Workshop for young scientists with research interests focused on physics at FAIR

Pseudoscalar mesons (P) decaying into lepton-antilepton pairs can provide a signal to physics beyond the Standard Model. Within the Standard Model P->l+l- proceeds via a two-photon intermediate state. Therefore it is a fourth order electromagnetic process, and thus suppressed. Determinations of upper limits has previously been performed for pi0, eta and eta' decaying to lepton-antilepton pairs. However, until now, no attempt has been made to measure etac->e+e-. The Beijing Electromagnetic Spectrometer III (BESIII) detector at the Beijing Electron-Positron Collider (BEPC-II) recently performed a beam energy scan resulting in a data set including ~60 pb-1 in the mass region of the etac. BESIII covers 93% of the 4pi solid angle and provides tracking, calorimetry, time of ight information for particle identification, and muon detection. BEPC-II is a double-ring electron-positron collider optimized for the charmonium region. The data recently collected at BESIII are uniquely suited for studying the etac->e+e- decay via the reverse process e+e-->etac. It is preferable to study e+e-->etac since the signal is expected to be cleaner than in other modes of access, for example J/psi-->gamma etac. The statistics of e+e-->etac is expected to be better in the new data set than in previously available data sets of J= . In this analysis the process e+e--> Ks Kpi is studied due to the large decay probability of etac->KsKpi.In this talk, the most recent results of this analysis will be presented.