Trilinear gauge boson couplings and bilepton

The trilinear gauge boson couplings in the SU(3)_C ⊗ SU(3)_L ⊗ U(1)_N (3-3-1)models are presented. We find that new Z₂ does not interact with the usual (in the standard model) gauge bosons Z,W ± size 12{ {} rSup { size 8{ +- {}} } } {} . Based on these results, production of new heavy gauge bosons at high energy colliders such as e⁺ e^- is calculated. We show that the cross sections obtained in the 3-3-1 model with right-handed neutrinos can be one order bigger than the same in the minimal 3-3-1 model. © 2001 Published by Elsevier Science B.V.

Although the standard model (SM) [1] of electroweak interactions has been verified to great precision in the recent years at LEP, SLC and other places, there remain a few unanswered questions concerning mainly the mass spectrum and the generation structure of quarks and leptons. In particular the question of the number of generations remains open and few progress has been made towards the understanding of the interrelation between generations. Amongst the possible models beyond the standard one, from modest extensions to GUTs, few address this question, the generations are usually assumed to be a replicate of the first one. The models based on the SU(3)_C ⊗ SU(3)_L ⊗ U(1)_N gauge group [2-6], are interesting form this point of view. They have the following intriguing features: Firstly the models are anomaly free only if the number of generations N is a multiple of three. If further one adds the condition of QCD asymptotic freedom, which is valid only if the number of generations of quarks is to be less than 5, it follows that the number of generations is equal to 3. The second characteristics of the 3-3-1 models is that one generation of quarks is treated differently from two others. This could lead to a natural explanation for the unbalancingly heavy top quark. The possibility of the third generation being different from the first two is not excluded experimentally. While the anomalous behaviour of the parameters R_b and A_b in the LEP data [8] has more or less disappeared, the effects are now 1.8σ away from the SM value for R_b and 3σ for A_b , there is still room for generation universality breaking in the third generation. The third interesting feature is that the Peccei-Quinn symmetry naturally occurs in these models [9]. Finally, from a phenomenological point of view, the 3-3-1 models are very interesting, they predict new physics at a scale only slightly above the SM scale (typically TeV) and even give upper bounds on the mass of some new particles. Therefore the models can be confirmed or ruled out in the next generation of collider experiments from Tevatron, LHC, or a future linear collider, in stark contrast with “grand desert” scenarios in Grand Unification Theories.

Despite the extremely precise measurements of the SM parameters, one important component has not been tested directly with precision: the non-abelian self-couplings of the weak gauge bosons. The measurements performed at LEP1 have provided us with an extremely accurate knowledge of the parameters of the Z gauge boson: its mass, partial awidths, and total awidth. There even is first evidence that the contributions of gauge-boson loops to the gauge-boson self-energies are indeed required [10]. Thus, an indirect confirmation of the existence of the trilinear gauge boson couplings (TGCs) has been obtained. With the excellent performance of the LEP machine at high energy in last couple of years, electroweak physics at LEP2 now truly merits the epithet “precise”. The core measurements of the LEP2 program, the W mass, and the vector boson self-couplings have been made with precision better, in some cases substantially so, than elsewhere. The mixing in the neutral gauge boson sector and the angular distributions as well as the W helicities in the final states of W ⁺W ⁻ production have been searched for at LEP2 [11]. Deviation of non-abelian couplings from expectation would signal new physics. In addition, precise measurements of gauge boson self-interactions will provide important information on the nature of electroweak symmetry breaking. The TGCs have been investigated by many authors [12-15], and some direct tests of these couplings have been made in [16]. TGCs in the beyond — the standard models, in which there exist heavy particles with mass much larger m_W have been investigated in [17]. In the 3-3-1 models, the TGCs have the structure of the standard model couplings, up to a coupling constant. Recent investigations have indicated that signals of new gauge bosons in the models may be observed at the CERN LHC [18] or Next Linear Collider (NLC) [19].

Our aim in this paper is to present TGCs in the 3-3-1 models and use these couplings to discuss new processes that could be measured at future high energy colliders. This paper is organized as follows. In Section 2 we give a brief review of two models: relation among real physical bosons and gauge fields, which is necessary in getting of TGCs. TGCs aregiven in this section. Section 3 is devoted to bilepton production at high energy collider e⁺e⁻ , and discussions are given in the last section — Section 4.

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