Strange quark suppression from a simultaneous Monte Carlo analysis of parton distributions and fragmentation functions
N. Sato, Carlota Andrés, Jacob Ethier, Wally Melnitchouk
Abstract
We perform the first simultaneous extraction of unpolarized parton distributions and fragmentation functions from a Monte Carlo analysis of inclusive and semi-inclusive deep-inelastic scattering, Drell-Yan lepton-pair production, and single-inclusive ${e}^{+}{e}^{\ensuremath{-}}$ annihilation data. We use data resampling techniques to thoroughly explore the Bayesian posterior distribution of the extracted functions, and use $k$-means clustering on the parameter samples to identify the configurations that give the best description across all reactions. Inclusion of the semi-inclusive data reveals a strong suppression of the strange quark distribution at parton momentum fractions $x\ensuremath{\gtrsim}0.01$, in contrast with the ATLAS observation of enhanced strangeness in ${W}^{\ifmmode\pm\else\textpm\fi{}}$ and $Z$ production at the LHC. Our study reveals significant correlations between the strange quark density and the strange $\ensuremath{\rightarrow}$ kaon fragmentation function needed to simultaneously describe semi-inclusive ${K}^{\ifmmode\pm\else\textpm\fi{}}$ production data from COMPASS and inclusive ${K}^{\ifmmode\pm\else\textpm\fi{}}$ spectra in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation from ALEPH and SLD, as well as between the strange and light antiquark densities in the proton.