arXiv subjects

Yu-Kuo Hsiao

Publications and source records attributed to Yu-Kuo Hsiao.

30 records · Page 2Linked to original sources

arXiv2021

Semileptonic $B^{-}\toπ^{+}π^{-}\ell^{-}\barν_\ell$ decay with $ππ$ invariant mass spectrum

BELLE has recently reported the measurement of the branching fraction of the semileptonic $B^{-}\toπ^{+}π^{-}\ell^{-}\barν_\ell$ decay, where $\ell$ represents an electron or a muon. With the new information on the $ππ$ invariant mass spectrum, we extract $|V_{ub}|=(3.31\pm 0.61)\times 10^{-3}$ in agreement with those from the other exclusive $B$ decays. In particular, we determine the non-resonant $B\toππ$ transition form factors, and predict the non-resonant branching fraction ${\cal B}(B^{-}\toπ^{+}π^{-}\ell^{-}\barν_\ell)=(3.5\pm 1.4^{+4.3}_{-2.4})\times 10^{-5}$, which is accessible to the BELLEII and LHCb experiments.

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arXiv2020

Charmed $Ω_c$ weak decays into $Ω$ in the light-front quark model

More than ten $Ω_c^0$ weak decay modes have been measured with the branching fractions relative to that of $Ω^0_c\toΩ^-π^+$. In order to extract the absolute branching fractions, the study of $Ω^0_c\toΩ^-π^+$ is needed. In this work, we predict ${\cal B}_π\equiv {\cal B}(Ω_c^0\toΩ^-π^+)=(5.1\pm 0.7)\times 10^{-3}$ with the $Ω_c^0\toΩ^-$ transition form factors calculated in the light-front quark model. We also predict ${\cal B}_ρ\equiv {\cal B}(Ω_c^0\toΩ^-ρ^+)=(14.4\pm 0.4)\times 10^{-3}$ and ${\cal B}_e\equiv{\cal B}(Ω_c^0\toΩ^-e^+ν_e)=(5.4\pm 0.2)\times 10^{-3}$. The previous values for ${\cal B}_ρ/{\cal B}_π$ have been found to deviate from the most recent observation. Nonetheless, our ${\cal B}_ρ/{\cal B}_π=2.8\pm 0.4$ is able to alleviate the deviation. Moreover, we obtain ${\cal B}_e/{\cal B}_π=1.1\pm 0.2$, which is consistent with the current data.

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arXiv2020

$SU(3)$ Flavor Symmetry for Weak Hadronic Decays of ${\bf B}_{bc}$ Baryons

Baryons with a heavy c-quark or a heavy b-quark and also two c-quarks have been discovered. These states are expected in QCD and therefore provide a test for the theory. There should be double beauty baryons, and also an intriguing possibility that baryons ${\bf B}_{bc}$ with a c-quark, a b-quark. These states are yet to be discovered. The main decay modes of ${\bf B}_{bc}$ are expected to be weak processes from theoretical understanding of their mass spectrum. These decay modes can provide crucial information about these heavy baryons ${\bf B}_{bc}$. We analyze two body hadronic weak decays for ${\bf B}_{bc}$ using $SU(3)$ flavor symmetry. Any one of the $c$ and $b$ decays will induce ${\bf B}_{bc}$ to decay. We find that the Cabibbo allowed decays ${\bf B}_{bc} \to {\bf B}_b + M$ due to $c \to s u \bar d$ can be crucial for exploration. The LHC may have the sensitivity to discover such decays. Other ${\bf B}_{bc}$ decays due to $b \to c q' \bar q$ are sub-leading. Several relations among branching ratios are obtained which can be used to test $SU(3)$ flavor symmetry.

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arXiv2016

A global $SU(3)/U(3)$ flavor symmetry analysis for $B\to PP$ with $η-η'$ Mixing

A large number of new experimental data on $B$ decay into two light pesudoscalar ($P$) mesons have been collected by the LHCb collaboration. Besides confirming information on $B_{u,d} \to PP$ decays obtained earlier by B-factories at KEK and SLAC, new information on $B_s\to PP$ and also more decay modes with $P$ being $η$ or $η'$ have been obtained. Using these new data, we perform a global fit for $B \to PP$ to determine decay amplitudes in the framework of $SU(3)/U(3)$ flavor symmetry. We find that $SU(3)$ flavor symmetry can explain data well. The annihilation amplitudes are found to be small as expected. Several CP violating relations predicted by $SU(3)$ flavor symmetry are in good agreement with data. Current available data can give constraints on the amplitudes which induce $P = η,\;η'$ decays in the framework of $U(3)$ flavor symmetry, and can also determine the $η-η'$ mixing angle $θ$ with $θ= (-18.4\pm1.2)^\circ$. Several $B \to PP$ decay modes which have not been measured are predicted with branching ratios accessible at the LHCb. These decays can provide further tests for the framework of $SU(3)/U(3)$ flavor symmetry for $B$ decays.

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arXiv2010

Longitudinal Weak Gauge Bosons Scattering in Hidden Z' Models

Longitudinal weak gauge boson scattering has been well known as a powerful method to probe the underlying mechanism of the electroweak symmetry breaking sector of the Standard Model. We point out that longitudinal weak gauge boson scattering is also sensitive to the gauge sector when the non-Abelian trilinear and quartic couplings of the Standard Model Z boson are modified due to the general mixings with another Z' boson in the hidden sector and possibly with the photon as well. In particular, these mixings can lead to a partially strong scattering effect in the channels of W^\pm_L W^\pm_L \to W^\pm_L W^\pm_L and W^\pm_L W^\mp_L \to W^\pm_L W^\mp_L which can be probed at the Large Hadron Collider. We study this effect in a simple U(1) extension of the Standard Model recently suggested in the literature that includes both the symmetry breaking Higgs mechanism as well as the gauge invariant Stueckelberg mass terms for the two Abelian groups. Other types of Z' models are also briefly discussed.

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arXiv2009

Study of \bar B\to Λ_c\bar Λ_c and \bar B\to Λ_c\bar Λ_c \bar K

We study the doubly charmful two-body and three-body baryonic B decays $\bar B\to Λ_c^+\bar Λ_c^-$ and $\bar B\to Λ_c^+\bar Λ_c^- \bar K$. As pointed out before, a naive estimate of the branching ratio ${\cal O}(10^{-8})$ for the latter decay is too small by three to four orders of magnitude compared to experiment. Previously, it has been shown that a large enhancement for the $Λ_c^+\barΛ_c^-\bar K$ production can occur due to a charmonium-like resonance (e.g. X(4630) discovered by Belle) with a mass near the $Λ_c\barΛ_c$ threshold. Motivated by the BaBar's observation of a resonance in the $Λ_c \bar K$ system with a mass of order 2930 MeV, we study in this work the contribution to $\bar B\toΛ_c^+\barΛ_c^-\bar K$ from the intermediate state $Ξ_c(2980)$ which is postulated to be a first positive-parity excited $D$-wave charmed baryon state. Assuming that a soft $q\bar q$ quark pair is produced through the $σ$ and $π$ meson exchanges in the configuration for $\bar B\to Ξ_c(2980)\barΛ_c$ and $Λ_c\barΛ_c$, it is found that branching ratios of $\bar B\to Λ_c^+\bar Λ_c^- \bar K$ and $\bar B\to Λ_c^+\bar Λ_c^-$ are of order $3.5\times 10^{-4}$ and $5\times 10^{-5}$, respectively, in agreement with experiment except that the prediction for the $Λ_c\barΛ_c K^-$ is slightly smaller. In conjunction with our previous analysis, we conclude that the enormously large rate of $\bar B\to Λ_c^+\bar Λ_c^-\bar K$ arises from the resonances $Ξ_c(2980)$ and X(4630).

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arXiv2009

Charmful baryonic B\to {\bf B\bar B'}M_c decays

We study the charmful three-body baryonic B decays with $D^{(*)}$ or $J/Ψ$ in the final state. We explain the measured rates of $\bar B^0\to n\bar p D^{*+}$, $\bar B^0\to p\bar p D^{(*)0}$, and $B^-\to Λ\bar p J/Ψ$. In particular, the branching fraction of $\bar B^0\toΛ\bar ΛD^0$ predicted to be of order $2.3\times 10^{-6}$ is in accordance with the Belle measurement, $(1.05^{+0.57}_{-0.44}\pm 0.14)\times 10^{-5}<2.6\times 10^{-5}$.

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arXiv2008

Baryonic D Decay $D_s^+\to p\bar n$ and Its Implication

The channel $D_s^+\to p\bar n$ is the only kinematically allowed baryonic D decay. It proceeds solely through the W-annihilation topology. Hence, a recent observation of this mode by CLEO will shed light on the dynamics of W-annihilation. At the short-distance level, its branching ratio is very small, of order $10^{-6}$, owing to chiral suppression. It receives long-distance contributions through final-state scattering of the leading tree and color-suppressed amplitudes. Assuming that the long-distance enhancement of W-annihilation in the baryonic D decay is similar to that in the mesonic $D_s^+$ decay, where the latter can be obtained from the analysis of the diagrammatic approach, we find that $D_s^+\to p\bar n$ becomes visible. The observation of this baryonic D decay implies the dynamical enhancement of the W-annihilation topology in the $D_s^+$ decay.

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arXiv2005

Productions of $K^*_0(1430)$ and $K_{1}$ in B decays

We study the productions of p-wave mesons $K^*_{0}(1430)$, $K_{1}(1270)$ and $K_{1}(1400)$ in B decays. By the generalized factorization approach, we find that the branching ratios of $B\to K^*_{0}(1430) ϕ$ are similar to those of $B\to K ϕ$ while the branching ratios of $B\to K_{1}(1270) ϕ$ and $B\to K_{1}(1400) ϕ$ are $O(10^{-5})$ and $O(10^{-6})$, respectively. In terms of the observation of $B\to K_{1}(1270) γ$ by BELLE, we can remove the sign ambiguity in the mixing angle for physical states $K_1(1270)$ and $K_{1}(1400)$. In addition, we analyze annihilation contributions in the decays $B\to K_1 ϕ$ and we conclude that they could be neglected.

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arXiv2003

Constraints on Supersymmetric Flavor Changing Parameters Using B->PP Decays

We study contributions of quark-squark-gluino interactions in Minimal Supersymmetric Standard Model (MSSM) to B->PP (PP =Kpi, pipi, KK) decays using QCD improved factorization method for the evaluation of the hadronic matrix elements and taking into account renormalization group running of the Wilson coefficients from SUSY scale (~ m_{\tilde q}) to the low energy scale (= m_b) applicable to B decays. Using the most recent experimental data we obtain constraints on flavor changing Supersymmetric (SUSY) parameters (δ_{ij})_{LL, RR}. For ΔS = -1 processes, b-> s gamma is usually considered to give the strongest limits. We, however, find that in some part of the parameter space B-> Kpi processes give stronger bounds. Implications for B^0_s -\bar B^0_s mixing is discussed. We also study cons traints obtained from ΔS = 0 processes B-> pipi, KK, rho gamma and B_d -\bar B_d mixing. In this case, in a large part of the parameter space B_d - \bar B_d provides the best bound, but B-> K^- K^0, rho gamma can still give interesting constraints in a complementary region of the parameter space.

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arXiv2003

$B \to η(η') K(π)$ in the Standard Model with Flavor Symmetry

The observed branching ratios for $B\to K η'$ decays are much larger than factorization predictions in the Standard Model (SM). Many proposals have been made to reconcile the data and theoretical predictions. In this paper we study these decays within the SM using flavor U(3) symmetry. If small annihilation amplitudes are neglected, one needs 11 hadronic parameters to describe $B\to PP$ decays where $P$ can be one of the $π$, $K$, $η$ and $η'$ nonet mesons. We find that existing data are consistent with SM with flavor U(3) symmetry. We also predict several measurable branching ratios and CP asymmetries for $B \to K (π) η(η')$, $η(η')η(η')$ decays. Near future experiments can provide important tests for the Standard Model with flavor U(3) symmetry.

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arXiv2002

CP violation in $B \to PP$ in the SM with SU(3) symmetry

In this paper we study CP violation in $B\to PP$ decays in the Standard Model using SU(3) flavor symmetry. With SU(3) symmetry only seven hadronic parameters are needed to describe $B\to PP$ decays in the SM when annihilation contributions are neglected. The relevant hadronic parameters can be determined using known experimental data from $B\to ππ$ and $B\to K π$. We predict branching ratios and CP asymmetries for some of the unmeasured $B \to PP$ decays. Some of the CP asymmetries can be large and measured at B factories. The effects of annihilation contributions can also be studied using present experimental data. Inclusion of annihilation contributions introduces six more hadronic parameters. We find that annihilation contributions are in general small, but can have significant effects on CP asymmetries and some $B_s \to PP$.

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