Thorsten Feldmann, Soumitra Nandi, Amarjit Soni
We investigate to what extent the recently measured value for a non-vanishing
direct CP asymmetry in D0 -> K+ K- and D0 -> pi+ pi- decays can be accommodated
in the Standard Model (SM) or extensions with a constrained flavour sector, for
instance from a sequential 4th generation of quarks (4G). From the comparison
with D0 -> K- pi+ branching ratios, we establish large U-spin symmetry (d <->
s) breaking effects with large strong phases between different interfering
amplitudes. On the basis of conservative estimates on amplitude ratios - which
are supported by an analysis of the breaking of a (c <-> u) symmetry in
non-leptonic B0 decays - we find that, in the SM, direct CP asymmetries in the
pi+ pi- or K+ K- modes (or in their difference) of the order of several per
mille are still plausible. Due to the constraints on the new CP phases in the
4G model, only moderate effects compared to the SM estimates are possible. We
suggest CP studies at LHCb as well as at (Super)B-factories of several
distinctive modes, such as D+ -> Kbar(*)0 pi+, phi pi+ and Ds -> K(*)0 pi+, phi
pi+ (K+) etc., which should shed more light on the short- and long-distance
issues underlying CP violation in non-leptonic D-meson decays.
View original:
http://arxiv.org/abs/1202.3795
No comments:
Post a Comment