Extraction of α From the CP Asymmetry in B^0/\bar B^0 --> pi+ pi- Decays
Abstract
The influence of strong and electroweak penguin amplitudes in
B/
B
¯
→
π
+
π
−
is investigated in connection with the determination of the unitarity triangle angle
α
of the CKM matrix. A relation between the observable asymmetry, the angle
α
, and the penguin amplitude is established. A model calculation of the penguin amplitude shows that the CP asymmetry in
B
0
→
π
+
π
−
decays is only mildly influenced by the penguin amplitudes. Experimental limits on pure penguin and penguin dominated processes are consistent with the model. This information also suggests in a rather model independent way that penguin amplitudes will not be a serious complicating factor in the determination of
α
from the
π
+
π
−
time dependent asymmetry.