The decay constant of the first excited pion from lattice QCD

UKQCD Collaboration; McNeile, C.; Michael, C.

The decay constant of the first excited pion from lattice QCD

Authors

UKQCD Collaboration

McNeile, C.

Michael, C.

Description

We review the theory that predicts that the decay constant of the excited light pseudo-scalar mesons are suppressed in the chiral limit relative to the pion decay constant. We compute the decay constant of the first excited pion ($π^\prime$) using unquenched QCD at a fixed lattice spacing with sea quarks of mass as low as a third the mass of the strange quark. The final result is very sensitive to the improvement conditions. We obtain $f_{π^\prime} / f_π$ = 0.078(93) in the chiral limit.
Updated references. Clarified discussion around equations 2 and 3