arXiv subjects

Chia-Wei Liu

Publications and source records attributed to Chia-Wei Liu.

At least 37 records · Page 2Linked to original sources

arXiv2025

Precise measurement of CP violating $τ$ EDM through $e^+ e^- \to γ^*, ψ(2s) \to τ^+ τ^-$

A nonzero electric dipole moment of a tauon, $d_τ$, signals CP violation and provides an important probe for new physics. We study methods to measure $d_τ$ at low energy $e^+ e^-$ colliders through the processes $e^+e^- \to γ^*, ψ(2S) \to τ^+τ^-$ with $τ^\pm$ decays into a charged hadron and a tau neutrino. We point out that, with measuring energies of the charged hadron, Im$(d_τ)$ can be measured. On the other hand, selecting events of $τ$ decays after traveling more than the detector resolution distance, Re$(d_τ)$ can also be determined. We find that the precision at Super Tau-Charm Facility (STCF) running at the center energy of $m_{ψ(2S)}$ for 10 year data accumulation, the precision of Im$(d_τ)$ and Re$(d_τ)$ are found to be 1.8 and 11 in unit of $ 10^{-18}~e\,\text{cm}$, respectively. The sensitivity for $d_τ$ measurement precision at the STCF can be reached its optimum at a central energy of $6.3~\text{GeV}$, achieving a precision of $0.7$ for Im$(d_τ)$ and $2.8$ for Re$(d_τ)$ in unit of $ 10^{-18}~e\,\text{cm}$.

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arXiv2025

Two-body charmed baryon nonleptonic weak decays with decuplet baryon involving SU(3) breaking effects

We study the singly charmed baryon two-body decays of $\mathbf{B}_c \rightarrow \mathbf{B}_D P$ under $SU(3)_{F}$ flavor symmetry, where ${\bf B}_{c}$ refers to anti-triplet singly charmed baryons, and ${\bf B}_{D}$ and $P$ denote decuplet baryons and pseudoscalar mesons, respectively. Compared to the literature, we adopt a concise and reasonable treatment of the $SU(3)$ flavor symmetry breaking, by considering the final-state mass dependence of partial waves. With 4 real parameters in total and 9 experimental data points, we achieve a minimal $χ^2/\text{d.o.f.} $ value of $ 1.46$, providing a satisfactory explanation to the experiment results. We evaluate the branching ratios and Lee-Yang parameters suggesting the absence of the strong phase in $\mathbf{B}_c \rightarrow \mathbf{B}_D P$, along with an unusual positive decay asymmetry $α\,(Ξ_{c}^{0}\rightarrow Ω^{-}K^{+})$. The predicted results of large $SU(3)_{F}$ breaking effects in $\mathbf{B}_c \rightarrow \mathbf{B}_D P$ can be verified in the further research by the experiments at BESIII, Belle-II and LHCb.

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arXiv2024

Hidden strangeness in meson weak decays to baryon pair

Our study focuses on the weak decay of $ D_s^+ \to p \overline{n} $, which is the only possible two-body baryonic decay in the $ D $ meson system. An analysis using perturbative quantum chromodynamics (pQCD) is challenging in this decay due to the small amount of energy released. In particular, naive factorization, suppressed by the light quark masses, results in a minor contribution to this channel. In the framework of final state interactions, the hidden strangeness in the intermediate state naturally avoids this chiral suppression from light quark masses. The branching fraction is predicted to be $ {\cal B}(D_s^+ \to p\overline{n}) = (1.43 \pm 0.10) \times 10^{-3} $, in agreement with the experimental value of $ (1.22 \pm 0.11) \times 10^{-3} $. We also analyze the decays of $ B $ mesons into two charmed baryons involving annihilation-type topological diagrams. In these decays, we conduct a joint analysis of naive factorization and final state interactions. Using the experimental upper bound of $ {\cal B}(B_s^0 \to Λ_c^+ \overlineΛ_c^-) < 8 \times 10^{-5} $, we set a constraint on the coupling constant $ g_{D^+ Λ_c^+ n} < 7.5 $. Final state interactions lead to a prediction of the decay parameter $ γ(B_s^0 \to Λ_c^+ \overlineΛ_c^-) > 0.8 $, whereas pQCD predicts it to be negative. We propose future measurements of $ B^0 \to Ξ_c^+ \overlineΞ_c^- $, predicting a significant $ SU(3)_F $ breaking effect with $ \frac{{\cal B}(B^0 \to Ξ_c^+ \overlineΞ_c^-)}{{\cal B}(B_s^0 \to Λ_c^+ \overlineΛ_c^-)} = 1.4\% $, contrary to the naive estimate of $ 5.3\% $. We strongly recommend future measurements.

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arXiv2024

Impact of parity violation on quantum entanglement and Bell nonlocality

Quantum entanglement (QE), evidenced by Bell inequality (BI) violations, reveals the nonlocality of nature. Fundamental interactions manifest in various forms, each with distinct effects on QE and BI, but have not yet been studied in depth. We investigate in detail the relationship between QE, Bell nonlocality, and parity-violating interactions in spin-1/2 bipartite systems arising from the decays of spin-0 and spin-1 particles within the quantum field theory (QFT). Our findings reveal that parity (P) violation can completely disentangle particle pairs, rendering Bell tests ineffective in distinguishing between classical and quantum theories. In the spin-0 case, complete disentanglement occurs at maximal P violation, which is similarly true for spin-1 decays. Without restrictions from the QFT, the predicted relation between entanglement and the Bell nonlocality may no longer be valid and we propose promising methods for testing it. Additionally, we emphasize the previously overlooked influence of magnetic fields within detectors, which alters predictions for QE and Bell nonlocality. This environmental effect induces spurious P and charge-parity (CP) violations and thus has to be subtracted for genuine P, CP, and Bell tests.

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arXiv2024

The SM expected branching ratio for $h \to γγ$ and an excess for $h \to Z γ$

The recent measurements of $h \to Z γ$ from ATLAS and CMS show an excess of the signal strength $μ_Z = (σ\cdot{\cal B})_{\mathrm{obs}}/(σ\cdot{\cal B})_{\mathrm{SM}}=2.2\pm 0.7$, normalized as 1 in the standard model~(SM). If confirmed, it would be a signal of new physics (NP) beyond the SM. We study NP explanation for this excess. In general, for a given model, it also affects the process $h \to γγ$. Since the measured branching ratio for this process agrees well with the SM prediction, the model is severely constrained. We find that a minimally fermion singlets and doublet extended NP model can explain simultaneously the current data for $h \to Z γ$ and $h\to γγ$. There are two solutions. Although both solutions enhance the amplitude of $h \to Z γ$ to the observed one, in one of the solutions the amplitude of $h \to γγ$ flips sign to give the observ ed branching ratio. This seems to be a contrived solution although cannot be ruled out simply using branching ratio measurements alone. However, we find another solution that naturally enhances $h \to Z γ$ to the measured value, but keeps the amplitude of $h \to γγ$ close to its SM prediction. We also comment on the phenomenology associated with these new fermions.

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arXiv2024

Categorizing $SU(3)_f$ representations of scalar mesons by $J/ψ$ decays

The scalar mesons are established for a long time, but their nature is still an open question. In this paper, we investigate the potential of categorizing their $SU(3)_f$ representations via $J/ψ\to SV$ and $γS$, offering a criterion that may illuminate this issue. Here, $S$ ($V$) denotes scalar (vector) mesons. Using the $SU(3)_f$ symmetry with the current data, we find that $f_0(500)$ and $f_0(980)$ are mostly made of singlet and octet $SU(3)_f$ representations, respectively, with the singlet-octet mixing angle of $θ= (82.9\pm4.4)^{\circ}$. This conclusion is consistent with the caculations of the quark-antiquark ($q\bar{q}$) hypothesis. For the scalar mesons in the range of 1-2 GeV, we discuss the mixings between $q\bar{q}$ and glueballs. Our numerical results suggest that $f_0(1710)$ is likely composed of the scalar glueball. We urge our experimental colleagues to measure $J/ψ\to ρa_0(980,\ 1450,\ 1710), $ $ K^*(892)^{\pm} K^*(700,\ 1430,\ 1950)^{\mp}$ and $ωf_0(500)$, which provide useful information in the $SU(3)_f$ analysis.

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arXiv2024

New Signature of low mass $Z^\prime$ in $J/ψ$ decays

We explore a new approach to search for a low-mass $Z^{\prime}$ particle through $J/ψ$ decays by identifying its existence through parity-violating phenomena in the isospin-violating final states of $Λ\overlineΣ^{0}$ and the corresponding charge conjugated states of $\overlineΛΣ^{0}$. Our investigation centers on a generation-independent and leptophobic $Z^{\prime}$ with its mass below 10 GeV. Given the present experimental conditions at the Beijing Spectrometer III~(BESIII) and the anticipated opportunities at the Super Tau Charm Factory~(STCF), we conduct Monte-Carlo simulations to predict possible events at both facilities. Notably, we foresee a substantial enhancement in the precision of the lower limit estimation of $α_{\text{NP}}$ as well as a reduction in statistical uncertainty with upcoming STCF experiments. Furthermore, it is essential to highlight that a null result in the measurement of $α_{\text{NP}}$ would impose stringent constraints, requiring the $Z^{\prime}-q-q$ couplings to be on the order of $10^{-2}$.

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arXiv2024

Nonleptonic three-body charmed baryon weak decays with H(15)

We study the nonleptonic three-body charmed baryon weak decays of $\mathbf{B}_{c}\rightarrow\mathbf{B}_{n}PP^{\prime}$ under the $SU(3)_{F}$ flavor symmetry, where $\mathbf{B}_{c}$ denotes the anti-triplet charmed baryon, comprising $(Ξ^{0}_{c},-Ξ^{+}_{c},Λ^{+}_{c})$, and $\mathbf{B}_{n}$ and $P(P^{\prime})$ represent octet baryon and pseudoscalar meson states, respectively. In addition to 12 parameters from the contributions of the color-antisymmetric part of the effective Hamiltonian, denoted as $H(\bar{\mathbf{6}})$, there are 4 parameters from the color-symmetric one, $H(\mathbf{15})$, which were not included in the previous study. With 16 parameters in total and 28 experimental data points, we obtain the minimal $χ^2$ over degree of freedom of $χ^{2}/d.o.f=1.5$, which is a great improvement comparing to that without $H(\mathbf{15})$. With the better fitting values, we evaluate the branching ratios and up-down asymmetries of $\mathbf{B}_{c}\rightarrow\mathbf{B}_{n}PP^{\prime}$, which present some interesting results such as $\mathcal{B}\,(Λ^{+}_{c}\rightarrow(Ξ(1690)^{0}\rightarrowΣ^{+}K^{-})\,K^{+})\equiv(1.5\pm0.4)\times10^{-3}$ and potential $SU(3)$ breaking effects in $Ξ^{+}_{c}\rightarrow pπ^{+}K^{-}$ and $Λ^{+}_{c}\rightarrow Σ^{+}π^{-}K^{+}$ to be verified by the experiments at BESIII, Belle-II and LHCb.

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arXiv2024

Complete determination of $SU(3)_F$ amplitudes and strong phase in $Λ_c^+ \to Ξ^0 K^+$

The BESIII collaboration has recently reported the first time measurement of the decay asymmetry $α(Λ_c^+ \to Ξ^0 K^+) = 0.01 \pm 0.16(stat.) \pm 0.03(syst.)$ and also a sizable phase shift of $δ_P-δ_S = -1.55 \pm 0.25$ or $1.59\pm 0.25$ between S- and P-wave amplitudes. This implies significant strong phase shifts in the decay amplitudes. The strong phases indicate the existence of rescattering or loop effects, which are challenging to calculate due to non-perturbative effects. By employing the flavor $SU(3)_F$ symmetry and applying the Körner-Pati-Woo theorem to reduce the number of parameters, we find that the current data already allow us to obtain, for the first time, model-independent decay amplitudes and their strong phases. The establishment of the existence of sizable strong phases opens a window for future investigations into CP violation. In our fit, a notable discrepancy emerges in the branching ratio of $Ξ_c^0 \to Ξ^- π^+$. The direct relationship between $Γ(Λ_c^+ \to Λe^+ν_e)$ and $Γ(Ξ_c^0 \to Ξ^- e^+ν_e)$, along with newly discovered $SU(3)_F$ relations, collectively suggests an underestimation of $\mathcal{B}(Ξ_c^0 \to Ξ^- π^+)$ in experimental findings.

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arXiv2024

Nonleptonic two-body weak decays of charmed baryons

We analyze the two-body nonleptonic weak decays of charmed baryons, employing the pole approximation in tandem with the $SU(3)_F$ symmetry. We are able to make novel predictions for decay channels of $Ω_c^0 \to {\bf B}_n P$ and ${\bf B}_{cc}\to {\bf B}_c^{A,S} P$ based on the experimental data of ${\bf B}_c^A \to {\bf B}_n P$. Here, ${\bf B}_n$, ${\bf B}_{c}^A$, ${\bf B}_c^S$ and ${\bf B}_{cc}$ are the low-lying octet, antitriplet charmed, sextet charmed and doubly charmed baryons, respectively, and $P$ is the pseudoscalar meson. Our findings reveal that the fitted effective Wilson coefficient ${\cal C}_+=0.469$ is notably smaller than the naive expectation, and the low-lying pole approximation fails to account for ${\cal B}(Λ_c^+ \to n π^+ , Ξ^0 K^+)$, despite consistencies with the soft-meson limit. We further recommend the decay channel $Ξ_{cc}^+ \to Ξ_c^0 π^+ \to Ξ^- π^+π^+π^+π^-$ for exploring evidence of $Ξ_{cc}^+$, estimating the branching fraction at $(1.1\pm 0.6)\times 10^{-3}$.

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arXiv2023

Isospin violating decays of vector charmonia

We study the isospin violating decays of vector charmonia to $Λ\overlineΣ^0$ and its charge conjugate. They are dominated by the single photon annihilation and can be evaluated reliably with timelike form factors. We utilize the quark-pair creation model, which is valid for the OZI suppressed decays, to evaluate the form factors. We obtain the branching fractions of ${\cal B}(J/ψ\toΛ\overlineΣ^0+c.c.)=(2.4\pm0.4)\times10^{-5}$ and ${\cal B}(ψ(2S)\toΛ\overlineΣ^0+c.c.)=(3.0\pm0.5)\times10^{-6}$, which are compatible with the measurements by the BESIII collaborations, respectively. The decay asymmetries are found to be $α_{J/ψ}=0.314$ and $α_{ψ(2S)}=0.461$, which can be examined at BESIII in the foreseeable future.

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arXiv2023

Study of singly heavy baryon lifetimes

We study the inclusive decay widths of singly heavy baryons with the improved bag model in which the unwanted center-of-mass motion is removed. Additional insight is gained by comparing the charmed and bottom baryons. We discuss the running of the baryon matrix elements and compare the results with the non-relativistic quark model (NRQM). While the calculated two-quark operator elements are compatible with the literature, those of the four-quark ones deviate largely. In particular, the heavy quark limit holds reasonably well in the bag model for four-quark operator matrix elements but is badly broken in the NRQM. We predict $1-τ(Ω_b)/ τ(Λ_b^0) = (8.34\pm2.22)\%$ in accordance with the current experimental value of $(11.5^{+12.2}_{-11.6})\%$ and compatible with $(13.2\pm 4.7)\%$ obtained in the NRQM. We find an excellent agreement between theory and experiment for the lifetimes of bottom baryons. We confirm that $Ω_c^0$ could live longer than $Λ_c^+$ after the dimension-7 four-quark operators are taken into account. We recommend to measure some semileptonic inclusive branching fractions in the forthcoming experiments to discern different approaches. For example, we obtain ${\cal BF} (Ξ_c^+ \to X e^+ ν_e) = (8.57\pm 0.49)\% $ and ${\cal BF} (Ω_c^0 \to X e^+ ν_e) = (1.88\pm 1.69)\% $ in sharp contrast to ${\cal BF} (Ξ_c^+ \to X e^+ ν_e) = (12.74^{+2.54}_{-2.45})\% $ and ${\cal BF} (Ω_c^0 \to X e^+ ν_e) = (7.59^{+2.49}_{-2.24})\% $ found in the NRQM.

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arXiv2023

Anatomy of $Λ_c^+$ semileptonic decays

We present a systematic study of $Λ_c^+ \to {\cal B}_q \ell^+ ν_\ell $ with ${\cal B}_q = (Λ, n)$ and $\ell =( e, μ)$, examining all the possible decay observables based on the homogeneous bag model (HBM) and lattice QCD (LQCD). With the HBM, we find that the branching fractions and polarization asymmetries of the daughter baryon $Λ$ are ${\cal B}(Λ_c^+ \to Λe^+ ν_e, Λμ^+ ν_μ, n \ell ^+ ν_\ell ) = (3.78 \pm 0.25, 3.67\pm 0.23, 0.40\pm 0.04 )\%$ and $α_Λ(Λ_c^+ \to Λe^+ ν_e,Λμ^+ ν_μ) =(-82.6,-82.3)\%$, respectively. From the LQCD, we obtain that $α_Λ(Λ_c^+ \to Λe^+ ν_e, μ^+ ν_μ) = (-87.4\pm 1.0,-87.2\pm 1.0)\%$. We also explore the time-reversal asymmetries due to new physics beyond the standard model. All our results are consistent with the current experimental data, while some of them are accessible to the experiments at BESIII and Belle II.

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arXiv2023

CP asymmetries in $B$ meson two-body baryonic decays

We study the CP-odd and CP-even observables of the $B$ mesons decaying into a baryon and antibaryon. We estimate these observables through the $^3P_0$ model and chiral selection rule. The decay branching ratios of $ B^+ \to p \overlineΛ$ and $ B^0 \to p \overline{p}$ are calculated to be $2.31 \times 10^{-7}$ and $1.27 \times 10^{ -8} $, which are consistent with the current experiments, respectively. The effects of the $B-\overline{B}$ oscillations are considered, which largely suppress the direct CP asymmetries in the $B_s^0$ decays. We suggest the experiments to visit $B_s^0 \to Λ(\to p π^-) \overlineΛ (\to \overline{ p} π^+) $, where the time-averaged CP-odd observables are estimated to be large. The direct CP asymmetries of $B^+ \to p \overlineΛ$ and $B^0 \to p\overline{p}$ are found to be $26.2\%$ and $-3.1\%$ for a positive strong phase and $-36.9\%$ and $4.2\%$ for a negative strong phase, respectively.

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arXiv2023

Heavy quark symmetry of $Λ_b^0$ decays in quark models

We study the heavy quark symmetry with the homogeneous bag model (HBM) and light-front quark model (LFQM) based on the decays of $Λ_b^0\toΛ_c^+\ell^-\overlineν_\ell~(\ell=e,μ,τ)$. In particular, we calculate various parameters in the heavy quark expansions, including the Isgur-Wise functions and their first order corrections. The parameters in the HBM are fitted from the mass spectra, while the ones in the LFQM are tightly constrained by the heavy quark symmetry, granting the predictive power of our results. We explicitly obtain that ${\cal B}(Λ_b^0\toΛ_c^+e^-\overlineν_e)=(5.69\pm 0.58, 5.35\pm 0.50)$, ${\cal B}(Λ_b^0\toΛ_c^+μ^-\overlineν_μ)=(5.67\pm 0.58 $, $5.33\pm 0.49)$, and $Γ(Λ_b^0\toΛ_c^+τ^-\overlineν_τ)/Γ(Λ_b^0\toΛ_c^+μ^-\overlineν_μ)=(0.3243\pm 0.0126$, $ 0.3506\pm 0.0046)$ for the numerical values of (HBM, LFQM). Our results of the branching fractions in both models agree well with the experimental data and lattice QCD calculations. In addition, we find that the hard gluon corrections decrease the branching fractions around $10\%$.

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arXiv2023

Resolving puzzle in $Ξ_c^0\to Ξ^-e^+ν_e$ with $Ξ_c-Ξ_c'$ mixing

We study the ratio of $R=2 Γ(Ξ_c^0 \to Ξ^- e^+ ν_e )/3Γ(Λ_c^+ \to Λe^+ ν_e )$, which is found to be $R= 1 (0.8)$ from the exact (broken) $SU(3)$ flavor symmetry, in sharp contrast to the average value of $R_{av}=0.59\pm 0.10 $ from the ALICE collaboration and lattice QCD results. We propose to use the mixing of $Ξ_c-Ξ_c'$ to resolve the puzzle. With the model-independent mass relations, we find that the mixing angle is $|θ_c| = 0.137(5)π$, which suppresses $Ξ_c\to Ξe^+ ν_e$ about $20\%$ model-independently, resulting in $R\approx 0.6$ with the $SU(3)$ flavor breaking effect. We explicitly demonstrate that $R= 0.70 \pm 0.09$ from the bag model, which is also consistent with $R_{av}$. To test the mixing mechanism, we recommend the experiments to measure the decays of $Ξ_c \to Ξ'(1530) e^+ ν_e$, whose branching fractions are determined to be $ ( 4.4\sim 8.7)\times 10^{-3}$ and $(1.3\sim 2.6 )\%$ for $Ξ_c^0$ and $Ξ_c^+$, respectively, but vanish without the mixing. In addition, nonvanishing values of ${\cal B}(Ξ_c^+\to Ξ^{\prime 0} (1530)π^+ )$ and ${\cal B}(Ξ_c^+\to Σ^{\prime +} (1530) \overline{K}^0 )$ will also be evidences of the mixing based on the Köner-Pati-Woo theorem, which are calculated as $(3.8\sim 7.5)\times 10^{-3}$ and $(6.6\sim 13)\times 10 ^{-4}$, respectively. We emphasize that $θ_c$ is sizable and should be given serious considerations in future studies on the heavy baryon systems.

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arXiv2023

Nonleptonic decays of $Ξ_{cc}\to Ξ_c π$ with $Ξ_c-Ξ_c'$ mixing

Aiming on testing the $Ξ_c-Ξ_c'$ mixing, we study the decays of $Ξ_{cc}\to Ξ_c π$ with $Ξ_{cc} = (Ξ_{cc}^{++} , Ξ_{cc} ^+ )$, $Ξ_c = (Ξ_c^{(\prime)+},Ξ_c^{(\prime)0})$ and $π= (π^+ , π^0)$. The soft-meson limit is considered along with the pole model, and the baryon matrix elements are evaluated by the bag model with and without removing the center-of-mass motion (CMM). We find that the four-quark operator matrix elements are about twice larger once the unwanted CMM is removed. We obtain that ${\cal R} = {\cal B}(Ξ_{cc}^+ \to Ξ_c^{\prime +} π^+ )/ {\cal B}(Ξ_{cc}^+ \to Ξ_c^{ +} π^+ ) = 0.87^{+0.17}_{-0.11} $ and $1.45$ with and without removing the CMM, where the former is close to the lower bound and the later is well consistent with ${\cal R} = 1.41 \pm 0.17 \pm 0.10$ measured at LHCb. In addition, we show that after including the mixing, the up-down asymmetry of $α( Ξ_{cc}^+ \to Ξ_c^{(\prime)0 } π^+)$ flips sign. Explicitly, we obtain that $α(Ξ_{cc}^{+} \to Ξ_c^{\prime +} π^0) = 0.52$ and $α(Ξ_{cc}^{+} \to Ξ_c^{ 0 } π^+) = 0.31$ with and without the CMM corrections, respectively, which are all negative if the mixing is absence. As a bonus, a positive value of $α(Ξ_{cc}^{+} \to Ξ_c^{\prime 0} π^+)$ in experiments can also serve as the evidence of the $W$-exchange contributions.

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arXiv2022

Bottomed baryon decays with invisible Majorana fermions

We study the invisible Majorana fermions of $χ$ in bottomed baryon decays with flavor-changing neutral currents (FCNCs) based on the model-independent effective Lagrangian between the quarks and invisible particles. From the bounds of the coupling constants extracted from the experiments, we examine the decay branching ratios of $Λ_b\toΛχχ$, $Ξ_b^{0(-)}\toΞ^{0(-)}χχ$, $Λ_b\to n χχ$, $Ξ_b^{-}\to Σ^{-} χχ$, $Ξ_b^{0}\to Σ^{0} χχ$, and $Ξ_b^{0}\to Λχχ$, which can be as large as $6.3,~9.2,~5.7,~5.8,~2.7$, and $1.0\times10^{-5}$ for $m_χ=2$ GeV, respectively. Some of these decays are accessible to the future experimental searches, such as Belle II.

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