TA-CON-2016-017

This contribution reports about the latest status of the feasibility studies for the measurement of time-like proton electromagnetic form factors (FF's) at the PANDA experiment at FAIR (Germany). Electromagnetic FF's are fundamental quantities which parameterize the electric and magnetic structure of hadrons. In the time-like region, the FF's can be accessed through reactions of the type $p\bar{p}\rightarrow l^{+} l^{-}$, where l = e, $\mu$, assuming that the interaction takes place through the exchange of a single virtual photon. Due to the low luminosity available at colliders in the past, an individual determination of the time-like electric and magnetic proton FF's was not feasible.
In frame of the PANDARoot software, which encompasses full detector simulation and event reconstruction, the statistical precision at which the proton FF's will be determined at PANDA is estimated for both signal reactions $p \bar{p} \rightarrow l^{+} l^{-}$ (l = e, $\mu$) at different antiproton beam momenta. The signal identification and the suppression of the main background process ($p\bar{p} \rightarrow \pi^{+} \pi^{-}$) are studied.
It will be the first time that muon pairs in the final state will be used for the measurement of the time-like electromagnetic FF's of the proton. One advantage of using this channel is that radiative corrections due to final state radiation are suppressed by the heavy mass of the muon. Measuring $\bar{p} p \rightarrow \mu^{+} \mu^{-}$ will also serve as a consistency check of the time-like electromagnetic FF data from $\bar{p} p \rightarrow e^{+} e^{-}$. For the generation and analysis of the processes of interest, different methods have been used and are compared. The results from the different analyses show that time-like electromagnetic FF's can be measured at PANDA with unprecedented statistical accuracy using both signal channels.