Tau energy equivalent
Atomic & nuclearMeasured
= 1776.86(12) MeV
- Value
- 1776.86 MeV
- Standard uncertainty
- 0.12 MeV
- Relative uncertainty
- 6.8 × 10−5 (68 parts per million)
- Status
- Measured
- Symbol
- Source
- CODATA 2022 via NIST · NIST entry
Use in a calculation
# tau energy equivalent, CODATA 2022 (NIST)
tau_energy_equivalent = 1.77686e3 # MeV, standard uncertainty 0.12
# SciPy: scipy.constants.physical_constants['tau energy equivalent']What it is
The rest energy of the tau lepton in mega-electronvolts. CODATA takes the tau mass from particle-physics measurements compiled by the Particle Data Group.
In other units
| Unit | Value | |
|---|---|---|
| CGS (cm2 g s−2) | 0.002 846 84 | |
| keV kiloelectronvolt | 1 776 860 | |
| GeV gigaelectronvolt | 1.776 86 | |
| erg erg | 0.002 846 84 |
Converted with ConstantID's unit table; digits are rounded to the precision of the value, and a long exact value is rounded only for display. The relative uncertainty is unchanged by conversion to an exactly defined unit.
How the value changed, 1998–2022
Each point is one CODATA adjustment, plotted as its difference from the 2022 value; the bars show one standard uncertainty (an arrowhead means the bar runs off the chart).
Relative uncertainty
| CODATA | Value (uncertainty) | Relative uncertainty | Change from previous |
|---|---|---|---|
| 2022 | 1776.86(12) | 6.8 × 10−5 | +0.0 σ of 2018 |
| 2018 | 1776.86(12) | 6.8 × 10−5 | +0.2 σ of 2014 |
| 2014 | 1776.82(16) | 9.0 × 10−5 | +0.0 σ of 2010 |
| 2010 | 1776.82(16) | 9.0 × 10−5 | −0.6 σ of 2006 |
| 2006 | 1776.99(29) | 1.6 × 10−4 | +0.0 σ of 2002 |
| 2002 | 1776.99(29) | 1.6 × 10−4 | −0.2 σ of 1998 |
| 1998 | 1777.05(29) | 1.6 × 10−4 |
“Change from previous” is the shift in the value divided by the standard uncertainty of the previous adjustment. Earlier values are converted into the current unit where NIST changed it (for example J s to J Hz⁻¹).