120359559
Z′-boson decays as a test of the four-color symmetry of quarks and leptons
The quark and leptonic widths of the Z′ boson that arises from four-color quark-lepton symmetry are calculated and compared with the predictions of the E6 and the left-right (LR) model. It is shown that this four-color symmetry leads to a specific relation of the type v′q+a′q between the vector and axial coupling constants for Z′-boson interaction with quarks and leptons. Calculations with allowance for the four-color symmetry in question yield leptonic widths of the Z′ boson that are considerably greater than those predicted within the E6 and the LR model and result in a relativelys mall hadronic-to-leptonic width ratio. Since these features are associated with the four-color symmetry, their observation would suggest its manifestation in Z′-boson decays.
118758893
Minimal four-color model with quark-lepton symmetry and constraints on the Z{prime}-boson mass
A minimal model with quark-lepton symmetry is considered. This model, which describes unified electroweak and strong interactions, is a minimal extension of the standard model that involves four-color symmetry of quarks and leptons. Predicted relations between the masses of leptoquarks and W{sup +-}, Z, and Z{prime} bosons are studied, and the contributions of an additional Z{prime} boson to the cross sections for e{sup +}e{sup -} annihilation and the asymmetry A{sub FB} at TRISTAN and LEP200 energies are analyzed. Experimental data are shown to be consistent with the existence of a relatively light Z{prime} boson associated with four-color quark-lepton symmetry. 12 refs., 3 figs., 1 tab.
120006374
Contributions of scalar leptoquarks to the cross sections for the production of quark-antiquark pairs in electron-positron annihilation
AbstractThe contributions of scalar-leptoquark doublets to the cross sections 
$$\sigma _{Q\tilde Q} $$
, for the production of quark-antiquark pairs in electron-positron annihilation are calculated within the minimal model based on the four-color symmetry of quarks and leptons. These contributions are analyzed versus the scalar-leptoquark masses and the mixing parameters of the model at colliding-particle energies in the range 250–1000 GeV. It is shown that the contributions in question are of greatest importance for processes leading to t-quark production. In particular, it is found that, with allowance for the contribution of the scalar leptoquark of charge 5/3 and mass in the range 250–500 GeV, the cross section 
$$\sigma _{t\tilde t} $$
 calculated at a mixing-parameter value of kt ∼ 1 may be severalfold larger than the corresponding cross section 
$$\sigma _{t\tilde t}^{(SM)} $$
 within the Standard Model. The possibility of setting constraints on the scalar-leptoquark masses and on the mixing parameters by measuring such contributions at future electron-positron colliders is indicated.
118835200
THE CHIRAL COLOR SYMMETRY OF QUARKS AND G′-BOSON CONTRIBUTIONS TO CHARGE ASYMMETRY IN $t \bar t$-PRODUCTION AT THE LHC AND TEVATRON
The contributions of G′-boson predicted by the chiral color symmetry of quarks to the charge asymmetry in -production at the LHC and to the forward–backward asymmetry in -production at the Tevatron are calculated and analyzed in dependence on two free parameters of the model, the G′ mass mG′ and mixing angle θG. The mG′ - θG regions of 1 σ consistency with the CMS data on the cross-section and on the charge asymmetry are found and compared with those resulted from the CDF data on the cross-section and on the forward–backward asymmetry of -production at the Tevatron with account of the current SM predictions for .
17736206
BOUNDS ON SCALAR LEPTOQUARK MASSES FROM S, T, U PARAMETERS IN THE MINIMAL FOUR-COLOR QUARK-LEPTON SYMMETRY MODEL
Abstract The contributions into radiative correction parameters S , T , U from the scalar leptoquarks are calculated in the minimal gauge model with the four-color quark-lepton symmetry. It is shown that the contributions into T and U from the scalar leptoquark doublets are not positive definite. Using the current experimental data on S , T , U the bounds on the scalar leptoquark masses are obtained. In particular, the existence of the relatively light scalar leptoquark with electric charge 2/3 is shown to be compatible with the current experimental data on S , T , U .
118447115
COLORED SCALAR PARTICLES PRODUCTION IN pp-COLLISIONS AND POSSIBLE MASS LIMITS FOR SCALAR GLUONS FROM FUTURE LHC DATA
Cross sections of the colored scalar particle production in pp-collisions are calculated and differential and total cross sections of the corresponding parton subprocesses are obtained. The total cross section of scalar gluon production in pp-collisions at the LHC is estimated and the dominant decays of scalar gluons are discussed. The production cross section of scalar gluons F with masses mF ≲ 1300 GeV is shown to be sufficient for the effective production of these particles at the LHC.
119354807
Neutrino masses and mixing: Singular mass matrices and quark lepton symmetry
Abstract We suggest an approach to explain the observed pattern of the neutrino masses and mixing which employs the weakly violated quark–lepton equality and does not require introduction of an ad hoc symmetry of the neutrino sector. The mass matrices are nearly equal for all quarks and leptons. They have very small determinant and hierarchical form with expansion parameter λ ∼ sin θ c ∼ m μ / m τ . The latter can be realized, e.g., in the model with U ( 1 ) family symmetry. The equality is violated at the ∼ λ 2 level. Large lepton mixing appears as a result of summation of the neutrino and charged lepton rotations which diagonalize corresponding mass matrices in contrast with the quark sector where the up quark and down quark rotations cancel each other. We show that the flip of the sign of rotation in the neutrino sector is a result of the seesaw mechanism which also enhances the neutrino mixing. In this approach one expects, in general, deviation of the 2-3 mixing from maximal, s 13 ∼ ( 1 – 3 ) λ 2 , hierarchical neutrino mass spectrum, and m e e 10 − 2 eV . The scenario is consistent with the thermal leptogenesis and (in SUSY context) bounds on lepton number violating processes, like μ → e γ .
15943616
High-energy neutrino conversion and the lepton asymmetry in the universe
We study the matter effects on oscillations of high-energy neutrinos in the Universe. A substantial effect can be produced by scattering of the neutrinos from cosmological sources $(z\ensuremath{\gtrsim}1)$ on the relic neutrino background, provided that the latter has large $\mathrm{CP}$ asymmetry: $\ensuremath{\eta}\ensuremath{\equiv}{(n}_{\ensuremath{\nu}}\ensuremath{-}{n}_{\overline{\ensuremath{\nu}}}{)/n}_{\ensuremath{\gamma}}\ensuremath{\gtrsim}1,$ where ${n}_{\ensuremath{\nu}},$ ${n}_{\overline{\ensuremath{\nu}}}$ and ${n}_{\ensuremath{\gamma}}$ are the concentrations of neutrinos, antineutrinos, and photons. We consider in detail the dynamics of conversion in the expanding neutrino background. Applications are given to the diffuse fluxes of neutrinos from gamma ray bursters, active galactic nuclei, and the decay of superheavy relics. We find that the vacuum oscillation probability can be modified by $\ensuremath{\sim}10\ensuremath{-}20%,$ and in extreme cases allowed by present bounds on $\ensuremath{\eta}$ the effect can reach $\ensuremath{\sim}100%.$ The signatures of matter effects would consist (i) for both active-active and active-sterile conversion, in a deviation of the numbers of events produced in a detector by neutrinos of different flavors, ${N}_{\ensuremath{\alpha}}$ $(\ensuremath{\alpha}=e,\ensuremath{\mu},\ensuremath{\tau}),$ and of their ratios from the values given by vacuum oscillations; such deviations can reach $\ensuremath{\sim}5\ensuremath{-}15%,$ and (ii) for active-sterile conversion, in a characteristic energy dependence of the ratios ${N}_{e}{/N}_{\ensuremath{\mu}}{,N}_{e}{/N}_{\ensuremath{\tau}}{,N}_{\ensuremath{\mu}}{/N}_{\ensuremath{\tau}}.$ Searches for these matter effects will probe large $\mathrm{CP}$ and lepton asymmetries in the Universe.
125220940
Vacuum oscillations of solar neutrinos: correlation between spectrum distortion and seasonal variations
Abstract We show that for vacuum oscillation solution of the solar neutrino problem there is a strict correlation between energy spectrum distortion and amplitude of seasonal variations of the solar neutrino flux. The slope parameter which describes distortion of the recoil electron energy spectrum and the seasonal asymmetry of fluxes has been calculated in relevant region of the oscillation parameters. The correlation of the slope and asymmetry gives crucial criteria for identification of this solution.
14713509
Neutrino mixing and quark-lepton complementarity
As a result of the identification of the solution to the solar neutrino problem, a rather precise relation ${\ensuremath{\theta}}_{\mathrm{s}\mathrm{u}\mathrm{n}}+{\ensuremath{\theta}}_{C}=\ensuremath{\pi}/4$ between the leptonic 1-2 mixing angle ${\ensuremath{\theta}}_{\mathrm{s}\mathrm{u}\mathrm{n}}$ and the Cabibbo angle has emerged. It would mean that the lepton and the quark mixing angles add up to the maximal, suggesting a deep structure by which quarks and leptons are interrelated. We refer to the relation as ``quark-lepton complementarity'' (QLC) in this paper. We formulate general conditions under which the QLC relation is realized. We then present several scenarios which lead to the relation and elaborate on phenomenological consequences which can be tested by the future experiments. We also discuss implications of the QLC relation for the quark-lepton symmetry and the mechanism of neutrino mass generation.
15195987
Leptonic Unitarity Triangle and CP-violation
The area of the unitarity triangle is a measure of CP-violation. We introduce the leptonic unitarity triangles and study their properties. We consider the possibility of reconstructing the unitarity triangle in future oscillation and non-oscillation experiments. A set of measurements is suggested which will, in principle, allow us to measure all sides of the triangle, and consequently to establish CP-violation. For different values of the CP-violating phase, {delta}{sub D}, the required accuracy of measurements is estimated. The key elements of the method include determination of |U{sub e3}| and studies of the {nu}{sub {mu}} - {nu}{sub {mu}} survival probability in oscillations driven by the solar mass splitting {Delta}m{sub sun}{sup 2}. We suggest additional astrophysical measurements which may help to reconstruct the triangle. The method of the unitarity triangle is complementary to the direct measurements of CP-asymmetry. It requires mainly studies of the survival probabilities and processes where oscillations are averaged or the coherence of the state is lost.