Proton mass.

value = pmass
[value,sigma] = pmass

pmass returns the mass of a proton in SI units (kg) in value and the standard deviation in sigma (if two output arguments are specified).

The value and the standard deviation are taken from the 2018 CODATA collection of recommended values.

amu, angstrom, avogadro, barn, bmagn, bohrrad, boltzm, clight, echarge, emass, eps0, evolt, faraday, gammae, gfree, hartree, hbar, molgas, mu0, nmagn, nmass, planck, rydberg