出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We report on a non-perturbative study of the scale-dependent renormalization factors of a multiplicatively
renormalizable basis of DB = 2 parity-odd four-fermion operators in quenched lattice
QCD. We also present some preliminary results of the matrix elements related to the mixing
parameter of the Bs-meson. In our lattice formulation, the heavy quark is treated in the static
approximation, while the strange one belongs to a doublet of twisted mass fermions at full twist,
i.e. with twist angle a =p /2. In this framework, the parity-even DB = 2 four-fermion operators
responsible for the mixing are rotated onto a linear combination of parity-odd operators in the
above-mentioned basis. Their physical matrix elements between static Bs-mesons are extracted
from lattice correlators with Schrödinger functional boundary conditions. We observe a suppression
of excited state contributions to the BBs mixing parameter and speculate about possible
explanations.
