  We make a systematic analysis of the effects of new physics in the B decay
amplitudes on the CP asymmetries in neutral B decays. Although these are
expected to be smaller than new physics effects on the mixing amplitude, they
are easier to probe in some cases. The effects of new contributions to the
mixing amplitude are felt universally across all decay modes, whereas the
effects of new decay amplitudes could vary from mode to mode. In particular the
prediction that the CP asymmetries in the B_d decay modes with $b\to c\bar c s,
b \to c\bar c d, b\to c \bar u d$ and $ b\to s \bar s s$ should all measure the
same quantity ($sin2\beta$ in the Standard Model) could be violated. Since the
above Standard Model prediction is very precise, new decay amplitudes which are
a few percent of the Standard Model amplitudes can be probed. Three examples of
models where measurable effects are allowed are given: effective supersymmetry,
models with enhanced chromomagnetic dipole operators, and supersymmetry without
R parity.
