Speaker: Dr. Arsenii Titov

Email: arsenii.titov@unipd.it

Institution: University of Pisa, Italy

Title: QCD Axion at the GeV Scale?

Abstract:

In a recent paper, Murayama proposed a GeV-scale axion theory where the up-quark mass is generated dynamically by the QCD chiral condensate, which at the same time spontaneously breaks a Peccei-Quinn symmetry. If correct, this would imply that the QCD axion has effectively already been discovered and is hidden among the known hadron resonances in the 1-2 GeV region. However, the proposed theory predicts a too large splitting between the masses of neutral and charged pions. Trying to solve this problem, we explore extensions. Despite some partial improvements, we identify a structural obstruction: the new Peccei-Quinn spurion breaks the accidental isospin symmetry of the chiral Lagrangian, leading to an enhanced higher-order operator. As a consequence, pion scatterings too are distorted. We also examine the limit where the axion becomes light, finding that it is excluded by fifth-force constraints.

El seminario será en la plataforma TEAMS: