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We look for asymmetries in the angular distributions of events from recent data on $e^+ +e^-to p +bar p +gamma$ from BABAR collaboration. From first principles, as the C-invariance of the electromagnetic interaction and the crossing symmetry, the presence of two-photon exchange would create a forward backward asymmetry in the data. The analysis of the available data shows no asymmetry, within an error of 2%. This result is consistent with a structureless model for the proton, based on a calculation of $e^+ +e^-to mu^+ + mu^- +gamma$ with a proper replacement of the muon mass. As no systematic deviations are seen, we can conclude that these data do not give any hint of the presence of the two photon contribution, in all the considered kinematical range.
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Though the neutron mass is larger than the proton mass and obviously one expects in $e^+e^-$ annihilation a creation of more $p bar p$ pairs in comparison with $n bar n$ at the same energy, just the opposite inequality for the corresponding total cross sections $sigma_{tot}(e^+e^- to n bar n) > sigma_{tot}(e^+e^- to p bar p)$ has been revealed in the analysis of only the present time existing proton electromagnetic form factors data by the unitary and analytic approach.
We use $bar p p$ and $e^+e^-$ annihilation data to further strengthen lower bounds on the partial lifetimes for the baryon-number-violating dinucleon decays $nn to e^+ e^-$ and $nn to mu^+mu^-$.
The s-channel annihilation of proton and antiproton into a neutral pion and a real or virtual photon followed by lepton pair emission is studied. Such mechanism is expected to play a role at moderate values of the total energy $sqrt{s}$, when the pion is emitted around $90^{circ}$ in the center of mass. A fair comparison with the existing data is obtained taking into account scattering and annihilation channels. The cross section is calculated and numerical results are given in the kinematical range accessible in the PANDA experiment at FAIR.
The Born cross section for the process $e^+ e^- to p bar p $ is measured using the initial state radiation technique with an undetected photon. This analysis is based on datasets corresponding to an integrated luminosity of 7.5 fb$^{-1}$, collected with the BESIII detector at the BEPCII collider at center of mass energies between 3.773 and 4.600 GeV. The Born cross section for the process $e^+ e^- to p bar p $ and the proton effective form factor are determined in the $pbar p$ invariant mass range between 2.0 and 3.8 GeV/$c^2$ divided into 30 intervals. The proton form factor ratio ($|G_E|/|G_M|$) is measured in 3 intervals of the $pbar p$ invariant mass between 2.0 and 3.0 GeV/$c^2$.
Using a $3.19~mathrm{fb}^{-1}$ data sample collected at the $sqrt{s}~=~4.178$ GeV with the BESIII detector, we search for the rare decay $D_{s}^{+} rightarrow p bar{p} e^{+} u_{e} $. No significant signal is observed, and an upper limit of $mathcal{B}(D_{s}^{+} rightarrow p bar{p} e^{+} u_{e}) < 2.0 times 10^{-4}$ is set at the 90% confidence level. This measurement is useful input in understanding the baryonic transition of $D_{s}^{+}$ mesons.
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