Reweighting NNPDFs: the W lepton asymmetry

Understand

We present a method for incorporating the information contained in new datasets into an existing set of parton distribution functions without the need for refitting.

• The method involves reweighting the ensemble of parton densities through the computation of the chi-square to the new dataset.
• We explain how reweighting may be used to assess the impact of any new data or pseudodata on parton densities and thus on their predictions.
• We show that the method works by considering the addition of inclusive jet data to a DIS+DY fit, and comparing to the refitted distribution.