Physics – High Energy Physics – High Energy Physics - Phenomenology
Scientific paper
2009-01-29
Phys.Rev.D79:076005,2009
Physics
High Energy Physics
High Energy Physics - Phenomenology
20 pages, 1 figure; v2: comments and references added, accepted for publication in PRD
Scientific paper
10.1103/PhysRevD.79.076005
The corrections induced by light quark masses to the current algebra result for the $\pi^0$ lifetime are reexamined. We consider NNLO corrections and we compute all the one-loop and the two-loop diagrams which contribute to the decay amplitude at NNLO in the two-flavour chiral expansion. We show that the result is renormalizable, as Weinberg consistency conditions are satisfied. We find that chiral logarithms are present at this order unlike the case at NLO. The result could be used in conjunction with lattice QCD simulations, the feasibility of which was recently demonstrated. We discuss the matching between the two-flavour and the three-flavour chiral expansions in the anomalous sector at order one-loop and derive the relations between the coupling constants. A modified chiral counting is proposed, in which $m_s$ counts as $O(p)$. We have updated the various inputs needed and used this to make a phenomenological prediction.
Kampf Karol
Moussallam Bachir
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