Pion and Kaon valence structure in a confining NJL model

We present recent results for the in-medium valence-quark distributions of
pion and kaon mesons in symmetric nuclear matter obtained by combining  a
confining Nambu--Jona-Lasinio (NJL) model  with  the quark-meson coupling
(QMC) model.  The NJL is a chiral effective theory that simulates many of
the key features of Quantum Chromodynamics (QCD) and is therefore a useful
tool to help explore and understand non perturbative phenomena in low
energy QCD, while the QMC model is a model of nuclear matter that
constrains many of the in-medium input quantities at saturation density
required for the study. Before presenting our findings we provide basics
features of these models. Our results indicate that the obtained valence quark distributions in
vacuum, for both the pion and kaon, could reasonably describe the
available experimental data over a wide range of Bjorken-x variable. On
the other hand, the in-medium valence u-quark distribution in the pion at
the experimental energy scale is found to be almost unchanged compared to
the in-vacuum case. However, the in-medium to in-vacuum ratios of both the
valence u-quark and valence s-quark distributions of the kaon meson 
increase with nuclear matter density, but show different x-dependence. 
Namely, the ratio for the valence u-quark distribution increases with x,
while that for the valence s quark decreases with x. These features are
enhanced at higher density regions.