Minimally flavored colored scalar in overline{B}to {D^{{left( * right)}}}tau overline{nu} and the mass matrices constraints

摘要

The presence of a colored scalar that is a weak doublet with fractional electric charges of |Q| = 2/3 and |Q| = 5/3 with mass below 1 TeV can provide an explanation of the observed branching ratios in ( Bto {D^{{left( * right)}}}tau overline{nu} ) decays. The required combination of scalar and tensor operators in the effective Hamiltonian for ( bto ctau overline{nu} ) is generated through the t-channel exchange. We focus on a scenario with a minimal set of Yukawa couplings that can address a semitauonic puzzle and show that its resolution puts a nontrivial bound on the product of the scalar couplings to ( overline{tau}b ) and ( overline{c}nu ). We also derive additional constraints posed by ( Zto boverline{b} ), muon magnetic moment, lepton flavor violating decays μ → eγ, τ → μγ, τ → eγ, and τ electric dipole moment. The minimal set of Yukawa couplings is not only compatible with the mass generation in an SU(5) unification framework, a natural environment for colored scalars, but specifies all matter mixing parameters except for one angle in the up-type quark sector. We accordingly spell out predictions for the proton decay signatures through gauge boson exchange and show that p → π0 e + is suppressed with respect to ( pto {K^{+}}overline{nu} ) and even p → K 0 e + in some parts of available parameter space. Impact of the colored scalar embedding in 45-dimensional representation of SU(5) on low-energy phenomenology is also presented. Finally, we make predictions for rare top and charm decays where presence of this scalar can be tested independently.