arXiv subjects

Xin-Heng Guo

Publications and source records attributed to Xin-Heng Guo.

83 records · Page 5Linked to original sources

arXiv2006

Study on the Form Factors at Effective Vertices of Diqarks Interacting with Gauge Bosons

The diquark structure in baryons is commonly accepted as a reasonable approximation which can much simplify the picture and reduce the length of calculations. However, a diquark by no means is a point-like particle, even though it is treated as a whole object. Therefore, to apply the diquark picture to the phenomenological calculations, at the effective vertices for the diquark-gauge boson interactions, suitable form factors must be introduced to compensate the effects caused by the inner structure of the diquark. It is crucial to derive the appropriate form factors for various interactions. In this work, we use the Bethe-Salpeter equation to derive such form factors and numerically evaluate their magnitudes.

hep-ph↗

arXiv2006

Study on Strong Decays of $D_{sJ}(2632)$

The resonance $D_{sJ}(2632)$ observed by SELEX, has attracted great interests and meanwhile brought up serious dispute. Its spin-parity, so far has not finally determined and if it exists, its quark-structure might be exotic. Following the previous literature where $D_{sJ}(2632)$ is assumed to be a radial-excited state of $1^-$, we consider the possibilities that it might be a $q\bar q$ ground state of $2^+$ or the first radial-excited state of $0^+$ $D_{sJ}(2317)$ and re-calculate its strong decay widths in terms of the Bethe-Salpeter equation. Our results indicate that there still is a sharp discrepancy between the theoretical evaluation and data.

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arXiv2006

Spectra of Free Diquark in the Bethe-Salpeter Approach

In this work, we employ the Bethe-Salpeter (B-S) equation to investigate the spectra of free diquarks and their B-S wave functions. We find that the B-S approach can be consistently applied to study the diqaurks with two heavy quarks or one heavy and one light quarks, but for two light-quark systems, the results are not reliable. There are a few free parameters in the whole scenario which can only be fixed phenomenologically. Thus, to determine them, one has to study baryons which are composed of quarks and diquarks.

hep-ph↗

arXiv2006

Direct CP violation in B \to ρ^0(ω) PS

We calculate the direct CP violating asymmetry parameter, $a_{CP}$, for $B \to π^{+} π^{-} π$ and $B \to π^{+} π^{-} K$ decays, in the case where $ρ^0-ω$ mixing effects are taken into account. We find that the direct CP asymmetry for $B^{-} \to π^{+} π^{-} π^{-}$, $\bar{B}^{0} \to π^{+} π^{-}π^{0}$, $B^{-} \to π^{+} π^{-} K^{-}$ and $\bar{B}^{0} \to π^{+} π^{-}\bar{K}^{0}$, reaches its maximum when the invariant mass $π^{+} π^{-}$ is in the vicinity of the $ω$ meson mass. The inclusion of $ρ^0-ω$ mixing provides an opportunity to erase, without ambiguity, the phase uncertainty mod$(π)$ in the determination of the CKM angles $α$ in case of $b\to u$ and $γ$ in case of $b \to s$.

hep-ph↗

arXiv2005

Study on production of exotic $0^+$ meson $D_{sJ}^{*}(2317)$ in decays of $ψ(4415)$

The newly observed $D_{sJ}^*$ family containing $D_{sJ}^{*}(2317)$, $D_{sJ}(2460)$ and $D_{sJ}(2632)$ attracts great interests. Determining their structure may be important tasks for both theorists and experimentalists. In this work we use the heavy quark effective theory (HQET) and a non-relativistic model to evaluate the production rate of $D_{sJ}^{*}(2317)$ from the decays of $ψ(4415)$, and we find that it is sizable and may be observed at BES III and CLEO, if it is a p-wave excited state of $D_s(1968)$. Unfortunately, the other two members of the family cannot be observed through decays of charmonia, because of the constraints from the final state phase space.

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arXiv2002

Cabibbo-suppressed non-leptonic decays of Lambda_c and final state interaction

With the diquark structure of Lambda_c, we investigate the branching ratios of Lambda_c -> n pi^+ and p pi^0. The results show that without considering the final state interaction (FSI), the branching ration of Lambda_c -> p pi^+ is only of order 10^{-6} whereas taking into account the FSI effects, this ratio could reach 10^{-4} and is at the same order as Lambda_c -> n pi^0. Concrete values depend on phenomenological parameters adopted in the calculations. These branching ratios can be measured in the experiments to come.

hep-ph↗

arXiv2000

Electromagnetic radiation of baryons containing two heavy quarks

The two heavy quarks in a baryon which contains two heavy quarks and a light one, can constitute a scalar or axial vector diquark. We study electromagnetic radiations of such baryons, (i) Ξ_{(bc)_1} -> Ξ_{(bc)_0}+γ, (ii) Ξ_{(bc)_1}^* -> Ξ_{(bc)_0}+γ, (iii) Ξ_{(bc)_0}^{**}(1/2, l=1) -> Ξ_{(bc)_0}+γ, (iv) Ξ_{(bc)_0}^{**}(3/2, l=1) -> Ξ_{(bc)_0}+γand (v) Ξ_{(bc)_0}^{**}(3/2, l=2) -> Ξ_{(bc)_0}+γ, where Ξ_{(bc)_{0(1)}}, Ξ^*_{(bc)_1} are S-wave bound states of a heavy scalar or axial vector diquark and a light quark, and Ξ_{(bc)_0}^{**}(l is bigger than 1) are P- or D-wave bound states of a heavy scalar diquark and a light quark. Analysis indicates that these processes can be attributed into two categories and the physical mechanisms which are responsible for them are completely distinct. Measurements can provide a good judgment for the diquark structure and better understanding of the physical picture.

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arXiv1999

Spectra of Baryons Containing Two Heavy Quarks in Potential Model

In this work, we employ the effective vertices for interaction between diquarks (scalar or axial-vector) and gluon where the form factors are derived in terms of the B-S equation, to obtain the potential for baryons including a light quark and a heavy diquark. The concerned phenomenological parameters are obtained by fitting data of $B^{(*)}-$mesons instead of the heavy quarkonia. The operator ordering problem in quantum mechanics is discussed. Our numerical results indicate that the mass splitting between $B_{3/2}(V), B_{1/2}(V)$ and $B_{1/2}(S)$ is very small and it is consistent with the heavy quark effective theory (HQET).

hep-ph↗

arXiv1999

Non-Spectator Diquark Effects on Lifetimes of Λ_b, Ω_{b}^{()} and Weak Decay Rates of Σ_{b}^{()}, Ξ_{b}^{(*)}

The difference of τ_{_B} and τ_{_{Λ_b}} indicates the role of the light flavors. We calculate the lifetimes of B-meson and Λ_b based on the weak effective Hamiltonian while assuming the heavy baryon is constructed by a heavy b-quark and a diquark containing two light quarks. In this scenario, we use the information of the measured ratio τ_{_{Λ_b}}/τ_{_B} as input to predict rates of the inclusive weak decays of Σ_{b}^{(*)} and Ξ_{b}^{(*)} into non-bottom final states. We find that these rates of Σ_{b}^{(*)} and Ξ_{b}^{(*)} are much larger than that of B-mesons and Λ_b. We also give the predictions for the lifetimes of Ω_b and Ω_{b}^{*}. Phenomenological implication of our result is discussed.

hep-ph↗

arXiv1998

Weak Semileptonic Decays of Heavy Baryons Containing Two Heavy Quarks

In the heavy quark limit a heavy baryon which contains two heavy quarks is believed to be composed of a heavy diquark and a light quark. Based on this picture, we evaluate the weak semileptonic decay rates of such baryons. The transition form factors between two heavy baryons are associated with those between two heavy mesons by applying the superflavor symmetry. The effective vertices of the W-boson and two heavy diquarks are obtained in terms of the Bethe-Salpeter equation. Numerical predictions on these semileptonic decay widths are presented and they will be tested in the future experiments.

hep-ph↗

arXiv1998

Possible Explanation Why τ_{B^{\pm}}\simτ_{B^0} But τ_{D^{\pm}}\sim τ_{D^0}

Data show that τ_{B^{\pm}}\simτ_{B^0}, but τ_{D^{\pm}}\sim 2τ_{D^0}. The naive interpretation which attributes τ_{D^{\pm}}\sim 2τ_{D^0} to a destructive interference between two quark diagrams for D^{\pm} decays, definitely fails in the B-case. We investigate Close and Lipkin's suggestion that the phases for producing radially excited states ψ_{2s} in the decay products of B-mesons can possess an opposite sign to the integrals for ψ_{1s} decay products. Their contributions can partially compensate each other to result in τ_{B^{\pm}}\simτ_{B^0}. Since D-mesons are much lighter than B-mesons, such possibilities do not exist in D-decays.

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