A Measurement of the Branching Ratio of ${\pi }^0$ Dalitz Decay using $K_L\to {\pi }^0{\pi }^0{\pi }^0$ Decays

Abstract

We present a measurement of $B({\pi }^0\to e^{+}{e}^{-}\gamma )/B({\pi }^0\to \gamma \gamma )$, the Dalitz branching ratio, using data taken in 1999 by the E832 KTeV experiment at Fermi National Accelerator Laboratory. We use neutral pions from fully reconstructed $K_L$ decays in flight; the measurement is based on about 60 thousand $K_L\to {\pi }^0{\pi }^0{\pi }^0\to \gamma \gamma \gamma \gamma e^{+}{e}^{-}\gamma$ decays. We normalize to $K_L\to {\pi }^0{\pi }^0{\pi }^0\to 6\gamma$ decays. We find $B({\pi }^0\to e^{+}{e}^{-}\gamma )/B({\pi }^0\to \gamma \gamma )$ $(m_{e^{+}{e}^{-}}$ > 15 MeV/$c^2)$ = $[3.920\pm 0.016(stat)\pm 0.036(syst)]\times 10^{-3}$. Using the Mikaelian and Smith prediction for the $e^{+}{e}^{-}$ mass spectrum, we correct the result to the full $e^{+}{e}^{-}$ mass range. The corrected result is $B({\pi }^0\to e^{+}{e}^{-}\gamma )/B({\pi }^0\to \gamma \gamma )=[1.1559\pm 0.0047(stat)\pm 0.0106(syst)]$%. This result is consistent with previous measurements and the uncertainty is a factor of three smaller than any previous measurement.

arXiv comment11 pages, 7 figures; v2 accepted version

References in corpus (7)

• Precise Measurements of Direct CP Violation, CPT Symmetry, and Other Parameters in the Neutral Kaon System
• Measurements of Direct CP Violation, CPT Symmetry, and Other Parameters in the Neutral Kaon System
• Measurements of KL Branching Fractions and the CP Violation Parameter |eta+-|
• The Dalitz decay pi0 -> e+ e- gamma revisited
• Radiative corrections to the Dalitz decay ${\pi }^0\to e^{+}{e}^{-}\gamma$ revisited
• Measurement of the ${\pi }^0$ electromagnetic transition form factor slope
• Precise determination of the branching ratio of the neutral-pion Dalitz decay