 [hep-ex]]

work page arXiv 2025
[18]

Ablikimet al.(BESIII), Search for the lepton number violation decayω→π +π+e−e−+c.c., (2025), arXiv:2504.21539 [hep-ex]

M. Ablikimet al.[BESIII], Chin.Phys.C 49 (2025), 103002 [arXiv:2504.21539 [hep-ex]]

work page arXiv 2025
[19]

Search for the charmonium semi-leptonic weak decay $J/\psi\rightarrow D_s^-e^+\nu_e+c.c.$

M. Ablikimet al.[BESIII], [arXiv:2510.25100 [hep-ex]]

work page internal anchor Pith review Pith/arXiv arXiv
[20]

Ablikimet al.[BESIII], JHEP 12 (2025) 077 [arXiv:2506.09386 [hep-ex]]

M. Ablikimet al.[BESIII], JHEP 12 (2025) 077 [arXiv:2506.09386 [hep-ex]]

work page arXiv 2025
[21]

Ablikim et al

M. Ablikimet al.[BESIII], [arXiv:2511.16083 [hep-ex]]

work page arXiv
[22]

Ablikimet al.[BESIII], [arXiv:2603.01777 [hep-ex]]

M. Ablikimet al.[BESIII], [arXiv:2603.01777 [hep-ex]]

work page arXiv