Observation of b to d gamma and determination of |Vtd/Vts|
The flavor changing neutral current process
b -> d? is a sensitive probe to the Standard Model of elementary particle physics. Using a sample of
386 Ã 106 B meson pairs accumulated by the Belle detector at the KEKB e+e? collider, we measure the branching fractions for the exclusive modes
B ?> ???, B0 -> ?0? and B0 -> ?? as follows:
B(B ?> ???) = 0.55 +0.42?0.36 +0.09?0.08
B(B0 -> ?0?) = 1.25 +0.37?0.33 +0.07?0.06
B(B0 -> ??) = 0.56 +0.34?0.27 +0.05?0.10
where the first error on each value is statistical and the second is systematic. Assuming that these three modes are related by isospin conservation
rules, we find the combined branching fraction
B(B -> (?, ?)?) = 1.32 +0.34?0.31 +0.10?0.09 .
This result is used to determine the ratio of CKM matrix elements,
|Vtd/Vts| = 0.199 +0.026?0.025 +0.018?0.015 .