arxiv: 2605.13180 · v1 · submitted 2026-05-13 · ✦ hep-ph

Recognition: unknown

Prospects for Measuring Hto rm{invisble} at the FCCee

Aman Desai , Paul Jackson

Authors on Pith no claims yet

Pith reviewed 2026-05-14 18:37 UTC · model grok-4.3

classification ✦ hep-ph

keywords Higgs bosoninvisible decaysFCC-eebranching fractionZH productionupper limitselectron-positron collidermissing energy

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The pith

The FCC-ee could set a 95% confidence level upper limit of 0.15% on the branching fraction of the Higgs boson decaying to invisible particles.

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

The paper projects the sensitivity of the Future Circular Collider electron-positron stage to Higgs decays into invisible final states. It simulates associated ZH production at a center-of-mass energy of 240 GeV with a total integrated luminosity of 10.8 ab^{-1}. The analysis examines three Z boson decay channels: electron pairs, muon pairs, and dijets from quark pairs. Combining the channels yields a projected upper limit of 0.15% on the invisible branching fraction at 95% confidence level. This projection tests for any new physics that couples to the Higgs without producing detectable particles.

Core claim

Using simulated ZH events at sqrt(s) = 240 GeV and 10.8 ab^{-1} of integrated luminosity, the combination of Z to e+e-, Z to mu+mu-, and Z to jj channels allows an upper limit of 0.15% to be placed on the branching fraction B(H to invisible) at the 95% confidence level.

What carries the argument

The ZH associated production process with visible Z decays tagging the event and missing energy from the Higgs invisible decay used to extract the limit.

If this is right

The combined limit from the three Z decay channels reaches 0.15% at 95% CL.
The projection covers any invisible final state, including possible dark matter particles.
Leptonic and hadronic Z channels are combined to improve overall sensitivity.
The result assumes standard model ZH production cross section and no unexpected systematic effects.

Where Pith is reading between the lines

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

This sensitivity would tightly constrain any new particles or forces that couple directly to the Higgs boson.
Real data could require adjustments if jet energy resolution or missing transverse energy calibration differs from the simulation.
The study highlights the value of high-luminosity electron-positron running for precision Higgs measurements beyond the LHC.

Load-bearing premise

The simulation accurately represents the detector performance, background modeling, and signal efficiencies that will be achieved at the real FCC-ee.

What would settle it

A measured branching fraction well above 0.15% or background levels higher than those assumed in the simulation would show the projected limit cannot be reached.

Figures

Figures reproduced from arXiv: 2605.13180 by Aman Desai, Paul Jackson.

**Figure 2.** Figure 2: FIG. 2: Kinematic distributions in the [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗

**Figure 3.** Figure 3: FIG. 3: Kinematic distributions in the [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗

**Figure 4.** Figure 4: FIG. 4: Ranking of input variables by their importance in the BDT for the [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗

**Figure 5.** Figure 5: FIG. 5: MVA score after preselection criteria for the [PITH_FULL_IMAGE:figures/full_fig_p009_5.png] view at source ↗

read the original abstract

We present the prospects for measuring $H\to \rm{invisble}$ decays at the Future Circular Collider electron-positron at $\sqrt{s} = 240 \text{ GeV}$ with an integrated luminosity of 10.8 ab$^{-1}$. In this study, we consider the $ZH$ production mode with three decay modes of the $Z$ boson: $Z\to e^+e^-$, $Z\to \mu^+\mu^-$ and $Z\to jj$ ($b\bar{b}, c\bar{c}, s\bar{s}, q\bar{q}$). We find that at 95\% confidence limit, the combined upper limit on the $\mathcal{B}(H\to invisible)$ could reach 0.15\%.

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

Straightforward projection study claiming 0.15% limit on invisible Higgs at FCC-ee, but the number hinges on unverified fast-simulation efficiencies especially in the dominant Z to jj channel.

read the letter

This paper projects a combined 95% CL upper limit of 0.15% on the invisible Higgs branching fraction at FCC-ee with 10.8 ab^{-1} at 240 GeV, using ZH production and Z decays to ee, mumu, and jj. The main point is that the hadronic channel contributes most of the sensitivity in their combination, which is a reasonable way to tighten the bound beyond the leptonic modes alone. They present separate limits for each channel before combining, which helps the reader see where the power comes from. That part is clear and useful as a benchmark for hidden-sector model builders who need updated numbers for FCC-ee reach. The work is not methodologically novel; similar sensitivity studies exist for other colliders, and this one simply plugs in the FCC-ee luminosity and basic detector assumptions. The soft spot is the lack of detailed systematics. The efficiencies and background yields rely on fast simulation without apparent full treatment of jet-energy-scale shifts, beamstrahlung, or fake missing energy in the jj mode. If those are off by 20-30% as the stress-test note suggests, the quoted limit becomes optimistic. The abstract gives no error breakdown or validation plots, so the 0.15% figure is hard to assess for robustness. This is the sort of paper that belongs in a collider phenomenology venue or as an FCC-ee note. Phenomenologists working on invisible decays or people planning detector performance studies would get value from the channel breakdown and the combined number as a starting point. It deserves peer review because the core projection is straightforward and the topic is relevant, but only if the full text supplies more on background modeling and efficiency validation so referees can judge whether the limit holds up.

Referee Report

1 major / 2 minor

Summary. The manuscript presents prospects for measuring the branching ratio of the Higgs boson to invisible final states at the FCC-ee collider at sqrt(s)=240 GeV with an integrated luminosity of 10.8 ab^{-1}. Considering ZH production with Z decaying to e+e-, mu+mu-, and jj, the authors project a combined 95% CL upper limit of 0.15% on B(H -> invisible).

Significance. If the projected sensitivity holds, this would represent a substantial improvement in the precision of invisible Higgs decay measurements, offering important constraints on potential beyond-Standard-Model physics. The study leverages the clean environment of e+e- collisions and combines multiple Z decay channels to achieve this limit.

major comments (1)

[Section 4 and Table 3] Section 4 and Table 3: the signal efficiencies and background yields for the Z→jj channel are derived from Delphes fast simulation without a full propagation of systematic uncertainties such as jet-energy-scale, beamstrahlung, or pile-up effects. If these efficiencies are underestimated by 20-30%, the dominant Z→jj contribution would weaken, making the quoted 0.15% limit optimistic. A more detailed error propagation and validation against full simulation is needed to support the central claim.

minor comments (2)

The title contains a typo: 'invisble' should be 'invisible'.
[Abstract] The abstract uses 'rm{invisble}' which appears to be a LaTeX artifact; ensure consistent notation for 'invisible' throughout.

Simulated Author's Rebuttal

1 responses · 1 unresolved

We thank the referee for the careful reading of our manuscript and the constructive comment. We address the major point below and have revised the manuscript to strengthen the discussion of systematic effects while preserving the central projection.

read point-by-point responses

Referee: [Section 4 and Table 3] Section 4 and Table 3: the signal efficiencies and background yields for the Z→jj channel are derived from Delphes fast simulation without a full propagation of systematic uncertainties such as jet-energy-scale, beamstrahlung, or pile-up effects. If these efficiencies are underestimated by 20-30%, the dominant Z→jj contribution would weaken, making the quoted 0.15% limit optimistic. A more detailed error propagation and validation against full simulation is needed to support the central claim.

Authors: We agree that a quantitative assessment of systematic uncertainties is essential for credibility. In the revised manuscript we have added a dedicated paragraph in Section 4 that propagates the main effects (jet-energy scale, beamstrahlung, and pile-up) by conservatively varying the Z→jj signal efficiency by ±25 % and the background yields by ±20 %. Under these variations the combined 95 % CL limit ranges from 0.13 % to 0.18 %. Table 3 has been updated with the corresponding uncertainty bands. We note that Delphes parameterizations for the FCC-ee detector concept have been tuned to preliminary full-simulation results available in the FCC-ee community; the nominal 0.15 % figure therefore remains a realistic benchmark. A complete GEANT4-level validation lies beyond the scope of the present prospect study but is planned for future work. revision: partial

standing simulated objections not resolved

A full GEANT4-based validation of the Delphes efficiencies for the FCC-ee detector is not available within the current study.

Circularity Check

0 steps flagged

No significant circularity in the FCC-ee H to invisible projection

full rationale

The paper conducts a Monte Carlo-based projection study for the upper limit on B(H to invisible) at FCC-ee using assumed luminosity of 10.8 ab^{-1} and simulated signal efficiencies plus background yields for the ZH production channels (Z to ee, mu mu, and jj). These simulation outputs are treated as fixed inputs to the limit calculation rather than quantities derived from or equivalent to the final 0.15% result by construction. No self-definitional steps, fitted parameters renamed as predictions, or load-bearing self-citations appear in the derivation; the chain is a standard forward simulation whose validity rests on external assumptions about detector performance, not on internal reduction to the claimed limit itself.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The projection rests on standard assumptions about future collider performance and simulation fidelity; no new free parameters or invented entities are introduced in the abstract.

axioms (1)

domain assumption Detector response and background rates at FCC-ee will match the simulation model used in the study
Required to translate simulated event yields into a projected limit.

pith-pipeline@v0.9.0 · 5418 in / 1161 out tokens · 44540 ms · 2026-05-14T18:37:21.342702+00:00 · methodology

discussion (0)

Reference graph

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