$B_s^0\rightarrow D_s^{-}$ and $B_s^0\rightarrow D_s^{*-}$ weak transition form factors are estimated for the whole physical region with a method based on an instantaneous approximated Mandelstam formulation of transition matrix elements and the instantaneous Bethe-Salpeter equation. We apply the estimated form factors to branching ratios, CP asymmetries and polarization fractions of non-leptonic decays within the factorization approximation. And we study the non-factorizable effects and annihilation contributions with the perturbative QCD approach. The branching ratios of semi-leptonic $B_s^0\rightarrow D_s^{(*)-}l^+ν_l$ decays are also evaluated. We show that the calculated decay rates agree well with the available experimental data. The longitudinal polarization fraction of $B_s\rightarrow D_s^*V(A)$ decays are $\sim0.8$ when $V(A)$ denotes a light meson, and are $\sim0.5$ when $V(A)$ denotes a $D_q$ ($q=d,s$) meson.
We calculate the two body Cabibbo allowed non-leptonic decays of charmed baryons $Λ_c$ and $Ξ_c$ which involve transitions of a heavy quark to a light quark. We use data on the Cabbibo favoured non-leptonic decays $Λ_c \rightarrow Λπ^{+}$ and $Λ_c \rightarrow Σ^{+} π^{0 }$ to obtain information on the form factors in the $c \rightarrow s $ transition. We also calculate the decay $Λ_c \rightarrow p ϕ$. Using HQET the information on form factors from the $c \rightarrow s $ transition is used to model the form factors in $b \rightarrow s $ transition which are then used in the study of $Λ_b \righ…
We calculate the semi-leptonic decays of $Λ_c$ and $Λ_b$ baryons which involve transitions of a heavy quark to a light quark. In a previous work we used data on the Cabibbo favoured non-leptonic decays of charmed baryons $Λ_c \rightarrow Λπ^{+}$ and $Λ_c \rightarrow Σ^{+} π^{0 }$ to obtain information on the form factors in the $c \rightarrow s $ transition. This form factor informations is used to study the semi-leptonic decay $Λ_c \rightarrow Λl ν$. Using SU(3) symmetry and HQET it is shown how a knowledge of form factors in $Λ_c \rightarrow Λl ν$ can be applied to $Λ_b \rightarrow p l ν$ de…
We estimate the non-leptonic B decays $B \rightarrow (ψ,ψ^\prime , χ_{1c})+K^i$, where $K^i$ are various K-meson resonances. We use the model of Isgur, Wise, Scora and Grinstein in the context of heavy quark effective theory, to calculate the hadronic matrix elements. Our estimates show that a substantial fraction of $B \rightarrow X_s ψ$ results in higher resonances of K-meson and besides $B \rightarrow K(K^*) ψ$, a considerable fraction of $B \rightarrow X_s (c\bar c)$ goes to $B \rightarrow (K,K^*)+( ψ^{\prime},χ_{1c})$.
The most recent measurements of the observables $R_{D^{(*)}}$ are in tension with the Standard Model offering hints of New Physics in $b\rightarrow c \ell \barν_{\ell}$ transitions. Motivated by these results, in this work we present an analysis on their $b\rightarrow u \ell \barν_{\ell}$ counterparts (for $\ell=e, ~μ, ~τ$). Our study has three main objectives. Firstly, using ratios of branching fractions, we assess the effects of beyond the Standard Model scalar and pseudoscalar particles in leptonic and semileptonic $B$ decays ($B^-\rightarrow \ell^- \barν_{\ell}$, $\bar{B}\rightarrow π\ell …
Anomalies in semi-leptonic $B$ decays could indicate new physics beyond the standard model(SM). There is an older puzzle in non-leptonic $B \to πK$ decays. The new particles, leptoquarks and diquarks, required to solve the semi-leptonic and the non-leptonic puzzles can also generate neutrino masses and mixing at loop level. We show that a consistent framework to explain the $B$ anomalies and the neutrino masses is possible and we make predictions for certain rare nonleptonic $B$ decays.
We study the semi-leptonic and non-leptonic $B$ weak decays which are governed by the $B\rightarrow D^{(*)}$ transitions. The branching ratios, CP asymmetries (CPA) and polarization fractions (FA) of non-leptonic decays are investigated in the factorization approximation. The $B\rightarrow D^{(*)}$ form factors are estimated in the Salpeter method. Our estimation on branching ratios generally agree with the existent experimental data. For CPA and polarizations, comparisons among the FA results, the perturbative QCD predictions and experimental data are made.
The semi-leptonic baryonic $b\to s$ decay, $Λ_b\rightarrow Λ\ell^+\ell^-$, has been studied and new angular observables and asymmetries have been proposed which can test the presence of new physics beyond the standard model.
We examine the role of resonant coupled channel final state interactions (FSI), as well as weak annihilation and exchange contributions in explaining all the two body hadronic $D\rightarrow PP$ decay modes data. In the un-unitarized amplitudes we include modified Wilson coefficients with non-factorizable corrections as parameters. For the hadronic form factors, the z-series expansion method is used to get the $q^2$ dependence. The FSI effects are incorporated via a phenomenological approach with widths of resonances to various channels taken from observations where available, and others as add…
We study the semi-leptonic and non-leptonic decays of $B_c$ meson to $D$-wave charmonia, namely, $η_{c2}(1^1\!D_2)$, $ψ_2(1^3\!D_2)$, and $ψ_3(1^3\!D_3)$. In our calculations, the instantaneous Bethe-Salpeter method is applied to achieve the hadronic matrix elements. This method includes relativistic corrections which are important especially for the higher orbital excited states. For the semi-leptonic decay channels with electron as the final lepton, we get the branching ratios $\mathcal{B}[B_c \rightarrow η_{c2}e\barν_e] = 5.9^{-0.8}_{+1.0}\times 10^{-4}$, $\mathcal{B}[B_c \rightarrow ψ_2e\b…
We study the contribution of the squark flavor mixing from the $LR(RL)$ component of the squark mass matrices to the direct CP violation of the $b\to sγ$ decay and the CP-violating asymmetry in the non-leptonic decays of $B$ mesons. The magnitude of the $LR(RL)$ component is constrained by the branching ratio and the direct CP violation of $b\to sγ$. We predict the correlation of the CP asymmetries among $A_{\text{CP}}^{b \to s γ}$, $\mathcal{S}_{ϕK_S}$ and $\mathcal{S}_{η'K^0}$ of the B decays. The precise data of these CP violations will give us the crucial test for our framework of the squa…
Considering the constraints of the lepton flavor violating (LFV) processes $μ\rightarrow 3e$ and $τ\rightarrow3μ$ on the LFV couplings $Z'\ell_{i}\ell_{j}$, in the contexts of the $E_{6}$ models, the left-right (LR) models, the "alternative" left-right (ALR) models and the 331 models, we investigate the contributions of the extra gauge boson $Z'$ to the decay rates of the processes $\ell_{i}\rightarrow\ell_{j}ν_{\ell}ν_{\ell}$, $τ\rightarrowμP $ and $P\rightarrow μe$ with $P=π^{0},η$ and $η'$. Our numerical results show that the maximal values of the branching ratios for these processes are no…
The most general Lorentz invariant spin-correlation functions for $τ^{-}\rightarrow ρ^{-}ν,a_1^{-}ν,K^{*-}ν, π^{-}ν,K^{-}ν$ are expressed in terms of eight semi-leptonic parameters. They are physically defined in terms of tau-decay partial-width-intensities for polarized-final-states. The parameters are also expressed in terms of a ``$(V-A)\ +\ $additional chiral coupling'' structure in the ${J^{Charged}}_{Lepton}$ current, so as to bound the scales $Λ$\ for ``new physics'' such as arising from leptonic CP violation, tau weak magnetism, weak electricity, and/or second-class currents. The two t…
We consider a scenario with only one sterile neutrino $ N $, negligible mixing with the active neutrinos $ ν_{L} $, where its interactions with ordinary particles could be described in a model independent approach based on an effective theory. Under such a framwork, we consider the contributions of the sterile neutrino $N$ to the pure leptonic decays $ M \rightarrow lν$ and $ ν\overlineν $, and the radiative leptonic decays $ M \rightarrow lνγ$ with $M$ denoting the pseudoscalar mesons $ B $, $ D $ and $ K$. We find that it can produce significant effects on some of these rare decay processes.
The transitions $B_{s,d}\rightarrow \ell^+\ell^-$ (for $\ell=e, μ, τ$), although extremely suppressed within the SM, are exceptionally clean channels particularly sensitive to New Physics contributions. So far only the branching ratio for the process $B_{s}\rightarrow μ^+μ^-$ has been measured experimentally and, although the results are in agreement with the SM prediction, there is still room for NP effects. Here we provide an overview of the theoretical status of rare decays. We present strategies that can allow us to discriminate between different NP scenarios. Finally, we include a discuss…
Recently several measurements in the neutral current sector $b\rightarrow s l^+l^-$ ($l=e$ or $μ$) as well as in the charged current sector $b \rightarrow c τ\barν$ show significant deviations from their Standard Model predictions. It has been shown that two different new physics solutions can explain all the anomalies in $b\rightarrow s l^+l^-$ sector. Both these solutions are in the form of linear combinations of the two operators $(\bar{s}γ^αP_Lb)(\barμγ_αμ)$ and $(\bar{s}γ^αP_Lb)(\barμγ_αγ_5μ)$. We show that the longitudinal polarization asymmetry of the muons in $B^*_s\rightarrow μ^+\,μ^-…
We present results of a lattice computation of the matrix elements of the vector and axial-vector currents which are relevant for the semi-leptonic decays $D \rightarrow K$ and $D \rightarrow K^*$. The computations are performed in the quenched approximation to lattice QCD on a $24^3 \times 48$ lattice at $β=6.2$ using an $O(a)$-improved fermionic action.
The universality of the weak interactions can be tested in semileptonic $b \to c$ transitions, and in particular in the ratios $R(D^{(*)}) \equiv Γ(B \rightarrow D^{(*)} τν)/Γ(B \rightarrow D^{(*)} \ell ν)$ (where $\ell = μ$ or $e$). Due to the recent differences between the experimental measurements of these observables by BaBar, Belle and LHCb on the one hand and the Standard Model predicted values on the other hand, we study the predicted ratios $R(D^{(*)}) = Γ(B \rightarrow D^{(*)} τ+$ "missing" $)/Γ(B \rightarrow D^{(*)} \ell ν)$ in scenarios with an additional sterile heavy neutrino of m…
We compute the vector meson decay constants fD*, fDs* from the simulation of twisted mass QCD on the lattice with Nf = 2 dynamical quarks. When combining their values with the pseudoscalar D(s)-meson decay constants, we were able (i) to show that the heavy quark spin symmetry breaking effects with the charm quark are large, fDs*/fDs = 1.26(3), and (ii) to check the factorization approximation in a few specific B-meson non-leptonic decay modes. Besides our main results, fD* = 278 \pm 13 \pm 10 MeV, and fDs* = 311 \pm 9 MeV, other phenomenologically interesting results of this paper are: fDs*/fD…
We propose a strategy for distinguishing the Dirac / Majorana character of heavy neutrinos with masses below the $W$ boson mass, using purely leptonic decays at the LHC. The strategy makes use of a forward-backward asymmetry of the opposite charge lepton in the $W^{+}\rightarrow l^{+}l^{+}l^{'-}ν$ decay. In order to check the experimental feasibility of the model, we show, through a numerical analysis, that in the decay $W^{+}\rightarrow e^{+}e^{+}μ^{-}ν$ the two positrons in the final state can be distinguished for different ranges of the heavy neutrino masses. Finally, we estimated the numbe…
We study constraints on the models of bosonic super-weakly interacting particle (super-WIMP) dark matter (DM) with DM masses $m_X \sim \mathcal{O}(1 - 100)$ keV from leptonic decays $M\rightarrow \ell \barν_\ell + X$, where $M=B^\pm, D^\pm, D_s^\pm$ is a heavy meson state. We focus on two cases where $X$ denotes either a light pseudoscalar (axion-like), or a light vector state that couples to the standard model (SM) through kinetic mixing. We note that for a small DM mass these decays are separately sensitive to DM couplings to quarks, but not its mass.
We consider the color suppressed (nonfactorizable) amplitude for the decay mode $\bar{B_{d}^0} \rightarrow π^0 π^{0} $. We treat the $b$-quark in the heavy quark limit and the energetic light ($u,d,s$) quarks within a variant of Large Energy Effective Theory combined with an extension of chiral quark models. Our calculated amplitude for $\bar{B_{d}^0} \rightarrow π^0 π^{0} $ is suppressed by a factor of order $Λ_{QCD}/m_b$ with respect to the factorized amplitude, as it should according to QCD-factorization. Further, for reasonable values of the (model dependent) gluon condensate and the const…
We reanalyze the extraction of the heavy Higgs boson signal $H\rightarrow W^+W^-\rightarrow \bar\ellν,\ell\barν$ $(\ell=e\hbox{ or }μ)$ from the Standard Model background at hadron supercolliders, taking into account revised estimates of the top quark background. With new acceptance criteria the detection of the signal remains viable. Requiring a forward jet-tag, a central jet-veto, and a large relative transverse momentum of the two charged leptons yields $S/\sqrt B>6$ for one year of running at the SSC or LHC.
In this paper, we study the productions of the newly detected states $D_{sJ}(3040)$ and $D_J(3000)$ observed by BABAR Collaboration and LHCb Collaboration. We assume these states to be the $D_s(2P)$ and $D(2P)$ states with the quantum number $J^P=1^+$ in our work. The results of improved Bethe-Salpeter method indicate that the semi-leptonic decays via $B_s$ and $B$ into $D_{sJ}(3040)$ and $D_J(3000)$ have considerable branching ratios, for example, Br($\bar{B}_s^0 \rightarrow D{_{sJ}^+}(3040)e^-\barν{_e}$)=$5.79\times10^{-4}$, Br($\bar{B}^0\rightarrow D_{J}^+(3000)e^-\barν{_e}$)=$2.63\times10^…
$Ω_b \rightarrow Ω_c^{(*)}$ semi-leptonic decays are studied in details. Relevant helicity amplitudes are written down. Both unpolarized and polarized $Ω_b$ cases are considered. Decay angular distributions, asymmetry parameters and semileptonic decay rates are calculated, with numerical results using leading order results of the large $N_c$ and heavy quark effective theory(HQET).
In this talk I consider the current status of $B \rightarrow D^{(*)} τν$ decays in the context of two-Higgs-doublet models. The BaBar collaboration has reported an excess in semileptonic $b \rightarrow c τν$ transitions that has gathered recent interest as a possible signature of new physics. The sensitivity of these decays to tree-level charged Higgs boson contributions is discussed, taking into account the constraints from other semileptonic and leptonic meson decays in which the charged Higgs would enter at the same level.
We estimate the potential size of the weak annihilation amplitudes in QCD factorization as allowed by experimental data. To achieve this goal, we establish a connection between the amplitudes in the QCD factorization and the so-called topological and $SU(3)$-invariant descriptions. Our approach is based purely on the analysis of the tensor structure of the decay amplitudes. By focusing on the processes $B\rightarrow P P$ and considering data from CP asymmetries and branching fractions, we perform a global fit to the $SU(3)$-irreducible quantities assuming minimal theoretical bias. Subsequently…
We present results of a lattice computation of the matrix elements of the vector and axial-vector currents which are relevant for the semi-leptonic decays $D \rightarrow K$ and $D \rightarrow K^*$. The computations are performed in the quenched approximation to lattice QCD on a $24^3 \times 48$ lattice at $β=6.2$, using an $O(a)$-improved fermionic action. In the limit of zero lepton masses the semi-leptonic decays $D \rightarrow K$ and $D \rightarrow K^*$ are described by four form factors: $f^{+}_K,V,A_1$ and $A_2$, which are functions of $q^2$, where $q^μ$ is the four-momentum transferred i…
The calculation of $t\bar{t}Z$ production including leptonic decays of both $Z$ boson and top quarks via a partially or fully off-shell calculation represents a definite step forward towards a more accurate description of events whose signatures originate from $t\bar{t}Z$ production. In this talk we review two studies that represent the state of the art of theoretical modeling of $t\bar{t}Z$ production by either performing the NLO QCD calculation of the fully decayed $pp\rightarrow e^+ν_eμ^-\barν_μb\bar{b}τ^+τ^-$ process (see Ref. [1]) or matching the NLO QCD calculation of $pp\rightarrow t\ba…
Recently LHCb has measured the branching ratio of the rare decay of $B_s^0\rightarrow μ^+ μ^- $ as $2.9^{+1.1}_{-1.0} \times10^{-9}$ which is at par with the predicted standard model (SM) value. This result does not predict the absence of new physics (NP), rather it confines the NP parameter-space in a more stringent fashion. In this paper we have used the general loop level Hamiltonian to constrain the parameter space for the NP couplings for $B_s^0\rightarrow μ^+ μ^- $ from the experimental branching ratio. Using the available parameter space for these couplings, we have explored the angular…
We calculate the process $γγ\rightarrow e^- \barν_e u \bar{d}$ with the full set of Feynman diagrams. We consider different implementations of the $W$ width and different combinations of the photon polarisations. The results of an improved narrow width approximation based on $γγ\rightarrow W^+ W^-$ with full spin-correlations that takes into account different angular cuts as well as cuts on the invariant masses are compared to those of the complete calculation.
We perform a global analysis of the $b\to cτν$ data using the recent lattice results on the $B_c\to J/ψ$ vector and axial-vector form factors. To explore the effects from the tensor operator of new physics beyond the standard model, we determine the tensor form factors by using the non-relativistic QCD (NRQCD) relations between tensor and (axial-)vector form factors. Based on the lattice+NRQCD form factors, we fit the Wilson coefficients and the new physics couplings in $R_2$, $S_1$ and $U_1$ leptoquark models by including the recently measured $R(Λ_c)$ and imposing the relaxed constraint $\ma…
We analyze the capability of the next generation of linear electron--positron colliders to unravel the spin and couplings of excited leptons predicted by composite models. Assuming that these machines will be able to operate both in the $e^+e^-$ and $e^-γ$ modes, we study the effects of the excited electrons of spin $\frac{1}{2}$ and $\frac{3}{2}$ in the reactions $e^-γ\rightarrow e^-γ$ and $e^+e^- \rightarrow γγ$. We show how the use of polarized beams is able not only to increase the reach of these machines, but also to determine the spin and couplings of the excited states.
We calculate the mass difference between the $Υ$ and $η_b$ and the $Υ$ leptonic width from lattice QCD using the Highly Improved Staggered Quark formalism for the $b$ quark and including $u$, $d$, $s$ and $c$ quarks in the sea. We have results for lattices with lattice spacing as low as 0.03 fm and multiple heavy quark masses, enabling us to map out the heavy quark mass dependence and determine values at the $b$ quark mass. Our results are: $M_Υ -M_{η_b} = 57.5(2.3)(1.0) \,\mathrm{MeV}$ (where the second uncertainty comes from neglect of quark-line disconnected correlation functions) and decay…
Many new physics scenarios predict the existence of the extra charged gauge boson $ W'$, which can induce the charged-current (CC) non-standard neutrino interactions (NSI). We investigate the constraints on the CC NSI in model-independent fashion via considering the $ W'$ contributions to the lepton flavor violating (LFV) decays $\ell_{i}\rightarrow \ell_{j}γ$, the pure leptonic flavor conservation (FC) decays $\ell_{i}\rightarrow \ell_{j}ν_{i}\bar{ν_{j}}$, leptonic decays of charged pion meson, semileptonic $τ$ decays, and superallowed $β$ decays. We find that the constraints on the pure lept…
A method to extract Wilson coefficients for semi-leptonic $b\rightarrow s$ transition and form factors for the hadronic process $B\rightarrow K^*μ^+μ^-$ is suggested. The method is based on data of angular distribution of the process $B\rightarrow K^*(\rightarrow K π)μ^+μ^-$ with the optimized observables plotted as functions of dilepton invariant mass squared. We have constructed plots of the observables using present knowledge of Wilson coefficients and form factors. Assuming these plots to be experimental data, we have discussed and used the strategy to determine the form factors and Wilson…
The clockwork is an extra-dimensional set-up for generating light particles with exponentially suppressed or hierarchical couplings of light particles with N massive states having comparable masses near the threshold scale of the mechanism in theories which contain no small parameters at the fundamental level. We explore the prospect of charged lepton flavour violation (cLFV) in a clockwork framework which encompasses Dirac mass terms as well as Majorana mass terms for the new clockwork fermions. We deive the masses of the non zero clockwork Majorana masses, and new particles in a clockwork fr…
Rare B hadron decays provide an excellent test bench for the Standard Model and can probe new physics models. We review the experimental progress of the searches for rare leptonic B decays ($b\rightarrow \ell^+ \ell^-$ and $b\rightarrow s \ell^+ \ell^-$) at LHC and Tevatron experiments.
Particularly interesting processes to test the Standard Model are non-leptonic $B^0_s \rightarrow D_s^{\pm} K^{\mp}$ transitions. As these decays occur via pure tree diagrams, they allow a theoretically clean determination of the angle $γ$ of the unitarity triangle. Considering recent LHCb results, an intriguing picture arises, showing tension with the Standard Model. Utilising the available experimental data, we perform a theoretical analysis in order to shed more light on these puzzling patterns. Do these puzzles actually indicate footprints of New Physics?
Rates and CP asymmetries of the non-leptonic two-body decay of $B_c$ are calculated based on the low energy effective Hamiltonian. We concentrate on such $b$ quark decays of the processes with $0^-$ and $1^-$ S-wave particles and/or $0^+$ and $1^+$ P-wave particles in the final states. The Salpeter method, which is the relativistic instantaneous approximation of the original Bethe-Salpeter equation, is used to derive hadron transition matrix elements. Based on the calculation, it is found that the best decay channels to observe CP violation are $B_c^-\rightarrow η_c +D^-(D^{*-}_0)$, which need…
The LHC$_b$ collaboration has systematically measured the rates of $B_c\to J/ψK$, $B_c\to J/ψD_s$, $B_c\to J/ψD_s^*$ and $B_c\to ψ(2S) π$. The new data enable us to study relevant theoretical models and further determine the model parameters. In this work, We calculate the form factors for the transitions $B_c\to J/ψ$ and $B_c\to ψ(2S)$ numerically, then determine the partial widths of the semi-leptonic and non-leptonic decays. The theoretical predictions on the ratios of $Γ(B_c\to J/ψK)/Γ(B_c\to J/ψπ)$, $Γ(B_c\to J/ψD_s)/Γ(B_c\to J/ψπ)$ and $Γ(B_c\to J/ψD_s^*)/Γ(B_c\to J/ψπ)$ are consistent w…
With anomalies found in cosmic ray observations and unsolved questions of the Standard Model of particle physics like the discrepancy in the muon's anomalous magnetic moment, the idea of an U(1) extension of the Standard Model arose. This extension allows for the interaction of Dark Matter by exchange of a photon-like massive force carrier $A'$ not included in the Standard Model. We discuss the possibility to constrain the dark photon parameter space by using data taken from rare kaon decays. Therefore we analyze the decay $K\rightarrow μνA'$ as a signal process and calculate the expected Stan…
The processes $p p \rightarrow V_1 V_2 + X \rightarrow \ell_1 \bar \ell_1 \ell_2 \bar \ell_2 + X$, where $V_i = W^{\pm}$ or $Z$ and $\ell_i$ denotes a lepton, are calculated to ${\cal O}(α_s)$. Total and differential cross sections, with acceptance cuts imposed on the final state leptons, are given for the Tevatron and LHC center of mass energies. Inclusive and exclusive $0$-jet and $1$-jet cross sections are given. The transverse momenta spectra of the leptons are significantly enhanced at high $p_T^{}$ by the QCD radiative corrections, especially at the LHC energy. Invariant mass and angular…
We study the CP violation in two-body nonleptonic decays of $B_c$ meson. We concentrate on the decay channels which contain at least one excited heavy meson in the final states. Specifically, the following channels are considered: $B_c\to c\bar c(2S, 2P)+\bar cq(1S, 1P)$, $B_c\to c\bar c(1S)+\bar cq(2S, 2P)$, $B_c\to c\bar c(1P)+\bar cq(2S)$, $B_c\to c\bar c(1D)+\bar cq(1S, 1P)$, and $B_c\to c\bar c(3S)+\bar cq(1S)$. The improved Bethe-Salpeter method is applied to calculate the hadronic transition matrix element. Our results show that some decay modes have large branching ratios, which is of …
As one of the extensions of the Standard Model, we investigate the anomalous four-point $τ-W-ν_τ-γ$ scalar- and tensor-type interactions, which originate from the gauge invariant dimension-five operators. The coupling constants are constrained by the measured branching ratio of the $τ^- \rightarrow μ^- ν_τ \bar{ν_μ} γ$ decay: $-4.9<κ_τ^S<9.4$ and $-1.4<κ_τ^T<2.8$ at the 95% confidence level for the scalar and tensor interactions, respectively.
We introduce a flavor ${\cal U}(1)$ symmetry à la Froggat-Nielsen to explain the magnitude of the CKM mixing angles as well bilarge mixing in the neutrino sector. In the framework of GUTs we also estimate the magnitude of the third leptonic mixing angle $θ_{13}$. Estimates for rare leptonic decays such as $μ\to e \ga $ are also provided. Finally, leptogenesis is exploited for estimating the magnitude of leptonic CP violation.
The existence of dark matter has been established in astrophysics. However, there is no candidate for DM in the Stand Model (SM). In SM, the Higgs boson can only decay invisibly via $H\rightarrow ZZ^\ast \rightarrow ν\barνν\barν$ or DM, so any evidence of invisible Higgs decay that exceeds BR (H$\rightarrow$inv.) will immediately point to a phenomenon that is beyond the standard model (BSM). In this paper, we report on the upper limit of BR (H$\rightarrow$invisible) estimated for three channels, including two leptonic channels and one hadronic channel, under the assumption predicted by SM. Wit…
We present here a study of the impact of a heavy neutrino (or heavy neutral lepton) on leptonic and semileptonic kaon decays. We used a simplified model consisting of 3 light neutrinos responsible for neutrino oscillations and a heavy sterile neutrino. We found that it can lead to large deviations from the Standard Model predictions for leptonic decays, in conflict with experimental measurements of $K_{e2}$ and the lepton universality test $R_K$. This allows to derive new constraints on the leptonic mixing for heavy sterile neutrinos. No tension was found when considering the semileptonic deca…
I present estimates of the branching fractions in the non-leptonic charmonium two-body decay rates for $B^0\rightarrow ψ(2S)π^0$ decay and the same decays of $B^+\rightarrow ψ(2S)π^+$, $B^0\rightarrow ψ(2S)K^0$ and $B^+\rightarrow ψ(2S)K^+$. These estimates are based on a generalized factorization approach making use of leading order (LO) and next-to-leading order (NLO) contributions. I find that when the large enhancements from the known NLO contributions by using the QCD factorization approach are taken into account, the branching ratios are the following: $Br(B^0\rightarrow ψ(2S)π^0)=(1.067…
A Roadmap for neutrino charge assignments in $U(2)_F$ Flavor Models: Implications for LFV processes and leptonic anomalous magnetic moments
Universitá di Roma Tre（罗马三大学）；INFN Sezione di Roma Tre（意大利国家核物理研究所罗马三分部）；Instituto de Física Corpuscular (IFIC), Universitat de València-CSIC（瓦伦西亚大学-西班牙国家科研委员会粒子物理研究所）
QCD running coupling constant $α_s(m_c)$ and $α_s(m_b)$ are determined from heavy quarkonia $c\overline{c}$ and $b\overline{b}$ decays. The decay rates of $V\rightarrow 3g$ and $V\rightarrow e^+ e^-$ for $V=J/ψ$ and $Υ$ are estimated by taking into account both relativistic and QCD radiative corrections. The decay amplitudes are derived in the Bethe-Salpeter formalism, and the decay rates are estimated by using the meson wavefunctions which are obtained with a QCD-inspired inter-quark potential. For the $V\rightarrow 3g$ decay we find the relativistic correction to be very large and to severel…
The penguin mediated processes $b\rightarrow s g$ and $b\rightarrow s l^+l^-$ are studied. In the Standard Model, for the leptonic modes improvement in experimental limits will put strigient bounds on the top mass, where the present limit from $b\rightarrow s μ^+μ^-$ is 390 GeV. For hadronic penguin processes, although the gluonic penguin dominates, we find the electroweak contribution are around 30\% for the upper range allowed top mass. The branching ratio for $B\rightarrow X_s ϕ$ is predicted to be in the range $(0.6\sim 2)\times 10^{-4}$. Effects of the charged Higgs in two Higgs doublet m…
Neutrino Physics is a mature branch of science with all the three neutrino mixing angles and two mass squared differences determined with high precision. Inspite of several experimental verifications of neutrino oscillations and precise measurements of two mass squared differences and the three mixing angles, the unitarity of the leptonic mixing matrix is not yet established, leaving room for the presence of small non-unitarity effects. Deriving the bounds on these non-unitarity parameters from existing experimental constraints, on cLFV decays such as, $ μ\rightarrow eγ$, $ μ\rightarrow τγ$, $…
Recent experimental results from the LHCb, BaBar and Belle collaborations on the semitauonic decays of $B$ meson, $\bar{B}\rightarrow D^{(\ast)}τ\barν$, showing a significant deviation from the Standard Model (SM), hint towards a new physics scenario beyond the SM. In this work, we show that these enhanced decay rates can be explained within the framework of $E_{6}$ motivated Alternative Left-Right Symmetric Model (ALRSM), which has been successful in explaining the recent CMS excesses and has the feature of accommodating high scale leptogenesis. The R-parity conserving couplings in ALRSM can …
