Tau mass in u
Atomic & nuclearMeasured
= 1.907 54(13) u
- Value
- 1.907 54 u
- Standard uncertainty
- 1.3 × 10−4 u
- 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 mass in u, CODATA 2022 (NIST)
tau_mass_in_u = 1.90754 # u, standard uncertainty 0.00013
# SciPy: scipy.constants.physical_constants['tau mass in u']What it is
The rest mass of the tau, the heaviest of the three charged leptons, in unified atomic mass units (daltons), where 1 u is one twelfth of the mass of a carbon-12 atom.
In other units
| Unit | Value | |
|---|---|---|
| CGS (g) | 3.167 54 × 10−24 | |
| MeV/c² MeV / c² | 1776.86 | |
| GeV/c² GeV / c² | 1.776 86 |
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 | 1.907 54(13) | 6.8 × 10−5 | +0.0 σ of 2018 |
| 2018 | 1.907 54(13) | 6.8 × 10−5 | +0.3 σ of 2014 |
| 2014 | 1.907 49(17) | 8.9 × 10−5 | +0.0 σ of 2010 |
| 2010 | 1.907 49(17) | 8.9 × 10−5 | −0.6 σ of 2006 |
| 2006 | 1.907 68(31) | 1.6 × 10−4 | +0.0 σ of 2002 |
| 2002 | 1.907 68(31) | 1.6 × 10−4 | −0.2 σ of 1998 |
| 1998 | 1.907 74(31) | 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).