Measurement of the $\varphi \to {\pi }^0{e}^{+}{e}^{-}$ transition form factor with the KLOE detector

Abstract

A measurement of the vector to pseudoscalar conversion decay $\varphi \to {\pi }^0{e}^{+}{e}^{-}$ with the KLOE experiment is presented. A sample of $\sim 9500$ signal events was selected from a data set of 1.7 fb${}^{-1}$ of $e^{+}{e}^{-}$ collisions at $\sqrt{s}\sim m_{\varphi }$ collected at the DA$\Phi$NE $e^{+}{e}^{-}$ collider. These events were used to obtain the first measurement of the transition form factor $|F_{\varphi {\pi }^0}(q^2)|$ and a new measurement of the branching ratio of the decay: $\mathrm{BR}(\varphi \to {\pi }^0{\mathrm{e}}^{+}{\mathrm{e}}^{-})=(1.35\pm 0.05_{-0.10}^{+0.05})\times 10^{-5}$. The result improves significantly on previous measurements and is in agreement with theoretical predictions.

Comments: 13 pages, 4 figures; matches published version