arXiv subjects

Ya-Dong Yang

Publications and source records attributed to Ya-Dong Yang.

At least 55 records · Page 3Linked to original sources

arXiv2020

$CP$ asymmetry in the angular distribution of $τ\to K_Sπν_τ$ decays

In this work, we study the $CP$ asymmetry in the angular distribution of $τ\to K_Sπν_τ$ decays, taking into account the known $CP$ violation in $K^0-\bar{K}^0$ mixing. It is pointed out for the first time that, once the well-measured $CP$ violation in the neutral kaon system is invoked, a non-zero $CP$ asymmetry would appear in the angular observable of the decays considered, even within the Standard Model. By employing the reciprocal basis, which is most convenient when a $K_{S(L)}$ is involved in the final state, the $CP$-violating angular observable is derived to be two times the product of the time-dependent $CP$ asymmetry in $K\to π^+π^-$ and the mean value of the angular distribution in $τ^\pm\to K^0(\bar{K}^0)π^\pm\barν_τ(ν_τ)$ decays. Compared with the Belle results measured in four different bins of the $Kπ$ invariant mass, our predictions lie within the margins of these measurements, except for a $1.7~σ$ deviation for the lowest mass bin. While being below the current Belle detection sensitivity that is of $\mathcal{O}(10^{-3})$, our predictions are expected to be detectable at the Belle II experiment, where $\sqrt{70}$ times more sensitive results will be obtained with a $50~\text{ab}^{-1}$ data sample.

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arXiv2020

Revisiting the $B$-physics anomalies in $R$-parity violating MSSM

In recent years, several deviations from the Standard Model predictions in semileptonic decays of $B$-meson might suggest the existence of new physics which would break the lepton-flavour universality. In this work, we have explored the possibility of using muon sneutrinos and right-handed sbottoms to solve these $B$-physics anomalies simultaneously in $R$-parity violating minimal supersymmetric standard model. We find that the photonic penguin induced by exchanging sneutrino can provide sizable lepton flavour universal contribution due to the existence of logarithmic enhancement for the first time. This prompts us to use the two-parameter scenario $(C^{\rm V}_9, \, C^{\rm U}_9)$ to explain $b \to s \ell^+ \ell^-$ anomaly. Finally, the numerical analyses show that the muon sneutrinos and right-handed sbottoms can explain $b \to s \ell^+ \ell^-$ and $R(D^{(\ast)})$ anomalies simultaneously, and satisfy the constraints of other related processes, such as $B \to K^{(\ast)} ν\barν$ decays, $B_s-\bar B_s$ mixing, $Z$ decays, as well as $D^0 \to μ^+ μ^-$, $τ\to μρ^0$, $B \to τν$, $D_s \to τν$, $τ\to K ν$, $τ\to μγ$, and $τ\to μμμ$ decays.

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arXiv2019

CP asymmetry in $τ\to K_Sπν_τ$ decays within the Standard Model and beyond

Motivated by the $2.8σ$ discrepancy observed between the BaBar measurement and the Standard Model prediction of the CP asymmetry in $τ\to K_Sπν_τ$ decays, as well as the prospects of future measurements at Belle II, we revisit this observable in this paper. Firstly, we reproduce the known CP asymmetry due to $K^0 -\bar{K}^0$ mixing by means of the reciprocal basis, which is convenient when a $K_{S(L)}$ is involved in the final state. As the $Kπ$ tensor form factor plays a crucial role in generating a non-zero direct CP asymmetry that can arise only from the interference of vector and tensor operators, we then present a dispersive representation of this form factor, with its phase obtained in the context of chiral theory with resonances, which fulfills the requirements of unitarity and analyticity. Finally, the $τ\to K_Sπν_τ$ decays are analyzed both within a model-independent low-energy effective theory framework and in a scalar leptoquark scenario. It is observed that the CP anomaly can be accommodated in the model-independent framework, even at the $1σ$ level, together with the constraint from the branching ratio of $τ^-\to K_Sπ^-ν_τ$ decay; it can be, however, marginally reconciled only at the $2σ$ level, due to the specific relation between the scalar and tensor operators in the scalar leptoquark scenario. Once the combined constraints from the branching ratio and the decay spectrum of this decay are taken into account, these possibilities are however both excluded, even without exploiting further the stronger bounds from the (semi-)leptonic kaon decays under the assumption of lepton-flavour universality, as well as from the neutron electric dipole moment and $D-\bar{D}$ mixing under the assumption of $SU(2)$ invariance of the weak interactions.

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arXiv2019

$B_{s(d)}-\bar{B}_{s(d)}$ Mixing and $B_s\toμ^+μ^-$ Decay in the NMSSM with the Flavour Expansion Theorem

In this paper, motivated by the observation that the Standard Model predictions are now above the experimental data for the mass difference $ΔM_{s(d)}$, we perform a detailed study of $B_{s(d)}-\bar{B}_{s(d)}$ mixing and $B_s\toμ^+μ^-$ decay in the $\mathbb{Z}_3$-invariant NMSSM with non-minimal flavour violation, using the recently developed procedure based on the Flavour Expansion Theorem, with which one can perform a purely algebraic mass-insertion expansion of an amplitude written in the mass eigenstate basis without performing any diagrammatic calculations in the interaction/flavour basis. Specifically, we consider the finite orders of mass insertions for neutralinos but the general orders for squarks and charginos, under two sets of assumptions for the squark flavour structures (\textit{i.e.}, while the flavour-conserving off-diagonal element $δ_{33}^\text{LR}$ is kept in both of these two sectors, only the flavour-violating off-diagonal elements $δ_{23}^\text{LL}$ and $δ_{i3}^\text{RR}$ ($i=1,2$) are kept in the \text{LL} and \text{RR} sectors, respectively). Our analytic results are then expressed directly in terms of the initial Lagrangian parameters in the interaction/flavour basis, making it easy to impose the experimental bounds on them. It is found numerically that the NMSSM effects with the above two assumptions for the squark flavour structures can accommodate the observed deviation for $ΔM_{s(d)}$, while complying with the experimental constraints from the branching ratios of $B_s\to μ^+ μ^-$ and $B\to X_sγ$ decays.

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arXiv2019

$b \to cτ\barν$ decays in supersymmetry with $R$-parity violation

In the past few years, several hints of lepton flavour universality (LFU) violation have emerged in the $b \to c τ\barν$ and $b \to s \ell^+ \ell^-$ data. Quite recently, the Belle Collaboration has reported the first measurement of the $D^*$ longitudinal polarization fraction in the $B \to D^* τ\barν$ decay. Motivated by this intriguing result, together with the recent measurements of $R_{J/ψ}$ and $τ$ polarization, we study $b \to c τ\barν$ decays in the Supersymmetry (SUSY) with $R$-parity violation (RPV). We consider $B \to D^{(*)} τ\barν$, $B_c \to η_c τ\barν$, $B_c \to J/ψτ\barν$ and $Λ_b \to Λ_c τ\barν$ modes and focus on the branching ratios, the LFU ratios, the forward-backward asymmetries, polarizations of daughter hadrons and $τ$ lepton. It is found that the RPV SUSY can explain the $R_{D^{(*)}}$ anomalies at $2σ$ level, after taking into account various flavour constraints. In the allowed parameter space, the differential branching fractions and LFU ratios are largely enhanced by the SUSY effects, especially in the large dilepton invariant mass region. In addition, a lower bound $\mathcal B(B^+ \to K^+ ν\barν) > 7.37 \times 10^{-6}$ is obtained. These observables could provide testable signatures at the High-Luminosity LHC and SuperKEKB, and correlate with direct searches for SUSY.

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arXiv2019

Phenomenology of $b\to cτ\barν$ decays in a scalar leptoquark model

During the past few years, hints of Lepton Flavour Universality (LFU) violation have been observed in $b \to c τ\barν$ and $b \to s \ell^+ \ell^-$ transitions. Recently, the $D^*$ and $τ$ polarization fractions $P_L^{D^*}$ and $P_L^τ$ in $B \to D^* τ\barν$ decay have also been measured by the Belle collaboration. Motivated by these intriguing results, we revisit the $R_{D^{(*)}}$ and $R_{K^{(*)}}$ anomalies in a scalar leptoquark (LQ) model, in which two scalar LQs, one being $SU(2)_L$ singlet and the other $SU(2)_L$ triplet, are introduced simultaneously. We consider five $b \to c τ\barν$ mediated decays, $B \to D^{(*)}τ\barν$, $B_c \to η_c τ\barν$, $B_c \to J/ψτ\barν$, and $Λ_b \to Λ_c τ\barν$, and focus on the LQ effects on the $q^2$ distributions of the branching fractions, the LFU ratios, and the various angular observables in these decays. Under the combined constraints by the available data on $R_{D^{(*)}}$, $R_{J/ψ}$, $P_L^τ(D^*)$, and $P_L^{D^*}$, we perform scans for the LQ couplings and make predictions for a number of observables. It is found numerically that both the differential branching fractions and the LFU ratios are largely enhanced by the LQ effects, with the latter being expected to provide testable signatures at the SuperKEKB and High-Luminosity LHC experiments.

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arXiv2019

Revisiting the radiative decays $J/ψ\rightarrow γη^{(\prime)}$ in perturbative QCD

In the framework of perturbative QCD, the radiative decays $J/ψ\rightarrowγη^{(\prime)}$ are revisited in detail, where the involved one-loop integrals are evaluated analytically with the light quark masses kept. We have found that the sum of loop integrals is insensitive to the light quark masses and the branching ratios $\mathcal{B}(J/ψ\rightarrowγη^{(\prime)})$ barely depend on the shapes of $η^{(\prime)}$ distribution amplitudes. With the parameters of $η-η^{\prime}$ mixing extracted from low energy processes and $J/ψ\rightarrowγη^{(\prime)}$ by means of nonperturbative matrix elements $\langle0|G_{μν}^a\tilde{G}^{a,μν}|η^{(\prime)}\rangle$ based on $U_{A}(1)$ anomaly dominance argument, we could not give the ratio $R_{J/ψ}$ in agreement with experimental result. However, using the parameters, especially the mixing angle $ϕ=33.5^{\circ}\pm0.9^{\circ}$, extracted from $γ^{\ast}γ-η^{\prime}$ transition form factor measured at $q^{2}=112~\mathrm{GeV}^{2}$ by BaBar collaboration, we obtain $R_{J/ψ}=4.70$ in good agreement with $R_{J/ψ}^{exp}=4.65\pm0.21$. As a crossing check, with $Γ^{exp}(η^{(\prime)}\rightarrowγγ)$ and our results for $J/ψ\rightarrowγη^{(\prime)}$, we get $ϕ=33.9^{\circ}\pm0.6^{\circ}$. The difference between the determinations of $ϕ$ is briefly discussed.

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arXiv2019

$b\to cτν$ Transitions in the Standard Model Effective Field Theory

The $R(D^{(\ast)})$ anomalies observed in $B\to D^{(\ast)}τν$ decays have attracted much attention in recent years. In this paper, we study the $B\to D^{(\ast)}τν$, $Λ_b\toΛ_cτν$, $B_c\to (J/ψ,\,η_c)τν$, $B\to X_cτν$, and $B_c\toτν$ decays, all being mediated by the same quark-level $b\to cτν$ transition, in the Standard Model Effective Field Theory. The most relevant dimension-six operators for these processes are $Q_{lq}^{(3)}$, $Q_{ledq}$, $Q^{(1)}_{lequ}$, and $Q^{(3)}_{lequ}$ in the Warsaw basis. Evolution of the corresponding Wilson coefficients from the new physics scale $Λ=1$~TeV down to the characteristic scale $μ_b\simeq m_b$ is performed at three-loop in QCD and one-loop in EW/QED. It is found that, after taking into account the constraint ${\cal B}(B_c\toτν)\lesssim 10\%$, a single $\left[C_{lq}^{(3)}\right]_{3323}(Λ)$ or $\left[C^{(3)}_{lequ}\right]_{3332}(Λ)$ can still be used to resolve the $R(D^{(\ast)})$ anomalies at $1σ$, while a single $\left[C^{(1)}_{lequ}\right]_{3332}(Λ)$ is already ruled out by the measured $R(D^{(\ast)})$ at more than $3σ$. By minimizing the $χ^2(C_i)$ function constructed based on the current data on $R(D)$, $R(D^\ast)$, $P_τ(D^\ast)$, $R(J/ψ)$, and $R(X_c)$, we obtain eleven most trustworthy scenarios, each of which can provide a good explanation of the $R(D^{(\ast)})$ anomalies at $1σ$. To further discriminate these different scenarios, we predict thirty-one observables associated with the processes considered under each NP scenario. It is found that most of the scenarios can be differentiated from each other by using these observables and their correlations.

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arXiv2019

Effect of scalar leptoquarks on the lepton flavor violation decays of B meson

Leptoquarks have been suggested to solve a variety of discrepancies between the expected and observed phenomenon. In this paper, we investigate the effect of scalar leptoquarks on the lepton flavor violating B meson rare decays which involve the quark level transition $\bar{b} \to \bar{s} \ell^-_i \ell^+_j(i \neq j)$. The leptoquark parameter space is constrained by using the recently measured upper limits on the $\mathcal{B}(B_s^0 \to \ell^-_i \ell^+_j)$ and $\mathcal{B}(B \to K^{(*)}\ell^-_i \ell^+_j)$. Using such constrained leptoquark parameter space, some relevant physical quantities are also predicted and we find that the constrained New Physics parameters in the leptoquark model have very obvious effects on the relevant physical quantities in this paper. With future measurements of observable in $B \to K^{(*)}\ell^-_i \ell^+_j$ decays at the LHCb, more and more differentiated from the other NP explanations could be tested.

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arXiv2019

R-parity violating solutions to the $R_{D^{(\ast)}}$ anomaly and their GUT-scale unifications

Recently, several $B$-physics experiments report interesting anomalies in the semi-leptonic decays of $B$-mesons, such as the excess in the $R_{D^{(\ast)}}$ measurements. These anomalies seem to suggest intriguing hints of lepton flavor non-universality, and the R-parity violating (RPV) interactions are candidates for explaining this non-universality. In this paper, we discuss the RPV interactions for resolving the $R_{D^{(\ast)}}$ anomaly with the Grand Unified Theory (GUT) assumption. To solve the $R_{D^{(\ast)}}$ anomaly, it is known that large RPV couplings and around $1~{\rm TeV}$ sfermion masses are required. At the same time, large RPV couplings are conducive to realize the bottom-tau Yukawa unification which appears in the GUT models. On the other hand, there are problems for realizing favorable sfermion masses in the constrained minimal supersymetric standard model. To resolve these problems, we show that two non-universalities, the non-universal sfermion masses and the non-universal gaugino masses, are favorable.

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arXiv2018

Self-consistency and covariance of light-front quark models: testing via $P$, $V$ and $A$ meson decay constants, and $P\to P$ weak transition form factors

In this paper, we test the self-consistencies of the standard and the covariant light-front quark model and study the zero-mode issue via the decay constants of pseudoscalar ($P$), vector ($V$) and axial-vector ($A$) mesons, as well as the $P\to P$ weak transition form factors. With the traditional type-I correspondence between the manifestly covariant and the light-front approach, the resulting $f_{V}$ as well as $f_{^1\!A}$ and $f_{^3\!A}$ obtained with the $\lbd=0$ and $\lbd=\pm$ polarization states are different from each other, which presents a challenge to the self-consistency of the covariant light-front quark model. However, such a self-consistency problem can be "resolved" within the type-II scheme, which requires an additional replacement $M\to M_0$ relative to the type-I case. Moreover, the replacement $M\to M_0$ is also essential for the self-consistency of the standard light-front quark model. In the type-II scheme, the valence contributions to the physical quantities~(${\cal Q}$) considered in this paper are alway the same as that obtained in the standard light-front quark model, $[{\cal Q}]_{\rm val.}=[{\cal Q}]_{\rm SLF}$, and the zero-mode contributions to $f_{V,^1\!A,^3\!A}$ and $f_-(q^2)$ exist only formally but vanish numerically, which implies further that $[{\cal Q}]_{\rm val.}\dot{=} [{\cal Q}]_{\rm full}$. In addition, the manifest covariance of the covariant light-front quark model is violated in the traditional type-I scheme, but can be recovered by taking the type-II scheme.

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arXiv2018

$R_{D^{(\ast)}}$, $R_{K^{(\ast)}}$ and neutrino mass in the 2HDM-III with right-handed neutrinos

Given that the two-Higgs-doublet model of type III (2HDM-III) has the potential to address the $R_{D^{(\ast)}}$ anomalies while the resolution to the $R_{K^{(\ast)}}$ deficits requires new degrees of freedom within this framework, we consider in this paper a unified scenario where the low-scale type-I seesaw mechanism is embedded into the 2HDM-III, so as to accommodate the $R_{D^{(\ast)}}$ and $R_{K^{(\ast)}}$ anomalies as well as the neutrino mass. We first revisit the $R_{D^{(\ast)}}$ anomalies and find that the current world-averaged results can be addressed at $2σ$ level without violating the bound from the branching ratio $\mathcal{B}(B_c^-\rightarrow τ^- \barν)\leqslant 30\%$. The scenario predicts two sub-eV neutrino masses based on a decoupled heavy Majorana neutrino and two nearly degenerate Majorana neutrinos with mass around the electroweak scale. For the $R_{K^{(\ast)}}$ anomalies, the same scenario can generate the required Wilson coefficients in the direction $ C_{9 μ}^{\rm NP}=-C_{10 μ}^{\rm NP}<0$, with $\mathcal{O}(1)$ Yukawa couplings for the muon and the top quark.

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arXiv2017

The $Λ_b\to Λ(\to pπ^-)μ^+μ^-$ decay in the aligned two-Higgs-doublet model

The rare baryonic decay $Λ_b\to Λ(\to pπ^-)μ^+μ^-$ provides valuable complementary information compared to the corresponding mesonic $b\to sμ^+μ^-$ transition. In this paper, using the latest high-precision lattice QCD calculation of the $Λ_b\toΛ$ transition form factors, we study this interesting decay within the aligned two-Higgs-doublet model, paying particularly attention to effects of the chirality-flipped operators generated by the charged scalars. In order to extract the full set of angular coefficients in this decay, we consider the following ten angular observables that can be derived from the analysis of the subsequent parity-violating $Λ\to pπ^-$ decay: the differential branching fraction ${\rm d}{\cal B}/{\rm d}q^2$, the longitudinal polarization fraction $F_L$, the lepton-, hadron- and combined lepton-hadron-side forward-backward asymmetries $A_{\rm FB}^\ell$, $A_{\rm FB}^Λ$ and $A_{\rm FB}^{\ellΛ}$, as well as the other five asymmetry observables $Y_i$~($i={\rm 2,\,3s,\,3sc,\,4s,\,4sc}$). Detailed numerical comparisons are made between the SM and NP values for these angular observables. It is found that, under the constraints from the inclusive $B\to X_sγ$ branching fraction and the latest global fit results of $b\to s\ell\ell$ data, the contributions of right-handed semileptonic operators $O^{\prime}_{9,10}$, besides reconciling the $P_5^{\prime}$ anomaly observed in $B^0\to K^{\ast 0}μ^+μ^-$ decay, could also enhance the values of ${\rm d}{\cal B}/{\rm d}q^2$ and $A_{\rm FB}^\ell$ in the bin $[15,20]~{\rm GeV}^2$, leading to results consistent with the current LHCb measurements.

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arXiv2017

$B^0\to K^{\ast 0}μ^+μ^-$ Decay in the Aligned Two-Higgs-Doublet Model

In the aligned two-Higgs-doublet model, we perform a complete one-loop computation of the short-distance Wilson coefficients $C_{7,9,10}^{(\prime)}$, which are the most relevant ones for $b\to s\ell^+\ell^-$ transitions. It is found that, when the model parameter $\left|ς_u\right|$ is much smaller than $\left|ς_d\right|$, the charged-scalar contributes mainly to chirality-flipped $C_{9,10}^\prime$, with the corresponding effects being proportional to $\left|ς_d\right|^2$. Numerically, the charged-scalar effects fit into two categories: (A) $C_{7,9,10}^\mathrm{H^\pm}$ are sizable, but $C_{9,10}^{\prime\mathrm{H^\pm}}\simeq0$, corresponding to the (large $\left|ς_u\right|$, small $\left|ς_d\right|$) region; (B) $C_7^\mathrm{H^\pm}$ and $C_{9,10}^{\prime\mathrm{H^\pm}}$ are sizable, but $C_{9,10}^\mathrm{H^\pm}\simeq0$, corresponding to the (small $\left|ς_u\right|$, large $\left|ς_d\right|$) region. Taking into account phenomenological constraints from the inclusive radiative decay $B\to X_sγ$, as well as the latest model-independent global analysis of $b\to s\ell^+\ell^-$ data, we obtain the much restricted parameter space of the model. We then study the impact of the allowed model parameters on the angular observables $P_2$ and $P_5'$ of $B^0\to K^{\ast 0}μ^+μ^-$ decay, and find that $P_5'$ could be increased significantly to be consistent with the experimental data in case B.

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arXiv2017

$Λ_b\toΛ_cτ\barν_τ$ decay in scalar and vector leptoquark scenarios

It has been shown that the anomalies observed in $\bar B\to D^{(\ast)}τ\barν_τ$ and $\bar B\to \bar K\ell^+\ell^-$ decays can be resolved by adding a single scalar or vector leptoquark to the Standard Model, while constraints from other precision measurements in the flavour sector can be satisfied without fine-tuning. To further explore these two interesting scenarios, in this paper, we study their effects in the semi-leptonic $Λ_b\toΛ_cτ\barν_τ$ decay. Using the best-fit solutions for the operator coefficients allowed by the current data of mesonic decays, we find that (i) the two scenarios give similar amounts of enhancements to the branching fraction $\mathcal B(Λ_b\toΛ_cτ\barν_τ)$ and the ratio $R_{Λ_c}=\mathcal B(Λ_b\toΛ_c τ\barν_τ)/\mathcal B(Λ_b\toΛ_c\ell\barν_\ell)$, (ii) the two best-fit solutions in each of these two scenarios are also indistinguishable from each other, (iii) both scenarios give nearly the same predictions as those of the Standard Model for the longitudinal polarizations of $Λ_c$ and $τ$ as well as the lepton-side forward-backward asymmetry. With future measurements of these observables in $Λ_b\toΛ_cτ\barν_τ$ decay at the LHCb, the two leptoquark scenarios could be further tested, and even differentiated from the other NP explanations for the $R_{D^{(\ast)}}$ anomalies. We also discuss the feasibility for the measurements of these observables at the LHC and the future $e^+e^-$ colliders.

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arXiv2016

Revisiting the one leptoquark solution to the $R(D^{(\ast)})$ anomalies and its phenomenological implications

It has been shown recently that the anomalies observed in $\bar B\to D^{(\ast)}τ\barν_τ$ and $\bar B\to \bar K\ell^+\ell^-$ decays could be resolved with just one scalar leptoquark. Fitting to the current data on $R(D^{(\ast)})$ along with acceptable $q^2$ distributions in $\bar B\to D^{(\ast)}τ\barν_τ$ decays, four best-fit solutions for the operator coefficients have been found. In this paper, we explore the possibilities of how to discriminate these four solutions. Firstly, we find that two of them are already excluded by the decay $B_c^-\to τ^-\barν_τ$, because the predicted decay widths have already overshot the total width $Γ_{B_c}$. It is then found that the remaining two solutions result in two effective Hamiltonians governing $b\to c τ\barν_τ$ transition, which differ by a sign and enhance the absolute value of the coefficient of $\bar c_Lγ_μb_L\,\bar τ_Lγ^μ{ν_τ}_L$ operator by about $12\%$. However, they give nearly the same predictions as in the SM for the $D^\ast$ and $τ$ longitudinal polarizations as well as the lepton forward-backward asymmetries in $\bar B\to D^{(\ast)}τ\barν_τ$ decays. For the other observables like $\mathcal B(B_c^-\to τ^-\barν_τ)$, $\mathcal B(B_c^- \to γτ^-\barν_τ)$, $R_{D^{(\ast)}}(q^2)$, ${\rm d}\mathcal B(\bar B\to D^{(\ast)}τ\barν_τ)/{\rm d}q^2$ and $\mathcal B(\bar B\to X_cτ\barν_τ)$, on the other hand, the two solutions give sizable enhancements relative to the SM predictions. With measurement of $B_c^-\to τ^-\barν_τ$ at LHCb and refined measurements of observables in $\bar B\to D^{(\ast)}τ\barν_τ$ at both LHCb and Belle-II, such a specific NP scenario could be further deciphered.

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arXiv2016

Revisiting $B_s \to μ^+μ^-$ in the two-Higgs doublet models with $Z_2$ symmetry

We revisit the rare leptonic decay $B_s \to μ^+ μ^-$ in the two-Higgs doublet models with a softly broken $Z_2$ symmetry, namely type-I, type-II, type-X and type-Y 2HDMs. We have derived the relevant full one-loop Wilson coefficients of the four 2HDMs from the recent calculation in the aligned two-Higgs doublet model by Li, Lu and Pich, which could be mapped to all the four 2HDMs for both large and small $\tanβ$. It is found that, a new term associated with the soft $Z_2$ symmetry breaking parameter $M$ can be enhanced by $\tan^2β$ in the type-II 2HDM, which has not been considered in the literature. Imposing both theoretical and experimental constraints, we have renewed the bounds on the parameter spaces of the four 2HDMs. Different from our previous paper, however, we find that all the four 2HDMs give sizable and similar contributions to $\overline{\mathcal B}(B_s \to μ^+ μ^-)$ within the stringently restricted parameter spaces, but very tiny as regards the mass-eigenstate rate asymmetry $\mathcal A_{ΔΓ}$; this makes it unfeasible to discriminate the four types of 2HDM with the correlations between the observables in $B_s \to μ^+ μ^-$ decay.

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arXiv2015

$B_{s,d}-\bar{B}_{s,d}$ mixings and $B_{s,d}\to\ell^+\ell^-$ decays within the Manohar-Wise model

In this paper, we perform a complete one-loop computation of the short-distance Wilson coefficients for $B_{s,d}-\bar{B}_{s,d}$ mixings and $B_{s,d}\to\ell^+\ell^-$ decays in the Manohar-Wise model, which extends the SM scalar sector by a colour-octet and weak-doublet scalar. Based on these calculations, combined constraints on the model parameters are derived from the current flavour data, including the $B_{s,d}-{\bar{B}}_{s,d}$ mixings, $B_{s,d}\toμ^+μ^-$, $B\to X_sγ$, $B\to K^{\ast}γ$, $B\toργ$, and $Z\to b \bar{b}$ decays. The future sensitivity to the model is also explored in the observables achievable with $50~{\rm fb}^{-1}$ of LHCb and $50~{\rm ab}^{-1}$ of Belle-II data. We find that the Manohar-Wise model could explain the current data, especially when the couplings of the charged colour-octet scalars to quarks are complex, with the resulting $χ^2_{\rm min}$ being significantly smaller than that of the SM. Finally, we investigate correlations among the two isospin asymmetries $Δ(K^*γ)$ and $Δ(ργ)$, as well as the averaged time-integrated branching ratios $\bar{\mathcal B}(B_{s,d}\to μ^+μ^-)$; some of them are found to be quite strong and could, therefore, provide further insights into the model, once more precise experimental measurements and theoretical predictions for these observables are available in the future.

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