Precision determination of electroweak parameters and the strange content of the proton from neutrino deep-inelastic scattering

TL;DR

This paper constructs a new parton distribution set from neutrino data, enabling more precise determination of electroweak parameters and CKM matrix elements, and resolving previous discrepancies in electroweak measurements.

Contribution

It introduces NNPDF1.2, a model-independent parton distribution set with quantified uncertainties, improving the accuracy of electroweak parameter extraction from neutrino scattering data.

Findings

Determined |V_cd|=0.244±0.019 and |V_cs|=0.96±0.07, with the latter more precise than previous measurements.

Reassessed the NuTeV _W measurement, aligning it with other electroweak data.

Provided a comprehensive uncertainty analysis of strange quark distributions in the nucleon.

Abstract

We use recent neutrino dimuon production data combined with a global deep-inelastic parton fit to construct a new parton set, NNPDF1.2, which includes a determination of the strange and antistrange distributions of the nucleon. The result is characterized by a faithful estimation of uncertainties thanks to the use of the NNPDF methodology, and is free of model or theoretical assumptions other than the use of NLO perturbative QCD and exact sum rules. Better control of the uncertainties of the strange and antistrange parton distributions allows us to reassess the determination of electroweak parameters from the NuTeV dimuon data. We perform a direct determination of the |V_cd| and |V_cs| CKM matrix elements, obtaining central values in agreement with the current global CKM fit: specifically we find |V_cd|=0.244\pm 0.019 and |V_cs|=0.96\pm 0.07. Our result for |V_cs| is more precise than any previous direct determination. We also reassess the uncertainty on the NuTeV determination of \sin^2\theta_W through the Paschos-Wolfenstein relation: we find that the very large uncertainties in the strange valence momentum fraction are sufficient to bring the NuTeV result into complete agreement with the results from precision electroweak data.