Abstract
We briefly summarize current experimental and theoretical results on the two important processes of the low-energy hadron physics involving neutral pions: the Dalitz decay of π0 and the rare decay π0 → e+e−. As novel results we present the complete set of radiative corrections to the Dalitz decays η(′) → l+l−γ beyond the soft-photon approximation, i.e. over the whole range of the Dalitz plot and with no restrictions on the energy of a radiative photon. The corrections inevitably depend on the η(′) → γ*γ(*) transition form factors.
Highlights
The rare decay of the neutral pion, i.e. the process π0 → e+e−, is loop- and helicity-suppressed compared to the two-photon decay, which makes it potentially sensitive to effects of new physics
One could immediately think that this might be a sign for new physics
In what follows we will investigate in detail the radiative corrections for neutral-pion decays in general
Summary
The rare decay of the neutral pion, i.e. the process π0 → e+e−, is loop- and helicity-suppressed compared to the two-photon decay, which makes it potentially sensitive to effects of new physics. That is why it drew attention of theorists during last years due to the precise measurement of its branching ratio done by KTeV experiment at Fermilab [1]: B(π0 → e+e−(γ), x > 0.95) KTeV = (6.44 ± 0.25 ± 0.22) × 10−8. In what follows we will investigate in detail the radiative corrections for neutral-pion decays in general Another possibility could be introducing a new model for the π0 electromagnetic transition form factor [3]. When the exactly calculated radiative corrections are taken into account, the original discrepancy reduces down to the inconclusive 2 σ level or below [3, 5]
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