Time-like proton form factors and heavy lepton production at PANDA experiment

Alaa Dbeyssi
2013 Proceedings of 51st International Winter Meeting on Nuclear Physics — PoS(Bormio 2013)   unpublished
Electromagnetic form factors (FFs) are fundamental quantities which describe the structure and the internal dynamics of hadrons. Assuming one-photon exchange, the production of electronpositron pairs in proton-antiproton annihilation allows to access electromagnetic FFs in the timelike region of the momentum transfer squared. At the future accelerator complex FAIR (Facility for Antiproton and Ion Research), in Darmstadt, the PANDA (antiProton ANnihilation at DArmstadt) collaboration plans to
more » ... sure proton time-like FFs using an antiproton beam of momentum up to 15 GeV/c and luminosity L = 2.10 32 cm −2 s −1 . In the present work the annihilation of an antiproton beam on a proton target into heavy leptons as muons or taus is considered. Calculating the production of taus or muons, the leptons mass can not be neglected, as it is generally done for electrons. The interest of FFs measurements with heavy leptons is related to the fact that radiative corrections are strongly suppressed. Moreover, polarization observables which are proportional to the lepton mass are enhanced. The differential cross section and polarization observables, when the beam and/or target are polarized, as well as the polarization of the outgoing leptons inp + p annihilations are derived at the Born approximation. The effect of the additional terms induced by the lepton mass on the observables is investigated. A numerical application is done using the VDM parametrization of proton FFs. Our results show an enhancement of the polarization observables of these heavy particles, in particular when the transverse polarization of the leptons is considered. The measurement of unstable lepton polarization can be done through the angular distribution of the decay products.
doi:10.22323/1.184.0059 fatcat:3s4r4jbkfndntgeobp7hwbmi3i