Corrections to Dashen's theorem

Abstract

The electromagnetic corrections to the masses of the pseudoscalar mesons π and K are considered. We calculate in chiral perturbation theory the contributions which arise from resonances within a photon loop at order O(e 2 m q ). Within this approach we find rather moderate deviations to Dashen's theorem.

A sum rule approach to the violation of Dashen's theorem

“…Thus, it is necessary to estimate the EM contributions to M There have been many attempts over the years in this direction [6] [7] [8] [9][10] [11][12] (a representative, but non-exhaustive list) and, very recently, a lattice calculation has appeared [13]. Several rather different approaches to this problem have been followed.…”

Pion masses and chiral scalar susceptibilities at finite temperature in SU(2) ChPT

“…As commented before, at T = 0 and in the chiral and soft pion limit, it was shown [14] that the pion mass difference can be parametrized exactly in terms of the difference of the vector-axial spectral functions, so the corrections to this formula must be proportional toM π , as was shown in [23] using ChPT at zero temperature. The modifications to the expression of Das et al for non-zero quark masses and temperatures are discussed in [16].…”

precise SM tests

“…At this conference Taku Izubuchi has presented an update of this calculation [42] which now includes also strange quarks in the sea. For example the electromagnetic contribution to the kaon mass difference has been calculated to be (M K + − M K 0 is split into a part due to the quark mass difference and the part due to e 2 effects): These results indicate rather small violations of Dashen's theorem (and the latter is even consistent with no violation at all), which is in contrast to what is typically obtained in analytical calculations performed in the framework of models [43,44,45,46]. While it is probably too early to draw…”