42690692
Magnetic effects and chiral-symmetry breaking in strongly coupled quantum electrodynamics.
We study analytically the effect of magnetic interactions on dynamical symmetry breaking in strongly coupled quantum electrodynamics. By solving the Schwinger-Dyson equation for the electron propagator in the asymptotic region with the inclusion of magnetic effects in the vertex function, we find a nonperturbative solution whose existence indicates a spontaneous breaking of chiral symmetry with a critical coupling constant depending on the magnetic-interaction strength.
120093276
CONSISTENT FACTORIZATION AND TWIST-3 CONTRIBUTIONS TO THE POLARIZED NUCLEON STRUCTURE FUNCTION g2(x,Q2)
Quark mass effects are clarified in the parton model approach to the transversely polarized nucleon structure function. The special propagator technique is employed to obtain manifestly gauge invariant results and extract the buried short-distance contributions inside the soft part after momentum factorization in the collinear expansion approach. A generalized massive special propagator for a massive quark is constructed. We identify the corresponding matrix elements of the transversely polarized structure function in deep inelastic scattering by the massive special propagator technique.
13594754
Heavy-flavor-conserving nonleptonic weak decays of heavy baryons.
The heavy-flavor-conserving nonleptonic weak decays of heavy baryons are studied in a formalism that incorporates both heavy-quark symmetry and chiral symmetry. The phenomenological {Delta}{ital S}=1 nonleptonic weak chiral Lagrangian for these transitions contains two independent coupling constants that describe the transitions between two flavor-SU(3) antitriplet heavy baryons, and the transitions between two flavor-SU(3) sextet heavy baryons. In the MIT bag model and the diquark model, only transitions between antitriplets are allowed. The coupling constants for these transitions are calculated in both models. The result is applied to specific nonleptonic decays such as {Xi}{sub {ital c}}{r arrow}{Lambda}{sub {ital c}}{pi}, and the branching ratios are found to be of the order of 10{sup {minus}4}. An example of a nonleptonic decay due to symmetry breaking is provided by {Omega}{sub {ital c}}{r arrow}{Xi}{sub {ital c}}{sup {prime}}{pi}, which is estimated to have a smaller branching ratio, of the order of 10{sup {minus}5}.
10063732
Effective Lagrangian approach to weak radiative decays of heavy hadrons.
Motivated by the observation of the decay B\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}K${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}^{\mathrm{*}}$\ensuremath{\gamma} by the CLEO Collaboration, we have systematically analyzed the two-body weak radiative decays of bottom and charmed hadrons. There exist two types of weak radiative decays: One proceeds through the short-distance b\ensuremath{\rightarrow}s\ensuremath{\gamma} transition and the other occurs through W exchange accompanied by a photon emission. Effective Lagrangians are derived for the W-exchange bremsstrahlung processes at the quark level and then applied to various weak electromagnetic decays of heavy hadrons. Predictions for the branching ratios of B${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}^{0}$\ensuremath{\rightarrow}${\mathit{D}}^{\mathrm{*}0}$\ensuremath{\gamma}, ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{b}}^{0}$\ensuremath{\rightarrow}${\mathrm{\ensuremath{\Sigma}}}_{\mathit{c}}^{0}$\ensuremath{\gamma}, ${\mathrm{\ensuremath{\Xi}}}_{\mathit{b}}^{0}$\ensuremath{\rightarrow}${\mathrm{\ensuremath{\Xi}}}_{\mathit{c}}^{0}$\ensuremath{\gamma}, and ${\mathrm{\ensuremath{\Xi}}}_{\mathit{b}}^{0}$\ensuremath{\rightarrow}\ensuremath{\Xi}${\mathcal{'}}_{\mathit{b}}^{0}$\ensuremath{\gamma} are given. In particular, we find scrB(B${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}^{0}$\ensuremath{\rightarrow}${\mathit{D}}^{\mathrm{*}0}$\ensuremath{\gamma})\ensuremath{\approxeq}0.9\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}6}$. Order of magnitude estimates for the weak radiative decays of charmed hadrons, ${\mathit{D}}^{0}$\ensuremath{\rightarrow}K${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}^{\mathrm{*}0}$\ensuremath{\gamma}, ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}^{+}$\ensuremath{\rightarrow}${\mathrm{\ensuremath{\Sigma}}}^{+}$\ensuremath{\gamma}, and ${\mathrm{\ensuremath{\Xi}}}_{\mathit{c}}^{0}$\ensuremath{\rightarrow}${\mathrm{\ensuremath{\Xi}}}^{0}$\ensuremath{\gamma}, are also presented. Within this approach, the decay asymmetry for antitriplet to antitriplet heavy baryon weak radiative transitions is uniquely predicted by heavy quark symmetry. The electromagnetic penguin contribution to ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{b}}^{0}$\ensuremath{\rightarrow}\ensuremath{\Lambda}\ensuremath{\gamma} is estimated by two different methods and its branching ratio is found to be of the order of 1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$. We conclude that weak radiative decays of bottom hadrons are dominated by the short-distance b\ensuremath{\rightarrow}s\ensuremath{\gamma} mechanism.
43012116
Are there really no experimental limits on a light Higgs boson from kaon decay?
We reexamine the theoretical estimates of the decay {ital K}{r arrow}{pi}{ital H} and the experimental constraints on the existence of a light Higgs boson from this process. We find that (i) pole diagrams generated from the Higgs-boson--gluon coupling via a loop of heavy quarks do contribute to {ital K}{r arrow}{pi}{ital H}, (ii) there is an additional contribution to the {ital K}{r arrow}{pi}{ital H} amplitude coming from the effective {ital KHW} and {pi}{ital HW} couplings, (iii) even if {ital B}, the unknown parameter in the chiral-Lagrangian description of {ital K}{endash}{pi}{ital H} transitions, is nonzero and even if the real part of the {ital K}{r arrow}{pi}{ital H} amplitude is canceled accidentally, the imaginary contribution alone suffices to rule out a Higgs boson lighter than 2{ital m}{sub {pi}}, and (iv) whether Higgs bosons in the mass range 2{ital m}{sub {pi}}{lt}m{sub H}{lt}350 MeV are excluded by the imaginary part of the {ital K}{r arrow}{pi}{ital H} amplitude depends on the branching ratio of {ital H}{r arrow}{mu}{sup +}{mu}{sup {minus}} and the top-quark mass. Decay modes {ital K}{sub {ital L}}{r arrow}{pi}{sup +}{pi}{sup {minus}}H and {ital K}{sup +}{r arrow}l{sup +}{nu}H are briefly discussed.
36067168
Dimensional regularization and perturbative solution of the chiral Schwinger model.
The anomalous chiral Schwinger model is regulated by the method of dimensional regularization and is solved by diagrammatic perturbative expansion. It is shown that there is a regulation ambiguity in the solution. The result disagrees with Das's assertion and agrees with that of Jackiw, Rajaraman, and others.
45380547
Glueball components of the meson f2(1270).
It is shown that in order to explain the ratios {ital x} and {ital y} of the helicity amplitudes for the process {ital J}/{psi}{r arrow}{gamma}+{ital f}{sub 2}(1270) and the experimental datum {ital R}={ital B}({psi}{prime}({bold 3685}){r arrow}{gamma}+{bold f}{sub {bold 2}}({bold 1270}))/{ital B}({ital J}/{psi}{r arrow}{gamma}+{ital f}{sub {bold 2}}({bold 1270})) =(9{plus minus}3)% in terms of the mixture between the meson {ital f}{sub 2}(1270) and a 2{sup ++} glueball, two {ital D}-wave components have to be considered in addition to the {ital S}-wave component of the 2{sup ++} glueball.