arXiv subjects

Yong-Lu Liu

Publications and source records attributed to Yong-Lu Liu.

30 records · Page 2Linked to original sources

arXiv2014

Higher Order Corrections to the Light-cone Distribution Amplitudes of the Sigma baryon

The Light-cone distribution amplitudes (LCDAs) of the $Σ^\pm$ baryons up to twist six are investigated on the basis of QCD conformal partial wave expansion approach. The calculations are carried out to the next-to-leading order of conformal spin accuracy. The nonperturbative parameters relevant to the LCDAs are determined in the framework of the QCD sum rule method. The explicit expressions of the LCDAs are given as the main results.

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arXiv2013

$η_{b}BB^{\ast}$ vertex from QCD sum rules

The form factor and the coupling constant in the $η_{b}BB^{\ast}$ vertex are evaluated in the framework of three-point QCD sum rules. The correlation functions responsible for the vertex is evaluated considering contributions of both $B$ and $B^{\ast}$ mesons as off-shell states. The form factors obtained are different for the two cases, whereas the final results of the coupling constant are compatible.

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arXiv2012

Improved Light-cone QCD Sum Rule Analysis Of The Rare Decays $Λ_b\rightarrowΛγ$ And $Λ_b\rightarrowΛl^+l^-$

We present a systematic light-cone QCD sum rule study of the exclusive rare radiative decay $Λ_b\rightarrowΛγ$ and rare semileptonic decay $Λ_b\rightarrowΛl^+l^-$ within the framework of the standard model. Although some LCSR studies on these rare processes can be found in different literatures, it is necessary to reanalyze them systematically for the reason that either the baryonic distribution amplitudes are improved or different interpolating currents for the $Λ_b$ baryon may lead to quite different results. In addition, the rare process $Λ_b\rightarrowΛγ$ has not yet been analyzed by LCSR with the Ioffe-type current. Taking all these reasons into account, we perform LCSR calculations of both the processes with two types of interpolating currents. Our calculations show that the choice of the interpolating current for the $Λ_b$ baryon can affect the predictions significantly, especially for the rare radiative decay process.

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arXiv2012

Can X(3872) be a $J^{P}=2^{-}$ tetraquark state?

In this article, we test the nature of X(3872), which is assumed to be a P-wave $[cq]$-scalar-diquark $[\bar{c}\bar{q}]$-axial-vector-antidiquark tetraquark state with $J^{P}=2^{-}$. The interpolating current representing the $J^{P}=2^{-}$ state is proposed. Technically, contributions of the operators up to dimension six are included in the operator product expansion (OPE). The mass obtained for such state is $m_{2^{-}}=(4.38\pm 0.15) GeV$. We conclude that it is impossible to describe the X(3872) structure as $J^{P}=2^{-}$ tetraquark state.

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arXiv2012

$B^{\ast}_{s1}B^{\ast}K$ form factor from QCD sum rules

In this article, we calculate the form factors and the coupling constant of the $g_{B^{\ast}_{s1}B^{\ast} K}$ vertex in the framework of the three-point QCD sum rules. Three point correlation functions responsible for the vertex are evaluated by considering both $B^{\ast}$ and $K$ mesons as off-shell states. The form factors obtained are different if the $B^{\ast}$ or the $K$ meson is off-shell but give the same coupling constant.

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arXiv2012

$B^{\ast}B^{\ast}ρ$ vertex from QCD sum rules

The form factors and the coupling constants in the $B^{\ast}B^{\ast}ρ$ vertex are evaluated in the framework of three-point QCD sum rules. The correlation functions responsible for the form factors are evaluated considering contributions of both $B^{\ast}$ and $ρ$ mesons as off-shell states. The obtained numerical results for the coupling constants are in agreement with light-cone QCD sum rules calculations.

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arXiv2012

Investigating different structures of the Z_{b}(10610) and Z_{b}(10650)

The recently observed narrow resonance $Z_{b}(10610)$ is examined with the assumptions both as a $B^{*}\bar{B}$ molecular state and a $[bd][\bar{b}\bar{u}]$ tetraquark state with quantum numbers $I^{G}J^{P}=1^{+}1^{+}$. Possible interpolating currents are constructed to describe the $Z_{b}(10650)$ as an axial-vector $B^{*}\bar{B}^{*}$ molecular state or a $[bd][\bar{b}\bar{u}]$ tetraquark state. Using QCD sum rules (QCDSR), we consider contributions up to dimension six in the operator product expansion (OPE) at the leading order in $α_{s}$. The mass is obtained as $(10.44\pm0.23) GeV$ for molecular state and $(10.50\pm0.19) GeV$ for tetraquark state, both of which coincide with the $Z_{b}(10610)$. The results $m_{B^{*}\bar{B}^{*}}=(10.45\pm0.31) GeV$ and $m_{[bd][\bar{b}\bar{u}]}=(10.48\pm0.33) GeV$ are consistent with the $Z_{b}(10650)$.

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arXiv2009

Improved analysis on the semi-leptonic decay $Λ_c\toΛ\ell^+ν$ from QCD light-cone sum rules

With the renewed distribution amplitudes of $Λ$, we present a reanalysis on the semi-leptonic decay $Λ_c\toΛ\ell^+ν$ by use of the light-cone sum rule approach with two kinds of interpolating currents. The form factors describing the decay process are obtained and used to predict the decay width. With the inclusion of up to twist-6 contributions the calculations give the decay width $Γ=(10.04\pm0.88)\times10^{-14}{GeV}$ for Chernyak-Zhitnitsky-type(CZ-type) current and $Γ=(6.45\pm1.06)\times10^{-14}{GeV}$ for Ioffe-type current. The Ioffe-type interpolating current is found to be better for the estimation of the decay rate from a comparison with experimental data.

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arXiv2009

Light-cone Distribution Amplitudes of Xi and their Applications

We present the light-cone distribution amplitudes of the Xi baryons up to twist six on the basis of QCD conformal partial wave expansion to the leading order conformal spin accuracy. The nonperturbative parameters relevant to the DAs are determined in the framework of the QCD sum rule. The light-cone QCD sum rule approach is used to investigate both the electromagnetic form factors of Xi and the exclusive semileptonic decay of Xi_c as applications. Our estimations on the magnetic moments are $μ_{Ξ^0}=-(1.92\pm0.34)μ_N$ and $μ_{Ξ^-}=-(1.19\pm0.03)μ_N$. The decay width of the process Xi_c->Xi e^+ν_e is evaluated to be $Γ=8.73\times10^{-14}{GeV}$, which is in accordance with the experimental measurements and other theoretical approaches.

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arXiv2009

Electromagnetic form factors of the $Λ$ and $Σ$ baryons in an alternative baryonic current approach

Light-cone sum rules are used to investigate the electromagnetic form factors of the $Λ$ and $Σ$ baryons by using the Ioffe type interpolating currents. The sum rules are affected to some extent by the choice of the interpolating currents from a comparison. Numerical calculations show that the magnetic form factor can be well fitted by the dipole formula for $Σ$ but not for $Λ$. The magnetic form factor of $Λ$ approaches zero with the momentum transfer faster than the dipole formula estimation.

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arXiv2009

Light-cone QCD Sum Rules for the $Λ$ Baryon Electromagnetic Form Factors and its magnetic moment

We present the light-cone QCD sum rules up to twist 6 for the electromagnetic form factors of the $Λ$ baryon. To estimate the magnetic moment of the baryon, the magnetic form factor is fitted by the dipole formula. The numerical value of our estimation is $μ_Λ=-(0.64\pm0.04)μ_N$, which is in accordance with the experimental data and the existing theoretical results. We find that it is twist 4 but not the leading twist distribution amplitudes that dominate the results.

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arXiv2009

Distribution amplitudes of $Σ$ and $Λ$ and their electromagnetic form factors

Based on QCD conformal partial wave expansion to leading order conformal spin accuracy, we present the light-cone distribution amplitudes (DAs) of $Σ$ and $Λ$ baryons up to twist 6. It is concluded that fourteen ndependent DAs are needed to describe the valence three-quark states of the baryons at small transverse separations. The nonperturbative parameters relevant to the DAs are determined within the framework of QCD sum rule method. With the obtained DAs, a simple investigation on the electromagnetic form factors of these baryons are given. The magnetic moments of the baryons are estimated by fitting the magnetic form factor with the dipole formula.

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