Johannes Rohrer | Searcharxiv

arXiv2007

Branching fractions, polarisation and asymmetries of B -> VV decays

We calculate the hard-scattering kernels relevant to the negative-helicity decay amplitude in B decays to two vector mesons in the framework of QCD factorisation. We then perform a comprehensive analysis of the 34 B->VV decays, including B_s decays and the complete set of polarisation observables. We find considerable uncertainties from weak annihilation and the non-factorisation of spectator-scattering. Large longitudinal polarisation is expected with certainty only for a few tree-dominated colour-allowed modes, which receive small penguin and spectator-scattering contributions. This allows for an accurate determination of the CKM angle alpha (or gamma) from S_L(rhorho) resulting in alpha=(85.6^{+7.4}_{-7.3}) degrees. We also emphasize that the rho K* system is ideal for an investigation of electroweak penguin effects.

hep-ph↗

arXiv2006

A precise determination of $α$ using $B^0\toρ^+ρ^-$ and $B^+\to K^{*0}ρ^+$

The effect of the penguin amplitude on extracting $α$ from CP asymmetries in $B^0\to ρ^+ρ^-$ decays is studied using information on the SU(3)-related penguin amplitude in $B^+\to K^{*0}ρ^+$. Conservative bounds on non-factorizable SU(3) breaking, small amplitudes, and the strong phase difference between tree and penguin amplitudes, are shown to reduce the error in $α$ in comparison with the one obtained using isospin symmetry in $B\toρρ$. Current measurements imply $α= [90 \pm 7 f{\rm exp})^{+2}_{-5} ({\rm th})]^\circ$.

hep-ph↗