New physics effects in tree-level decays and the precision in the determination of the quark mixing angle gamma

作者：Brod Joachim; Lenz Alexander; Tetlalmatzi Xolocotzi Gilberto; Wiebusch Martin

来源：Physical Review D - Particles, Fields, Gravitation and Cosmology, 2015, 92(3): 033002.

DOI：10.1103/PhysRevD.92.033002

We critically review the assumption that no new physics is acting in tree-level B-meson decays and study the consequences for the ultimate precision in the direct determination of the Cabibbo-Kobayashi-Maskawa (CKM) angle gamma. In our exploratory study we find that sizeable universal new physics contributions, Delta C-1,C-2, to the tree-level Wilson coefficients C-1,C-2 of the effective Hamiltonian describing weak decays of the b quark are currently not excluded by experimental data. In particular, we find that Im Delta C-1 and Im Delta C-2 can easily be of order +/- 10% without violating any constraints from data. Such a size of new physics effects in C-1 and C-2 corresponds to an intrinsic uncertainty in the CKM angle gamma of the order of vertical bar delta gamma vertical bar approximate to 4 degrees, which is slightly below the current experimental precision. The accuracy in the determination of gamma can be improved by putting stronger constraints on the tree-level Wilson coefficients, in particular C-1. To this end we suggest a more refined theoretical study as well as more precise measurements of the observables that currently provide the strongest bounds on hypothetical new weak phases in C-1 and C-2. We note that the semileptonic CP asymmetries seem to have the best prospect for improving the bound on the weak phase in C-1.

• 出版日期2015-8-3