ar X iv : h ep - p h / 05 12 02 1 v 1 1 D ec 2 00 5 Short study of the η - η ′ system in the two mixing angle scheme

ar X iv : h ep - p h / 05 10 20 6 v 1 1 5 O ct 2 00 5 Two mixing angle description of radiative

An analysis of various radiative V P γ decays is performed using the two mixing angle description of the η-η ′ system. The agreement is excellent. Our results are expressed both in the " octet-singlet " and in the " quark-flavour " basis. It turns out that at the present experimental accuracy, the two angles are significantly different in the former, but not in the latter basis.

ar X iv : h ep - p h / 01 07 17 5 v 1 1 6 Ju l 2 00 1 η - η ′ mixing in U ( 3 ) chiral perturbation theory 1

We investigate η-η ′ mixing in infrared regularized U (3) chiral perturbation theory by calculating the η and η ′ masses up to one-loop order. From this analysis it becomes obvious that even at leading order η-η ′ mixing does not obey the usually assumed one-mixing angle scheme if large N c counting rules are not employed.

ar X iv : h ep - p h / 04 05 03 9 v 1 5 M ay 2 00 4 η , η ′ → π + π − γ with coupled channels

ar X iv : h ep - p h / 02 11 28 5 v 1 1 8 N ov 2 00 2 1 η nucleus optical potential in a chiral unitary approach

The self-energy of an η in a nuclear medium is calculated in a chiral unitary model, and applied to η states in nuclei. Our calculation predicts an attractive η nucleus optical potential which can accommodate many η bound states in different nuclei.

ar X iv : h ep - p h / 93 12 23 9 v 1 7 D ec 1 99 3 CERN - TH . 7109 / 93 HIGHER - ORDER CORRECTIONS TO THE LARGE

Next-to-leading 1/N c corrections to the upper bound on M η /M η ′ recently obtained by Georgi are considered. These corrections are just what is needed to reconcile the bound with the observed η and η ′ masses.