We show that a fourth family of quarks with $m_{t'}$ in the range of (400 - 600) GeV provides a rather simple explanation for the several indications of new physics that have been observed involving CP asymmetries of the b-quark. The built-in hierarchy of the 4$\times$4 mixing matrix is such that the $t'$ readily provides a needed {\it perturbation} ($\approx 15%$) to $\sin 2 β$ as measured in $B \to ψK_s$ and simultaneously is the dominant source of CP asymmetry in $B_s \to ψϕ$. The correlation between CP asymmetries in $B_s \toψϕ$ and $B_d\toϕK_s$ suggests $m_{t'} \approx$ (400 - 600) GeV. Such heavy masses point to the tantalizing possibility that the 4th family plays an important role in the electroweak symmetry breaking.
I introduce a model to explain the recent anomalies in the muon anomalous magnetic moment and the rare semi-leptonic $B$ meson decays. The Standard Model is extended by a $U(1)^\prime$ gauge symmetry and a complete fourth family fermions which are vector-like under the gauge symmetry. We found parameter points which can explain the anomalies consistently with the other observables. We then propose an interesting possibility to have signals with four muons or more from vector-like lepton pair production.
In this paper, we investigate the effects of the fourth generation of quarks on the double-lepton polarization asymmetries in the $B_s \rar ϕ\ell^+ \ell^-$ decay. It is shown that these asymmetries in $B_s \rar ϕ\ell^+ \ell^-$ decay compared with those of $B \rar K \ell^+ \ell^-$ decay are more sensitive to the fourth-generation parameters. We conclude that an efficient way to establish the existence of the fourth generation of quarks could be the study of these asymmetries in the $B_s \rar ϕ\ell^+ \ell^-$ decay.
We investigate the forward-backward asymmetries in the pair production of fourth family fermions through the new Z' interactions in the e+e- collisions. The Z' boson having family universal couplings can contribute to the pair production of fourth family fermions via the s-channel exchange. The linear colliders will provide a clean environment for the physics of Z' boson to measure its couplings precisely. The effects of the Z' boson to the asymmetries are shown to be important in some parameter regions for different Z' models. Among these parameters, the invariant mass distribution m_FFbar wi…
In this study a systematical analysis of various polarization asymmetries in inclusive $b \rar s \ell^+ \ell^-$ decay in the standard model (SM) with four generation of quarks is carried out. We found that the various asymmetries are sensitive to the new mixing and quark masses for both of the $μ$ and $τ$ channels. Sizeable deviations from the SM values are obtained. Hence, $b \rar s \ell^+ \ell^-$ decay is a valuable tool for searching physics beyond the SM, especially in the indirect searches for the fourth-generation of quarks ($t', b')$.
In this work we study the implication of the fourth generation standard model (SM4) to the single and double lepton polarization asymmetries in the $B\rightarrow K^{\ast}\ell^{+}\ell^{-}$, $(l=μ,τ)$ decay. To see the variation in the values of lepton polarization asymmetries from the standard model values, we have taken lower bound values of CMS and ATLAS for $m_{t^\prime}=404$GeV and 552GeV respectively whereas $ϕ_{sb}$ is vary in two allowed regions $75^\circ-115^\circ$ and $240^\circ-290^\circ$ while for the numerical values of these asymmetries $|λ_{t^\prime}|$ is set to be $6\times10^{-3}…
We consider the Standard Model (SM) with the addition of a $\mathrm{U(1)^\prime}$ gauge symmetry and a complete fourth family of quarks and leptons which are vector-like with respect to the full $\mathrm{SU(3)_C}\times \mathrm{SU(2)_L} \times \mathrm{U(1)_Y}\times \mathrm{U(1)^\prime}$ gauge symmetry. The model provides a unified explanation of experimental anomalies in $(g - 2)_μ$ as well as $b \rightarrow s \ell^+ \ell^-$ decays. We find good fits to the deviations from the SM, while at the same time fitting all other SM observables. The model includes a new $Z^\prime$ gauge boson, a $\mathr…
A general analysis of the consequences of including a fourth neutrino in the standard model matter content, on CP violating observables at neutrino oscillation experiments, is presented. Neutrino oscillations in vacuum and with matter effects are studied. For the former we update and generalize previous studies on CP asymmetries with an additional active neutrino using an updated fit of the PMNS mixing matrix. We study the values of the new CP violating phases which maximize the different CP asymmetries in T2K and MINOS-like setups aiming to elucidate if the new phases yield measurable effects…
This study examines the influence of the fourth generation quarks on the double lepton polarizations forward--backward asymmetries in B \rar K^\ast \ell^+ \ell^- decay. We obtain that for both (muon, tau) channels the magnitude and the sign of the differential forward--backward asymmetries and the magnitude of the average forward--backward asymmetries are quite sensitive to the 4th generation quarks mass and mixing parameters. It can serve as a good tool to search for new physics effects, precisely, to search for the fourth generation quarks(t', b') via its indirect manifestations in the loop …
Within the paradigm of warped extra dimensions, third generation quarks are expected to be the most sensitive to effects beyond the Standard Model. The anomalies observed at the LEP and Tevatron colliders in the forward-backward asymmetries of the bottom (A_FB^b) and top (A_FB^t) quarks can thus be seen as early signatures of warped extra-dimensional scenarios. We propose a realization of such a scenario, with a gauge custodial symmetry in the bulk, which allows to address simultaneously the A_FB^b anomaly and the discrepancies observed recently on A_FB^t at high top quark rapidities and ttbar…
The $R_{D^{(*)}}$ anomalies are among the longest-standing and most statistically significant hints of physics beyond the Standard Model. Many models have been proposed to explain these anomalies, including the interesting possibility that right-handed neutrinos could be involved in the $B$ decays. In this paper, we investigate future measurements at Belle II that can be used to tell apart the various new physics scenarios. Focusing on a number of $τ$ asymmetry observables (forward-backward asymmetry and polarization asymmetries) which can be reconstructed at Belle II, we calculate the contrib…
The Standard Model (SM) is amended by one generation of quarks and leptons which are vector-like (VL) under the SM gauge group but chiral with respect to a new $\mathrm{U}(1)_{3-4}$ gauge symmetry. We show that this model can simultaneously explain the deviation of the muon $g-2$ as well as the observed anomalies in $b\rightarrow sμ^+μ^-$ transitions without conflicting with the data on Higgs decays, lepton flavor violation, or $B_s-\bar{B}_s$ mixing. The model is string theory motivated and GUT compatible, i.e. UV complete, and fits the data predicting VL quarks, leptons and a massive $Z'$ at…
We investigate the influence of the fourth generation of quarks on the branching ratio, the CP-asymmetry and the polarization asymmetries in $B \rar ρ\ell^+ \ell^-$ decay. Taking $|V_{t'd}V_{t'b}|\sim 0.001$ with phase about $10^\circ$, which is consistent with the $sin2ϕ_1$ of the CKM and the $B_d$ mixing parameter $Δm_{B_d}$, we obtain that for both ($μ, τ$) channels the branching ratio is increased and the magnitude of CP-asymmetry and polarization asymmetries decreased by the mass and mixing parameters of the 4th generation of quarks . These results can serve as a good tool to search for n…
We show that, if a fourth generation is discovered at the Tevatron or LHC, one could study CP violation in b' \to s decays. Asymmetries could reach 30% for b'\to sZ for m_{b'} \lesssim 350 GeV, while it could be greater than 50% for b'\to sγand extend to higher m_{b'}. Branching ratios are 10^{-3}--10^{-5}, and CPV measurement requires tagging. Once measured, however, the CPV phase can be extracted with little theoretical uncertainty.
We consider several hints for new physics involving CP-asymmetries in B-decays and interpret them in terms of generic contributions to effective Wilson coefficients. The effects we focus on are: the differences in the fitted value of sin(2 beta) versus the ones directly measured via the time dependent CP asymmetries in B -> J/psi K or via B -> (phi,eta') K; the difference between the direct CP asymmetries in B- -> K- pi0 and B0 -> K- pi+ and the ~2.2 sigma indications for the CP-asymmetry in Bs -> J/psi phi. To alleviate concerns regarding the disagreement between inclusive and exclusive Vub, …
The sixth order QED radiative corrections to lepton anomalies due to the fourth order vacuum polarization insertions within the Mellin-Barnes representation
We discuss a simple renormalisable, gauge invariant model with a fermiophobic $Z'$ boson: it has no couplings to the three Standard Model (SM) chiral families, but does couple to a fourth vector-like (VL) family. The SM Higgs couples to the fourth VL lepton, leading to an enhanced contribution to the muon anomalous magnetic moment $\left(g-2\right)_μ$. The latter contribution requires a non-vanishing coupling of $Z'$ to right-handed muons, which arises within this model due to mixing effects between the SM and VL fermions, along with $Z'$ couplings to the second generation SM lepton doublet an…
In this paper we present an in-depth analysis of a recently proposed Standard Model extension with a complete fourth generation of quarks and leptons, which are vector-like with respect to the Standard Model gauge group and charged under a new spontaneously broken vector-like $\mathrm{U(1)^\prime}$ gauge symmetry. The model is designed to explain the known muon anomalies, i.e. the observed deviations from Standard Model predictions in the anomalous magnetic moment of the muon, $Δa_μ$, and in $b \rightarrow s \ell^+ \ell^-$ processes. We perform a global $χ^2$ analysis of the data with $65$ mod…
The predicted value of the higgs mass $m_H$ is analyzed assuming the existence of the fourth generation of leptons ($N, E$) and quarks ($U, D$). The steep and flat directions are found in the five-dimensional parameter space: $m_H$, $m_U$, $m_D$, $m_N$, $m_E$. The LEPTOP fit of the precision electroweak data is compatible (in particular) with $m_H \sim 300$ GeV, $m_N \sim 50$ GeV, $m_E \sim 100$ GeV, $m_U +m_D \sim 500$ GeV, and $|m_U -m_D| \sim 75$ GeV. The quality of fits drastically improves when the data on b- and c-quark asymmetries and new NuTeV data on deep inelastic scattering are igno…
Imagine to discover a new fourth family of leptons at the Large Hadron Collider (LHC) but no signs of an associated fourth family of quarks. What would that imply? An intriguing possibility is that the new fermions needed to compensate for the new leptons gauge anomalies simultaneously address the big hierarchy problem of the Standard Model. A natural way to accomplish such a scenario is to have the Higgs itself be composite of these new fermions. This is the setup we are going to investigate in this paper using as a template Minimal Walking Technicolor. We analyze a general heavy neutrino mas…
We investigate the possibility of adding a fourth generation of quarks. We also extend the Standard Model gauge group by adding another SU(N) component. In order to cancel the contributions of the fourth generation of quarks to the gauge anomalies we must add a generation of fermions coupling to the SU(N) group. This model has many features similar to the Standard Model and, for example, includes a natural generalisation of the Standard Model charge quantisation rule. We discuss the phenomenology of this model and, in particular, show that the infrared quasi-fixed point values of the Yukawa co…
The rare decays of $Λ_b$ baryon governed by the quark level transitions $ b \to s$, are investigated in the fourth quark generation model popularly known as SM4. Recently it has been shown that SM4, which is a very simple extension of the standard model, can successfully explain several anomalies observed in the CP violation parameters of $B$ and $B_s$ mesons. We find that in this model due to the additional contributions coming from the heavy $t'$ quark in the loop, the branching ratios and other observables in rare $Λ_b$ decays deviate significantly from their SM values. Some of these modes …
We study some rare decays of $B_s$ meson governed by the quark level transitions $ b \to s$, in the fourth generation model popularly known as SM4. Recently it has been shown that SM4, which is a simple extension of the SM3, can successfully explain several anomalies observed in the CP violation parameters of $B$ and $B_s$ mesons. We find that in this model due to the additional contributions coming from the heavy $t'$ quark in the loop, the branching ratios and other observables in rare $B_s$ decays deviate significantly from their SM values. Some of these modes are within the reach of LHCb e…
The weak decays of B_{c} --> D_{s}^{*}l^{+}l^{-} (l=mu,tau) are investigated in the Standard Model with fourth generation (SM4). Taking fourth generation quark mass m_{t'} of about 300 to 600 GeV with the CKM matrix elements V_{t'b}^{*}V_{t's} in the range (0.03-1.2)*10^{-2} and using the new CP odd phase (phi_{sb}) to be 90^{o} the analysis of decay rates, forward-backward asymmetries, lepton polarization asymmetries and the helicity fractions of D_{s}^{*} meson in B_{c} --> D_{s}^{*}l^{+}l^{-} (l=mu,tau) is made. It is shown that the values of these physical observables are greatly influence…
We study the effect from a sequential fourth generation quark on penguin-dominated two-body nonleptonic B meson decays in the next-to-leading order perturbative QCD formalism. With an enhancement of the color-suppressed tree amplitude and possibility of a new CP phase in the electroweak penguin, we can account better for A_{CP}(B^0 -> K^+ pi^-)-A_{CP}(B^+ -> K^+ pi^0). Taking |V_{t's}V_{t'b}| \sim 0.02 with phase just below 90^\circ, which are consistent with the b -> s l^+ l^- rate and the B_s mixing parameter Δm_{B_s}, we find a downward shift in the mixing-induced CP asymmetries of B^0 -> K…
In this talk I will present the work that we did in \cite{1}\cite{2}\cite{3}\cite{4}\cite{5} related to observed lepton universality violation by Babar, Belle and LHCb in R($D^{(*)}$) and $R_{K^{(*)}}$ as well as the reported deviation in muon (g-2) by BNL. We had shown that all these anomalies as well as Baryon-genesis, Dark-matter and small neutrino masses could be explained by introducing new exotic scalars, leptons and scalar-leptoquarks only. It turn out that some of these models have very peculiar signatures such as prediction of existence of heavy stable charged particle \cite{1}\cite{2…
Attention is drawn to the several 2-3 $σ$ "anomalies" in B, $B_s$ mixings and decays involving CP-observables. Perhaps the most interesting theoretical scenario that could cause such effects is based on warped extra-dimensional models and indeed some of the effects were predicted there. However, a rather simple explanation is that based on a fourth family of quarks with masses in the range of(400 - 600) GeV. The built-in hierarchy of the 4$\times$4 mixing matrix is such that the $t'$ readily provides a needed {\it perturbation} ($\approx 15%$) to $\sin 2 β$ as measured in $B \to ψK_s$ and simu…
The latest electroweak precision data are analyzed assuming the existence of the fourth generation of leptons ($N, E$) and quarks ($U, D$), which are not mixed with the known three generations. If all four new particles are heavier than $Z$ boson, quality of the fit for the one new generation is as good as for the Standard Model. In the case of neutral leptons with masses around 50 GeV (``partially heavy extra generations'') the minimum of $χ^2$ is between one and two extra generations. The predicted value of the higgs mass $m_H$ in the presence of the fourth generation can be made rather larg…
Simple models are proposed where the baryon and lepton number are gauged and spontaneously broken near the weak scale. The models use a fourth generation that is vector-like with respect to the strong, weak and electromagnetic interactions to cancel anomalies. One does not need large Yukawa couplings to be consistent with the experimental limits on fourth generation quark masses and hence the models are free of Landau poles near the weak scale. We discuss the main features of simple non-supersymmetric and supersymmetric models. In these models the light neutrino masses are generated through th…
We propose an interpretation of the diboson excess recently observed by the ATLAS and CMS collaborations in terms of Kaluza-Klein excitations of electroweak gauge bosons stemming from a realization of a warped extra-dimensional model that is protected by a custodial symmetry. Besides accounting for the LHC diboson data, this scenario also leads to an explanation of the anomalies that have been observed in the measurements of the forward-backward asymmetries for bottom quarks at LEP and top quarks at the Tevatron.
We calculate a number of observables related to particle-antiparticle mixing and the branching ratios for the most interesting rare and CP-violating K and B decays in the Standard Model (SM3) extended by a fourth generation of quarks and leptons (SM4). A model-independent parameterisation of these observables in terms of gauge-independent functions is adopted, which is useful for studying the breaking of the universality between K, Bd and Bs systems through non-minimal flavour violating interactions. We calculate first the mass differences Delta M_i in the neutral K and B system, the mixing-in…
While a chiral fourth generation of quarks is almost ruled out from the data on Higgs boson production and decay at the Large Hadron Collider, vector-like quarks are still a feasible option to extend the fermionic sector of the Standard Model. Such an extension does not suffer from any anomalies and easily passes the constraints coming from oblique electroweak parameters. We consider such minimal extensions with $SU(2)$ singlet and doublet vector-like quarks that may mix with one, or at the most two, of the Standard Model quarks. Constraints on the new mixing angles and phases are obtained fro…
