We study the low energy phenomena induced by the lightest charged Higgs in the private Higgs (PH) model, in which each quark flavor is associated with a Higgs doublet. We show that the couplings of the charged Higgs scalars to fermions are fixed and the unknown parameters are only the masses and mixing elements of the charged Higgs scalars. As the charged Higgs masses satisfy with $M_b<M_{c}\ll M_{s} \ll M_{d,u}$, processes involving $B$-meson are expected to be the ideal places to test the PH model. In particular, we explore the constraints on the model from experimental data in $B$ physics, such as the branching ratio (BR) and CP asymmetry (CPA) of $B\to X_s \ga$, $B_{d,s}-\bar B_{d,s}$ mixings and the BR for $B\to K^* \ell^{+} \ell^{-}$. We illustrate that the sign of the Wilson coefficient for $B\to X_s \ga$ can be different from that in the standard model, while this flipped sign can be displayed by the forward-backward asymmetry of $B\to V \ell^{+} \ell^{-}$ with $V$ a vector meson. We also demonstrate that $B_{d,s}-\bar B_{d,s}$ mixings and their time-dependent CPAs are negligible small and the BR of $B\to K^* \ell^{+} \ell^{-}$ can have a more strict bound than that of $B\to X_s \ga$.
At the present time, there are hints of new physics (NP) in several observables involving $b \to c \ell^- {\barν}_\ell$ decays. In this talk, I describe measurable angular distributions for ${\bar B} \to D^* μ^- {\barν}_μ$ and ${\bar B} \to D^* τ^- (\to π^- ν_τ) {\barν}_τ$ decays, including the most general NP contributions. These angular distributions contain enough information to pin down the Lorentz structure of the NP, which will help to identify it. They also have the ability to reveal the presence of non-SMEFT (non-decoupling) NP.
In view of the importance of the nonperturbative resolved contributions for the overall uncertainties of the two inclusive penguin decays $\bar B \to X_s γ$ and $\bar B \to X_{s,d} \ell^+\ell^-$ we reanalyse these contributions using new estimates of moments of the subleading shape functions and of other input parameters. Within a systematic approach we find a significant reduction of the nonperturbative uncertainties in the inclusive decay $\bar B \to X_{s,d} \ell^+\ell^-$, but a much less pronounced reduction in the inclusive decay $\bar B \to X_s γ$ compared to a recent analysis on the reso…
Testing axial and electromagnetic nucleon form factors in time-like regions in the processes $\bar p + n\to π^- +\ell^-+\ell^+$ and $\bar p+ p\to π^0 +\ell^- + \ell^+$, $\ell=e$, $μ$
Angular and invariant-mass observables in the four-body Higgs decay $h\to\ell\barν_\ell\bar{\ell}^\primeν_{\ell^\prime}$
Zhengzhou University（郑州大学）；Chongqing University of Posts & Telecommunications（重庆邮电大学）；Chongqing University（重庆大学）；Chongqing University of Science and Technology（重庆科技大学）
Motivated by the first search for the rare charged-current $B$ decay to four leptons, $\ell \barν_\ell \ell^{(\prime)} \bar{\ell}^{(\prime)}$, we calculate the decay amplitude with factorization methods. We obtain the $B\to γ^*$ form factors, which depend on the invariant masses of the two lepton pairs, at leading power in an expansion in $Λ_{\rm QCD}/m_b$ to next-to-leading order in $α_s$, and at $\mathcal{O}(α_s^0)$ at next-to-leading power. Our calculations predict branching fractions of a few times $10^{-8}$ in the $\ell^{(\prime)} \bar{\ell}^{(\prime)}$ mass-squared bin up to $q^2=1~\text…
New possibility for further measurements of nucleon form factors at large momentum transfer in time-like region: $\bar{p}+{p}\to \ell^+ +\ell^-$, $\ell=e$ or $μ$
These proceedings review the differential decay rates and the branching ratios of the tau and muon decays $τ\to \ell \ell' \ell' ν\barν$ (with $\ell,\ell'=μ,e$) and $μ\to e e e ν\bar ν$ in the Standard Model at NLO. These five-body leptonic decays are a tool to study the Lorentz structure of weak interactions and to test lepton flavour universality. They are also a source of SM background to searches for the lepton-flavour-violating decays $μ\to e e e$ and $τ\to \ell \ell' \ell'$. Even if the shift in the branching ratios induced by radiative corrections turns out to be small and of order 1% -…
We calculate the differential branching fraction, lepton forward-backward asymmetry and direct CP asymmetry for $B_{d,s}\toγ\ell\bar{\ell}$ decays with an energetic photon. We employ factorization methods, which result in rigorous next-to-leading order predictions in the strong coupling at leading power in the large-energy/heavy-quark expansion, together with estimates of power corrections and a resonance parameterization of sub-leading power form factors in the region of small lepton invariant mass $q^2$. The $B_{d,s}\toγ\ell\bar{\ell}$ decay shares features of the charged-current decay $B_u …
We study the effects of the identical leptons in the final state of the $B^+\to \ell^+ \ell^- \ell^+\barν_{\ell}$ decay. The amplitude of the process is described by the same form factors as the amplitude of the ${B\to \ell \ell \ell'\barν'_{\ell}}$ decay for non-identical leptons in the final state. However, the differential distributions are strongly different, as the ${B^+\to \ell^+ \ell^- \ell^+\barν_{\ell}}$ amplitude contains both the direct ($M_a$) and the exchange ($M_b$) diagrams. We calculate a number of the differential distirbutions. In particular, we propose an interesting observa…
The observation of anomalies in the charged current $b\rightarrow c\bar{\ell}ν_{\ell}$ transitions hints the possibility of the existence of new physics beyond the standard model. Inspired by the work done in the beauty quark sector, we explore new physics in the charm quark sector with $c \rightarrow (s,d)\bar{\ell}ν_{\ell}$ charged current transitions. We analyze the decay modes $D_{(s)}^+ \to η^{(')} \bar{\ell} ν_{\ell}$ within an effective Lagrangian framework which includes both standard model and new physics contributions. We use the available experimental measurements of the semileptoni…
In this paper we investigate the next-to-leading power contribution to the $B_s \to γγ$ and $B_s \to γ\ell\bar{\ell}$ decays from the strange quark mass effect with the dispersion approach which is QCD inspired and more predictive. We have presented the analytic expression of the quark mass contribution in the $B_s \to γγ$ and $B_s \to γ\ell\bar{\ell}$ decays, together with a new term that is missed in the previous study. The numerical results of the strange quark mass contribution to the $B_s \to γγ$ decay is about 6% relative to the total branching ratio, while it is relatively small in the …
We discuss the consequences of deviations from the Standard Model observed in $b\to sμ^+μ^-$ transitions for flavour-changing neutral-current processes involving down-type quarks and neutrinos. We work within an effective field theory approach respecting the SM gauge symmetry, including right-handed currents, a flavour structure based on approximate U(2) symmetry, and assuming only SM-like light neutrinos. We discuss correlations among $B\to h_sν\barν$ ($h_s=K,K^*,X_s$), $K^+\toπ^+ν\barν$ and $K_L\toπ^0ν\barν$ branching ratios in the case of linear Minimal Flavour Violation and in a more gener…
We report on recent progress in the field of nonlocal (so-called resolved) contributions to the inclusive penguin decays which presently belong to the largest uncertainties in these inclusive decay modes. There is still a very large scale and a large charm mass dependence in the present leading order results which can in the future be decreased by including the $α_s$ corrections.
Constraint on compactification scale via recently observed baryonic $Λ_b\rightarrow Λ\ell^+ \ell^-$ channel and analysis of the $Σ_b \rightarrow Σ\ell^+ \ell^-$ transition in SM and UED scenario
We investigate rare decays of Higgs via exchange of two almost degenerate heavy on-shell Majorana neutrinos $N_j$ ($j=1,2$): $Γ_{\pm} = Γ(h \to ν_k N_j \to ν_k \ell^{\pm} π^{\mp})$, and into the open quark channels $Γ_{\pm} = Γ(h \to ν_k N_j \to ν_k \ell^{\pm} U D)$, where $U D$ are two jets of open quarks (${\bar U} D$, or $U {\bar D}$, where $U=u, c$ and $D=d, s$). The related CP violation asymmetry $A_{\rm CP} = (Γ_{-} - Γ_{+})/(Γ_{-} + Γ_{+})$ is studied in detail. We take into account the $N_1$-$N_2$ overlap and oscillation effects. We can see that for certain, presently acceptable, range…
We perform a calculation of the strong interaction effects between the $B$ and $D$ mesons in the $\bar{B} \to D \barν \ell$ reaction, as a crossing process of reactions with $BD$ in the final state, where the strong interaction between the mesons leads to a bound $BD$ state. We find corrections to the tree level amplitude of the order of $15-25\%$. We further see the effect of the corrections studied in the $R_D$ ratio for the rates of $\bar{B} \to D \barν_ττ$ and $\bar{B} \to D \barν_e \ell$ decays and find corrections of the order of $10\%$. Given the claims of $1.5\%$ precision in this rati…
At present, there are discrepancies with the predictions of the standard model in ${\bar B}^0 \to D^{*+} \ell^- {\barν}_\ell$ decays, hinting at the presence of new physics (NP) in $b \to c τ^- {\barν}$. Various NP models have been proposed to explain the data. In this talk, I discuss how the measurement of CP-violating observables in ${\bar B}^0 \to D^{*+} \ell^- {\barν}_\ell$ can be used to differentiate the NP scenarios.
