We show that gauge coupling unification is realized in the presence of unbroken U(1)H which has a large kinetic mixing of O(0.1) with hypercharge. We find that the unification is essentially determined by the kinetic mixing only, and it is rather robust against the existence of vector-like matter fields charged under U(1)H and/or SU(5). This implies that we can easily accommodate the Peccei-Quinn solution to the strong CP problem. With a large U(1)H gauge coupling required to induce the large kinetic mixing, hidden matter fields significantly contribute to the electromagnetic anomaly. Consequently, the axion-photon coupling is enhanced by about a factor of 10-100 with respect to the GUT-axion models with E/N = 8/3.

Norimi Yokozaki, an assistant professor at Tohoku University from 2016. He received his Ph.D. from Hiroshima University in 2010.

He had been a postdoctoral research fellow at the University of Tokyo from 2010 to 2014 and at INFN Rome from 2014 to 2016.

He has worked on model building, phenomenology and cosmology of new physics beyond the Standard Model such as supersymmetry.