arXiv subjects

H. W. Huang

Publications and source records attributed to H. W. Huang.

6 recordsLinked to original sources

arXiv2004

Signatures of the handbag mechanism in wide-angle photoproduction of pseudoscalar mesons

Wide-angle photoproduction of pseudoscalar mesons is investigated under the assumption of dominance of the handbag mechanism considering both quark helicity flip and non-flip. The partonic subprocess, meson photoproduction off quarks, is analysed with the help of a covariant decomposition of the subprocess amplitudes which is independent of a specific meson generation mechanism. As examples of subprocess dynamics, however, the twist-2 as well as two-particle twist-3 contributions are explicitly calculated. Characteristic features of the handbag approach are discussed in dependence upon the relative magnitudes of the invariant functions. Differential cross sections and spin correlations are predicted to show a characteristic behaviour which allows to test the underlying assumption of handbag dominance.

hep-ph↗

arXiv2003

One-Loop Helicity Amplitudes for Parton Level Virtual Compton Scattering

We calculate the one-loop QCD virtual corrections to all helicity amplitudes for parton level virtual Compton scattering processes. We include the amplitudes both on quark target process $γ^* q\toγq$ and on gluon target process $γ^*g\toγg$. The infrared pole structure of the amplitudes is in agreement with the prediction of Catani's general formalism for the singularities of one-loop amplitudes, while expressions for the finite remainder are given in terms of logarithms and dilogarithms that are real in the physical region.

hep-ph↗

arXiv2002

Proton mass effects in wide-angle Compton scattering

We investigate proton mass effects in the handbag approach to wide-angle Compton scattering. We find that theoretical uncertainties due to the proton mass are significant for photon energies presently studied at Jefferson Lab. With the proposed energy upgrade such uncertainties will be clearly reduced.

hep-ph↗

arXiv2001

Perturbative and non-perturbative QCD corrections to wide-angle Compton scattering

We investigate corrections to the handbag approach for wide-angle Compton scattering off protons at moderately large momentum transfer: the photon-parton subprocess is calculated to next-to-leading order QCD and contributions from the generalized parton distribution E} are taken into account. Photon and proton helicity flip amplitudes are non-zero due to these corrections which leads to a wealth of polarization phenomena in Compton scattering. Thus, for instance, the incoming photon asymmetry or the transverse polarization of the proton are non-zero although small.

hep-ph↗

arXiv2000

Large momentum transfer electroproduction of mesons

Assuming the proton's light-cone wave function to be dominated by small parton virtualities and small intrinsic transverse momenta, we show that the electroproduction amplitudes at large momentum transfer factorize into parton-level subprocess amplitudes and form factors representing 1/x-moments of skewed parton distributions. On the basis of a wave function overlap model for the form factors we present detailed predictions for the electroproduction cross sections. We also comment on large momentum transfer photoproduction.

hep-ph↗

arXiv1995

Gluonic and leptonic decays of heavy quarkonia and the determination of $α_s(m_c)$ and $α_s(m_b)$

QCD running coupling constant $α_s(m_c)$ and $α_s(m_b)$ are determined from heavy quarkonia $c\overline{c}$ and $b\overline{b}$ decays. The decay rates of $V\rightarrow 3g$ and $V\rightarrow e^+ e^-$ for $V=J/ψ$ and $Υ$ are estimated by taking into account both relativistic and QCD radiative corrections. The decay amplitudes are derived in the Bethe-Salpeter formalism, and the decay rates are estimated by using the meson wavefunctions which are obtained with a QCD-inspired inter-quark potential. For the $V\rightarrow 3g$ decay we find the relativistic correction to be very large and to severely suppress the decay rate. Using the experimental values of ratio $R_g\equiv \frac {Γ(V\longrightarrow 3g)}% {Γ(V\longrightarrow e^{+}e^{-})}\approx 10,~32 $ for $V=J/ψ, ~Υ$ respectively, and the calculated widths , we find $α_{s}(m_c)=0.29\pm 0.02 $ and $α_s(m_b)=0.20\pm 0.02$. These values for the QCD running coupling constant are substantially enhanced, as compared with the ones obtained without relativistic corrections, and are consistent with the QCD scale parameter $Λ_{\overline {MS}}^{(4)}% \approx 200MeV$. We also find that these results are mainly due to kinematic corrections and not sensitive to the dynamical models.

hep-ph↗