Alladi Ramakrishnan Hall

The fourth chiral generation is still alive

Anirban Kundu

Calcutta University

A fourth chiral generation, although attractive as a source of new CP-violating phases, is considered to be dead from the current Higgs data. In this talk, I will show that, contrary to the common perception, the data does not eliminate the possibility of a sequential fourth generation that get their masses through the same Higgs mechanism as the first three generations. The inability to fix the sign of the bottom-quark Yukawa coupling from the available data plays a crucial role in accommodating a chiral fourth generation which is consistent with the bounds on the Higgs signal strengths. I will also show that the effects of such a fourth generation can remain
completely hidden not only in the production of the Higgs boson through gluon fusion but also to its subsequent decays, and provide a practical example illustrating how our general prescription can be embedded in a realistic model.