Heavy-flavor contribution to Bhabha scattering

We evaluate the last missing piece of the two-loop QED corrections to the high-energy electron-positron scattering cross section originating from the vacuum polarization by heavy fermions. The calculation is performed within a new approach applicable to a wide class of perturbative problems with mass hierarchy. The result is crucial for the high-precision physics program at existing and future e(+) e(-) colliders.     

Two-loop corrections to Bhabha scattering

The two-loop radiative photonic corrections to Bhabha scattering are computed in the leading order of the small electron mass expansion up to the nonlogarithmic term. After including the soft photon bremsstrahlung, we obtain the infrared-finite result for the differential cross section, which can directly be applied to a precise luminosity determination of the present and future e+ e- colliders.     

Hard photon corrections for Bhabha scattering

Numerical results for the α³ differential cross section for e⁺e^? → e⁺e^? are presented for the case of e⁺e^? colliding beams. Special care is given to the hard photon corrections. Acoplanarity distributions for e⁺e^? → e⁺e^?γ are also presented. Attention is drawn to experimental conditions which require the calculation of still higher order corrections.     

Neutral vector bosons in Bhabha scattering

The colliding-beam experiments ofe ⁺ ande ^?-annihilation scattering mediated by a weakly coupled neutral vector bosonW ⁰ as suggested by various authors are recalculated in more detail. It is shown that the height of the resonance, which is to be expected at the mass-shell energies of W⁰, can be determined exactly by renormalizing the second-order self-energy diagram ofW ⁰. It is further shown, how the special form of the cross-section could serve as a test for the correctness of aV- A ansatz in neutral current interactions.     

Radiative corrections to the Bhabha scattering

In this review we consider the high energy processes in QED frames in peripherical kinematics. The key feature of this kinematics is that processes have a large cross section which do not decrease with the increasing of the initial center of mass energy. Two purposes to study peripheral processes are: the background processes with large total cross sections and the structure of jets in the fragmentation region.     

Bhabha scattering near the Z0

A complete analysis of EM radiative corrections to Bhabha scattering near the Z₀ is presented Compact analytic formulae are given which include exact one-loop results and soft-and-collinear photon effects resummed to all orders. Detection of back-to-back e⁺e⁻ pairs can be therefore used as a high precision monitor of luminosity at LEP/SLC energies.     

Resonant Bhabha scattering at MeV energies

We discuss, on a phenomenological level, the possible appearance of resonances ine ⁺+e ^? scattering at energies in the MeV region. The expected resonance cross section and angular distribution are examined. The observability depends crucially on the attainable energy resolution which is limit by the momentum distribution of the electrons contained in the target.     

Hard pair production in large-angle Bhabha scattering

The cross section of hard pair production in large-angle Bhabha scattering is calculated in the leading and next-to-leading logarithmic approximations. Eight regions of the collinear kinematics, when the final particles imitate a process of the 2 → 2 type, and three semicollinear regions, when the final particles imitate a process of the 2 → 3 type, are considered. Analytical formulae for differential cross sections are presented.     

Bhabha scattering with higher order weak loop corrections

We present a compact incorporation of the weak loop effects in the Bhabha cross section with the accuracy required by the present precision experiments. Special care is taken of the leading 2-loop effects from a heavy top quark which are of the type ²(m _t /M _Z )⁴. We find very satisfactory agreement between two independent calculations which are based on different gauges and different renormalizations. The compact formulation in terms of form factors allows a straight-forward implementation into analytic or Monte Carlo QED calculations.     

Virtual hadronic and leptonic contributions to Bhabha scattering

Using dispersion relations, we derive the complete virtual QED contributions to Bhabha scattering due to vacuum polarization effects. We apply our result to hadronic corrections and to heavy lepton and top quark loop insertions. We give the first complete estimate of their net numerical effects for both small and large angle scattering at typical beam energies of meson factories, the CERN Large Electron-Positron Collider, and the International Linear Collider. With a typical amount of 1-3 per mil they are of relevance for precision experiments.     

Investigation of vacuum polarization in t-channel radiative Bhabha scattering

We discuss the possibility of a precision measurement of vacuum polarization in t-channel radiative Bhabha scattering at a high luminosity collider. For illustration, the achievable precision is estimated for the BaBar experiment at PEP-II and for the OPAL experiment at LEP. Received: 6 June 2001 / Published online: 21 September 2001     

Hadronic vacuum polarization effects in Bhabha and Moller scattering

Effects of hadronic vacuum polarization in the reactions e⁺e^? → e⁺e^? and e^±e^± → e^±e^± are discussed. The cross sections with spin polarization are given. Measurements of these effects could directly determine in the hadronic vacuum polarization at spacelike momentum transfers and could improve tests of quantum electrodynamics.     

Radiative corrections to Bhabha scattering and mupair production from the hadronic vacuum polarization

The known first order radiative corrections to Bhabha scattering and mupair production are extended to include the hadronic vacuum polarization. For the evaluation, the measured total cross-section for e⁺e^? → hadrons together with some assumptions on its high-energy behaviour is used. The results show that the inclusion of the hadronic vacuum polarization in the radiative corrections is required for precision tests of quantumelectrodynamics at high energies.     

Unitary approximation for radiative high energy scattering processes: Application to Bhabha scattering

We describe how to apply the unitary approximation to high energy scattering processes which involve the radiation of arbitrarily many photons. We compare our results to calculations of inclusive quantities using leading log resummation techniques well known from QCD. In contrast to the latter method the unitary approximation is also appropriate for differential cross sections. The Monte Carlo implementation of the method is discussed and detailed results are given for the case of radiative Bhabha scattering.     

Deep-inelastic electron scattering from carbon

We have measured the deep-inelastic electron scattering from carbon up to and including the Δ-region at 36°, 60°, 90° and 145°. The systematic decomposition of the transverse and longitudinal response functions has been obtained by means of a Rosenbluth-type analysis of the data in the momentum transfer interval 200 MeV/c /s |q| /s 600 MeV/c. A comparison with theoretical calculations which extend over the quasielastic and Δ-peak regions is presented. A reduction of the differences between our data and theory seems obtainable through the introduction of meson-exchange currents, resonant and non-resonant meson production, and the use of the shell model. Our experimental Coulomb sum-rule estimates at higher $\text{|}\text{q}\text{|}$ agree with independent particle model predictions. We compare our results in the vicinity of the Δ-peak with the total absorption cross section for real photons.