Decay constants of the pion and its excitations in holographic QCD

Understand

We investigate the leptonic decay constants of the pion and its excitations with a 5-d holographic model for quantum chromodynamics.

• We prove numerically that the leptonic decay constants of the excited states of the pion vanish in the chiral limit when chiral symmetry is dynamically broken.
• This nontrivial result is in agreement with a solid prediction of quantum chromodynamics and is based on a generalized Gell-Mann-Oakes-Renner relationship involving the decay constants and masses of the excited states of the pion.
• We also obtain an extended partially conserved axial-vector current relation that includes the fields of the excited states of the pion, a relation that was proposed long ago in the context of current algebra.