119271341
Quark mass hierarchy in 3-3-1 models
We study the mass spectrum of the quark sector in an special type I-like model with gauge symmetry $SU(3)_c \otimes SU(3)_L \otimes U(1)_X$. By considering couplings with scalar triplets at large ($\sim TeV$) and small ($\sim GeV$) scales, we obtain specific zero-texture mass matrices for the quarks which predict three massless quarks ($u,d,s$) and three massive quarks ($c,b,t$) at the electroweak scale ($\sim$ GeV). Taking into account mixing couplings with three heavy quarks at large scales predicted by the model, the three massless quarks obtain masses at small order that depends on the inverse of the large scale. Thus, masses of the form $m_u \lesssim m_d < m_s \sim MeV$ and $ m_{c,b,t} \sim GeV$ can be obtained naturally from the gauge structure of the model.
18818705
Heavy quark signals from radiative corrections to the Z-prime boson decay in 3-3-1 models
One-loop corrections to the ${Z}^{\ensuremath{'}}$ decay width are derived and analyzed in the framework of the general form of the 3-3-1 models. We identify two important sources of corrections: oblique corrections associated to the ${Z}^{\ensuremath{'}}$ propagator through vacuum polarizations induced by virtual particle-antiparticle pairs of new heavy quarks $J$, and vertex corrections to the ${Z}^{\ensuremath{'}}q\overline{q}$ vertex through virtual exchange of new ${K}^{{Q}_{1,2}}$ gauge bosons. Fixing a specific renormalization scheme, we obtain dominant oblique corrections that exhibit a quadratic dependence on the $J$ quark mass, which are absorbed into two oblique parameters: a global parameter ${\ensuremath{\rho}}_{f}^{\ensuremath{'}}$ which modify the ${Z}^{\ensuremath{'}}$ decay width, and a parameter ${\ensuremath{\kappa}}_{f}^{\ensuremath{'}}$ that define effective ${Z}^{\ensuremath{'}}$ couplings. Numerical results in an specific 3-3-1 model gives a strong contribution of the oblique corrections from about 1.3% in the $d(s)$ quark channel to 10.5% in the neutrino channel, for ${m}_{J}=2\text{ }\text{ }\mathrm{TeV}$. The vertex corrections contribute to the oblique corrections up to 1.4% for the same channel and ${m}_{J}$ value. For $pp$ collisions at the CERN LHC collider, we find that the corrections significantly modify the shape of the cross section distributions for ${e}^{+}{e}^{\ensuremath{-}}$ and $t\overline{t}$ final states, where the distributions including the radiative corrections increases up to 1.23 times the tree-level distribution for the dielectron events and to 1.07 for the top events when ${m}_{J}=3\text{ }\text{ }\mathrm{TeV}$.
15573535
NEW PHYSICS EFFECTS IN THE FLAVOR-CHANGING NEUTRAL COUPLINGS OF THE TOP QUARK
We survey the flavor-changing neutral couplings (FCNC) of the top quark predicted by some extensions of the Standard Model: THDM, SUSY, Left–Right symmetric, TC2, 331, and models with extra quarks. Since the expected sensitivity of the LHC and ILC for the tcV (V = γ, g, Z) and tcH couplings is of order of a few percent, we emphasize the importance of any new physics effect that gives a prediction for these FCNC couplings within this limit. We also review the constraints imposed on these couplings from low-energy precision measurements.
7716128
Z and Z' decays with and without FCNC in 331 models
In the context of the 331 models, we consider constraints on the extra neutral boson Z{sup '} predicted by the model, where three different quark family assignments are identified. Using the ansatz of Matsuda as an specific texture for the quark mass matrices, we obtain allowed regions associated with the Z-Z{sup '} mixing angle, the mass of the Z{sup '} boson and the parameter {beta} which determines different 331 models. The Z{sub 1} and Z{sub 2} decays with and without flavor changing are also considered. The flavor changing decays of the Z{sub 1} boson into quarks at tree level are highly suppressed by the Z-Z{sup '} mixing angle, obtaining the same order of magnitude as the standard model prediction at one-loop level. The Z{sub 2} decay widths are calculated with and without flavor changing, where oblique radiative corrections at one loop accounts for about 1%-4% deviations.
124002542
Quark masses and mixing in $SU\left(3\right)_{C}\otimes SU\left(3\right)_{L}\otimes U\left(1\right)_{X}\otimes S_{3}$ models
By imposing a specific $S_{3}$ discrete symmetry for fermions and scalars, we extend the group of the model based on the gauge symmetry $SU(3)_{C}\otimes SU(3)_{L}\otimes U(1)_{X}$. We found that after the symmetry breaking of the continuous group, all the down type quarks acquire tree level masses, while in the up sector only the top quark and a new heavy T quark obtain masses at tree level. By imposing hierarchical Yukawa couplings between the ordinary down-type quarks and new heavy down-type quarks, we may explain the relation $m_{d}<<m_{s}<<m_{b}$. The massless up-type quarks get small mass terms through effective six dimensional operators according to the gauge and discrete symmetries. In particular, the smallness of the u quark can be understood by a small deviation in the universality of the dimensionless couplings associated to the effective operators. We also obtain with only four free parameters, the magnitudes of the CKM matrix elements and the Jarlskog invariant, within experimental error values.
119520979
Bounds for lepton flavor violation and the pseudoscalar Higgs boson in the general two Higgs doublet model using the $g-2$ muon factor
Current experimental data from the $g-2$ muon factor, seems to show the necessity of physics beyond the Standard Model (SM), since the difference between SM and experimental predictions is 2.6$\sigma $. In the framework of the General Two Higgs Doublet Model (2HDM), we calculate the muon anomalous magnetic moment to get lower and upper bounds for the Flavour Changing (FC) Yukawa couplings in the leptonic sector. We also obtain lower bounds for the mass of the pseudoscalar Higgs ($m_{A^0}$) as a function of the parameters of the model.
118371403
Phenomenological aspects of the exotic T quark in 331 models
In the context of 331 models we analyze the phenomenology of exotic T quarks with electric charge 2/3. We establish bounds for the corresponding masses and mixing angles and study the decay modes T→bW, tZ and qH. It is found that the decays into scalars are strongly dependent on the model parameters and can be the dominant ones in a scenario with approximate flavor symmetry.