Saturday, April 11, 2015
NEUTRON-PROTON MASS DIFFERENCE FROM FIRST PRINCIPLES
The neutron-proton mass difference -- approximately 2 and a half times the mass of an electron -- was calculated for the first time from the basic principles and properties of the "Standard Model".
In this calculation, according to the authors, the mass "difference results from the competition between electromagnetic and mass isospin breaking effects". The calculation was done using a lattice (to approximate space-time) and four model quarks.
A report is available on ARXIV: http://arxiv.org/pdf/1406.4088.pdf
The paper is published in SCIENCE Mar 27, 2015.
Science Magazine > 27 March 2015 > Borsanyi et al., 347 (6229): 1452-1455
The authors are: Sz. Borsanyi , S. Durr, Z. Fodor, C. Hoelbling, S. D. Katz, S. Krieg, L. Lellouch, T. Lippert1, A. Portelli, K. K. Szab, and B. C. Toth, from Germany, Hungary, France and the UK.
Neutron Mass: 939.565 MeV/c^2 = 1.67493*10^-27kg
Proton Mass: 938.272 MeV/c^2 = 1.67262*10^-27kg
difference: 1.293 MeV/c^2 = 0.00231*10^-27kg
Electron Mass: 0.511 MeV/c^2 = 0.0009109*10^-27kg
For more background...
THE STANDARD MODEL - WIKIPEDIA
The fact that the neutron is heavier than the proton is essential to the stability of matter, so understanding this fact is extremely important!