Andrei Afanasev — Page 4

arXiv1998

Measuring Polarized Gluon and Quark Distributions with Meson Photoproduction

We calculate polarization asymmetries in photoproduction of high transverse momentum mesons, focusing on charged pions, considering the direct, fragmentation, and resolved photon processes. The results at very high meson momentum measure the polarized quark distributions and are sensitive to differences among the existing models. The results at moderate meson momentum are sensitive to the polarized gluon distribution and can provide a good way to measure it. Suitable data may come as a by-product of deep inelastic experiments to measure $g_1$ or from dedicated experiments.

hep-ph↗

arXiv1997

Photo-- and Electroproduction of $J^{PC}=1^{-+}$ exotics

We estimate the kinematic dependence of the exclusive photo-- and electroproduction of $J^{PC}=1^{-+}$ exotic mesons due to $π$ exchange. We show that the kinematic dependence is largely independent of the exotic meson form factor, which is explicitly derived for a $1^{-+}$ isovector hybrid meson in the flux-tube model of Isgur and Paton. The relevance to experiments currently planned at Jefferson Lab is indicated.

hep-ph↗

arXiv1997

Probing Polarized Parton Distributions with Meson Photoproduction

Polarization asymmetries in photoproduction of high transverse momentum mesons are a flavor sensitive way to measure the polarized quark distributions. We calculate the expected asymmetries in several models, and find that the asymmetries are significant and also significantly different from model to model. Suitable data may come as a by-product of deep inelastic experiments to measure $g_1$ or from dedicated experiments.

hep-ph↗

arXiv1996

Virtual Compton Scattering on the Proton at High s and Low t

Virtual Compton Scattering (VCS) at low transferred momenta to the proton ($t$) and sufficiently high c.m. energies ($s$) may be used to a) study $Q^2$--dependence of leading $t$--channel exchanges and b) look for onset of scaling behavior with increasing $Q^2$. I discuss the implications for perturbative and nonperturbative QCD and suggest possible experiments.

hep-ph↗

arXiv1996

Form Factors of Kaon Semileptonic Decays

A calculation of the semi--leptonic decays of the kaon ($K_{l3}$) is presented. The results are direct predictions of a covariant model of the pion and kaon introduced earlier by Ito, Buck, Gross. The weak form factors for $K_{l3}$ are predicted with absolutely no parameter adjustments of the model. We obtained for the form factor parameters: $f_-(q^2=m_l^2)/f_+(q^2=m_l^2)=-0.28$ and $λ_+$= 0.028, both within experimental error bars. Connections of this approach to heavy quark symmetry will also be discussed.

hep-ph↗

arXiv1996

Unified Description of Kaon Electroweak Form Factors

A calculation of the semi--leptonic decays of the kaon ($K_{l3}$) is presented. The results are direct predictions of a covariant model of the pion and kaon introduced earlier by Ito, Buck, Gross. The weak form factors for $K_{l3}$ are predicted with absolutely no parameter adjustments of the model. We obtained for the form factor parameters: $f_-(q^2=m_l^2)/f_+(q^2=m_l^2)=-0.28$ and $λ_+$= 0.028, both within experimental error bars. Connections of this approach to heavy quark symmetry will also be discussed.

hep-ph↗

arXiv1996

Atomic Electron Motion for Möller Polarimetry in a Double-Arm Mode

We analyse an effect of electron Fermi motion at atomic shells on the accuracy of electron beam polarization measurements with a Möller polarimeter operating in a double--arm mode. It is demonstrated that the effect can result in either {\it increase} or {\it decrease} of the measured polarization depending on the detector positions. The effect is simulated for the Möller polarimeter to be installed at CEBAF Hall A.

hep-ex↗