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Preliminary non-perturbative results of the Bs mixing parameter in the static limit from quenched tmQCD

Presenter: Filippo Palombi — DESY Zeuthen

F. Palombi, M. Papinutto, C. Pena, H. Wittig

We present some preliminary results of a non-perturbative study of the matrix elements related to the mixing parameter of the Bs-meson in the static limit of quenched lattice QCD. In our lattice formulation, the strange quark belongs to a doublet of twisted mass fermions at full twist, i.e. α=π/2. Heavy quarks are regularized according to the HYP2 static action. In this framework, the parity-even ΔB=2 four-fermion operators responsible for the mixing in the static approximation are rotated onto a linear combination of two purely multiplicatively renormalizable parity-odd operators. Their physical matrix elements between static Bs-mesons are extracted from lattice correlators with Schrödinger functional boundary conditions. We show that, owing to the vacuum saturation approximation, excited state contributions to the Bs mixing parameter are highly suppressed.