Radiative corrections to pair production of unstable particles: Results for E+E− → 4 fermions

Abstract

Radiative corrections to processes that involve the production and subsequent decay of unstable particles are complex due to various theoretical and practical problems. The so-called double-pole approximation offers a way out of these problems. This method is applied to the reaction e + e − → W + W − → 4 fermions, which allows us to address all the key issues of dealing with unstable particles, like gauge invariance, interactions between different stages of the reaction, and overlapping resonances. Within the double-pole approximation the complete O(α) electroweak corrections are evaluated for this off-shell W -pair production process. Examples of the effect of these corrections on a number of distributions are presented. These comprise mass and angular distributions as well as the photon-energy spectrum.

Four-fermion production with RACOONWW

“…For the latter reason, in Ref. [19] the invariant masses of the W bosons were defined strictly in terms of the invariant masses of the corresponding decay fermion pairs. As a result, the invariant-mass distributions in M ± = k 2 ± received large corrections from final-state radiation, namely −20 MeV, −39 MeV, and −77 MeV for τ + ν τ , µ + ν µ , and e + ν e final states at √ s = 184 GeV, respectively.…”

Impact of the W boson decay width on photon bremsstrahlung accompanying W pair production

“…[8,7,9,10,11]. It is well known that heavy unstable particles such as the W boson can radiate before and after their decay.…”

“…The pole-scheme approach to processes involving unstable particles has been used to calculate the full O(α) correction to the pair production of W bosons in e + e − collisions [9,10]. In this paper we use the results of Refs.…”

“…In this paper we use the results of Refs. [7,9] as a basis for the calculations. Because of the way the pole-scheme is constructed, one can classify all the radiative corrections into two types: factorizable, which act inside separate hard subprocesses (production and decay); and nonfactorizable, which interconnect various hard subprocesses.…”

“…[7]. 9 This enables us to utilize more events and makes studies in γγ collisions potentially more statistically powerful than in the e + e − -case.…”