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Han-Wen Huang

Publications and source records attributed to Han-Wen Huang.

14 recordsLinked to original sources

Study of $B\to K^* ρ, K^*ω$ Decays with Polarization in Perturbative QCD Approach

The $B \to K^{*}ρ$, $ K^{*}ω$ decays are useful to determine the CKM angle $ϕ_3=γ$. Their polarization fractions are also interesting since the polarization puzzle of the $B\to ϕK^*$ decay. We study these decays in the perturbative QCD approach based on $k_T$ factorization. After calculating of the non-factorizable and annihilation type contributions, in addition to the conventional factorizable contributions, we find that the contributions from the annihilation diagrams are crucial. They give dominant contribution to the strong phases and suppress the longitudinal polarizations. Our results agree with the current existing data. We also predict a sizable direct CP asymmetries in $B^+ \to K^{*+}ρ^0$, $B^0 \to K^{*+}ρ^-$, and $B^+ \to K^{*+}ω$ decays, which can be tested by the oncoming measurements in the B factory experiments.

hep-ph

Electroproduction of psi' and polarized gluon distribution in a proton

In order to get information about the polarized gluon distribution in a proton, we studied the electroproduction of ψ' in polarized electron and polarized proton collisions in the framework of the NRQCD factorization approach. The value of the cross section dΔσ/ dp_T^2 for color-octet mechanism is about 5 times larger than that for color-singlet one, and it might be another test of the color-octet model if the polarized gluon distribution Δg(x) is well known. Furthermore, we found that this reaction is quite effective for testing the model of gluon polarization by measuring the double spin asymmetry A_{LL} for the initial electron and proton. Though the shape of p_T^2 distribution of A_{LL} is quite similar for the production mechanism with color-octet and color-singlet, we can see a big difference in A_{LL} among various models of the polarized gluon distribution function Δg(x).

hep-ph

Double Scattering Effect in Transverse Momentum Distribution of Inclusive $J/ψ$ Production in Photo-Nucleus Collision

In terms of multiple scattering picture, we calculate the double scattering effect in the transverse momentum distribution of $J/ψ$ photoproduction. Applying the generalized factorization theorem, we find that the contributions from double scattering can be expressed in terms of twist-4 nuclear parton correlation functions, which is the same as that used to explain the nuclear dependence in di-jet momentum imbalance and in direct photon production. Using the known information on the twist-4 parton correlation functions, we estimate that the double scattering contributes a small suppression in $J/ψ$ photoproduction. In the analysis we only take into account the leading order in the small velocity expansion for the nonperturbative parts related to the quarkonium.

hep-ph

QCD Radiative Correction to the Hadronic Annihilation Rate of $1^{+-}$ Heavy Quarkonium

Hadronic annihilation rate of $1^{+-}$ heavy quarkonium is given to next-to-leading order in $α_s$ and leading order in $v^2$ using a recently developed factorization formalism which is based on NRQCD. The result includes both the annihilation of P-wave color-singlet $Q\bar{Q}$ component, and the annihilation of S-wave color-octet $Q\bar{Q}$ component of the quarkonium. The notorious infrared divergences due to soft gluons, i.e., the Logarithms associated with the binding energy, encountered in previous perturbative calculations of $1^{+-}$ quarkonium decays are found to be explicitly cancelled, and a finite result for the decay width to order $α_s^3$ is then obtained.

hep-ph

The $p_T$ Distribution of $J/ψ$ in QGP

We consider the contributions of both color-singlet and octet $c\bar c$ bound states for studying the suppression of $J/ψ$ production in quark gluon plasma (QGP) and have found that the existence of the color-octet $c\bar c$ may cause the $p_T-$distribution of $J/ψ$ a decrease with $p_T$ after a critical value $(p_T)_{max}$, which is quite different from the behavior in Hadronic Matter (HM).

hep-ph

QCD predictions for annihilation decays of P-wave quarkonia to next-to-leading order in $α_s$

The decay rates of P-wave heavy quarkonia to light hadrons are presented to leading order in $v^2$ and next-to-leading order in $α_s$. They include contributions from both the color-singlet component and the color-octet component of quarkonia. Applying these results to charmonium and using measured decay rates for the $χ_{c1}$ and $χ_{c2}$ by E760, we determine the two nonperturbative decay matrix elements, and then predict the hadronic decay rates of $χ_{c0}$ and $h_c$, and the electromagnetic decay rates of $χ_{c0}$ and $χ_{c2}$. The obtained decay rates of $χ_{c0}\to LH$ and $χ_{c0}\toγγ$ are in agreement with the Crystal Ball result, and also with the new measurement by BES. However, the results for $Γ(χ_{c0}\to LH)$ are dependent on the choice of renormalization scale.

hep-ph

Cancellation of Infrared Divergences in Hadronic Annihilation Decays of Heavy Quarkonia

In the framework of a newly developed factorization formalism which is based on NRQCD, explicit cancellations are shown for the infrared divergences that appeared in the previously calculated hadronic annihilation decay rates of P-wave and D-wave heavy quarkonia. We extend them to a more general case that to leading order in $v^2$ and next-to-leading order in $α_s$, the infrared divergences in the annihilation amplitudes of color-singlet $Q\bar{Q}(^{2S+1}L_J)$ pair can be removed by including the contributions of color-octet operators $Q\bar{Q}(^{2S+1}(L-1)_{J'})$, $Q\bar{Q}(^{2S+1}(L-3)_{J''})$, ... in NRQCD. We also give the decay widths of $^3D_J\rightarrow LH$ at leading order in $α_s$.

hep-ph

QCD Corrections to $b \to s e^+e^-$ Decay

We give a more complete calculation of $b \to s e^+e^- $ decay including leading log QCD corrections from $m_{top}$ to $M_W$ in addition to corrections from $M_{W}$ to $m_b$. The differential decay rate is found to be slightly suppressed for a large invariant mass of the $e^+e^- $ pair; while the integrated width is slightly enhanced comparing with the results without the QCD running from $m_{top}$ to $M_W$.

hep-ph

$B\to X_sτ^+τ^-$ in a two Higgs doublet model

The inclusive rate and forward-backward asymmetry of dilepton angular distribution for a B-meson to decay to strange hadronic final states and a $τ^+τ^-$ pair in a two Higgs doublet model are computed. In particular, contributions of neutral Higgs bosons to the decay are included. QCD corrections to the effective Hamiltonian for $B\rightarrow X_sτ^+τ^-$ are calculated using the leading logarithmic approximation.

hep-ph

Possible retardation effects of quark confinement on the meson spectrum

The reduced Bethe-Salpeter equation with scalar confinement and vector gluon exchange is applied to quark-antiquark bound states. The so called intrinsic flaw of Salpeter equation with static scalar confinement is investigated. The notorious problem of narrow level spacings is found to be remedied by taking into consideration the retardation effect of scalar confinement. Good fit for the mass spectrum of both heavy and light quarkomium states is then obtained.

hep-ph

Electromagnetic Annihilation Rates of $χ_{c0}$ and $χ_{c2}$ with Both Relativistic and QCD Radiative Corrections

We estimate the electromagnetic decay rates of $χ_{c0}\rightarrow γγ$ and $χ_{c2}\rightarrowγγ$ by taking into account both relativistic and QCD radiative corrections. The decay rates are derived in the Bethe-Salpeter formalism and the QCD radiative corrections are included in accordance with factorization assumption. Using a QCD-inspired interquark potential, we obtain relativistic BS wavefunctions of $χ_{c0}$ and $χ_{c2}$ by solving BS equations for the corresponding $^{2S+1}L_J$ states. Our numerical result for the ratio $R=\frac{Γ(χ_{c0}\rightarrowγγ)}{Γ(χ_{c2} \rightarrowγγ)}$ is about $11-13$ which agrees with the update E760 experimental data. Explicit calculations show that the relativistic corrections due to spin-dependent interquark forces induced by gluon exchange enhance the ratio $R$ substantially and its value is insensitive to the choice of parameters that characterize the interquark potential. Our expressions for the decay widths are identical with that obtained in the NRQCD theory to the next-to-leading order in $v^2$ and $α_s$. Moreover, we have determined two new coefficents in the nonperturbative matrix elements for these decay widths.

hep-ph

Pseuduscalar Heavy Quarkonium Decays With Both Relativistic and QCD Radiative Corrections

We estimate the decay rates of $η_c\rightarrow 2γ$, $η_c'\rightarrow 2γ$, and $J/ψ\rightarrow e^+ e^-$, $ψ^\prime\rightarrow e^+e^-$, by taking into account both relativistic and QCD radiative corrections. The decay amplitudes are derived in the Bethe-Salpeter formalism. The Bethe-Salpeter equation with a QCD-inspired interquark potential are used to calculate the wave functions and decay widths for these $c\bar{c}$ states. We find that the relativistic correction to the ratio $R\equiv Γ(η_c \rightarrow 2γ)/ Γ(J/ ψ\rightarrow e^+ e^-)$ is negative and tends to compensate the positive contribution from the QCD radiative correction. Our estimate gives $Γ(η_c \rightarrow 2γ)=(6-7) ~keV$ and $Γ(η_c^\prime \rightarrow 2γ)=2 ~keV$, which are smaller than their nonrelativistic values. The hadronic widths $Γ(η_c \rightarrow 2g)=(17-23) ~MeV$ and $Γ(η_c^\prime \rightarrow 2g)=(5-7)~MeV$ are then indicated accordingly to the first order QCD radiative correction, if $α_s(m_c)=0.26-0.29$. The decay widths for $b\bar b$ states are also estimated. We show that when making the assmption that the quarks are on their mass shells our expressions for the decay widths will become identical with that in the NRQCD theory to the next to leading order of $v^2$ and $α_s$.

hep-ph