Renormalization of the ΔB=2 four-quark operators in lattice nonrelativistic QCD

We calculate perturbative renormalization constants for the ΔB=2 four-quark operators in lattice NRQCD. Continuum operators b̄γμ(1-γ5)qb̄γ μ(1-γ5)q and b̄(1-γ5)qb̄(1-γ5)q, which are necessary in evaluating the mass and width differences in Bd(s)0-B̄d(s)0 systems, are matched at one loop with corresponding lattice operators constructed from the NRQCD heavy quarks and the script O sign(a)-improved light quarks. Using these perturbative coefficients, we also reanalyze our previous simulation results for the matrix elements of the above operators. Our new results are free from the systematic error of script O sign(αs/(aMb)) in contrast with the previous ones with matching coefficients evaluated in the static limit