The strange quark content of the nucleon in 2+1 flavor lattice QCD

The strangeness of the nucleon, <N|ss|N> - <0|ss|0>, is a quantity of interest for interpreting the results of dark matter detection experiments as well as for exploring the structure of the nucleon itself. We present a calculation of this quantity in 2+1 flavor lattice QCD using a range of lattice spacings and quark masses. The method is based on calculating quark-line disconnected contributions on the MILC lattice configurations, which include the effects of dynamical strange quarks. After continuum and chiral extrapolations, the value is <N|ss|N> - <0|ss|0> = 0.69 +/- 0.07(stat) +/- 0.09(sys) in the msbar(2GeV) regularization.