1202.1480 (Simon Dinter et al.)

Sigma terms and strangeness content of the nucleon with $N_f=2+1+1$
twisted mass fermions    [PDF]

Simon Dinter, Vincent Drach, Roberto Frezzotti, Gregorio Herdoiza, Karl Jansen, Giancarlo Rossi

We study the nucleon matrix elements of the quark scalar-density operator
using maximally twisted mass fermions with dynamical light ($u$,$d$), strange
and charm degrees of freedom. We demonstrate that in this setup the nucleon
matrix elements of the light and strange quark densities can be obtained with
good statistical accuracy, while for the charm quark counterpart only a bound
can be provided. The present calculation which is performed at only one value
of the lattice spacing and pion mass serves as a benchmark for a future more
systematic computation of the scalar quark content of the nucleon.

View original: http://arxiv.org/abs/1202.1480