New phenomena in laser-assisted leptonic decays of the negatively charged boson W −

Abstract

The majority of studies and experiments performed at electron-positron colliders over the last two decades have focused on studying W and Z weak force-carrying bosons and accurately measuring all their properties, not only because they play an important role in establishing Standard Model theory and providing an accurate test of its predictions of particle interactions, but also because they are a unique tool for probing manifestations of the new physics beyond the standard model. Therefore, it would be particularly important to discuss some of the new phenomena and changes that can arise in these bosons when their decay occurs under an external electromagnetic field. In a recent paper, we investigated the laser effect on the final products of Z boson decay and found that laser had an unprecedented effect on branching ratios. In this work and within the standard Glashow-Weinberg-Salam model of electroweak interactions, we study theoretically the leptonic decay of the W −-boson in the presence of a circularly polarized electromagnetic field and we examine the laser effect, in terms of its field strength and frequency, on the leptonic decay rate and the phenomenon of multiphoton processes. The calculations are carried out using the exact relativistic wave functions of charged particles in an electromagnetic field. It was found that the laser significantly contributed to reducing the probability of W −-boson decay. We show that the laser-assisted decay rate is equal to the laser-free one only when the famous Kroll-Watson sum rule is fulfilled. The notable effect of the laser on the leptonic decay rate was reasonably interpreted by the well-known quantum Zeno effect or by the opening of channels other than leptonic ones to decay. This work will pave the way for an upcoming one to study the hadronic decay of the W −-boson and then explore the laser effect on its lifetime and branching ratios.