Precise measurement of Bhabha scattering at a center-of-mass energy of 57.77 GeV

Abstract

Bhabha scattering at a center-of-mass energy of 57.77 GeV has been measured using the VENUS detector at KEK TRISTAN. The precision is better than 1% in scattering angle regions of ͉cos͉р0.743 and 0.822рcosр0.968. A model-independent scattering-angle distribution is extracted from the measurement. The distribution is in good agreement with the prediction of the standard electroweak theory. The sensitivity to underlying theories is examined, after unfolding the photon-radiation effect. The q 2 dependence of the photon vacuum polarization, frequently interpreted as a running of the QED fine-structure constant, is directly observed with a significance of three standard deviations. The Z 0 exchange effect is clearly seen when the distribution is compared with the prediction from QED ͑photon exchanges only͒. The agreement with the standard theory leads us to constraints on extensions of the standard theory. In all quantitative discussions, correlations in the systematic error between angular bins are taken into account by employing an error matrix technique. ͓S0556-2821͑97͒00801-1͔

Model-Independent Bounds on Kinetic Mixing

“…e + e − colliders measure the SM neutral current interactions and when m Z < ∼ √ s ≤ m Z 0 , the Z couples dominantly to the electromagnetic current, which causes a kink to appear in the running of the fine structure constant. Differential Bhabha scattering measures α EM (q 2 ) and there is a wealth of data from experiments such as OPAL [19], DELPHI [20], SLD [21], TASSO [22], CELLO [23] and TRISTAN [24]. As a result, the new vector boson changes the predictions for differential Bhabha scattering.…”

Lorentz violation bounds on Bhabha scattering

“…Moreover, Bhabha scattering is one of the most fundamental reactions in QED processes and has been extensively studied in colliders [27][28][29]. It is particularly important since it is used to determine the luminosity of the e + e − collisions [30,31]. This fact motivated us to evaluate and analise the behavior of the differential cross section for Bhabha scattering in the presence of nonminimal couplings and to directly obtain upper bounds on LV coefficients.…”

Lorentz violation, gravitoelectromagnetic field and Bhabha scattering

“…The Bhabha scattering (e + e − −→ e + e − ) is a process usually used in tests of experiments at high energy accelerators [34][35][36][37][38]. To include the Lorentz-violating effects the interaction vertex between fermions and gravitons is modified.…”