Y. K. Hsiao, C. Q. Geng
We perform the simultaneous $|V_{ub}|$ and $|V_{cb}|$ extractions with only the exclusive $Λ_b$ decays of $Λ_b\to (p,Λ_c^+)μ\bar ν_μ$, $Λ_b\to pπ^-$ and $Λ_b\to Λ_c^+ (π^-, D^-)$. We obtain that $|V_{ub}|=(3.7\pm 0.3)\times 10^{-3}$ and $|V_{cb}|=(45.9\pm 2.7)\times 10^{-3}$. Our value of $|V_{ub}|$ is larger than that of $(3.27\pm 0.15\pm 0.16\pm 0.06)\times 10^{-3}$, previously extracted by the LHC Collaboration from the exclusive $Λ_b$ decays also, but nearly identical to $(3.72\pm 0.19)\times 10^{-3}$ from the exclusive $B$ decays. On the other hand, our extracted result of $|V_{cb}|$ favors the value of $(42.2\pm 0.8)\times 10^{-3}$ from the inclusive $B$ decays.
C. Q. Geng, Chia-Wei Liu, Tien-Hsueh Tsai
We analyze the decay processes of ${\bf B}_c \to {\bf B}_n M$ with the $SU(3)_F$ flavor symmetry and spin-dependent amplitudes, where ${\bf B}_c({\bf B}_n)$ and $M$ are the anti-triplet charmed (octet) baryon and nonet meson states, respectively. In the $SU(3)_F$ approach, it is the first time that the decay rates and up-down asymmetries are fully and systematically studied without neglecting the ${\cal O}(\overline{15})$ contributions of the color anti-symmetric parts in the effective Hamiltonian. Our results of the up-down asymmetries based on $SU(3)_F$ are quite different from the previous theoretical values in the literature. In particular, we find that the up-down symmetry of $ α(Λ_c^+\to Ξ^0 K^+)_{SU(3)} = 0.94^{+0.06}_{-0.11}$, which is consistent with the recent experimental data of $0.77\pm0.78$ by the BESIII Collaboration, but predicted to be zero in the literature. We also examine the $K_S^0-K_L^0$ asymmetries between the decays of ${\bf B}_c \to {\bf B}_n K_S^0$ and ${\bf B}_c \to {\bf B}_n K_L^0$ with both Cabibbo-allowed and doubly Cabibbo-suppressed transitions.
C. Q. Geng, Chia-Wei Liu, Tien-Hsueh Tsai
We systematically study the semileptonic decays of ${\bf B_c} \to {\bf B_n}\ell^+ ν_{\ell}$ in the light-front constituent quark model, where ${\bf B_c}$ represent the anti-triplet charmed baryons of $(Ξ_c^0,Ξ_c^+,Λ_c^+)$ and ${\bf B_n}$ correspond to the octet ones. We determine the spin-flavor structures of the constituents in the baryons with the Fermi statistics and calculate the decay branching ratios (${\cal B}$s) and averaged asymmetry parameters ($α$s) with the helicity formalism. In particular, we find that ${\cal B}( Λ_c^+ \to Λe^+ ν_{e}, ne^+ ν_{e})=(3.55\pm1.04, 0.36\pm0.15)\%$, ${\cal B}( Ξ_c^+ \to Ξ^0 e^+ ν_{e},Σ^0 e^+ ν_{e},Λe^+ ν_{e})=(11.3\pm3.35), 0.33\pm0.09,0.12\pm0.04\%$ and ${\cal B}( Ξ_c^0 \to Ξ^- e^+ ν_{e},Σ^- e^+ ν_{e})=(3.49\pm0.95,0.22\pm0.06)\%$. Our results agree with the current experimental data. Our prediction for ${\cal B}( Λ_c^+ \to n e^+ ν_{e})$ is consistent with those in the literature, which can be measured by the charm-facilities, such as BESIII and BELLE. Some of our results for the $Ξ_c^{+(0)}$ semileptonic channels can be tested by the experiments at BELLE as well as the ongoing ones at LHCb and BELLEII.
Y. K. Hsiao, C. Q. Geng
We examine the validity of the generalized factorization method and calculate the angular correlations in the charmful three-body baryonic decays of $\bar B^0\to Λ\bar p D^{(*)+}$. With the timelike baryonic form factors newly extracted from the measured baryonic $B$ decays, we obtain ${\cal B}(\bar B^0\to Λ\bar p D^+,Λ\bar p D^{*+})=(1.85\pm 0.30,2.75\pm 0.24)\times 10^{-5}$ to agree with the recent data from the BELLE Collaboration, which demonstrates that the theoretical approach based on the factorization still works well. For the angular distribution asymmetries, we find ${\cal A}_θ(\bar B^0\to Λ\bar p D^+,Λ\bar p D^{*+})=(-0.030\pm 0.002\,,+0.150\pm 0.000)$, which are consistent with the current measurements. Moreover, we predict that ${\cal A}_θ(\bar B^0\to p\bar p D^{0},p\bar p D^{*0})=+0.04\pm 0.01$. Future precise explorations of these angular correlations at BELLE and LHCb as well as super-BELLE are important to justify the present factorization approach in the charmful three-body baryonic decays.
Y. K. Hsiao, C. Q. Geng
We study two-body $B_{(c)}\to M_c(π,K)$ and semileptonic $B_{c}\to M_c\ell^-\bar ν_\ell$ decays with $M_c=(J/ψ,X_c^0)$, where $X_c^0\equiv X^0(3872)$ is regarded as the tetraquark state of $c\bar cu\bar u(d\bar d)$. With the decay constant $f_{X_c^0}=(234\pm 52)$~MeV determined from the data, we predict that ${\cal B}(B^-\to X_c^0π^-)=(11.5\pm 5.7)\times 10^{-6}$, ${\cal B}(\bar B^0\to X_c^0\bar K^0)=(2.1\pm 1.0)\times 10^{-4}$, and ${\cal B}(\bar B^0_s\to X_c^0\bar K^0)=(11.4\pm 5.6)\times 10^{-6}$. With the form factors in QCD models, we calculate that ${\cal B}(B_c^-\to X_c^0π^-,X_c^0 K^-)=(6.0\pm 2.6)\times 10^{-5}$ and $(4.7\pm 2.0)\times 10^{-6}$, and ${\cal B}(B_c^-\to J/ψμ^-\bar ν_μ, X_c^0 μ^-\bar ν_μ)=(2.3\pm0.6)\times 10^{-2}$ and $(1.35\pm 0.18)\times 10^{-3}$, respectively, and extract the ratio of the fragmentation fractions to be $f_c/f_u=(6.4\pm 1.9)\times 10^{-3}$.
Y. K. Hsiao, C. Q. Geng
We consider $X(3872)$ and $Y(4140)$ as the vector tetraquark states of $X_c^0\equiv c\bar c u\bar u(d\bar d)$ and $c\bar c s\bar s$, respectively. By connecting $Λ_b\to X_c^0Λ$ to $B^-\to X_c^0 K^-$, we predict that the branching ratios of $Λ_b\to Λ(X(3872)^0\to) J/ψπ^+π^-$ and $Λ_b\to Λ(Y(4140)\to) J/ψφ$ are $(5.2\pm 1.8)\times 10^{-6}$ and $(4.7\pm 2.6)\times 10^{-6}$, which are accessible to the experiments at the LHCb, respectively. The measurements of these $Λ_b$ modes would be the first experimental evidences for the $XYZ$ states in baryonic decays.
Y. K. Hsiao, C. Q. Geng
We extract the Cabibbo-Kobayashi-Maskawa matrix element $V_{cb}$ from the exclusive decays of $Λ_b\to Λ_c\ell\bar ν_\ell$ and $Λ_b\to Λ_c M_{(c)}$ with $M=(π^-,K^-)$ and $M_c=(D^-,D^-_s)$, where the branching ratios of $Λ_b\to ΛM_{(c)}$ measured with high precisions have not been used in the previous studies. Explicitly, we find $|V_{cb}|=(44.0\pm 3.5)\times 10^{-3}$, which agrees with the value of $(42.11\pm 0.74)\times 10^{-3}$ from the inclusive $B\to X_c\ell\bar ν_\ell$ decays. Furthermore, based on the most recent ratio of $|V_{ub}|/|V_{cb}|$ from the exclusive $Λ_b$ decays, we obtain $|V_{ub}|=(4.2\pm 0.4)\times 10^{-3}$, which is close to the value of $(4.49\pm 0.24)\times 10^{-3}$ from the inclusive $B\to X_u\ell\bar ν_\ell$ decays. We conclude that our determinations of $|V_{cb}|$ and $|V_{ub}|$ from the exclusive $Λ_b$ decays favor the inclusive extractions in the $B$ decays.
C. Q. Geng, C. P. Kao
We investigate the longitudinal lepton polarization asymmetry in the exclusive processes $B\to K l^+l^-$ and $B\to K^* l^+l^-$. We include both short and long-distance contributions to the asymmetry in our discussions. We find that average values of the polarization asymmetries of the muon and tau for $B\to K^{(*)}μ^+μ^-$ and $B\to K^{(*)}τ^+τ^-$ are $-0.8\ (-0.7)$ and $-0.2\ (-0.5)$, respectively.
C. Q. Geng, Y. K. Hsiao
We study the angular distributions of the baryon-antibaryon low-mass enhancements in the three-body baryonic B decays of $B\to p\bar{p}M$ (M=K and $π$) in the framework of the perturbative QCD. By writing the most general forms for the transition form factors of $B\to p\bar{p}$, we find that the angular distribution asymmetry in $B^-\to p\bar{p}K^-$ measured by the Belle Collaboration can be explained. We give a quantitative description on the Dalitz plot asymmetry in $B^-\to p\bar{p}K^-$ shown by the BaBar Collaboration and demonstrate that it is equivalent to the angular asymmetry. In addition, we present our results on $\bar B^0\to p\bar{p}K_S$ and $B^-\to p\bar{p}π^-$ and we obtain that their angular asymmetries are $-0.35\pm0.11$ and $0.45\pm0.10$, respectively, which can be tested by the ongoing experiments at the B factories.
C. Q. Geng, Y. K. Hsiao
It is the first time that the study of three-body baryonic B decays offers an independent determination of the nucleon form factors for the time-like four momentum transfer $(t>0)$ region, such as $G^{p,n}_M(t)$ of vector currents and those of axial ones. Explicitly, from the data of $\bar B^0\to n\bar p D^{*+}$ and $Λ\bar pπ^+$ we find a constant ratio of $G^n_M(t)/G^p_M(t)=-1.3\pm0.4$, which supports the FENICE experimental result. The vector and axial-vector form factors of $p\bar n$, $p\bar p$ and $n\bar n$ pairs due to weak currents are also presented, which can be tested in future experiments.
C. Q. Geng, S. H. Ho, J. N. Ng
We study a new type of effective interactions in terms of the $CPT$-even dimension-six Chern-Simons-like term, which could originate from superstring theory, to generate the cosmological birefringence. We use the neutrino number asymmetry to induce a sizable rotation polarization angle in the data of the cosmic microwave background radiation polarization. The combined effect of the new term and the neutrino asymmetry provides an alternative way to understand the birefringence.
Kazuharu Bamba, C. Q. Geng, S. H. Ho
We study a new scenario for baryogenesis due to the spontaneous breaking of the $CPT$ invariance through the interaction between a baryon current and a hypermagnetic helicity. The hypermagnetic helicity (Chern-Simons number) of $U(1)_Y$ provides a $CPT$ violation background for the generation of baryons via sphaleron processes, which protects these baryons from the sphaleron wash-out effect in thermal equilibrium. It is shown that if the present amplitude of the resultant magnetic fields are sufficiently large, for a wide range mass scale (from TeV to the Planck scale), the observational magnitude of the baryon asymmetry of the Universe can be realized.
C. Q. Geng, Y. K. Hsiao
We review the direct CP and T violation in the three-body baryonic B decays in the standard model. In particular, we emphasize that the direct CP violating asymmetry in $B^\pm\to p\bar p K^{*\pm}$ is around 22% and the direct $T$ violating asymmetry in $\bar B^0 \ra Λ\bar p π^+$ can be as large as 12%, which are accessible to the current B factories at KEK and SLAC as well as SuperB and LHCb.
C. Q. Geng, C. C. Lih
We study the decays of $τ^- \to ν_τ P^-γ(P=π^-, K^-)$ in the light front quark model. We calculate the form factors and use them to evaluate the decay widths. We find that, in the standard model, the decay widths are $1.62\times 10^{-2} (3.86\times10^{-3}) Γ_{τ^- \to ν_τ π^-}$ and $1.91\times 10^{-3} (5.38\times 10^{-4}) Γ_{τ^- \to ν_τ K^-}$ with the cuts of $E_γ=50 (400)$ MeV and $t_{0}=800 (1200)$ MeV for $τ^- \to ν_τ π^- γ$ and $τ^- \to ν_τ K^- γ$, respectively. We also show that with including the radiative decay widths, the experimental rate for $τ^-\to ν_τP^-$ can be explained.
C. Q. Geng, Y. K. Hsiao, Chia-Wei Liu, Tien-Hsueh Tsai
We explore the breaking effects of the $SU(3)$ flavor symmetry in the singly Cabibbo-suppressed anti-triplet charmed baryon decays of ${\bf B}_c\to {\bf B}_n M$, with ${\bf B}_c=(Ξ_c^0,Ξ_c^+,Λ_c^+)$ and ${\bf B}_n(M)$ the baryon (pseudo-scalar) octets. We find that these breaking effects can be used to account for the experimental data on the decay branching ratios of ${\cal B}(Λ_c^+\to Σ^{0} K^{+},Λ^{0} K^{+})$ and $R'_{K/π}$=${\cal B}(Ξ^0_c \to Ξ^- K^+)$/${\cal B}(Ξ^0_c \to Ξ^- π^+)$. In addition, we obtain that ${\cal B}(Ξ_{c}^{0} \to Ξ^{-} K^{+},Σ^{-} π^{+})=(4.6 \pm 1.7,12.8 \pm 3.1)\times 10^{-4}$, ${\cal B}(Ξ_c^0\to pK^-,Σ^+π^-)=(3.0 \pm 1.0, 5.2 \pm 1.6)\times 10^{-4}$ and ${\cal B}(Ξ_c^+\to Σ^{0(+)} π^{+(0)})=(10.3 \pm 1.7)\times 10^{-4}$, which all receive significant contributions from the breaking effects, and can be tested by the BESIII and LHCb experiments.
C. Q. Geng, C. C. Liu
We study the rare decays of $B_{s} \to M_s\ell \bar{\ell}$ ($M_s=η, η',φ$ and $\ell=ν,e,μ,τ$) in the standard model. With the hadronic form factors evaluated in the light front and constituent quark models, we estimate the decay branching ratios, respectively. We also discuss the longitudinal lepton polarization and forward-backward asymmetries.
Chuan-Hung Chen, C. Q. Geng
We study the contribution of a generic charged Higgs $(H^+)$ to the muon anomalous magnetic moment $a_μ$ with the SUSY soft breaking parameters. We find out that the deviation between the experimental data and the predicted SM value on $a_μ$ can be explained by the two-loop charged Higgs diagrams even with $m_{H^+}\sim 400 GeV$.
C. Q. Geng, C. W. Hwang, C. C. Lih, W. M. Zhang
We study the tensor form factors for $P \to P$ and $P \to V$ transitions in the light-front quark model with $P$ and $V$ being pseudoscalar and vector mesons, respectively. We explore the behaviors of these form factors in the entire physical range of $0\leq p^2\leq (M_i - M_f)^2$. At the maximum recoil of $p^2=0$, we compare our results of the form factors in $B\to π,K,ρ,K^*$ with various other calculations in the literature.
Y. K. Hsiao, P. Y. Lin, C. C. Lih, C. Q. Geng
We study the charmful decays of the two-body ${\cal B}_b\to {\cal B}_n M_c$ decays, where ${\cal B}_b$ represents the anti-triplet of $(Λ_b,Ξ_b^0,Ξ_b^-)$, ${\cal B}_n$ stands for the baryon octet and $M_c$ denotes as the charmed meson of $D^{(*)}_{(s)}$, $η_c$ and $J/ψ$. Explicitly, we predict that ${\cal B}(Λ_b\to D_s^- p)=(1.8\pm 0.3)\times 10^{-5}$, which is within the measured upper bound of ${\cal B}(Λ_b\to D_s^- p)<4.8(5.3)\times 10^{-4}$ at 90\%\,(95\%) C.L., and reproduce ${\cal B}(Λ_b\to J/ψΛ)=(3.3\pm 2.0)\times 10^{-4}$ and ${\cal B}(Ξ_b^-\to J/ψΞ^-)=(5.1\pm 3.2)\times 10^{-4}$ in agreement with the data. Moreover, we find that ${\cal B}(Λ_b \to Λη_c)=(1.5 \pm 0.9) \times 10^{-4}$, ${\cal B}(Ξ_b^-\toΞ^-η_c)=(2.4\pm1.5) \times 10^{-4}$ and ${\cal B}(Ξ_b^0\toΞ^0η_c,Ξ^0 J/ψ)=(2.3\pm1.4,4.9\pm3.0)\times 10^{-4}$, which are accessible to the experiments at the LHCb.
Y. K. Hsiao, C. Q. Geng
We use the exclusive baryonic $B$ decays to determine the Cabibbo-Kobayashi-Maskawa (CKM) matrix element $V_{ub}$. From the relation $|V_{ub}|^2/|V_{cb}|^2=({\cal B}_π/{\cal B}_D){\cal R}_{ff}$ based on $B^-\to p\bar p π^-$ and $\bar B^0\to p\bar p D^0$ decays, where $|V_{cb}|$ and ${\cal B}_π/{\cal B}_D\equiv{\cal B}(B^-\to p\bar p π^-)/{\cal B}(\bar B^0\to p\bar p D^0)$ are the data input parameters, while ${\cal R}_{ff}$ is the one fixed by the $B\to p\bar p$ transition matrix elements, we find $|V_{ub}|=(3.48^{+0.87}_{-0.63}\pm 0.40\pm 0.07)\times 10^{-3}$ with the errors corresponding to the uncertainties from ${\cal R}_{ff}$, ${\cal B}_π/{\cal B}_D$ and $|V_{cb}|$, respectively. Being independent of the previous results, our determination of $|V_{ub}|$ has the central value close to those from the exclusive $\bar B\to π\ell\bar ν_\ell$ and $Λ_b\to pμ^-\bar ν_μ$ decays, but overlaps the one from the inclusive $\bar B\to X_u \ell\bar ν_\ell$ with the current uncertainties. The extraction of $|V_{ub}|$ in the baryonic $B$ decays is clearly very useful for the complete determination of the CKM matrix elements as well as the exploration of new physics.