Disconnected contributions to D-meson semi-leptonic decay form factors
  We calculate the disconnected contribution to the form factor for the semileptonic decay of a D-meson into a final state, containing a flavor singlet eta meson. We use QCDSF n_f=2+1 configurations at the flavor symmetric point m_u=m_d=m_s and the partially quenched approximation for the relativistic charm quark. Several acceleration and noise reduction techniques for the stochastic estimation of the disconnected loop are tested. 
G. S. Bali, S. Collins, R. Horsley, I. Kanamori, Y. Nakamura, D.   Pleiter, P. P\'erez-Rubio, P. E. L. Rakow, A. Sch\"afer, ...
hep-lat hep-ph