Meson transition form factors at KLOE/KLOE-2

Ivano Sarra,G Giardina,G Mandaglio,G Venanzoni,S Eidelman

doi:10.1051/epjconf/20147200023

Abstract

In this work we present a study of the Dalitz decay ϕ → η e + e − , with η → π 0 π 0 π 0 , performed using 1.7 fb −1 of e + e − collisions collected at KLOE in the 2004-2005 data taking period. The resulting branching fraction is: BR( ϕ → η e + e − ) = (1.059 ± 0.007(stat.) ± 0.038(norm.)) ± 10 −4 . We have also studied the invariant mass of the dilepton system, extracting the slope of the transition form factor: b ϕη = (1.17 ± 0.10) GeV −2 . The ϕ → π 0 e + e − rare decay is also being studied using the same data sample. The branching ratio will be measured, with a consistent reduction of the actual total uncertainty. The double off shell π 0 Transition Form Factor will also be measured for the first time in the time-like region, with the momentum transfer given by the e + e − invariant mass.

Highlights

Conversion decays of vector and pseudoscalar mesons (A → Bγ∗) are closely related to corresponding radiative decays (A → Bγ)
The nature of the mesons and their underlying quark and gluon structure can be described by the transition form factor function of A into B (FAB(q2)), that can be extracted from data by studying the probability of the conversion decay as a function of the squared invariant mass of the lepton pair
The other main background contribution comes from the radiative decay φ → π0γ, with the real photon converting to an e+e− pair on the beampipe and drift-chamber walls

Summary

Introduction

Conversion decays of vector and pseudoscalar mesons (A → Bγ∗) are closely related to corresponding radiative decays (A → Bγ). The nature of the mesons and their underlying quark and gluon structure can be described by the transition form factor function of A into B (FAB(q2)), that can be extracted from data by studying the probability of the conversion decay as a function of the squared invariant mass of the lepton pair.

Results

Conclusion