37706866
Exclusive quasifree pion photoproduction on complex nuclei in the Delta region.
2293560
Kaon photoproduction on the neutron using deuterium.
The three processes \ensuremath{\gamma}+d\ensuremath{\rightarrow}${\mathrm{\ensuremath{\Lambda}}}^{0}$(${\mathrm{\ensuremath{\Sigma}}}^{0}$)+${\mathit{K}}^{0}$+p and \ensuremath{\gamma}+d\ensuremath{\rightarrow}${\mathrm{\ensuremath{\Sigma}}}^{\mathrm{\ensuremath{-}}}$+${\mathit{K}}^{+}$+p are investigated in the framework of the impulse approximation. The exclusive reactions d(\ensuremath{\gamma},Kp)Y where the proton is detected in coincidence with the ${\mathit{K}}^{0}$ or ${\mathit{K}}^{+}$ should provide unique signatures for each of the processes. In most kinematic situations the final-state Yp interaction is insignificant and the elementary process cross section for \ensuremath{\gamma}+n\ensuremath{\rightarrow}Y+K can be reliably extracted. Cross-section estimates are given for several models of the basic production operator.
14522537
Effects of the quantity sigma TS on the spin structure functions of nucleons in the resonance region.
In this paper, we investigate the effects of the quantity {sigma}{sub {ital TS}} on the spin structure functions of nucleons in the resonance region. The Schwinger sum rule for the spin structure function {ital g}{sub 2}({ital x},{ital Q}{sup 2}) at the real photon limit is derived for the nucleon treated as a composite system, and it provides a crucial constraint on the longitudinal transition operator which has not been treated consistently in the literature. The longitudinal amplitude {ital S}{sub 1/2} is evaluated in the quark model with the transition operator that generates the Schwinger sum rule. The numerical results of the quantity {sigma}{sub {ital TS}} are presented for both spin structure functions {ital g}{sub 1}({ital x},{ital Q}{sup 2}) and {ital g}{sub 2}({ital x},{ital Q}{sup 2}) in the resonance region. Our results show that this quantity plays an important role in the low {ital Q}{sup 2} region, which can be tested in future experiments at CEBAF. {copyright} {ital 1996 The American Physical Society.}
42674415
PQCD analysis of inclusive semileptonic decays of B mesons.
We develop the perturbative QCD formalism for inclusive semileptonic {ital B} meson decays, which includes Sudakov suppression from the resummation of large radiative corrections near the high end of charged lepton energy. Transverse degrees of freedom of partons are introduced to facilitate the factorization of {ital B} meson decays. Ambiguities appearing in the quark-level analysis are then avoided. A universal distribution function, arising from the nonperturbative Fermi motion of the {ital b} quark, is constructed according to the heavy quark effective field theory based operator product expansion, through which the mean and the width of the distribution function are related to hadronic matrix elements of local operators. Charged lepton spectra of the {ital B}{r_arrow}{ital X}{sub {ital ul}}{nu} decay are presented. We find 50{percent} suppression near the end point of the spectrum. The overall suppression on the total decay rate is 8{percent} for the free quark model, and is less than 7{percent} for the use of smooth distribution functions. With our predictions, it is then possible to extract the Cabibbo-Kobayashi-Maskawa matrix element {parallel}{ital V}{sub {ital ub}}{parallel} from experimental data. We also discuss possible implications of our analysis when confronted with the rather small observed semileptonic branching ratio in {ital B} mesonmore » decays. {copyright} {ital 1996 The American Physical Society.}« less
17940028
Perturbative QCD analysis of B meson decays.
The resummation of large QCD radiative corrections, including leading and next-to-leading logarithms, in the pion electromagnetic form factor is reviewed. A similar formalism is applied to exclusive processes involving heavy mesons, and leads to Sudakov suppression for the semileptonic decay {ital B}{r_arrow}{pi}{ital l}{nu}. It is found that, with the inclusion of Sudakov effects, a perturbative QCD analysis of this decay is reliable for the energy fraction of the pion above 0.4. Combining predictions from soft pion theorems we estimate that the upper limit of the matrix element {parallel}{ital V}{sub {ital ub}}{parallel} is 2.8{endash}4.8{times}10{sup {minus}3} from different models of the {ital B} meson wave function. {copyright} {ital 1996 The American Physical Society.}
32917384
Analytic calculation of the vacuum wave function for (2+1)-dimensional SU(2) lattice gauge theory.
The long wavelength vacuum wave function of (2+1)-dimensional SU(2) lattice gauge theory is calculated by the method of truncated eigenvalue equation. Third order results are consistent with Monte Carlo measurement and display a good scaling behavior extending to the deep weak coupling region.
45165928
Self-consistent solutions for vacuum currents around a magnetic flux string.
We consider the feedback effects of the vacuum currents induced by a magnetic flux string in 2+1 dimensions. Self-consistent induced charge and current densities that satisfy both the Dirac and Maxwell equations are given for the dimensionless coupling constant [ital g]==[ital e][sup 2]/[ital m][r arrow]0 and [ital g][r arrow][infinity]. These quantities for arbitrary [ital g] are inferred from the results of the two limiting cases, and also studied numerically.