相关论文: $b \to s(d) \gamma$ with a Vector-like Quark as Fo…

Split-UED allows for the possibility that the lowest lying KK excitations of the Standard Model fermions can be much lighter than the corresponding gauge or Higgs KK states. This can happen provided the fermion bulk masses are chosen to be…

We consider the scenario where the composite Higgs arising as a pNGB in a two-site model with a non-local term included. Constraints from pion scattering and electroweak precision test are considered. We discuss the effects of composite…

Heavy vector-like quarks (VLQs) appear in many models of beyond the Standard Model physics. Direct experimental searches require these new quarks to be heavy, $\gsim$ 800-1000 GeV. We perform a global fit of the parameters of simple VLQ…

In this paper we investigate the next-to-leading power contribution to the $B_s \to \gamma\gamma$ and $B_s \to \gamma\ell\bar{\ell}$ decays from the strange quark mass effect with the dispersion approach which is QCD inspired and more…

The extension of the standard model with pairs of the vector-like families is studied. The quark mixing matrices for the left- and right-handed charged currents, as well as those for the flavour changing neutral currents, the Z and Higgs…

We analyze the phenomenological implications of introducing vector-like leptons on the Higgs sector in the Higgs Triplet Model. We impose only a parity symmetry which disallows mixing between the new states and the ordinary leptons. If the…

In the scenario with four quark generations, we perform a fit using flavor-physics data and determine the allowed values -- preferred central values and errors -- of all of the elements of the 4X4 quark mixing matrix. In addition to the…

Experimental searches for vector-like quarks have until now only considered their decays into Standard Model particles. However, various new physics scenarios predict additional scalars, so that these vector-like quarks can decay to new…

We show that a simple extension of the Standard Model involving the introduction of vector-like quarks and heavy neutrinos, provides an explanation of the so called B-anomalies in $b\to s\ell\bar\ell$ transitions. Vector-like quarks can…

If the fourth generation fermions exist, the new quarks could influence the branching ratio of the rare $B\to K^{*}\nu\bar{\nu}$ decay. Two possible solutions of the fourth generation CKM factor $(V^{*}_{\acute{t}s}V_{\acute{t}b})^(\pm)$…

Pair production of new vector-like quarks in $pp$ collisions is considered model independent as it is usually dominated by QCD production. Nonetheless, the presence of a new massive color octet (heavy gluon) in some composite Higgs models…

The discovery of Standard-Model like Higgs at 125 GeV may raise more questions than the answers it provides. In particular, the hierarchy problem remains unsolved, and the Standard Model Higgs quartic self-coupling becomes negative below…

We propose the $B_c\to B_u^*\gamma$ decay as the most suitable probe for the flavour changing neutral transition $c\to u\gamma$. We estimate the short and long distance contributions to this decay within the standard model and we find them…

By studying symmetric mass textures for the up and down quark sectors, and expanding in a small parameter $\lambda \sim sin\theta_C$, bounds are set on entries commonly assumed to vanish. Consequences of a 2 + 1 family structure which can…

Rare flavour changing neutral current (FCNC) decays of top, beauty and charm quarks can provide a powerful probe for as yet unobserved particles. Recent results on FCNC $b \to s$, $c \to u$ and $t$ transitions from the LHC experiments are…

We consider the effects of a fourth generation of chiral fermions within the MSSM. Such a model offers the possibility of having the lightest neutral Higgs boson significantly heavier than in the three generation MSSM. The model is highly…

We consider a model where the standard model is extended by the addition of a vector-like isosinglet down-type quark b'. We perform a chi square fit to the flavor physics data and obtain the preferred central values along with errors of all…

To avoid possible electroweak vacuum instability in the vector-like fermion model, we introduce a new singlet scalar to the model, which couples to the vector-like fermion, and also mixes with the Higgs boson after spontaneous symmetry…

Tree-level Flavor-Changing Neutral Currents (FCNC) are characteristic of models with extra vector-like quarks. These new couplings can strongly modify the B^0 CP asymmetries without conflicting with low--energy constraints. In the light of…

If the fourth generation fermions exist, the new quarks could influence the branching ratios of the decays of $B\to X_s \gamma$ and $B\to X_sl^+l^-$. We obtain two solutions of the fourth generation CKM factor $V^{*}_{t^{'}s}V_{t^{'}b}$…