Test of the fourth quark generation from the Cabibbo–Kobayashi–Maskawa matrix

Abstract

The structure of the mixing matrix in the electroweak quark sector with four generations of quarks is investigated. We conclude that the area of the unitarity quadrangle is not a good choice as a possible measure of the CP violation. In search of new physics, we analyze how the existence of the fourth quark family may influence on the values of the Cabibbo–Kobayashi–Maskawa matrix and we show that one can test for the existence of the fourth generation using the Jarlskog invariants of the known quarks only. The analysis based on the measured unitary triangle exhibits some tension with the assumption of three quark generations. The measurement of the unitarity triangle obtained from the scalar product of the second row/column of the CKM matrix by the complex conjugate of third row/column can provide information about the existence of the fourth generation of quarks.