Pair production of W and Z bosons and the goldstone boson equivalence theorem

Abstract

W and Z boson pairs are the signals of the production of many types of new, heavy particles, e.g., heavy Higgs bosons, new Z′ bosons, heavy quark and lepton pairs, and heavy gaugino pairs. I show that the W and Z bosons which result from the decay of these heavy particles are predominantly longitudinally polarized, while those produced from background processes are primarily transversely polarized. I study W and Z boson pair production from quark-antiquark annihilation and present compact formulae for the cross sections to produce vector bosons of definite polarization. I also discuss W and Z boson pair production from gluon fusion via a virtual quark loop. Use is made throughout of the equivalence theorem, which relates the properties of longitudinally polarized vector bosons to the corresponding Goldstone bosons which are absorbed via the Higgs mechanism. I also discuss some subtleties related to the equivalence theorem which have not been previously addressed.