Speaker: Antonin Portelli Lattice QCD calculations began recently to produce theoretical
predictions with sub-percent precision of non-perturbative hadronic
observables. It means that these simulations technics may have reached
the necessary accuracy to predict the small corrections coming from the
breaking of isospin symmetry. Isospin symmetry is explicitly broken in
the Standard Model by the non-zero differences of mass and electric
charge between the up and down quarks. Both of these corrections are
expected to have a comparable size of the order of one percent
relatively to hadronic energies. Although these contributions are small,
they play a crucial role in the structure of nuclear matter. Indeed,
the positive mass difference between the neutron and the proton is
responsible for the stability of the hydrogen atom and it allows the
beta decay of the neutron which is a vital process in nuclear
transmutation. As we will see, one of the main challenge in including
isospin breaking effect in lattice simulations is to take into account
the electromagnetic interaction in the calculation.
In this talk I will explain how to define properly QCD and QED on a
finite and discrete space-time. I will then consider the different
approaches to compute on the lattice correlation functions of QCD+QED
observables. I will then review the recent lattice results concerning
the isospin corrections to the light hadron spectrum.
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