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.
11320046
Bounds on scalar leptoquark and scalar gluon masses from current data on S, T, U
The contributions into radiative correction parameters S, T, U from scalar leptoquark and scalar gluon doublets are investigated in the minimal four color symmetry model. It is shown that the existence of the relatively light scalar leptoquarks and scalar gluons (with masses of order of 1 TeV or less) is consistent with the current experimental data on S, T, U and the more light particles (with masses below 400 GeV) improve the fit. In particular, the lightest scalar leptoquarks with masses below 300 GeV are consistent with the current data on S, T, U at $\chi^2 < 3.1(3.2)$ for $m_H=115(300) GeV$ in comparison with $\chi^2 = 3.5(5.0)$ in the Standard Model. The lightest scalar gluon in this case is expected to lie below $ 850(720) GeV.$ The possible significance of such particles in the t-quark physics at LHC is emphasized and their effect on the gauge coupling constant unification is briefly discussed.
116859657
Scalar Leptoquark Contributions into $l_i\to l_j\gamma$ Processes
The contributions of scalar leptoquarks in lepton flavor violating (LFV) processes of type $l_i\to l_j \gamma$ are investigated in frame of the minimal model with the four color symmetry and Higgs mechanism of quark and lepton mass generation. It is shown that experimental data on the decays $\mu\to e \gamma$, $\tau \to \mu \gamma$, $\tau\to e \gamma$ allow the existence of light scalar leptoquarks of type under consideration, with masses of order 1 TeV or below.
123688621
Dominant decays of scalar leptoquarks and scalar gluons in the minimal four-color symmetry model
AbstractFermionic and weak decays of the scalar leptoquarks S = S1(+), S1(−), and Sm and the scalar gluons F = F1 and F2 predicted by the minimal model involving four-color symmetry and the Higgs mechanism of quark-and lepton-mass splitting are considered. The widths and the branching ratios are calculated for these decays, and the results are analyzed versus the couplings and masses of decaying particles. It is shown that, at relatively small mass splittings Δm within scalar doublets (Δm < mW), the fermionic decays S1(+) → tlj+, S1(−) → vi
$$\tilde b$$
, Sm → t
$$\tilde \nu $$
j, F1 → t
$$\tilde b$$
, and F2 → t
$$\tilde t$$
, which are characterized by few-GeV widths for mS, mF < 1 TeV and decay branching ratios close to unity, are dominant, but that, for Δm > mW, the weak decays S → S′W and F → F’W compete with the above fermionic decays. In the case of mS < mt, the processes S1(+) → clj+, S1(−) → vi
$$\tilde b$$
, Sm → blj+, and Sm → c
$$\tilde \nu $$
j, whose total branching ratios are Br(S1(+) → cl+) ≈ Br(S1(−) → v
$$\tilde b$$
) ≈ 1, Br(Sm → bl+) ≈ 0.9, and Br(Sm → c
$$\tilde \nu $$
) ≈ 0.1, appear to be dominant decays of scalar leptoquarks. Searches for these decays at LHC and the Tevatron are of interest.
18861681
Bounds on scalar leptoquark and scalar gluon masses from S, T, U in the minimal four color symmetry model
Abstract The contributions into radiative correction parameters S, T, U from scalar leptoquark and scalar gluon doublets are investigated in the minimal four color symmetry model. It is shown that the current experimental data on S, T, U allow the scalar leptoquarks and the scalar gluons to be relatively light (with masses of order of 1 TeV or less), the lightest particles are preferred to lie below 400 GeV. In particular, the lightest scalar leptoquarks with masses below 300 GeV are shown to be compatible with the current data on S, T, U at χ2
118565164
Cross Section and Forward-Backward Asymmetry of $t\bar{t}$ Production in the Model with Four Color Symmetry
The contributions to the cross section $\sigma_{t\bar{t}}$ and to the forward-backward asymmetry $A_{\rm FB}^{t \bar t}$ of $t\bar{t}$ production at the Tevatron from $Z'$-boson and scalar leptoquarks $S^{(\pm)}_a$ and scalar gluons $F_a$ predicted by the minimal model with four color quark-lepton symmetry are calculated. These contributions are shown to be small in tree approximation and can be significant with account of the 1-loop $gt\bar{t}$ effective vertex induced by the scalar doublets. The lower mass limit for scalar gluons $m_F \gtrsim 320\, GeV$ from the Tevatron data is obtained and it is shown that for $m_{F_1}\lesssim 990\,GeV$ the scalar gluon $F_1$ can be evident at LHC at the significance not less that $3\sigma$ (for $\sqrt{s}=14$ TeV, $L=10\,fb^{-1}$).
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.
41885673
Quark and gluon form factors to three loops.
We compute the form factors of the photon-quark-anti-quark vertex and the effective vertex of a Higgs-boson and two gluons to three-loop order within massless perturbative quantum chromodynamics. These results provide building blocks for many third-order cross sections. Furthermore, this is the first calculation of complete three-loop vertex corrections.
15650057
Quark lepton complementarity and renormalization group effects
We consider a scenario for the quark-lepton complementarity relations between mixing angles in which the bimaximal mixing follows from the neutrino mass matrix. According to this scenario in the lowest order the angle {theta}{sub 12} is {approx}1{sigma} (1.5 degree sign -2 degree sign ) above the best fit point coinciding practically with the tribimaximal mixing prediction. Realization of this scenario in the context of the seesaw type-I mechanism with leptonic Dirac mass matrices approximately equal to the quark mass matrices is studied. We calculate the renormalization group corrections to {theta}{sub 12} as well as to {theta}{sub 13} in the standard model (SM) and minimal supersymmetric standard model (MSSM). We find that in a large part of the parameter space corrections {delta}{theta}{sub 12} are small or negligible. In the MSSM version of the scenario, the correction {delta}{theta}{sub 12} is in general positive. Small negative corrections appear in the case of an inverted mass hierarchy and opposite CP parities of {nu}{sub 1} and {nu}{sub 2} when leading contributions to {theta}{sub 12} running are strongly suppressed. The corrections are negative in the SM version in a large part of the parameter space for values of the relative CP phase of {nu}{sub 1} andmore » {nu}{sub 2}: {phi}>{pi}/2.« less
123522314
DENSITY PERTURBATIONS AND RESONANT CONVERSION OF NEUTRINOS
The influence of local density perturbations on the resonant neutrino conversion is studied. General relations are established between the features of the perturbations and the changes in the conversion probabilities. In the extreme case of very fast changes of density in a thin layer, the problem is solved analytically. We consider the possibility of appearance or shift of local ρ-perturbations in the sun to induce appreciable variations of the solar neutrino signals, in particular in the Cl-Ar experiment.
17377891
Right-handed neutrinos at CERN LHC and the mechanism of neutrino mass generation
We consider the possibility to detect right-handed neutrinos, which are mostly singlets of the standard model gauge group, at future accelerators. Substantial mixing of these neutrinos with the active neutrinos requires a cancellation of different contributions to the light neutrino mass matrix at the level of 10{sup -8}. We discuss possible symmetries behind this cancellation and argue that for three right-handed neutrinos they always lead to conservation of total lepton number. Light neutrino masses can be generated by small perturbations violating these symmetries. In the most general case, LHC physics and the mechanism of neutrino mass generation are essentially decoupled; with additional assumptions, correlations can appear between collider observables and features of the neutrino mass matrix.