Narrow Results

We evaluate the total cross-sections of top-charm associated production induced by SUSY–QCD FCNC at the LHC within the general unconstrained MSSM framework. Our results show that these production rates may be as large as a few pb for favorable parameter values allowing by current precise experiments. It means that the LHC may produce abundant events of this process, and the SUSY FCNC effects through the above process may be observable in the future experiments.

The current experimental status of the searches for the very rare decays and is discussed. These channels are highly sensitive to various extensions of the Standard Model, especially in the scalar and pseudoscalar sector. The recent, most sensitive measurements from the CDF, ATLAS, CMS and LHCb collaborations are discussed and the combined upper exclusion limit on the branching fractions determined by the LHC experiments is shown to be 4.2×10^-9 for and 0.8×10^-9 for . The implications of these tight bounds on a selected set of New Physics models is sketched.

In this work, we overhaul previous studies of Flavor Changing Neutral Current processes in the context of the Reduced Minimal 3-3-1 (RM331) model. We sift the individual contributions from the CP-even scalars and the Z′ gauge boson using two different parametrizations schemes and compare our results with current measurements. In particular, studying the meson system we find the most stringent bounds in the literature on this model, namely and .

We study rare decays , and in NSIs. We calculate the NSIs branching ratios of these decays. There is a strong dependence of these on new physics parameter. They provide stringent constraints on , and (α, β = e, μ).

We consider flavor-changing decays of neutral Higgs bosons in the context of CP-conserving BGL model — a variant of 2HDM Type 3 model suggested by Branco, Grimus and Lavoura — in which tree-level FCNC couplings are suppressed by elements of known fermion mixing matrices. The relevant regions of parameter space compatible with experimental restrictions on the SM Higgs properties are studied. We also include current bounds on $h\to \mu \tau$ into consideration. In addition, different FCNC decay modes are analyzed for heavier Higgs states $(H/A)$ and conservative estimates for $\mathrm{\text{Br}}(A/H\to \mu \tau )$ are provided. We updated previous studies and found that it cannot be more than 30% for heavy Higgses with masses around 350 GeV.

We investigate the nonstandard neutrino interactions (NSI) in the rare decays of $B_c^{+}$ mesons involving neutrinos in the final state. It is suggested that the interference between Standard Model and nonstandard interaction can provide sizeable contribution. We calculate the limits on NSI free parameters (${𝜖}_{\tau \tau }^{uL}$, ${𝜖}_{\tau \tau }^{dL}$) and compare them with experimental data.

The measurements of the top quark flavor changing neutral current interactions are one of the most important goals of the top quark physics program in the present and the future collider experiments. These measurements provide direct information on nonstandard interactions of the top quark. Within the framework of new physics beyond the Standard Model, these interactions can be defined by an effective Lagrangian. In this study, we have investigated the potential of the future $\mu p$ colliders on the top quark flavor changing neutral current interactions through the subprocesses $\gamma q\to t\to Wb$, where $q=u,c$. These subprocesses have been produced through the main reaction $\mu p\to \mu \gamma p\to \mu WbX$ at the LHC-$\mu p$, the FCC-$\mu p$ and the SPPC-$\mu p$. For the main reaction, the total cross-sections have been calculated as a function of the anomalous $tq\gamma$ couplings. In addition, sensitivities on $\mathrm{\text{BR}}(t\to q\gamma )$ at 95% Confidence Level have been calculated. We obtain that the best constraints on $\mathrm{\text{BR}}(t\to q\gamma )$ are at the order of $10^{-7}$ which is four orders of magnitude better than the LHC’s experimental results.

The one-loop contributions to the flavor-changing neutral current decays of the top quark into a light quark and a gauge boson or Higgs boson, namely, $t\to qV,qh$, with q being u or c, and V being $\gamma$, g, or Z, are analyzed in this study within the framework of the minimal R-symmetric supersymmetric standard model. The charginos in this model have been separated into two sets, i.e. $\chi$-chargino and $\rho$-chargino. The numerical results reveal that gluino or $\rho$-chargino predominantly dictate the predictions for BR ($t\to qV,qh$), while the impact of neutralino or $\chi$-chargino contributions is insignificant. By incorporating the constraints imposed by the squark mixing parameters from $\bar{B}\to X_s\gamma$ and $B_{d,s}^0\to {\mu }^{+}{\mu }^{-}$, the theoretical predictions for BR($t\to qg$) can be significantly augmented to approximately $\mathcal{𝒪}(10^{-5}-10^{-6})$. On the other hand, the values of BR($t\to q\gamma ,qZ,qh$) are predicted to be at least four orders of magnitude below the current experimental limits.