Theoretical Aspects of W Physics

Abstract

High-precision predictions for W-production processes are complicated by the instability of the W bosons, requirements of gauge invariance, and the necessity to include radiative corrections. Salient features and recent progress concerning these issues are discussed for the process ee → WW → 4f .

Finite width effects and gauge cancellations in W- and Z-boson production in the framework of modified perturbation theory

“…It should be noted that among the diagrams of Fig. 1 there are both factorizable and nonfactorizable configurations in the sense of the classification of [7,11,12]. Nevertheless, at the Fig.…”

“…It should be noted that among the diagrams of Fig. 1 there are both factorizable and nonfactorizable configurations in the sense of the classification of [7,11,12]. Nevertheless, at the intermediate step, when the soft-photons are supplied with the mass, the non-factorizable configurations of Fig.…”

“…However, this approach could not solve another problem, which was in the fermion-loop scheme, too. This problem concerns the incompleteness of the description within the declared precision of description because of the loss of one-loop order of PT in the resonance region [11,12].…”

“…Consideration of all two-loop corrections maybe solves the problem. Nevertheless, this solution is certainly impractical [11,12]. Besides, the question remains unclear how the two-loop corrections to the vertex functions, which in fact contribute in NNLO, can compensate the gauge violation that occurs in NLO.…”

Modified Perturbation Theory for Pair Production and Decay of Fundamental Unstable Particles

“…The pinch-technique method does not have this problem, but there is another difficulty which is the common one in both cases. Namely for reaching the O(α n ) precision without violating the gauge cancellation in the framework of these methods it is not enough to calculate corrections up to the O(α n ) order; it is necessary to calculate all the O(α n+1 ) loop corrections, too, at least their imaginary-part contributions, which is impractical (see, in particular, discussion in [20]).…”