We present results concerning the light and strange quark contents of the nucleon using $N_f=2+1+1$ flavours of maximally twisted mass fermions. The corresponding $sigma$-terms are casting light on the origin of the nucleon mass and their values are important to interpret experimental data from direct dark matter searches. We discuss our strategy to estimate systematic uncertainties arising in our computations. Our preliminary results for the $sigma-$terms read $sigma_{pi N} = 37(2.6)(24.7) mev$ and $sigma_s=28(8)(10) mev$. We present our recent final analysis of the $y_N$ parameter and found $y_N=0.135(46)$ including systematicscite{Alexandrou:2013nda}.
تحميل البحث