Feasibility studies for the measurement of proton time-like electromagnetic form factors in processes of $\bar{p} p \rightarrow \mu^{+} \mu^{-}$ at PANDA-FAIR
Iris Zimmermann
RN-EMP-2017-002.pdf
(2.31 MB)
This release note reports about feasibility studies for the measurement of time-like proton electromagnetic form factors (FF's) using reactions of the type $\bar{p} p \rightarrow \mu^{+} \mu^{-}$ at the PANDA experiment at FAIR. Electromagnetic form factors 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, $\mu$, under the assumption of one photon exchange. It will be the first time that muon pairs in the final state will be used for the individual measurement of the TL em 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 TL em FF data from $\bar{p} p \rightarrow e^{+} e^{-}$. 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 the signal reaction $p \bar{p} \rightarrow \mu^{+} \mu^{-}$ at different antiproton beam momenta. The signal identification and the suppression of the main background process ($p\bar{p} \rightarrow \pi^{+} \pi^{-}$) are studied. In addition, the expected statistical precision of the effective TL proton FF is presented at different beam momenta. Possible systematic error sources are considered for the estimation of the total uncertainties.