Constraints on the SU(3) electroweak model

Abstract

We consider a recent proposal by Dimopoulos and Kaplan to embed the electroweak SU(2) L × U(1) Y into a larger group SU(3) W × SU(2) × U(1) at a scale above a TeV. This idea is motivated by the prediction for the weak mixing angle sin 2 θ W = 1/4, which naturally appears in these models so long as the gauge couplings of the high energy SU(2) and U(1) groups are moderately large. The extended gauge dynamics results in new effective operators that contribute to four-fermion interactions and Z pole observables. We calculate the corrections to these electroweak precision observables and carry out a global fit of the new physics to the data. For SU(2) and U(1) gauge couplings larger than 1, we find that the 95% C.L. lower bound on the matching (heavy gauge boson mass) scale is 11 TeV. We comment on the fine-tuning of the high energy gauge couplings needed to allow matching scales above our bounds. The remnants of SU(3) W breaking include multi-TeV SU(2) L doublets with electric charge (±2, ±1). The lightest charged gauge boson is stable, leading to cosmological difficulties.

Randall–Sundrum reality at the LHC

“…In order to suppress unwanted higher dimensional operators, which are not sufficiently suppressed by the TeV-scale cutoff on the IR brane in the RS1 model, SM gauge fields [2,3,4,5] and fermions [6,7] are considered to propagate in the bulk space. In this new setup [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16], denoted as the RS model, RS can address both the hierarchy problem and fermion mass hierarchies. From the electroweak precision measurements and various flavor physics, the new Kaluza-Klein (KK) modes of the bulk SM fields are constrained to be heavier than a few TeV [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23].…”

Composite quarks and leptons in higher space-time dimensions

“…To ensure that only a desired set of fermionic zero modes are massless in 4D we restrict general U(1)-twisted boundary conditions to some discrete Z K ones. It is easy to verify then that any K = 2, 3, 4, 6, 9, 12 will provide the desired solutions of (9,11,12):…”

“…Solving the equations (9,11,12) one has to remember that due to periodicity R-charges q are defined up to an arbitrary integer number, q = q + k, k ∈ Z. To ensure that only a desired set of fermionic zero modes are massless in 4D we restrict general U(1)-twisted boundary conditions to some discrete Z K ones.…”

“…All extra composite states are massive with masses of the order of the order of 1 R C . If one identifies the quark-lepton decuplet of SU(5) with fermionic components of D 2 superfield then one has to determine the R-charges from the equations (9,11) and the equation…”

“…It is well known that the compactification of extra space-time dimensions (depending on the detail of dimensional reduction) was happened quite successful to get realistic four dimensional models where supersymmetry [7,8,9], gauge symmetry [10,11] and certain discrete symmetries such as P and CP [12] are broken in an intrinsically geometric way. Following to this line of arguments we find that owing to a certain Scherk-Schwarz compactification [7] the composite quarks and leptons are turned out to be massless in four dimensions, while all unwanted states (residing in the bulk) are massive.…”