Narrow Results

Fermionic decays of the scalar leptoquarks , , S_m and of the scalar gluons F=F₁, F₂ predicted by the four-color symmetry model with the Higgs mechanism of the quark–lepton mass splitting are investigated. Widths and branching ratios of these decays are calculated and analyzed in dependence on coupling constants and on masses of the decaying particles. It is shown that the decays , , , , are dominant with the widths of order of a few GeV for m_S, m_F< 1 TeV and with the total branching ratios close to 1. In the case of m_S<m_t the dominant scalar leptoquark decays are , , , with the total branching ratios , and . A search for such decays at the LHC and Tevatron may be of interest.

The contributions of scalar and gauge leptoquarks into widths of , B⁰→e^∓τ^± decays are calculated in the models with the vectorlike and chiral four-color symmetry and with the Higgs mechanism of the quark–lepton mass splitting. From the current data on and B⁰ decays the mass limits for scalar and chiral leptoquarks and the updated vector leptoquark mass limits are obtained. It is shown that unlike the gauge leptoquarks the scalar leptoquark mass limits are weak, of order or below their direct mass limits. The search for such scalar leptoquarks at LHC and the further search for leptonic decays are of interest.

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 m_F ≲ 1300 GeV is shown to be sufficient for the effective production of these particles at the LHC.

The cross section of the μ⁺μ^- pair production in pp-collisions at the LHC is calculated with account of the Z' boson induced by the minimal four-color quark–lepton symmetry (MQLS). The μ⁺μ^- invariant mass spectrum with account of the MQLS Z' boson is analyzed in dependence on the Z' mass. The mass region for the MQLS Z' boson observable at the LHC is found in dependence on the significance and on the integrated luminosity.

A gauge model with chiral color symmetry is considered and possible effects of the color G′-boson octet predicted by this symmetry are investigated in dependence on two free parameters, the mixing angle θ_G and G′ mass m_G′. The allowed region in the m_G'–θ_G plane is found from the Tevatron data on the cross section and forward–backward asymmetry of the production. The mass limits for the G′-boson are shown to be stronger than those for the axigluon. A possible effect of the G′-boson on the production at the LHC is discussed and the mass limits providing for the G′-boson evidence at the LHC are estimated in dependence on θ_G.

The contributions of G'-boson predicted by the chiral color symmetry of quarks to the cross section and to the forward–backward asymmetry of production at the Tevatron are calculated with account of the difference of the strengths of the and interactions. The results are analyzed in dependence on two free parameters of the model, the mixing angle θ_G and G' mass m_G'. The G'-boson contributions to and are shown to be consistent with the Tevatron data on and , the allowed region in the m_G' - θ_G plane is discussed and around m_G' = 1.2 TeV, θ_G = 14° the region of 1σ consistency is found.

The scalar color octet contribution to the resonance $t\bar{t}$-pair production at the LHC is calculated and analyzed by taking into account the one-loop effective two-gluon vertex. It is shown that this contribution from the scalar color octet $F_2$ predicted by the minimal model with the four-color quark–lepton symmetry is for $\sqrt{s}$ = 13 TeV of about a few percent for 750 $<m_{F_2}<$ 1800 GeV and can exceed 10% for 400 $<m_{F_2}<$ 750 GeV. It is also pointed out that the search for the scalar octet $F_2$ as the resonance in the dijet mass spectra seems to be difficult because of the smallness of its one-loop effective two-gluon interaction.

The contributions of the vector leptoquarks of Pati–Salam type to the branching ratios of $K_L^0,B^0,B_s\to l{l}^{\prime }$ decays are calculated with account of the fermion mixing in the leptoquark currents of the general type. Using the general parametrizations of the mixing matrices the lower vector leptoquark mass limit $m_V$$>$ 86 TeV is found from the current experimental data on these decays. The branching ratios of the decays $B^0,B_s\to l{l}^{\prime }$ predicted at $m_V$ = 86 TeV are calculated. These branching ratios for the decays $B^0,B_s\to {\mu }^{+}{\mu }^{-},e\mu$ are close to the experimental data whereas those for the decays $B^0\to e^{+}{e}^{-},e\tau ,\mu \tau$ and $B_s\to e^{+}{e}^{-}$ are by order of 2–4 less than their current experimental limits. For the decays $B_s\to e\tau ,\mu \tau$ these branching ratios are of orders $10^{-10}$ and $10^{-9}$, respectively. The predicted branching ratios will be useful in the current and future experimental searches for these decays.

The contributions of the chiral gauge leptoquarks $V^{L,R}$ induced by the chiral four-color quark–lepton symmetry to the branching ratios of $K_L^0,B^0,B_s\to l_1{l}_2$ decays are calculated and analyzed using the general parametrizations of the fermion mixing matrices in the leptoquark currents. From the current experimental data on these decays under assumption $m_{V^L}\ll m_{V^R}$, the lower mass limit $m_{V^L}cos{\gamma }_L>5.68\mathrm{\text{TeV}}$ is found, which in particular case of equal gauge coupling constants gives $m_{V^L}>8.03\mathrm{\text{TeV}}$. The branching ratios of the decays under consideration predicted by the chiral gauge leptoquarks are calculated and analyzed in dependence on the leptoquark masses and the mixing parameters. It has shown that in consistency with the current experimental data, these branching ratios for $B_s,B^0\to \mu e$ decays can be close to their experimental limits and those for $B_s,B^0\to \tau e,\tau \mu$ decays can be of order of $10^{-7}$. The calculated branching ratios will be useful in the further experimental searches for these decays.

In this paper, we study an effective field theory (EFT) for a singlet scalar extension of the standard model (SM). The tree- and one-loop level effective actions are derived by integrating out the heavy singlet scalar in the Lagrangian for the UV theory and by applying to the functional method, respectively. In the UV model, the light scalar field identified with the SM Higgs is assumed to be massless in the symmetric phase. When the heavy singlet scalar acquires a vacuum expectation value, the $Z_2$ symmetry is broken and a mass term of the light scalar is induced. In light of EFT we derive, the electroweak vacuum resulting in 126GeV Higgs mass can be attained when the induced squared-mass term of the light scalar in the scalar potential becomes negative. This condition can occur when the constant of the scalar coupling between the two different scalars is allowed to be negative. We investigate how the EFT can be constrained by theory and experiments. We also examine whether or not electroweak phase transition (EWPT) in this scenario can be a first order. Some numerical results leading to the first-order EWPT while satisfying the constraints studied are presented.

The Muon g-2 experiment measures the anomalous magnetic moment of muon. The previous measurement at Brookhaven National Laboratory, experiment E821, completed in 2001 found a greater than 3σ discrepancy from the predicted value. The new generation Muon g-2 experiment at Fermi National Laboratory is expected to accumulate 21 times more statistics and achieve a factor of four improvement in the precision with an upgraded apparatus and reduced systematic uncertainties. With both improvements from experiments and theoretical calculations, a more precise test of the Standard Model value will be made. The experiment construction was completed and the commissioning run successfully finished in Summer 2017. The physics data taking will begin in early 2018.