9 Symmetry Violations and Quark Flavour Physics
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Fig. 9.30 Flavor-tagged t distributions and raw CP asymmetries for the Belle measurements
of sin 2β. The top plots show the B 0 → (c ¯
c)K S (η f = −1) measurement and the bottom plots
show the measurement for B 0 → J/ψK L (η f = +1) The distributions are background subtracted.
Figure adapted from [98]
The resulting value sin (2β) = 0.760 ± 0.034 [101] is slightly larger than the ones
measured at the B-factories. It is important to notice that despite the much larger
number of signal candidates used for the LHCb measurement the total error is
comparable with the ones of Belle and BABAR. The reason is the significantly
larger mistag probability at a hadron collider which leads to a reduction of the
statistical power of the events. Using all available measurements of sin (2β) an
average value of
sin (2β) = 0.691 ± 0.017