SU(4)L×U(1)Xmodels with little Higgs mechanism

Abstract

We discuss the aspects of the fermions and gauge bosons in SU (4)L × U (1)X models with little Higgs. We introduce a set of fermions which ensures the cancellation of gauge anomaly, and explicitly show the cancellation of one-loop quadratic divergence to the Higgs mass from all fermion multiplets and all gauge bosons. We present the interactions of the standard model fermions with the physical gauge bosons. We also discuss some phenomenological implications of the model based on recent experimental results.

LHC Phenomenology of Z′ and Z″ bosons in the SU(4)L × U(1)X little Higgs model

“…( ) ( ) models with a regular Higgs mechanism [19], and their low-energy phenomenology is also similar if the fermion family is assigned to be the same [22]. As a result, the mass bounds and the LHC discovery potentials of the ¢ Z and  Z bosons obtained in this paper can be applicable to models with a regular Higgs mechanism.…”

“…so that the duplicated extra-heavy fermions T and B remove the quadratic divergences due to their SM fermion partners t and b, respectively. As discussed in [22] in detail, the couplings of the neutral Higgs to the t b ( ) and T B ( ) quarks are obtained from the quark Yukawa Lagrangian by expanding the nonlinear sigma fields F i as…”

“…Similarly, the extra-heavy charged gauge bosons are decoupled from the SM sector. Therefore, this model does not receive strong electroweak constraints in the charged sector [22], and this is true for the other LHMs with a simple group [20,25]. This is the reason why especially the extra neutral (flavor-conserving) gauge bosons are most interesting for the low-energy phenomenology and collider signature studies in these kinds of LHMs.…”

“…After the EWSB, among the 15 gauge fields a m A associated with SU 4 , L ( ) the three neutral gauge bosons A 3 , A 8 , and A 15 mixed with the U 1 X ( ) gauge boson A X are associated with a 4 × 4 nondiagonal mass matrix. After the mass matrix is diagonalized, a zero eigenvalue corresponds to the photon A, and the three physical neutral gauge bosons Z, ¢ Z , and  Z get the masses as follows [22]…”

“…However, the K-S model has a set of anomalous fermions with a simple family-universal embedding, which requires additional fermion multiplets at the scale Λ due to nonvanishing quadratic divergences from light fermions and gauge anomalies. Alternatively, we consider the modified K-S model by embedding an anomaly-free set of fermions, as proposed in [21], so that one-loop quadratic divergences for the Higgs mass are canceled for all fermion flavors as a continuation of our previous work [22].…”