Recent results from CMS-2 and SND experiments at VEPP-2M

Abstract

New results on various channels of e + e − annihilation into hadrons from CMD-2 and SND experiments at VEPP-2M in Novosibirsk are described. e + e − → π 0 γ and e + e − → ηγ were studied in the whole energy range. Cross sections of e + e − annihilation into various hadronic final states were measured.

Heavy-Flavor Contribution to Bhabha Scattering

“…As the first application, we consider the Bhabha scattering at the energy of 1 GeV which plays a crucial role in the determination of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment [27,28]. The second-order contributions (α/π) 2 δ (2) of heavy leptons and quarks to the differential cross section are plotted as function of the scattering angle in Figs.…”

R measurements with ISR in BaBar — hadronic part of muon magnetic dipole moment

“…This ratio R´sµ is measured as a function of Ô s, the center of mass energy of the final system f . The QED kernel, K´sµ varies very little over the whole range [7], from 0 63 at s 4m 2 π to 1 at s ∞. There is, however, a very strong dependence on energy.…”

“…The contribution of the hadronic vacuum polarization is calculated via the dispersion integral [4,7] :…”