A precise determination of α using B 0 → ρ + ρ − and B + → K ∗0 ρ +
Martin Beneke, Michael Gronau, Johannes Rohrer, Michael Spranger
Abstract
The effect of the penguin amplitude on extracting
α
from CP asymmetries in
B
0
→
ρ
+
ρ
−
decays is studied using information on the SU(3)-related penguin amplitude in
B
+
→
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→ρρ
. Current measurements imply
α=[90±7fexp
)
+2
−5
(th)
]
∘
.