Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userRare $Lambda_{b}to Lambdaell^{+}ell^{-}$ decay in the two-Higgs doublet model of type-III
47
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The rare exclusive dileptonic $Lambda_{b}to Lambdaell^{+}ell^{-}$ $(ell =mu, tau)$ decays are investigated in the general two-Higgs-doublet model of type III. A significant enhancement to the branching ratios, differential branching ratios, leptons forward-backward asymmetry, and the $Lambda$ baryon polarizations over the standard model is obtained. Measurements of these quantities will be useful for establishing the two-Higgs doublet model.
rate research
Read More
The form factors of the $Lambda_{b} to N^ast ell^+ ell^-$ decay are calculated in the framework of the light cone QCD sum rules. In the calculations the contribution of the negative parity $Lambda_b^ast$ baryon is eliminated by constructing the sum rules for different Lorentz structures. Furthermore the branching ratio of the semileptonic $Lambda_b to N^ast ell^+ ell^-$ decay is calculated. The numerical study for the branching ratio of the $Lambda_{b} to N^ast ell^+ ell^-$ decay indicates that it is quite large and could be measurable at future planned experiments to be conducted at LHCb.
Form factors of the rare $Lambda_{b}(Lambda_{b}^*)to Nell^{+}ell^{-}$ decays are calculated in the framework of the light cone QCD sum rules by taking into account of the contributions from the negative parity baryons. Using the obtained results on the form factors, the branching ratios of the considered decays are estimated. The numerical survey for the branching ratios of the $Lambda_b rar Nell^+ell^- $ and $Lambda_b^ast rar Nell^+ell^- $ decays indicate that these transitions could be measurable in LHCb in near future. Comparison of our predictions on the form factors and branching ratios with those existing in the literature is also performed.
We comprehensively study the charged-Higgs contributions to the leptonic $B^-_q to ell bar u$ ($q=u,c$) and semileptonic $bar B to X_q ell bar u$ ($X_u=pi, rho; X_c=D,D^*$) decays in the type-III two-Higgs-doublet model (2HDM). We employ the Cheng-Sher ansatz to suppress the tree-level flavor-changing neutral currents (FCNCs) in the quark sector. When the strict constraints from the $Delta B=2$ and $bto s gamma$ processes are considered, parameters $chi^u_{tq}$ from the quark couplings and $chi^ell_ell$ from the lepton couplings dictate the leptonic and semileptonic $B$ decays. It is found that when the measured $B^-_uto tau bar u$ and indirect bound of $B^-_c to tau bar u$ obtained by LEP1 data are taken into account, $R(D)$ and $R(pi)$ can have broadly allowed ranges; however, the values of $R(rho)$ and $R(D^*)$ are limited to approximately the standard model (SM) results. We also find that the same behaviors also occur in the $tau$-lepton polarizations and forward-backward asymmetries ($A^{X_q,tau}_{FB}$) of the semileptonic decays, with the exception of $A^{D^*,tau}_{FB}$, for which the deviation from the SM due to the charged-Higgs effect is still sizable. In addition, the $q^2$-dependent $A^{pi,tau}_{FB}$ and $A^{D,tau}_{FB}$ can be very sensitive to the charged-Higgs effects and have completely different shapes from the SM.
In this paper, the lepton flavor violating $tau^- to mu^-PP (PP=K^+K^-,K^0bar{K}^0,pi^+pi^-,pi^0pi^0)$ decays are studied in the framework of the two Higgs doublet model(2HDM) III. We calculate these decays branching ratios and get the bounds of model parameter $|lambda_{taumu}|$ from the experimental upper limits. Our results show that, the neutral Higgs bosons have tree-level contributions to these decays. Among these decays, the $tau^- to mu^- K^+K^-$ decay is most sensitive to $|lambda_{taumu}|$. In the existing parameters space, these decays could reach the measure capability of B factory. These processes can provide some valuable information to future research and furthermore present the reliable evidence to test the 2HDM III model.
The radiative corrections to the decay processes of the neutral ($CP$-even) Higgs boson ($H$) into a longitudinal gauge boson pair, {it i.e.}, $H rightarrow Z_{L}Z_{L}$ and $H rightarrow W_{L}^{+}W_{L}^{-}$ are analyzed in the two-Higgs doublet model by assuming that all of the Higgs boson masses are much greater than the $W$ and $Z$ bosons. These calculations are motivated to see if one could see potentially large virtual effects to these decay rates due to the charged and $CP$-odd neutral Higgs boson masses ($m_{G}$ and $m_{A}$, respectively) which are supposed to be larger than $m_{H}$. It is pointed out that, although the radiative corrections to the decay width $Gamma (Hrightarrow W_{L}^{+}W_{L}^{-})$ depend sensitively in general on $m_{G}$ and $m_{A}$, there occurs a screening effect, {it i.e.,} cancellation in leading terms once we set $m_{G}=m_{A}$, so that the radiative corrections tend to be minimized. It is also pointed out that the decay rate $Gamma (Hrightarrow Z_{L}Z_{L})$ is fairly insensitive to the other heavier Higgs masses and is possibly a good measuring tool of the Higgs mixing angle. The mechanism of these screening phenomena in the Higgs decays is explained on the basis of a new screening theorem, which we postulate with reference to the custodial symmetry in the Higgs potential.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
