Nucleon form factors, B-meson factories and the radiative return

Abstract

Abstract. The feasibility of a measurement of the electric and magnetic nucleon form factors at B-meson factories through the radiative return is studied. Angular distributions allow a separation of the contributions from the two form factors. The distributions are presented for the laboratory and the hadronic rest frame, and the advantages of different coordinate systems are investigated. It is demonstrated that Q 2 values up to 8 or even 9 GeV 2 are within reach. The Monte Carlo event generator PHOKHARA is extended to nucleon final states, and results are presented which include Next-to-Leading Order radiative corrections from initial-state radiation. The impact of angular cuts on rates and distributions is investigated and the relative importance of radiative corrections is analysed.

Measurement of initial-state–final-state radiation interference in the processese+e−→μ+μ−γandLees1, Poireau2, Tisserand3 et al. 2015Phys. Rev. D19060View full textAdd to dashboardCite

“…5(a) is proportional to the pion form factor F π ðs 0 Þ at a reduced energy squared 2 GeV 2 Þj ∼ 0.01, as estimated from an extrapolation of existing data [6,12] using a 1=s dependence. This model is studied with the PHOKHARA 4.0 [13] generator, in which the FSR current has a point-like Lorentz structure, including a contact term, globally multiplied by the pion form factor. In this model, the A 0 ðm ππ Þ distribution is expected to increase quadratically with mass on the ρ resonance, with a change of sign at the ρ mass…”

“…(13)] are the overall result of the acceptance-induced and detector asymmetries discussed above. They are determined using the full simulation, separately for the N AE samples.…”

The radiative return method - a short theory review

“…The nucleons final states were discussed in [17], while the three pion current was modeled and implemented into the PHOKHARA event generator in [18].…”

“…The method, which was proposed in [17], was used by BaBar collaboration [30] for separation of the proton form factors. The obtained results show clearly its competitiveness.…”

Study ofe+e−→pp¯using initial state radiation withBABAR

“…differential cross-section for e + e − → ppγ can be found, for example, in Ref. [3]. The θ p dependencies of the G E and G M terms are reminiscent of the sin 2 θ p and 1+cos 2 θ p angular distributions for electric and magnetic form factors in the e + e − → pp process.…”