The short answer
This guide separates the measured record from shortcuts in its retelling.
Read the evidence
Keep the evidence attached to its claim
The same observation can answer some questions while leaving others open.
| Record or task | What it supports | What remains open |
|---|---|---|
| Detector events | Interactions selected and analysed | An identical numerical flux |
| Flux | Particles per area per time | An event yield without detector response |
| Central-value subtraction | A check on a simplified claim | The collaboration’s full joint analysis or significance |
Chronology
A timeline of the turning points
Published neutral-current evidence
The collaboration published flavour-transformation evidence.
Earlier institutional recognition
The Franklin Institute recognised McDonald and Totsuka.
Physics Nobel
McDonald shared the award with Takaaki Kajita.
The experiment compared different sensitivities
SNO compared charged-current, neutral-current and elastic-scattering channels to test the electron-only hypothesis.
The Franklin Institute’s historical account explains the role of heavy water and the underground setting. The primary paper retains the detector analysis and assumptions behind the inference. McDonald’s leadership is part of a collaboration’s result, with the team’s author and institutional credits preserved.
Flux is not a detector event count
The paper distinguishes selected interactions from inferred flux, expressed per area and time.
Worked unit exercise: a fictional uniform flux of 2×10⁶ cm⁻² s⁻¹ crosses a 1 cm² area for 3 s. Multiplication gives 6×10⁶ crossings. It does not give six million detected interactions: converting crossings to events requires interaction probabilities, target properties and detection response. No historical SNO event yield is calculated here.
Sources for this section: [1]
Central values are not a substitute for a fit
Reported CC and NC fluxes, in 10⁶ cm⁻² s⁻¹, include 1.76 and 5.09; the flavour analysis gives a non-electron component of 3.41 under the standard ⁸B spectrum assumption. Subtracting the first two central values gives 3.33, not that quoted component.
That arithmetic checks an oversimplified account; it does not independently reproduce the data analysis. The paper changes variables to test whether the non-electron component is zero, avoiding a prior calculation of channel-signal correlations.
Sources for this section: [1]
Reference answers: what the evidence does and does not say
Question: can the central-value subtraction alone reproduce the reported significance, or directly measure every neutrino’s mass?
Answer: no. The published significance belongs to the specified analysis with its uncertainty treatment. Flavour transformation has implications for neutrino physics, but these selected numbers do not provide a direct individual mass measurement. A source-faithful summary should identify the collaboration, channels, assumptions and result, and leave a claim about independently reproducing its statistical analysis for work that actually performs it.
Continue the chronology
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Explore Canada through connected lives
Connected biographies
Researchers and their work
1943–
Arthur McDonald
Experimental physicist and research collaboration leaderArthur McDonald led the SNO collaboration as it used heavy water deep underground to compare solar-neutrino signals, building a career across Canada and Princeton.Read biographyQuick answers
Common questions
- Why is 5.09 minus 1.76 not the reported 3.41 component?
- The component comes from the stated flavour analysis, not a subtraction exercise.
- Are six million crossings six million detected events?
- No. The fictional multiplication supplies crossings only, without interaction and detection probabilities.
Primary and institutional sources
How this history was checked
Compare the inspected records with the question, calculation and stated limits below. This article was reviewed on 29 October 2026.