Related papers: Rare Z Decays
We consider a class of minimal extensions of the Standard Model with an extra massive neutral gauge boson Z'. They include both family-universal models, where the extra U(1) is associated with (B-L), and non-universal models where the Z' is…
Rare decays $\Lambda_b \to \Lambda \gamma$ and $\Lambda_b \to \Lambda l^{+} l^{-}$ (l= e, $\mu$) are examined. We use QCD sum rules to calculate the hadronic matrix elements governing the decays. The $\Lambda$ polarization in the decays is…
With respect to large samples of $B_c$ mesons expected to be produced at CERN Large Hadron Collider(LHC) and the large branching ratios $Br(B_{c}\to \tau\bar\nu)$ and $Br(B_{c}\to \mu\bar\nu)$, we suggest that $B_c$ purely leptonic decays…
We discuss two dedicated observables in exclusive B -> K* l+ l- decay that can be used to study effects of physics beyond the standard model, namely the forward-backward asymmetry in the lepton spectrum and the isospin-asymmetry between…
Top physics provides a fertile ground for new-physics searches. At present, most top observables appear to be in good agreement with the respective Standard Model predictions. However, in the case of decay modes that are suppressed in the…
Experimental and theoretical progress concerning the rare decay \pi^0 \to e^+e^- is briefly reviewed. It includes the latest data from KTeV and a new model independent estimate of the decay branching which show the deviation between…
We discuss predictions for the lepton-flavour changing decays Z --> e mu, mu tau, e tau which may be searched for at the Giga-Z option of the Tesla Linear Collider project with Z resonance production rates as high as 10^9. We try to be as…
The Standard Model predicts several rare Higgs boson decay channels, among which are the decays to a Z boson and a photon, to a low-mass lepton pair and a photon, and to a meson and a photon. The observation of some of these decays could…
Using the most general, model-independent form of effective Hamiltonian, the exclusive, rare $B \rar K^\ast \nu \bar \nu$ decay is analyzed. The sensitivity of the branching ratios and missing mass-squared spectrum to the new Wilson…
We study the rare decays of $B_c^+\to D_{q}^{(*)+}l\bar{l}$ ($q=d,s$ and $l=\nu_l,e,\mu,\tau)$ in the standard model. The form factors are evaluated in the light front and constituent quark models, respectively. We find that the decay…
We compute the t->WZb decay rate, in the Standard Model, at the leading order in perturbation theory, with special attention to the effects of the finite widths of the W and Z bosons. These effects are extremely important, since the t->WZb…
The calculation of the rare $t$-quark decay $t \to b W b \bar{b}$ within the Standard Model as well as the charged Higgs contribution to this decay is presented. The role of possible background processes is discussed. It is shown that this…
This study investigates the Higgs rare decays $h^0\rightarrow Z\gamma,V Z$ within the next to minimum B-L supersymmetric model(NB-LSSM), where $V$ represents a vector meson $(\phi,J/\psi,\Upsilon(1S),\rho^0,\omega)$. Compared to the minimal…
The couplings of the low scale type I see-saw model are severely constrained by the requirement of reproducing the correct neutrino mass and mixing parameters, by the non-observation of lepton number and charged lepton flavour violating…
This study examines the rare decay $B \to K_0^*(1430)\,\ell^+ \ell^-$ as a possible probe for new physics beyond the standard model (SM). We first analyze this channel within the SM and then include scalar leptoquark (LQ) contributions. We…
Indirect searches, and in particular rare decays, have proven to be a fruitful field to search for New Physics beyond the Standard Model. While the down-quark sector (B and K) have been studied in detail, less attention was devoted to charm…
Rare decays are flavour changing neutral current processes that are loop-suppressed in the Standard Model (SM). New particles in SM extensions can therefore give significant contributions, modifying branching fractions and angular…
Rare kaon decays offer a powerful tool for investigating new physics in $s\to d$ transitions. Currently, many of the interesting decay modes are either measured with rather large uncertainties compared to their theoretical predictions or…
An overview of recent theoretical developments in rare leptonic B decays is given. New physics effects on branching ratio and CP violation in the decays are analyzed in models beyond SM (supersymmetric models and two Higgs doublet models).
We study extensions of the standard model by one generation of vector-like leptons with non-standard hypercharges, which allow for a sizable modification of the h -> gamma gamma decay rate for new lepton masses in the 300 GeV - 1 TeV range.…