arXiv subjects

Si-Hong Zhou

Publications and source records attributed to Si-Hong Zhou.

At least 19 recordsLinked to original sources

arXiv2026

Precise theoretical prediction on branching fractions and polarizations of $D \to V V$ decays

We present a precise and systematic analysis of $D \to V V$ decays within the factorization-assisted topological-amplitude approach, where $D$ denotes the set $\{D^0, \, D^+,\, D^+_s\}$ and $V$ represents the vector mesons $ρ, K^*, ω$, and $ϕ$. Given the limited current experimental data, the factorization-assisted topological-amplitude approach serves as a available phenomenological framework for predicting charmed meson decays to both vector mesons. In this framework, incorporating flavor SU(3) symmetry breaking effects, we can express nonfactorizable contributions of different modes as a minimal set of universal parameters globally fitted to experimental data. Utilizing 36 experimental data points for $D \to VV$ decays, we precisely extract ten nonfactorizable parameters associated with the $C$ and $E$ topological diagrams with $χ^2/\mathrm{d.o.f.}=8.43$. We find that a large strong phase in the longitude $E$ amplitude cause strong destructive interference with the $C$ longitudinal component, yielding $f_\parallel >f_L $, contrary to the naive factorization predictions. Additionally, for modes processing exclusively by the $E$ diagram, the amplitude hierarchy $|S|<|D|$ leads to a $D$-wave branching fraction larger than that of the $S$-wave. This explains recent observations that contradict $S$-wave dominance predictions. The predicted branching fractions and polarizations for 28 decay modes are consistent with existing experimental data. Unobserved modes, especially those with branching fractions of order $10^{-3}\sim10^{-2}$, the $D$-wave dominated modes, and modes exhibiting $f_\parallel >f_L $, await measurement by BESIII, STCF, Belle II, and LHCb.

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arXiv2025

Updated branching ratios and $CP$ asymmetries in $D \to PV$ decays

Motivated by extensive new high-precision experimental data, we present an updated analysis of the two-body charm decays $D \to PV$ (with $P =π,K, η^{(\prime)}$ and $V =ρ, K^*, ω, ϕ$) within the factorization-assisted topological-amplitude (FAT) approach. In the framework, flavor SU(3) symmetry breaking effect is incorporated into the topological amplitudes, allowing the nonfactorizable contributions from topological diagrams to be expressed as a minimal set of universal parameters determined through a global fit to experimental data. Thanks to the sufficient data with high precision, we are now able to quantify the nonfactorizable contribution of so-called ``factorization" $T$ diagram, which is essential for explaining the observed branching ratios. The parameters for the $C$, $E$, and $A$ diagrams are also updated with significant improved precision, and notably, the resulting strong phases differ substantially from those in the earlier FAT analysis. We find that the $C$ topological amplitude features substantial nonfactorizable effects in the charm sector. These refined parameters enable predictions of significantly improved accuracy, yielding branching ratios in good agreement with current data and the latest results in topological diagram approach, and the predicted direct $\mathit{CP}$ asymmetries differ distinctly form previous FAT results due to updated strong phases. In several modes, the $\mathit{CP}$ asymmetries are predicted to reach $\mathcal{O}(10^{-3})$, thereby making them promising observables for future high-precision experiments at LHCb, BESIII and Belle II. Predictions for unobserved decay modes, especially those with branching fractions of order $10^{-4}\sim10^{-3}$, are also provided for forthcoming experimental tests.

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arXiv2025

Contributions of $ρ(770,1450)\to ωπ$ for the Cabibbo-favored $D \to hωπ$ decays

Recently, the BESIII Collaboration has observed the three-body decays $D_s^+\to ηωπ^+$, $D^+\to K^0_Sπ^+ω$ and $D^0\to K^-π^+ω$. In this work, we investigate the contributions of the subprocesses $ρ^+\to ωπ^+$ in these Cabibbo-favored decays $D \to hωπ$, with $ρ^+= \{ρ(770)^+, ρ(1450)^+, ρ(770)^+\&ρ(1450)^+\}$ and $h=\{ η, K^0_S, K^-\}$, by introducing these subprocesses into the decay amplitudes of relevant decay processes via the vector form factor $F_{ωπ}$ which has measured in the related $τ$ and $e^+e^-$ processes; we provide the first theoretical predictions for the branching fractions of the quasi-two-body decays $D_s^+\toη[ρ^+\to]ωπ^+$, $D^+\to K^0_S[ρ^+\to]ωπ^+$ and $D^0\to K^-[ρ^+\to]ωπ^+$. Our findings reveal that the contributions from the subprocess $ρ(770)^+\toωπ^+$ are significant in these observed three-body decays $D_s^+\toηωπ^+$, $D^+\to K^0_S ωπ^+$ and $D^0\to K^- ωπ^+$, notwithstanding the contributions originating from the Breit-Wigner tail effect of $ρ(770)^+$. The numerical results of this study suggest that the dominant resonance contributions for the three-body decays $D_s^+\toηωπ^+$ and $D^+\to K^0_S ωπ^+$ are originated from the $P$-wave intermediate states $ρ(770)^+$, $ρ(1450)^+$ and their interference effects.

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arXiv2025

Analysis of three-body charmed $B$ meson decays $B \to {D}(V^* \to){V P}$

We systematically analyze the decays $B_{(s)} \to D_{(s)} (V^* \to)\, V\, P$, where $V^*$ represents a vector resonance ($ρ, \, ω$ or $K^*$), and $V P$ denotes the final-state meson pairs $ ω\, π$, $ ρ\, π$ and $ ρ\, K$. The intermediate subprocesses $B_{(s)} \to D_{(s)} V^*$ are calculated in the factorization-assisted topological-amplitude approach, while the intermediate resonant states $V^*$ are modeled using a relativistic Breit-Wigner distribution, subsequently decaying into $VP$ through strong interactions. We predict the off-shell effects of the ground-state resonances ($ρ,\, ω, \, K^*$) in $B_{(s)} \to D_{(s)} (V^* \to )V P$. Our results show that the virtual contributions from $ρ\to ω\, π$, $ω\to ρ\, π$, and $K^* \to ρ\, K$ are crucial for these three-body decays, $B_{(s)} \to D_{(s)} V\, P$. In particular, the branching fractions arising from the $ρ$ and $ω$ virtual effects can be comparable to the total decay rates of $B_{(s)} \to D_{(s)} ω\, π$ and $B_{(s)} \to D_{(s)} ρ\, π$, respectively. Decays with branching fractions of order $10^{-6}-10^{-4}$ are expected to be measurable at Belle II and LHCb. Compared with previous perturbative QCD predictions for $B_{(s)} \to D_{(s)} (ρ\to)\, ω\, π$, our results are consistent but exhibit higher precision.

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arXiv2025

Analysis of three-body hadronic $D$-meson decays

Motivated by recent experimental advances in three-body hadronic $D$ decays from BESIII, we present a systematic analysis of $D_{(s)} \to P_1 (V \to) P_2 P_3 $ decay processes, where $V$ denotes vector resonances ($ρ, K^*, ω$, $ϕ$) and $P_{1,2,3}$ are light pseudoscalar mesons ($π,K, η^{(\prime)}$). Using the factorization-assisted topological-amplitude (FAT) approach we calculate the intermediate subprocesses $D_{(s)} \to P_1 V$, incorporating relativistic Breit-Wigner distributions to model the subsequent $V \to P_2 P_3$ strong decays. By comprehensively including all relevant resonances ($ρ, K^*, ω, ϕ$), we calculate branching fractions for these decay modes as well as the Breit-Wigner-tail effects in $D_{(s)} \to P_1 (ω\to) KK$ processes. Our framework comprehensively incorporates both factorizable and nonfactorizable contributions, significantly improving theoretical predictions in the nonperturbative regime where conventional methods face challenges due to the limited mass scale of charm mesons. The FAT approach yields results in good agreement with experimental data, demonstrating its effectiveness in capturing nonfactorizable contributions with improved precision. Our predictions for yet-unobserved decay modes, particularly those with branching fractions in the order of $10^{-4}$ to $10^{-3}$, are expected to be tested in future high-precision experiments at BESIII and LHCb.

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arXiv2024

Analysis of three-body decays $B \to D (V \to ) PP $ under the factorization-assisted topological-amplitude approach

Motived by the accumulated experimental results on three-body charmed $B$ decays with resonance contributions in Babar, LHCb and Belle (II), we systematically analyze $B_{(s)} \to D_{(s)} (V \to) P_1 P_2 $ decays with $V$ representing a vector resonance ($ρ, K^*, ω$ or $ϕ$) and $P_{1,2}$ as a light pseudoscalar meson (pion or kaon). The intermediate subprocesses $B_{(s)} \to D_{(s)} V$ are calculated with the factorization-assisted topological-amplitude (FAT) approach and the intermediate resonant states $V$ described by the relativistic Breit-Wigner distribution successively decay to $P_1 P_2$ via strong interaction. Taking all lowest resonance states ($ρ, K^*, ω, ϕ$) into account, we calculate the branching fractions of these decay modes as well as the Breit-Wigner-tail effects for $B_{(s)} \to D_{(s)} (ρ,ω\to) KK$. Our results agree with the data by Babar, LHCb and Belle (II). Among the predictions that are still not observed, there are some branching ratios of order $10^{-6}-10^{-4}$ which are hopeful to be measured by LHCb and Belle II. Our approach and the perturbative QCD approach (PQCD) adopt the compatible theme to deal with the resonance contributions. What's more, our data for the intermediate two-body charmed $B$-meson decays in FAT approach are more precise. As a result, our results for branching fractions have smaller uncertainties, especially for color-suppressed emission diagram dominated modes.

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arXiv2023

Complete analysis on QED corrections to $B_{q}\, \to\, τ^+\, τ^-$

Motivated by a dynamical enhancement of the electromagnetic corrections by a power of $Λ_{\mathrm{QCD}}/m_b$ in $B_{d,s}\, \to\, μ^+\, μ^-$ at next-to-leading order (NLO), we extend the QED factorization effects on the leptonic $B$ meson decays with light muon leptons to tauonic final states, $B_{d,s} \, \to\, τ^+\, τ^-$, using soft-collinear effective theory (SCET). This extension is necessary owing to the appearance of the large $τ$ mass, which will lead to different power counting in SCET and also different results. We provide a complete NLO electromagnetic corrections to $B_{d,s} \, \to\, τ^+\, τ^-$, which include hard functions and hard-collinear functions below the bottom quark mass scale $μ_b$. The power enhanced electromagnetic effects from hard-collinear contributions on $B_{d,s}\, \to\, μ^+\, μ^-$ discussed before also exist in $B_{d,s} \, \to\, τ^+\, τ^-$. However the logarithm term arising from contributions of hard-collinear photon and lepton virtualities for $B_{d,s}\, \to\, τ^+\, τ^-$ is not large as it is in muon case due to the hard-collinear scale of $τ$ mass, which lead to only approximately $0.04\%$ QED corrections to the branching fraction of $B_{d,s} \, \to\, τ^+\, τ^-$ compared with overall reduction about $0.5\%$ in $B_{d,s}\, \to\, μ^+\, μ^-$.

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arXiv2023

Analysis of three-body charmless $B$-meson decays under the factorization-assisted topological-amplitude approach

We analyze quasi-two-body charmless $B$ decays $B_{(s)} \to P_1 V \to P_1 P_2 P_3$ with $V$ representing a vector resonant, and $P_{1,2,3}$ as a light pseudo-scalar meson, pion, kaon or $η^{(\prime)}$. The intermediate processes $B_{(s)} \to P_1 V $ are calculated in the factorization-assisted topological-amplitude approach and the vector resonant effects are described by the Breit-Wigner propagator, which successively decay to $P_1 P_2$ via strong interaction. Taking into account of all vector resonances in ground state, $ρ, K^*, ω, ϕ$, we present the related branching fractions, and calculate the virtual effects for $B_{(s)} \to π, K (ρ,ω\to) KK$. We also predict direct $\it{CP}$ asymmetries of three body B decay modes with $ρ, K^*$ resonances as intermediate states. Our predicted branching fractions of decay modes dominated by the color-favored tree diagram or the color-favored penguin diagram are consistent with the perturbative QCD approach's predictions as well as QCD factorization approach. While for those nonperturbative contribution dominated decay modes, the branching ratios in this work are in better agreement with current experimental data than the PQCD predictions and the QCD factorization results due to their shortage of the nonperturbative contributions or $1/m_b$ power corrections. Many of the decays channels, especially for direct $\it{CP}$ asymmetries, are waiting for the future experiments.

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arXiv2021

Analysis of three-body charmed B meson decays under the factorization-assisted topological-amplitude approach

We analyze the quasi-two-body charmed $B$ decays $B^{+,0}_{(s)} \to D_{(s)}^* P_2 \to D_{(s)} P_1 P_2$ with $P_{1,2}$ as a pion or kaon. The intermediate processes $B_{(s)} \to D_{(s)}^* P_2 $ are calculated with the factorization-assisted topological-amplitude approach and the resonant effects are calculated with the Breit-Wigner formalism. Taking all p-wave resonance states $ \bar D_{(s)}^*$ into consideration, we present the related branching fractions, calculate the Breit-Wigner-Tail effects, and investigate the flavor $SU(3)$ breaking effects. Most of our branching fractions are consistent with the perturbative QCD approach's predictions as well as the current experimental data. With more precision calculation of the intermediate two body charmed B meson decays, our quasi-two-body B decays calculation has significantly less theoretical uncertainty than the perturbative QCD approach. Many of those channels without any experimental data will be confronted with the future more accurate experiment measurements. Our results of the Breit-Wigner-tail effects also agree with the experimental very well. In $B^0$ decays this effect can reach approximately to $5\%$. It is also found that the Breit-Wigner-tail effects are not sensitive to the widths of their corresponding resonances. The flavor $SU(3)$ symmetry breaking effect is also investigated.

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arXiv2021

The factorization-assisted topological-amplitude approach and its applications

Heavy meson decays provide an important platform for studies of both QCD and electroweak dynamics, which may contain some portals to understanding of nonperturbative QCD and physics beyond the Standard Model. The factorization-assisted topological-amplitude approach was proposed to study two-body non-leptonic $D$ meson decays, where a promising QCD inspired approach from first principles is still missing. It was also applied to $B$ meson decays whose subleading power contributions are difficult to calculate. By factorizing topological amplitudes into short distance Wilson coefficients and long distance hadronic matrix elements either to be calculated or to be parameterized, it provides an effective framework to extract information of nonperturbative dynamics involved. With important flavor SU(3) breaking effects taken into account, the data of the decay branching ratios (and also CP asymmetries in $B$ decays) can be fitted well. The extracted amplitudes were further applied to make predictions for other observables, such as CP asymmetries in $D$ decays, mixing parameters in the $D^0-\bar{D}^0$ system, and so on. By this review, we will describe the formulation of the factorization-assisted topological-amplitude approach and summarize its applications in $D$ and $B$ meson decays and highlight some of its achievements.

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arXiv2021

Revisiting radiative leptonic $B$ decay

In this paper, we summarize the existing methods of solving the evolution equation of the leading-twist $B$-meson LCDA. Then, in the Mellin space, we derive a factorization formula with next-to-leading-logarithmic (NLL) resummation for the form factors $F_{A,V}$ in the $B \to γ\ellν$ decay at leading power in $Λ/m_b$. Furthermore, we investigate the power suppressed local contributions, factorizable non-local contributions (which are suppressed by $1/E_γ$ and $1/m_b$), and soft contributions to the form factors. In the numerical analysis, which employs the two-loop-level hard function and the jet function, we find that both the resummation effect and the power corrections can sizably decrease the form factors. Finally, the integrated branching ratios are also calculated for comparison with future experimental data.

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arXiv2020

The SVZ sum rules and the heavy quark limit for $Λ_{Q}$

In this work, we evaluate the accuracy of the leading order results in Shifman-Vainshtein-Zakharov (SVZ) sum rules and the leading power results in the heavy quark limit for the mass of $Λ_{Q}$. Up to dim-5 condensate contributions are considered. By comparing with the experimental results, we find that the leading order results in SVZ sum rules can reach about 5\% accuracy both for $Λ_{b}$ and $Λ_{c}$, and it seems that better results can be obtained from the sum rules of the heavy quark limit both for $Λ_{b}$ and $Λ_{c}$. We re-check that the SVZ sum rules in the heavy quark limit coincide with the HQET sum rules. As a byproduct, we also have an exploratory discussion on the $ud$ diquark in $Λ_{Q}$.

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arXiv2019

Extraction of the CKM phase $γ$ from charmless two-body B meson decays

Utilizing all the experimental measured charmless $B \to PP$, $PV$ decay modes, where $P(V)$ denotes a light pseudoscalar (vector) meson, we extract the CKM angle $γ$ by global fit. All the unknown hadronic parameters are fitted with $γ$ together from experimental data, so as to make the approach least model dependent. The different contributions for various decay modes are classified by topological weak Feynman diagram amplitudes, which are to be determined by the global fit. To improve the precision of this approach, we consider flavor SU(3) breaking effects of topological diagram amplitudes among different decay modes by including the form factors and decay constants. The fitted result for CKM angle $γ$ is $(69.8 \pm 2.1 \pm 0.9) ^{\degree}$. It is consistent with the current world average with a better precision.

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arXiv2018

Charged lepton flavor violating Higgs decays at future $e^+e^-$ colliders

After the discovery of the Higgs boson, several future experiments have been proposed to study the Higgs boson properties, including two circular lepton colliders, the CEPC and the FCC-ee, and one linear lepton collider, the ILC. We evaluate the precision reach of these colliders in measuring the branching ratios of the charged lepton flavor violating Higgs decays $H\to e^\pmμ^\mp$, $e^\pmτ^\mp$ and $μ^\pmτ^\mp$. The expected upper bounds on the branching ratios given by the circular (linear) colliders are found to be $\mathcal{B}(H\to e^\pmμ^\mp) < 1.2\ (2.1) \times 10^{-5}$, $\mathcal{B}(H\to e^\pmτ^\mp) < 1.6\ (2.4) \times 10^{-4}$ and $\mathcal{B}(H\to μ^\pmτ^\mp) < 1.4\ (2.3) \times 10^{-4}$ at 95\% CL, which are improved by one to two orders compared to the current experimental bounds. We also discuss the constraints that these upper bounds set on certain theory parameters, including the charged lepton flavor violating Higgs couplings, the corresponding parameters in the type-III 2HDM, and the new physics cut-off scales in the SMEFT, in RS models and in models with heavy neutrinos.

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arXiv2017

Global Analysis of Charmless $B$ Decays into Two Vector Mesons in Soft-Collinear Effective Theory

Under the framework of soft-collinear effective theory, we analyze the charmless $B\to VV$ decays in a global way at leading power in $1/m_b$ and leading order in $α_s$ with $V$ denoting a light vector meson. In the flavor SU(3) symmetry, decay amplitudes for the 28 decay modes are expressed in terms of 8 nonperturbative parameters. With 35 experimental results, we fit these 8 nonperturbative parameters. Annihilation contributions are neglected due to power suppression in the $m_b\to \infty$ limit, so we include in the fit the nonperturbative charm penguins, which will play an important role in understanding the direct CP asymmetries. Charming penguins are also responsible for the large transverse polarizations of penguin-dominated and color-suppressed decays. With the best fitted parameters, we calculate all possible physical observables of 28 decay modes, including branching fractions, direct CP asymmetries, and the complete set of polarization observables. Most of our results are compatible with the present experimental data when available, while the others can be examined on the ongoing LHCb experiment and the forthcoming Belle-II experiment. Moreover, the agreements and differences with results in QCD factorization and perturbative QCD approach are also discussed. A few observables are suggested to discriminate these different approaches.

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arXiv2017

Charmless Two-Body B Meson Decays In Factorization Assisted Topological Amplitude Approach

We analyze charmless two-body non-leptonic $B$ decays under the framework of factorization assisted topological amplitude approach. Unlike the conventional flavor diagram approach, we consider flavor $SU(3)$ breaking effect assisted by factorization hypothesis for topological diagram amplitudes of different decay modes, by factorizing out the corresponding decay constants and form factors. The non-perturbative parameters of topology diagram magnitudes $χ$ and strong phase $ϕ$ are universal that can be extracted by $χ^2$ fit from current abundant experimental data of charmless $B$ decays. The number of free parameters and the $χ^2$ per degree of freedom are both reduced comparing with previous analysis. With these best fitted parameters, we predict branching fractions and $CP$ asymmetry parameters of nearly 100 $B_{u,d}$ and $B_s$ decay modes. The long-standing $ππ$ and $πK$-$CP$ puzzles are solved simultaneously.

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arXiv2016

Analysis of Charmless Two-body B decays in Factorization Assisted Topological Amplitude Approach

We analyze charmless two-body non-leptonic B decays $B \to PP, PV$ under the framework of factorization assisted topological amplitude approach, where $P(V)$ denotes a light pseudoscalar (vector) meson. Compared with the conventional flavor diagram approach, we consider flavor $SU(3)$ breaking effect assisted by factorization hypothesis for topological diagram amplitudes of different decay modes, factorizing out the corresponding decay constants and form factors. The non-perturbative parameters of topology diagram magnitudes $χ$ and strong phase $ϕ$ are universal that can be extracted by $χ^2$ fit from current abundant experimental data of charmless B decays. The number of free parameters and the $χ^2$ per degree of freedom are both reduced comparing with previous analysis. With these best fitted parameters, we predict branching fractions and $CP$ asymmetry parameters of nearly 100 $B_{u,d}$ and $B_s$ decay modes. The long-standing $ππ$ and $πK$-$CP$ puzzles are resolved simultaneoulsy.

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arXiv2016

Two-body Charmed $B$ Meson Decays In Factorization Assisted Topological Amplitude Approach

We analyze the two-body charmed $B$ meson decays $B_{u,d,s} \to D^{(*)}P(V)$ in the factorization assisted topological amplitude approach, where $P(V)$ denoting a light pseudoscalar (vector) meson. Different from the conventional topological diagram approach, flavor $SU(3)$ symmetry breaking effects are taken into account. Therefore only four universal nonperturbative parameters are introduced to describe the contribution from non-factorization diagrams for all the decay channels. The number of free parameters and the $χ^2$ per degree of freedom are both significantly reduced comparing with the conventional topological diagram approach. With the 4 fitted parameters, we predict the branching fractions of 120 decay modes induced by both $b\to c$ and $b\to u$ transitions, which are well consistent with the measured data or to be tested on the future experiments. We also investigated the relative size of different topological diagrams, isospin violation, flavor $SU(3)$ symmetry breaking effects, compared with previous approaches.

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