34810684
Restudy of the open-superstring tree amplitudes by looking at their field-theoretical limits.
We carry out complete computations of some open- and closed-superstring tree amplitudes by using the bosonized covariant vertices. Some open-superstring amplitudes so obtained are shown to be different from those obtained in the light-cone gauge approach by some numerical factors. The low-energy limits of our five open-superstring amplitudes are then shown to match the five super Yang-Mills field amplitudes while the five light-cone gauge open-superstring amplitudes fail to do so.
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.
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.
32623506
Gauge dependence of the effective potential for bilocal composite fields in Abelian gauge theories.
The Nielsen-Fukuda-Kugo identity expressing the gauge dependence of effective potentials is generalized to the case of the effective potential for bilocal composite fields in quantum electrodynamics. The resulting identity serves to show the gauge independence of the ground-state energy in the presence of dynamical chiral-symmetry breaking. As a by-product we derive a formula giving the gauge dependence of fermion propagators. It is shown explicitly that the effective potential in the quenched planar approximation does not respect the identity. The Nielsen-Fukuda-Kugo identity is also derived for the effective potential in the auxiliary-field approach.
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.
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}.
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.