Constantinou, M.Dimopoulos, P.Frezzotti, R.Jansen, K.Gimenez, V.Lubicz, V.Mescia, FedericoPanagopoulos, H.Papinutto, M.Rossi, G. C.Simula, S.Skouroupathis, A.Stylianou, F.Vladikas, A.ETM Collaboration2019-04-082019-04-082011-01-011550-7998https://hdl.handle.net/2445/131795We present an unquenched N f = 2 lattice computation of the B K parameter which controls K 0 − ¯¯¯¯ K 0 oscillations. A partially quenched setup is employed with two maximally twisted dynamical (sea) light Wilson quarks, and valence quarks of both the maximally twisted and the Osterwalder-Seiler variety. Suitable combinations of these two kinds of valence quarks lead to a lattice definition of the B K parameter which is both multiplicatively renormalizable and O ( a ) improved. Employing the nonperturbative RI-MOM scheme, in the continuum limit and at the physical value of the pion mass we get B RGI K = 0.729 ± 0.030 , a number well in line with the existing quenched and unquenched determinations.20 p.application/pdfeng(c) American Physical Society, 2011Física de partículesExperimentsParticle physicsExperimentsinfo:eu-repo/semantics/article6238132019-04-08info:eu-repo/semantics/openAccess