Limit on the production of a light vector gauge boson in phi meson decays with the KLOE detector

Understand

We present a new limit on the production of a light dark-force mediator with the KLOE detector at DAPHNE.

• This boson, called U, has been searched for in the decay phi --> eta U, U --> e+ e-, analyzing the decay eta --> pi0 pi0 pi0 in a data sample of 1.7 fb-1.
• No structures are observed in the e+e- invariant mass distribution over the background.
• This search is combined with a previous result obtained from the decay eta --> pi+ pi- pi0, increasing the sensitivity.