Universal unitarity triangle and physics beyond the standard model

A. J. Buras, P. Gambino, M. Gorbahn, S. Jäger, L. Silvestrini

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485 Scopus citations


We make the simple observation that there exists a universal unitarity triangle for all models, like the SM, the Two Higgs Doublet Models I and II and the MSSM with minimal flavour violation, that do not have any new operators beyond those present in the SM and in which all flavour changing transitions are governed by the CKM matrix with no new phases beyond the CKM phase. This universal triangle can be determined in the near future from the ratio (δM)d/(δM)s and sin 2β measured first through the CP asymmetry in Bd/0 → ψKS and later in K → πνν̄ decays. Also suitable ratios of the branching ratios for B → Xd,sνν̄ and Bd,s → μ+μ- and the angle γ measured by means of CP asymmetries in B decays can be used for this determination. Comparison of this universal triangle with the nonuniversal triangles extracted in each model using ε, (δM)d and various branching ratios for rare decays will allow to find out in a transparent manner which of these models, if any, is singled out by experiment. A virtue of the universal triangle is that it allows to separate the determination of the CKM parameters from the determination of new parameters present in the extensions of the SM considered here.

Original languageEnglish
Pages (from-to)161-167
Number of pages7
JournalPhysics Letters B
Issue number1-2
StatePublished - 15 Feb 2001


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