arXiv subjects

Zhi-Peng Xing

Publications and source records attributed to Zhi-Peng Xing.

At least 19 recordsLinked to original sources

arXiv2026

Decoding the Amplitude Pair with Distinct CPV Phases in Charmed Baryon Decays

In this Letter, we propose a strategy to extract information on the hierarchical amplitude pair in singly Cabibbo-suppressed (SCS) charmed baryon two-body decays, with a dominant amplitude proportional to $λ_s = V_{cs}^* V_{us}$ from tree operators and sub-leading one proportional to $λ_b = V_{cb}^* V_{ub}$ from both penguin and tree contributions. The coexistence of these two amplitudes is essential for generating nonzero CP violation (CPV) effects. Since the $λ_b$ amplitude is strongly suppressed, its experimental determination is highly challenging. However, by exploiting SU(3) flavor symmetry, which relates the well-measured Cabibbo-favored (CF) amplitudes to the SCS tree amplitudes, information on the $λ_b$ amplitude can be extracted. Using current experimental data, a conservative analysis yields $λ_b$ amplitudes can be as large as about $10\%$ of the corresponding tree amplitudes with a significance of $2.1σ$. In addition, the Lee-Yang parameters of these decays provide an independent probe of this elusive term. We further identify two golden decay channels, $Ξ_c^0 \to p K^-$ and $Ξ_c^0 \to Σ^+ π^-$, which are particularly well suited for experimental studies of CPV.

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arXiv2026

Unraveling weak radiative hyperon decays with broken flavor symmetry

We present a broken $SU(3)$ flavor analysis of weak radiative decays of spin-1/2 hyperons, incorporating current-current and electromagnetic-penguin contributions as well as charge- and mass-insertion effects. Six independent reduced amplitudes describe all decay channels, while a minimal relation between the parity-conserving and parity-violating form factors reduces to eight free parameters. A global fit to the ten available observables yields $χ^2/\mathrm{d.o.f.}=0.98$ and accommodates the large negative asymmetry in $Σ^+\to pγ$. The resulting nonzero effective form factor $g_{b_8}$ provides a possible flavor-symmetry realization of the parity-violating amplitude while remaining compatible with Hara's theorem, which constrains the current-current contribution in the exact symmetry limit. Our analysis favors a sizable negative value of $α_γ(Ξ^- \to Σ^- γ)$, which differs from the current experimental result by approximately $1.3σ$. Future precision measurements of this observable will provide a decisive test of this prediction.

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arXiv2026

Angular distribution of $Λ_c^+ \to Λ^*_{1405/1520}(\toΣπ)\ell^+ν_\ell$ and implications for form factors

We study the cascade semileptonic decay $Λ_c^+\toΛ^*_{1405/1520}(\toΣπ)\ell^+ν_\ell$ using the helicity amplitude formalism, and derive the full four-body angular distribution. The contributions from the spin-$1/2$ and spin-$3/2$ intermediate resonances, their interference effects, and the corresponding angular coefficients are obtained explicitly. Using available form-factor inputs, we provide numerical predictions for the invariant-mass distribution, helicity-angle distributions, and angular asymmetries. Based on these observables, we discuss strategies for extracting the relevant form factors and analyze the sensitivity of the angular observables to variations in the form factors. Finally, we investigate the strong phases in the $Λ_c^+\toΛ^*$ form factors and discuss how the strong-phase difference can be extracted from the angular distribution. Our results offer useful theoretical guidance for future experimental analyses.

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arXiv2025

Predictions for CP violation in anti-triplet beauty baryon to charmonium decays

Motivated by the recent 3.9$σ$ evidence for CP violation from the LHCb collaboration in decays of an anti-triplet beauty baryon to a charmonium, an octet baryon, and a pseudoscalar meson, we perform, for the first time, a systematic analysis of this class of decays within the framework of flavor $SU(3)$ symmetry. Several predictions for branching ratios and CP violating relations which can be tested in future experiments are found, in particular $ΔA_{CP} = A_{CP}(Λ_b^0 \to p π^- J/ψ) - A_{CP}(Λ_b^0 \to p K^- J/ψ) = A_{CP}(Λ_b^0 \to n π^0 J/ψ) - A_{CP}(Λ_b^0 \to (n K_S, n K_L) J/ψ)$. Our results provide guidance to test the availability of $SU(3)$ symmetry and search for possible CP violation effects in this class of decays.

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arXiv2025

Implications of recent LHCb data on CPV in b-baryon four body decays

Motivated by the recent CPV observation, we investigate the CPV of b-baryon charmless four body decays under the U-spin symmetry. However, we find that only U-spin symmetry cannot provide effective predictions, particularly for $Λ_b$ decays. For giving more useful predictions, we also give a simple dynamic analysis. By counting the power($λ=\sqrt{\frac{Λ_{QCD}}{m_b}}$) of each topological diagram, we find that for the specific decay $B_b^2\to R(B_1^2 M^2 M^{\bar 2})M^2$, only one U-spin amplitude can contribute in the leading power, while for $B_b^2\to R(B_1^2 M^2)R( M^{\bar 2}M^2)$, only two U-spin amplitudes can contribute in this leading power. Then the most effective prediction can be given as \begin{align} &A_{CP}^{dir}(Λ_b^0 \to R( p π^- π^+ )π^-) = (-12.99 \pm 2.83\pm2.59\pm0.65)\%,\notag \end{align} Considering the $Λ_b$ can effectively produced in LHCb, we strongly encourage a more precise experimental investigation of it.

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arXiv2025

Probing $B^+ \to K^+$ semi-leptonic FCNC decay with new physics effects under PQCD approach

Recently, the Belle II Collaboration reported the branching fraction $\mathcal{B}(B^+ \to K^+ ν\barν)=(2.3\pm0.7)\times10^{-5}$ with a significance of $3.5σ$, which is $2.7σ$ above the SM expectation. Motivated by this measurement, we calculate this decay channel at the NLO and twist-3 level using the PQCD approach. By combining the lattice QCD data and our results, we obtain form factors with improved accuracy. Using these form factors, we precisely estimate the branching ratios of $B^+ \to K^+$ semileptonic FCNC decays, including $B^+ \to K^+ν\barν$ and $B^+ \to K^+\ell^+\ell^-$. To explain the anomalies in these two processes, we introduce a leptoquark model as a new physics scenario. Using five possible types of leptoquarks, we successfully explain the latest experimental measurements, and further constraints on the leptoquarks are derived.

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arXiv2025

SU(3) flavor symmetry analysis of hyperon non-leptonic two body decays

This paper present a systematic study of hyperon non-leptonic two-body decays induced by light quark transitions, particularly the $s \rightarrow u\bar{u}d$ process, within the framework of SU(3) flavor symmetry. The effective weak Hamiltonian is decomposed into irreducible SU(3) representations, including the 27-plet and octet components, and applied to analyze decays of octet and decuplet baryons and charmed baryons. Both the irreducible representation amplitude (IRA) approach and the topological diagrammatic analysis (TDA) are employed to construct decay amplitudes and constrain the parameter space. SU(3) symmetry-breaking effects arising from the strange quark mass are incorporated systematically. A global fit to current experimental data allows us to extract form factors and predict branching ratios and asymmetry parameters for several decay channels, including $Λ^0 \rightarrow pπ^-$, $Σ^+ \rightarrow pπ^0$, and $Ω^- \rightarrow Ξ^0π^-$. Our results demonstrate the predictive power of SU(3) flavor symmetry while highlighting significant symmetry-breaking effects, especially in amplitudes related to the 27-plet. Notably, the $Σ^+ \rightarrow pπ^0$ decay channel exhibits a deviation exceeding $1σ$ from experimental measurements, suggesting the possible presence of new decay mechanisms or contributions beyond the Standard Model. This work provides a systematic framework for future tests of the Standard Model and the search for new physics in hyperon decays.

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arXiv2025

Towards the strong decays of light strange four-quark states with $J^P=1^+$

This thesis considers the decays of fully light four quark exotic as the main subject. In the context, we study the possible decays from general symmetric analysis: $uu\bar d\bar s$, $dd\bar s\bar u$, $ds\bar u \bar u$, and $su\bar d \bar d$. Using the light quark flavor symmetry, we discuss the decay modes of decuplet and 27 multiplet with $J^P=1^+$. Further more, the phenomenological hadronic molecular approach is employed for the calculation of respective decay modes. Our results show that the total decay widths of $T_{ρK}$ and $S_{ρK^*}$ can reach several MeV. The two-body and three-body decay widths are further obtained respectively. These are excepted to be fairly valuable supports for future search experiments.

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arXiv2025

Probing ALP couplings to electroweak gauge bosons

Motivated by the more and more abundant experimental data, we revisit the couplings of axion-like particle (ALP) to electroweak gauge bosons across the ALP mass range from MeV to 100 GeV. The current and future experimental limits on the couplings are extended. The ALP coupling to $W$-bosons gives rise to flavor-changing ALP-quark couplings at the one-loop level. These flavor-changing couplings deserve further investigation under current experimental constraints, especially those stemming from rare meson decays and neutral meson mixing processes. Additionally, flavor-conserving couplings of the ALP to Standard Model (SM) fermions arise at the one-loop level as well from ALP-electroweak gauge boson couplings, even in the absence of tree-level couplings to these SM fermions, with consequent ALP decays to the SM fermions leading to constraints on the ALP-electroweak gauge boson couplings. We also investigate processes relevant to $Z$-boson measurements, such as the invisible decay $Z\to aγ$, subsequent decays $Z\to 3γ$ and $Z\to γll$, as well as constraints from oblique parameters ($S,\, T,\, U$). Our study highlights that rare two-body decays of pseudoscalar mesons offer the most sensitive probes of ALP couplings to electroweak gauge bosons from the loop-induced flavor-violating interactions for ALP masses below the kinematic threshold, while $Z$-boson decays complementarily explore larger ALP masses. Future lepton colliders, such as CEPC and FCC-ee operating at the $Z$-pole, along with SHiP, provide further opportunities to probe ALP couplings to electroweak gauge bosons.

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arXiv2025

Analysis of Charmed Baryon Decays with Strong Phases under SU(3) Symmetry

The SU(3) analysis is considered a powerful tool in charmed baryon decays. Motivated by recent measurements of anti-triplet charmed baryon two-body decays from the Belle, Belle II, and BESIII Collaborations, we have finally determined the last two IRA form factors, $f^{a\prime}$ and $g^{a\prime}$, which were absent in previous work. By considering both real and complex form factor cases in our work, we find that the phases of the form factors are necessary and that complex form factors can explain the experimental data well. Using the fitted form factors, we further numerically study the equivalence of the SU(3) irreducible representation amplitude (IRA) and topological diagrammatic approach (TDA) methods. We find that the IRA and TDA methods can be numerically equivalent with the addition of the new form factors. Based on the conclusions above, and considering some interesting scenarios, the CP violation effects can be predicted in these processes at the order of $O(10^{-3})$. This suggests a promising opportunity to observe CP violation for the first time in charmed baryon decays. Although our predictions depend on some assumptions, considering that the experimental data is far from sufficient to determine CPV through SU(3) analysis, our study is meaningful and instructive for observing CPV at experimental facilities.

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arXiv2024

Implications on CP violation of charmless three body decays of bottom baryon from the U-spin analysis

Motivated by recent LHCb measurements of CP violation in $Λ_b$ three-body decays, we conduct an analysis of CP asymmetry in three-body decays of bottom baryons utilizing U-spin symmetry. We first develop a convenient representation that facilitates the incorporation of U-spin symmetry into our analysis. By integrating weak and strong phases into the derived amplitude, we obtain the CP asymmetry and establish relationships between CP asymmetries in U-spin related decay channels. With the help of experimental measurements, we provide numerical predictions for the CP asymmetries for other decay channels, particularly $Λ_b \to Σ^0 K^+ K^-$, $Ξ^0_b \to Λπ^+ π^-$, $Λ_b \to Σ^0 K^+ π^-$, and $Ξ^0_b \to ΣK^- π^+$. Furthermore, we provide a quantity that can be used as a null test of standard model and deviations from 0 will reflect the possible new physics. These results are valuable for CPV measurements in baryon decays, and can be tested in future experiments.

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arXiv2024

SU(3) symmetry analysis in charmed baryon two body decays with penguin diagram contribution

An increasing number of experimental measurements from the BESIII, Belle, and Belle-II collaborations encourage investigations into charmed baryon two-body decay processes. By including contributions from the penguin diagrams that are ignored in previous studies, we perform a global analysis with SU(3) flavor symmetry. Assuming all form factors are real, we achieve a remarkable minimal $χ^{2}/d.o.f = 0.788$ and find that the contribution of the amplitude proportional to $V_{cb}^*V_{ub}$ is of the order $\sim 0.01$, comparable with the contribution of the tree-level diagram. Additionally, by using the KPW theorem to reduce the number of amplitudes from 13 to 7 in the leading contribution, it becomes possible to consider the complex form factor case for the leading IRA amplitude in the global analysis. However, the analysis of complex form factors significantly conflicts with the experimental data $Br(Ξ_c^0\toΞ^-π^+)$, and by excluding this data, $χ^2/d.o.f$ is reduced from 5.95 to 1.19. Although the analysis of complex form factors shows a significant central value of the penguin diagram contribution, the large errors from the corresponding form factors make it a challenge to precisely determine its true contribution. Consequently, the direct CP violation in decay processes is predicted to be approximately zero. With more data in future experiments, the penguin diagram contribution with the amplitude proportional to $V_{cb}^*V_{ub}$ will be precisely determined, allowing for a more accurate prediction of CP violation. Our analysis necessitates further theoretical investigations and experimental measurements in the future.

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arXiv2024

Test of Bell Locality Violation in Flavor Entangled Neutral Meson Pair

The quasi-spin entanglement of neutral mesons to test the Bell nonlocality is systematically studied. In the case of CP violation, the concrete expression of the Bell inequality for entangled neutral meson pairs is derived. The violation of Bell inequality in the oscillations of $B_d^0-\bar{B}_d^0$, $B_s^0-\bar{B}_s^0$, $D^0-\bar{D}^0$ and $K^0-\bar{K}^0$ meson pair systems are found at certain evolution time including the latest experimental data. Our study is helpful for studying CP-violating involved flavor entanglement and testing Bell inequality violation in the current and future high energy experiment facilities.

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arXiv2024

Heavy baryon decays into light meson and dark baryon within LCSR

We studied the decays of Heavy baryon into a pseudoscalar meson and a dark baryon in the recently developed $B$-Mesogenesis scenario, where the two types of effective Lagrangians proposed by the scenario are both considered. The decay amplitudes of $Λ_b^0$ are calculated by light-cone sum rules using its light-cone distribution amplitudes. The decay amplitudes of $Ξ_b^{0,\pm}$ are related with those of $Λ_b^0$ through a flavor SU(3) analysis. The uncertainties of threshold parameter and the Borel parameter are both considered in the numerical calculation. The values of effective coupling constants in the $B$-Mesogenesis are taken as their upper limits that obtained from our previous study on the inclusive decay. The upper limits of the decay branching fractions are presented as functions of the dark baryon mass.

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arXiv2024

Light baryon in three quark picture light front approach and its application: hyperon weak radiative decays

Motivated by recent experimental data on $Σ^+\to pγ$ at BESIII, we investigate a class of hyperon weak radiative decays. To estimate these processes, in our research, we employ a new type of light-front quark model with a three-quark picture for octet baryons. In the three-quark picture, with the use of $SU(3)_f$ and spin symmetries, we present a general form of the light front wave function for each octet baryon. By including contributions from the penguin diagram and W exchange diagram, we perform a complete calculation on the branching ratios ($Br$) and the asymmetry parameter ($α$) for hyperon weak radiative decay processes. Our results are helpful for discovering additional hyperon weak radiative decay processes in experimental facilities, and our research will promote the theoretical study of baryons.

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arXiv2023

Dark photon effects with the kinetic and mass mixing in Z boson decay processes

Motivated by the most recent measurement of tau polarization in $Z\to τ^+τ^-$ by CMS, we have introduced a new $U(1)_X$ gauge boson field X, which can have renormalizable kinetic mixing with the standard model $U(1)_Y$ gauge boson field Y. In addition to the kinetic mixing of the dark photon, denoted as $σ$, there may also be mass mixing introduced by the additional Higgs doublet with a vacuum expectation value (vev) participating in $U(1)_X$ and electroweak symmetry breaking simultaneously. The interaction of the Z boson with the SM leptons is modified by the introduction of the mixing ratio parameter $ε$, which quantifies the magnitude of both the mass and kinetic mixing of the dark photon. Initially, we use the tau lepton as an example to explore the Z boson phenomenology of the dark photon model with both kinetic and mass mixing. The goal is to determine the allowed parameter regions by taking into account constraints from the vector and axial-vector couplings $g_{V,A}^τ$, the decay branching ratio $Br(Z\to τ^- τ^+)$ and tau lepton polarization in $Z\to τ^-τ^+$. We found that the mixing ratio plays important role in the Z boson features by choosing different $ε$ values. Furthermore, we aim to generalize our analysis from the tau-lepton case to include all fermions by conducting global fits. This allows us to identify viable regions by incorporating relevant fermion constraints and the W/Z mass ratio. Correspondingly, we obtain the fit results with the kinetic mixing parameter $σ=0.074\pm0.021$, mixing ratio $ε=-1.37\pm0.46$, and dark photon mass $m_X=275\pm39$ GeV. Our global analysis indicates a preference for a dark photon mass larger than $m_Z$.

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arXiv2023

On the four-quark operator matrix elements for the lifetime of $Λ_{b}$

Heavy quark expansion can nicely explain the lifetime of $Λ_{b}$. However, there still exist sizable uncertainties from the four-quark operator matrix elements of $Λ_{b}$ in $1/m_{b}^{3}$ corrections, which describe the spectator effects. In this work, these four-quark operator matrix elements are investigated using full QCD sum rules for the first time. At the QCD level, contributions from up to dimension-6 four-quark operators are considered. Our method of calculating high-dimensional operator matrix elements is promising to be used to resolve the $Ω_{c}$ lifetime puzzle.

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arXiv2023

Global analysis of measured and unmeasured hadronic two-body weak decays of antitriplet charmed baryons

A large amount of data on hadronic two body weak decays of anti-triplet charmed baryons $T_{c\bar 3}$ to an octet baryon $T_8$ and an octet or singlet pseudoscalar meson $P$, $T_{c \bar 3} \to T_8 P$, have been measured. The SU(3) flavor symmetry has been applied to study these decays to obtain insights about weak interactions for charm physics. However not all such decays needed to determine the SU(3) irreducible amplitudes have been measured forbidding a complete global analysis. Previously, it has been shown that data from measured decays can be used to do a global fit to determine all except one parity violating and one parity conserving amplitudes of the relevant SU(3) irreducible amplitudes causing 8 hadronic two body weak decay channels involving $Ξ^0_c$ to $η$ or $η'$ transitions undetermined. It is important to obtain information about these decays in order to guide experimental searches. In this work using newly measured decay modes by BESIII and Belle in 2022, we carry out a global analysis and parameterize the unknown amplitudes to provide the ranges for the branching ratios of the 8 undetermined decays. Our results indicate that the SU(3) flavor symmetry can explain the measured data exceptionally well, with a remarkable minimal $χ^2/d.o.f.$ of 1.21 and predict 80 observables in 45 decays for future experimental data to test. We then vary the unknown SU(3) amplitudes to obtain the allowed range of branching ratios for the 8 undetermined decays. We find that some of them are within reach of near future experimental capabilities. We urge our experimental colleagues to carry out related searches.

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