NOTE TIME CHANGE: Nuclear Particle Astrophysics (NPA) Seminar: Zoltan Fodor, Institute of Theoretical Physics, Eotvos Lorand University,”Ab initio calculation of the neutron-proton mass difference”

Wednesday May 6, 2015, 1:00 PM → 2:00 PM US/Eastern

WLC 108

The existence and stability of atoms rely on the fact that neutrons are more massive than protons. The mass difference is only 0.14% of the average. This tiny mass splitting has significant astrophysical and cosmological implications. A slightly smaller or larger value would have led to a dramatically different universe. Here we show, how this difference results from the competition between electromagnetic and mass isospin breaking effects. First we discuss how the masses of hadrons are generated. Then we compute the neutron-proton mass splitting and show that it is greater than zero by five standard deviations. In addition, this neutron-proton mass splitting is determined as a function of quark-mass difference and electromagnetic coupling. As a tool we perform lattice Quantum-Chromodynamics plus Quantum-Electrodynamics computations.

Fodor_NPA_Seminar_05062015.pdf