arXiv subjects

Tao Huang

Publications and source records attributed to Tao Huang.

At least 343 records · Page 19Linked to original sources

arXiv2005

B-Meson Wavefunction in the Wandzura-Wilczek Approximation

The B-meson wavefunction has been studied with the help of the vacuum-to-meson matrix element of the nonlocal operators in the heavy quark effective theory. In order to obtain the Wandzura-Wilczek-type B-meson wavefunction, we solve the equations which are derived from the equation of motion of the light spectator quark in the B meson by using two different assumptions. Under the condition that $ω_0=2\barΛ$, the solutions for the B-meson wavefunction in this paper agree well with the one obtained by directly taking the heavy quark limit $m_b\to\infty$. Our results show that the equation of motion of the light spectator quark in the B meson can impose a strong constraint on the B-meson wavefunctions $Ψ_\pm(ω,z^2)$. Based on the obtained results, we claim that both its distribution amplitudes $ϕ_B(ω)$ and $\barϕ_B(ω)$ are important for calculating the B meson decays.

hep-ph↗

arXiv2004

Signal of the pion string at high-energy collisions

We study the possible signals of a pion string associated with the QCD chiral phase transition in LHC Pb - Pb collision at energy $ \sqrt{s}=5.5$ TeV. In terms of the Kibble-Zurek mechanism we discuss the production and evolution of the pion string. The pion string is not topologically stable, it decays into neutral pions and sigma mesons which in turn decay into pions. Our results show that all the neutral pions from the pion string are distributed at the low momentum and the ratio of neutral to charged pions from the pion string violates the isospin symmetry. For the momentum spectra of the total pions, the signal from the sigma particle decay which is from the pion string will be affected by the large decay width of the sigma significantly.

hep-ph↗

arXiv2004

A Model for the Twist-3 Wave Function of the Pion and Its Contribution to the Pion Form Factor

A model for the twist-3 wave function $ψ_p(x,\mathbf{k_\perp})$ of the pion has been constructed based on the moment calculation by applying the QCD sum rules, whose distribution amplitude has a better end-point behavior than that of the asymptotic one. With this model wave function, the twist-3 contributions including both the usual helicity components ($λ_1+λ_2=0$) and the higher helicity components ($λ_1+λ_2=\pm 1$) to the pion form factor have been studied within the modified pQCD approach. Our results show that the twist-3 contribution drops fast and it becomes less than the twist-2 contribution at $Q^2\sim 10GeV^2$. The higher helicity components in the twist-3 wave function will give an extra suppression to the pion form factor. The model dependence of the twist-3 contribution to the pion form factor has been studied by comparing three different models. When all the power contributions, which include higher order in $α_s$, higher helicities, higher twists in DA and etc., have been taken into account, it is expected that the hard contributions will fit the present experimental data well at the energy region where pQCD is applicable.

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arXiv2004

Domain Wall in the Linear Sigma Model

We discuss the role of the axial $U(1)_A$ symmetry in the chiral phase transition using the $U(N_f)_R\times U(N_f)_L$ linear sigma model with two massless quark flavors. We expect that above a certain temperature the axial $U(1)_A$ symmetry will be effectively restored as well as $SU(N_f)_R\times SU(N_f)_L$. Then we can construct a string-like static solution the $η$ string and a kink-like classical solution the domain wall during the chiral phase transition. We give out the possible signals for detecting the domain wall in ultrarelativistic heavy-ion collisions.

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arXiv2004

$B\to Kπ$ Decays with $1/m_b$ Corrections in $QCD$ Factorization

It is commonly believed that a careful investigation of the subleading terms is crucial for a better understanding of the $QCD$ factorization in charmless B decays. In this work the penguin-dominated $B\to Kπ$ decays are discussed systematically, including the subleading corrections in $1/m_b$ due to soft and hard gluons, besides the annihilation contributions. Soft-gluon effects for all the relevant 4-quark effective operators are calculated within the framework of the light-cone QCD sum rules (LCSR). Our observation is that such soft and hard corrections are less important than the annihilation effects, enhancing only the branching ratios by a few percent; the resultant increase in the branching ratios due to the overall ${\cal O}(1/m_b)$ effects is between about $(22-27)%$ of the QCD factorization results with the ${\cal O}(α_s)$ corrections, as the weak phase $γ(=\textmd{Im}V_{ub}^*)$ ranges from $40^0$ to $80^0$. Impacts of the involved uncertainties are discussed in some details.

hep-ph↗

arXiv2004

Nonfactorizable soft contributions in the $B\longrightarrow η_c K,χ_{c0} K$ decays with the light-cone sum rules approach

In this article, we calculate the nonfactorizable soft contributions in the $B \to η_c K, χ_{c0} K$ decays with the light cone QCD sum rules approach. Our results show that the nonfactorizable corrections from the soft gluon exchanges in the decay $B \to η_c K$ are of $(15-30)%$ and should not be neglected. As for the decay $B \to χ_{c0} K$, the factorizable contributions are zero and the nonfactorizable contributions from the soft hadronic matrix elements are too small to accommodate the experimental data.

hep-ph↗

arXiv2004

Twist-3 Distribute Amplitude of the Pion in QCD Sum Rules

We apply the background field method to calculate the moments of the pion two-particles twist-3 distribution amplitude (DA) $ϕ_p(ξ)$ in QCD sum rules. In this paper,we do not use the equation of motion for the quarks inside the pion since they are not on shell and introduce a new parameter $m_0^p$ to be determined. We get the parameter $m_0^p\approx1.30GeV$ in this approach. If assuming the expansion of $ϕ_p(ξ)$ in the series in Gegenbauer polynomials $C_n^{1/2}(ξ)$, one can obtain its approximate expression which can be determined by its first few moments.

hep-ph↗

arXiv2004

The twist-3 distribution amplitudes in the $B\toπ$ transition form factor

We derive an expression for the $B\toπ$ transition form factor only depending the twist-3 distribution amplitudes by choosing an adequate chiral current correlator in the light-cone QCD sum rules. Our result show that the contribution from the twist-3 distribution amplitudes to the $f_{Bπ}^+(q^2)$ give a constraint on the twist-3 light-cone distribution amplitude.

hep-ph↗

arXiv2003

Lepton Dipole Moments and Rare Decays in the CP-violating MSSM with Nonuniversal Soft-Supersymmetry Breaking

We investigate the muon anomalous magnetic dipole moment (MDM), the muon electric dipole moment (EDM) and the lepton-flavour-violating decays of the $τ-$lepton, $τ\to μγ$ and $τ\to 3μ$, in the CP-violating Minimal Supersymmetric Standard Model (MSSM) with nonuniversal soft-supersymmetry breaking. We evaluate numerically the muon EDM and the branching ratios $B(τ\to μγ)$ and $B(τ\to 3μ)$, after taking into account the experimental constraints from the electron EDM and muon MDM. Upon imposition of the experimental limits on our theoretical predictions for the aforementioned branching ratios and the muon MDM, we obtain an upper bound of about $10^{-23} e\cdot cm$ on the muon EDM which lies well within the explorable reach of the proposed experiment at BNL.

hep-ph↗

arXiv2003

$B-π$ weak form factor with chiral current in the light-cone sum rules

In this article, we calculate the $B\to π$ transition form factor $f^{+}_{Bπ}(q^2)$ by including perturbative $O(α_s)$ corrections to the twist-2 terms with chiral current in the light-cone QCD sum rule approach. The corrections to the product $f_Bf^{+}_{Bπ}(q^2)$ in the leading twist approximation is found to be about 30%, while a similar magnitude corresponding to $O(α_s)$ corrections for $f_B(q^2)$ in the two-point sum rule cancel them and result in small net corrections for $f^{+}_{Bπ}(q^2)$. Our results confirm the observations made in previous light-cone QCD sum rule studies.

hep-ph↗

arXiv2002

B-->KK decays with the soft-gluon corrections

We analyze the B->KK decays with the soft-gluon corrections by using the QCD light-cone sum rules (LCSR). Although QCD factorization approach calculates the leading order factorization parts and the radiative corrections from hard- gluon exchanges at $α_{s}$ order, it is worthwhile to estimate the nonfactorizable soft-gluon contributions from all the tree and penguin diagrams systematically. Our results show that the soft-gluon effects always decrease the branching ratios and give a few percentage corrections at most in the B->KK decays.

hep-ph↗

arXiv2002

Strong Couplings of Heavy Mesons to A Light Vector Meson in QCD

We make a detailed analysis of the $BBρ(DDρ)$ and $B^*Bρ(D^{*}Dρ)$ strong couplings $g_{BBρ}(g_{DDρ})$ and $g_{B^*Bρ}(g_{D^{*}Dρ})$ using QCD light cone sum rules(LCSR). The existing some negligence is pointed out in the previous LCSR calculation on $g_{B^*Bρ} (g_{D^{\ast}Dρ}$) and an updated estimate is presented. Our findings can be used to understand the behavior of the $B,D \to ρ$ semileptonic form factors at large momentum transitions.

hep-ph↗

arXiv2002

Reexamined radiative Decay $ B_{q}^*\to B_{q}γ$ in Light Cone QCD

The radiative decay $ B_{q}^*\to B_{q}γ(q=u,d, or s) $ is reexamined with a modified light-cone QCD sum rule method, in which adequate chiral operators are chosen as the interpolating fields in the correlators used for a sum rule estimate of the relevant coupling $ g_{B_{q}^*B_{q}γ} $. The resulting sum rules not only show the physical picture consistent with the underlying physics in $ B_{q}^*\to B_{q}γ$ but also avoid the pollution by the nonlocal matrix element $< γ(q) | \bar{q}(x) γ_μγ_{5}q(0) | 0>$, which starts with twist-3 and thus may bring a large uncertainty to the sum rule predictions. Also, a comparison is made with the previous results from light-cone QCD sum rules and chiral perturbation theory.

hep-ph↗

arXiv2002

$σ$ Meson In $J/Ψ$ Decays

Recently BES at BEPC found evidence for the existence of the $σ$ meson in the process of $J/Ψ\to σω\toππω$. In this paper we firstly discuss the relevant coupling $g_{σππ}$ and show that the linear $σ$ model gives rise to a reasonable description of the $σ$ decay into $π$'s, then we calculate the coupling constant $g^{th}_{J/Ψσω}$ by using the perturbative QCD technique and the light-cone wave functions of the $σ$ and $ω$ mesons. The results show that the theoretical value of $g^{th}_{J/Ψσω}$ is within the range of experimental value $g_{J/Ψσω}$.

hep-ph↗

arXiv2001

A Phenomenological Analysis of Higher Fock State Contributions to the $χ_{cJ}$ Decays

We present a phenomenological analysis of higher Fack state contributions to the $χ_{cJ}$ decays by using the recent BES experimental data. It is found that the higher Fock state $\mid (c\bar{c})_{8}g>$ makes an important contributions to the inclusive and exclusive processes with respect to that from the valence Fock state $\mid c\bar{c} >$ of the $χ_{cJ}$ and some constraints of these contributions are obtained for the $χ_{c0}$ and $χ_{c2}$ states in order to fit the experimental data.

hep-ph↗

arXiv2001

The heavy-to-light transitions in the light-cone QCD sum rules

We have analyzed the $B\to π$ and $B_{s}\to K$ semileptonic form factors and $B\to Vγ(V=K^*,ρ,ω)$ processes in the light-cone QCD sum rules. In order to enhance the predictivity and reliability of numerical results the chiral-current correlator is employed and the twist-3 light-cone wavefunction can be effectively eliminated from the sum rules.

hep-ph↗

arXiv2001

The $B_{s}\to K$ Form Factor in The Whole Kinematically Accessible Range

A systematic analysis is presented of the $B_{s}\to K$ form factor $f(q^{2}) $ in the whole range of momentum transfer $q^{2}$, which would be useful to analyzing the future data on $B_{s}\to K$ decays and extracting $| V_{ub}|$. With a modified QCD light cone sum rule (LCSR) approach, in which the contributions cancel out from the twist 3 wavefunctions of $K$ meson, we investigate in detail the behavior of $f(q^{2})$ at small and intermediate $q^{2}$ and the nonperturbative quantity $f_{B^{\ast}}g_{B^{\ast}B_{s}K}$ $(f_{B^{\ast}}$ is the decay constant of $B^{\ast}$ meson and $g_{B^{\ast}B_{s}K}$ the $B^{\ast}B_{s}K$ strong coupling), whose numerical result is used to study $q^{2}$ dependence of $f(q^{2})$ at large $q^{2}$ in the single pole approximation. Based on these findings, a form factor model from the best fit is formulated, which applies to the calculation on $f(q^{2})$ in the whole kinematically accessible range. Also, a comparison is made with the standard LCSR predictions.

hep-ph↗

arXiv2001

Improved approach to the heavy-to-light form factors in the light-cone QCD sum

A systematic analysis shows that the main uncertainties in the form factors are due to the twist-3 wave functions of the light mesons in the light-cone QCD sum rules. We propose an improved approach, in which the twist-3 wave functions doesn't make any contribution and therefore the possible pollution by them can be avoided, to re-examine $B \to π$ semileptonic form factors. Also, a comparison between the previous and our results from the light-cone QCD sum rules is made. Our method will be beneficial to the precise extracting of $\mid{V_{ub}}\mid$ from the experimental data on the processes $B \to π\ell \widetilde{ν_\ell}$.

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