Neutrino Mass Hierarchy Calculator

Tune lightest mass and splittings to explore spectra. See eigenvalues, sums, and effective observables instantly. Use it for lectures, labs, reports, and checks daily.

Inputs
Units are eV and eV². Angles in degrees.
Choose which eigenstate is lightest.
Nonnegative. Try 0 to 0.2.
Solar splitting (positive).
Atmospheric-scale splitting magnitude.
Controls |Ue1| and |Ue2| weights.
Controls |Ue3| weight.
Clear
Example output table
Shown for m0 = 0.010 eV using the default splittings and angles.
Ordering m0 (eV) m1 (eV) m2 (eV) m3 (eV) Σm (eV) mβ (eV) mββ min (eV) mββ max (eV)
Normal 0.010 0.01 0.0132 0.0512 0.0744 0.0133 0.0018 0.0119
Inverted 0.010 0.0512 0.0519 0.01 0.113 0.0508 0.0192 0.0505
Formula used
This calculator uses the standard three-neutrino framework with two independent mass-squared splittings.
Mass reconstruction
Normal: m1 = m0
m2² = m1² + Δm21²
m3² = m1² + |Δm3ℓ²|

Inverted: m3 = m0
m1² = m3² + |Δm3ℓ²|
m2² = m1² + Δm21²
Observables
Σm = m1 + m2 + m3
mβ = √( |Ue1|² m1² + |Ue2|² m2² + |Ue3|² m3² )
mββ = | Ue1² m1 + Ue2² m2 e^{iα} + Ue3² m3 e^{iβ} |
The reported mββ is a phase-agnostic range: [max(0, a−b−c, b−a−c, c−a−b), a+b+c] with a=|Ue1|²m1, b=|Ue2|²m2, c=|Ue3|²m3.
How to use this calculator
  1. Select the mass ordering (normal or inverted).
  2. Enter the lightest mass m0 and the two splittings in eV².
  3. Provide mixing angles θ12 and θ13 in degrees.
  4. Press Submit to compute masses and observables.
  5. Use Download CSV or Download PDF to export results.

Hierarchy decision inputs and constraints

The calculator starts from the lightest mass m0 and the two independent splittings. Use Δm21² for the solar scale and |Δm3ℓ²| for the atmospheric scale. In normal ordering, m1 is the lightest; in inverted ordering, m3 is the lightest. For small m0, the spectrum is strongly hierarchical; for larger m0, it becomes quasi-degenerate.

Mass eigenvalues and ordering signatures

With fixed splittings, increasing m0 lifts all three eigenvalues while preserving their squared differences. Normal ordering typically yields m3 separated above m1 and m2. In inverted ordering, m1 and m2 cluster above m3. Comparing the plotted bars helps communicate this signature in lectures and reports.

Sum of masses for cosmology checks

The sum Σm = m1 + m2 + m3 is a compact diagnostic for cosmological bounds. When m0 is near zero, Σm approaches a minimum set by the splittings. As m0 grows, Σm increases nearly linearly, so sensitivity improves for quasi-degenerate spectra. Exporting CSV is useful for scanning m0 grids.

Effective beta mass for endpoint experiments

The effective mass mβ weights each eigenvalue by |Uei|² and uses squared masses. θ12 and θ13 control these electron-flavor weights and therefore shift mβ even at fixed splittings. The plot overlays mβ as a horizontal guide, helping connect oscillation inputs to kinematic searches.

Neutrinoless decay range from unknown phases

The calculator reports an mββ interval rather than a single value. The maximum occurs when all contributions add coherently. The minimum can be suppressed by destructive interference and may reach zero when triangle conditions are satisfied. This range is a practical way to discuss phase uncertainty without choosing specific Majorana phases.

Workflow tips for systematic exploration

Start by reproducing your preferred benchmark inputs and verify the derived splittings. Next, sweep m0 over a physically relevant range and compare ordering behavior in the graph. Save several scenarios as PDF summaries for documentation. For publications, keep units explicit and report both ordering assumptions alongside Σm, mβ, and the mββ range.

FAQs

What does “mass hierarchy” mean here?

It refers to whether m1 is lightest (normal ordering) or m3 is lightest (inverted ordering), given the measured mass-squared splittings from oscillations.

Why is Δm21² always positive?

By convention, Δm21² = m2² − m1² is defined with m2 above m1, so it is taken as positive when reporting solar-scale oscillation results.

What is the meaning of |Δm3ℓ²|?

It is the magnitude of the atmospheric-scale splitting between m3 and the lighter pair. The sign depends on ordering, so this tool uses the absolute value as input.

Why does mββ appear as a range?

Unknown Majorana phases can make the three contributions add or cancel. The calculator reports the physically allowed minimum and maximum without fixing those phases.

Can this tool determine the true ordering?

No. It explores consequences of each ordering for a chosen parameter set. Determining ordering requires experimental inputs beyond the parameters entered here.

Which inputs most strongly change Σm?

The lightest mass m0 dominates Σm once it exceeds the scale set by the splittings. The splittings mainly set the minimum Σm when m0 is close to zero.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.