7 research outputs found
Near threshold radiative 3 production in annihilation
We consider the final state in electron-positron
annihilation at cms energies not far from the threshold. Both initial and final
state radiations of the hard photon is considered but without interference
between them. The amplitude for the final state radiation is obtained by using
the effective Wess-Zumino-Witten Lagrangian for pion-photon interactions valid
for low energies. In real experiments energies are never such small that
and mesons would have negligible effect. So a phenomenological
Breit-Wigner factor is introduced in the final state radiation amplitude to
account for the vector mesons influence. Using radiative 3 production
amplitudes, a Monte Carlo event generator was developed which could be useful
in experimental studies.Comment: 15 pages, Latex, 6 figures. Misprints corrected. Version to be
published in JHE
Update of g-2 of the muon and Delta alpha
We update our Standard Model predictions for g-2 of the muon and for the
hadronic contributions to the running of the QED coupling, Delta
alpha^5_had(M_Z^2). Particular emphasis is put on recent changes in the
hadronic contributions from new data in the 2pi channel and from the energy
region just below 2 GeV.Comment: 6 pages, 10 figures, proceedings of the PhiPsi09 conference, 13-16
Oct. 2009, Beijing, Chin
Calculation of the Two-Loop Heavy-Flavor Contribution to Bhabha Scattering
We describe in detail the calculation of the two-loop corrections to the QED
Bhabha scattering cross section due to the vacuum polarization by heavy
fermions. Our approach eliminates one mass scale from the most challenging part
of the calculation and allows us to obtain the corrections in a closed
analytical form. The result is valid for arbitrary values of the heavy fermion
mass and the Mandelstam invariants, as long as s,t,u >> m_e^2.Comment: 43 pages, 8 figures; added reference
The Standard Model Prediction of the Muon Anomalous Magnetic Moment
This article reviews and updates the Standard Model prediction of the muon
g-2. QED, electroweak and hadronic contributions are presented, and open
questions discussed. The theoretical prediction deviates from the present
experimental value by 2-3 standard deviations, if e+e- annihilation data are
used to evaluate the leading hadronic term.Comment: 30 pages, 8 figures. v2: Updated version to appear in J.Phys.G.
Comments and references added, typo corrected in eq.(17