In this project we ask if it is possible to deduce the number of QCD colors (Nc) directly from low energy experiments with photons, pions, eta/eta’ mesons and kaons. Contrary to the common lore, it is impossible to see the Nc with just pions and photons and are the decays of the eta/eta’ meson, η/η'→γγ and η/η'→ππγ that are proportional to Nc and should replace the textbook process π→γγ lending support to Nc=3. We will study these decays at next-to-leading order in the combined chiral and 1/Nc expansion and including the ππ rescattering effects by means of dispersion relations, to determine whether these decays are suited to confirm the number of to colors be Nc=3.
The work will require state-of-the-art reading, as well as analytical and computational skills. It will be developed at the University of Barcelona, but remote supervision is possible.