Fermion masses inSO(10)with a single adjoint Higgs field

Abstract

It has recently been shown how to break SO(10) down to the standard model in a realistic way with only one adjoint Higgs field. The expectation value of this adjoint must point in the BϪL direction. This has consequences for the possible form of the quark and lepton mass matrices. These consequences are explored in this paper, and it is found that one is naturally led to consider a particular form for the masses of the heavier generations. This form implies typically that there should be large ͑nearly maximal͒ mixing of the and neutrinos. An explanation that does not involve large tan␤ also emerges for the fact that b and are light compared to the top quark. ͓S0556-2821͑98͒01413-1͔

Predicting quark and lepton masses and mixings

“…(2). Much of the structure of such a model has already been described in [1] and [2]. In addition to what was presented there, there have to be SO(10) 10's of Higgs fields to be integrated out to give the δ and δ ′ entries, as in Fig.…”

“…One of the guiding principles in constructing the model was that the mass terms should be of a kind that can arise simply in SO(10) with small representations of Higgs fields [2]. Two critical points emerged from that work: namely, that it is quite natural in unified theories for there to be flavor-asymmetric contributions to the fermion mass matrices, and that these can explain some of the puzzling features of the spectrum.…”

A single source for all flavor violation

“…More specifically, the mixing responsible for flavor violation is between the 5 i and the 5 ′ A multiplets. This means that the model is of the "lopsided" type [6][7][8][9][10][11][12][13][14]. Because the origin of flavor changing is in the 5 sector, it shows up more strongly in left-handed leptons (which are in 5 multiplets) than in left-handed quarks (which are in 10 multiplets).…”

B−Lviolating nucleon decay and GUT scale baryogenesis inSO(10)

“…4 (b [19][20][21][22]. While R-parity is no longer automatic in these models (unlike in the case of 126 H models), it can be ensured by a discrete Z 2 symmetry which distinguishes 16 H from the chiral fermions 16 i and which remains unbroken.…”

“…(16), (18), (20) can be estimated as follows. For this purpose let us assume that ω is the field ω from 10 H with Yukawa couplings as given in Eq.…”