arxiv: 2604.22079 · v1 · submitted 2026-04-23 · ✦ hep-ex

Recognition: unknown

bto sell^+ell^- (ell = e, μ, τ) and bto sνbarν at Belle and Belle II

Belle II Collaborations), Meihong Liu (on behalf of the Belle

Pith reviewed 2026-05-08 13:08 UTC · model grok-4.3

classification ✦ hep-ex

keywords rare B decaysb to s transitionsmissing energyneutrino final statestau lepton pairsinclusive measurementsflavor changing neutral currents

0 comments

The pith

Belle and Belle II data enable reinterpretation of B to K nu nu and first inclusive B to Xs nu nu measurement using missing energy.

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

The paper presents results from the combined Belle and Belle II dataset of 1.2 ab inverse collected at the Υ(4S) resonance in e+ e- collisions. It emphasizes that the clean environment and precisely known initial state make these data suitable for rare b to s transitions that produce neutrinos and thus missing energy. The work includes a reinterpretation of the exclusive B+ to K+ nu nu mode, the first inclusive measurement of B to Xs nu nu extracted directly from missing energy in B decays, and searches for several modes with tau lepton pairs such as B0 to K*0 tau+ tau- and B+ to K+ tau+ tau-. These channels test the standard model in flavor-changing neutral currents where new physics could appear.

Core claim

Owing to the clean event environment and the well-constrained initial-state kinematics at the Υ(4S) resonance, the Belle and Belle II data support the reinterpretation of B+ to K+ nu nu, the first inclusive measurement of B to Xs nu nu with missing energy directly from B decays, and searches for B0 to K*0 tau+ tau-, B0 to KS0 tau+ tau-, and B+ to K+ tau+ tau-.

What carries the argument

Reconstruction of missing energy signatures in B decays enabled by the known initial-state kinematics of e+ e- collisions at the Υ(4S) resonance.

If this is right

The inclusive B to Xs nu nu rate provides a direct test of standard model branching fraction predictions that is less sensitive to form factor uncertainties than exclusive modes.
Limits or signals in the tau-pair modes constrain contributions from new physics that couple preferentially to third-generation leptons.
The same data set yields updated constraints on Wilson coefficients in the effective theory for b to s transitions.
Reinterpretation of existing exclusive modes improves consistency checks across different final states.

Where Pith is reading between the lines

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

These missing-energy techniques could be applied to other rare processes such as B to invisible final states or modes with multiple neutrinos.
Combining the inclusive neutrino rate with exclusive measurements may tighten bounds on right-handed currents or leptoquark models.
Higher statistics from continued Belle II running would allow differential distributions in the inclusive channel to be measured.

Load-bearing premise

The clean event environment and well-constrained initial-state kinematics at the Υ(4S) resonance allow reliable extraction of signals in channels with missing energy from neutrinos or taus.

What would settle it

A measurement of the missing energy distribution in the B to K nu nu channel that shows no statistically significant excess over background expectations after efficiency corrections and sideband subtraction.

read the original abstract

The Belle and Belle~II experiments have accumulated a combined data set of $1.2~\mathrm{ab}^{-1}$ of $e^+e^- \to B\bar{B}$ collisions at the $\Upsilon(4S)$ resonance. Owing to the clean event environment and the well-constrained initial-state kinematics, these data are particularly well suited for studying channels involving missing energy from neutrinos. This includes the reinterpretation of $B^+\to K^+\nu\bar{\nu}$ and the first inclusive measurement of $B\to X_s\nu\bar{\nu}$ with the missing energy directly from $B$ decays, as well as searches involving missing energy from $\tau$ decays, such as $B^0\to K^{*0}\tau^+\tau^-$, $B^0\to K_S^{0}\tau^+\tau^-$, and $B^+\to K^{+}\tau^+\tau^-$.

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

This is a high-level summary of Belle and Belle II results on rare b to s decays, with a first inclusive nu nu-bar measurement but few analysis details.

read the letter

The main thing to know is that this is a short summary of experimental results from Belle and Belle II on rare b to s transitions, with emphasis on modes that have neutrinos or taus in the final state. The new elements are the first inclusive measurement of B to X_s nu nu bar using the combined dataset, plus updated searches for B to K tau tau and similar channels. These build on the clean kinematics at the Upsilon(4S), where the total energy and momentum are known precisely, so missing energy can be calculated directly from the visible particles. The paper does well at explaining why B factories are good for these missing-energy channels and at listing the specific modes being pursued. It correctly notes that this setup helps with channels that would be harder at hadron colliders. On the soft side, the text stays at a high level and does not give the actual measured values, limits, or details on how backgrounds were subtracted or how efficiencies were determined. Without those, it's difficult to assess how solid the results are or how much they tighten constraints on new physics. The abstract and summary mention the measurements but leave the quantitative part out. This kind of overview is aimed at people working in flavor physics who need to stay current on experimental progress without diving into every technical paper. A reader interested in the latest bounds on Wilson coefficients or new particle contributions would get value from knowing what is being measured now. It deserves a serious referee because it reports genuine new experimental work, even if presented concisely. The claims about the data's suitability are standard and well-supported by the B-factory setup. I would recommend sending it to peer review if it's intended for a proceedings volume, with the expectation that the authors expand on the analysis methods in the full version.

Referee Report

0 major / 0 minor

Summary. The manuscript summarizes the capabilities of the combined Belle and Belle II dataset of 1.2 ab^{-1} at the Υ(4S) for b→sℓ⁺ℓ⁻ (ℓ = e, μ, τ) and b→sνν̄ decays. It highlights the advantages of the clean e⁺e⁻ environment and precisely known initial-state kinematics for missing-energy channels, including reinterpretation of B⁺→K⁺νν̄, the first inclusive B→X_sνν̄ measurement, and searches for B⁰→K^{*0}τ⁺τ⁻, B⁰→K_S⁰τ⁺τ⁻, and B⁺→K⁺τ⁺τ⁻.

Significance. The central claim—that B-factory kinematics enable reliable extraction of signals with missing energy from neutrinos or taus—is a standard, well-established feature of Υ(4S) data and does not rely on unstated assumptions about perfect tagging or background modeling. If the referenced measurements are carried out, they would usefully complement LHCb results on these FCNC processes, particularly for inclusive and τ modes where the known four-momentum provides direct access to E_miss and p_miss.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive assessment of our manuscript and for recommending minor revision. The referee's summary accurately captures the content and scope of our work on b→sℓ⁺ℓ⁻ and b→sνν̄ decays using the combined Belle and Belle II dataset. No specific major comments were provided in the report.

Circularity Check

0 steps flagged

No significant circularity: experimental summary only

full rationale

This is a conference-style summary of Belle/Belle II experimental results on rare B decays. No theoretical derivation, model, or equation chain is presented. The central statements about data suitability for missing-energy channels rest on the standard, externally known kinematics of Υ(4S) e⁺e⁻ collisions (total four-momentum known to high precision), not on any internal fit, self-definition, or self-citation that reduces the claim to its own inputs. No load-bearing step matches any of the enumerated circularity patterns.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

As an experimental measurement paper the central claims rest on detector performance, background subtraction techniques, and Standard Model comparison rather than new theoretical constructs; no free parameters or invented entities are introduced in the abstract.

axioms (1)

domain assumption The Standard Model provides the baseline predictions against which experimental results are compared.
Implicit when reporting measurements of rare decays expected to be suppressed in the SM.

pith-pipeline@v0.9.0 · 5480 in / 1218 out tokens · 47921 ms · 2026-05-08T13:08:31.784938+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

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HEPDATA: https://www.hepdata.net/record/146803