# Strange quark suppression from a simultaneous Monte Carlo analysis of parton distributions and fragmentation functions

## TL;DR

This study performs a comprehensive Monte Carlo analysis to simultaneously extract parton distributions and fragmentation functions, revealing a suppressed strange quark distribution at certain momentum fractions, contrasting with some collider observations.

## Contribution

It introduces a novel simultaneous extraction method using Monte Carlo and clustering techniques, providing new insights into strange quark suppression and correlations in parton distributions.

## Key findings

- Strange quark distribution is strongly suppressed at x > 0.01.
- Significant correlations between strange quark density and fragmentation functions.
- Contrasts with ATLAS observations of enhanced strangeness in W/Z production.

## 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 $e^+ e^-$ 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 $x \gtrsim 0.01$, in contrast with the ATLAS observation of enhanced strangeness in $W^\pm$ and $Z$ production at the LHC. Our study reveals significant correlations between the strange quark density and the strange $\to$ kaon fragmentation function needed to simultaneously describe semi-inclusive $K^\pm$ production data from COMPASS and inclusive $K^\pm$ spectra in $e^+ e^-$ annihilation from ALEPH and SLD, as well as between the strange and light antiquark densities in the proton.