4c. What is the significance of CP in B decay? guided tour ---> --> ->

According to the Standard Model, CP violation occurs in the weak interaction, more specifically when quarks undergo weak transformations and turn into quarks with different electric charge.  All of the possible interactions of this type are represented by the matrix known as the CKM matrix, discussed earlier (in FAQ 3b).  We need to know all of the elements in the matrix, both their real and imaginary parts, to test the relationships predicted by the Standard Model.  To measure the imaginary parts, we need to measure CP violation in many meson decays.  For K meson decays the elements we can look at are mostly in the second column of the matrix.  With B decays we can look in the third row and the third column.  With the combination of both, we cover nearly all of the matrix and should be able to check all of the matrix relationships.  Some decays are predicted to display CP violation, others are not.