The Paschos-Wolfenstein relation in a hadronic picture

Abstract

The Paschos-Wolfenstein (PW) relation joins neutral- and charged-current neutrino- and antineutrino-induced cross sections into an expression that depends on the weak mixing angle $\sin^2 θ_W$. Contrary to the traditional approach with partonic degrees of freedom, we adopt a model built on hadronic degrees of freedom to perform a study of the PW relation at intermediate energies (100 MeV to 2 GeV). With upcoming high-statistics scattering experiments such as MINER$ν$A and FINeSSE, a scrutiny of the PW relation is timely. Employing a relativistic Glauber nucleon knockout model for the description of quasielastic neutrino-nucleus reactions, the influence of nuclear effects on the PW relation is investigated. We discuss nuclear-model dependences and show that the PW relation is a robust ratio, mitigating the effect of final-state interactions, for example to the 1% level. The role played by a possible strangeness content of the nucleon is investigated. It appears that the uncertainties arising from the poorly known strangeness parameters and the difficulties in nuclear modelling seriously limit the applicability of the PW relation as an intermediate-energy electroweak precision tool. On the other hand, we show that nuclear effects may be sufficiently well under control to allow the extraction of new information on the axial strangeness parameter. Results are presented for $^{16} {O}$ and $^{56} {Fe}$.