13,482 research outputs found
Effects of the magnetic dipole moment of charged vector mesons in their radiative decay distribution
We consider the effects of anomalous magnetic dipole moments of vector mesons
in the decay distribution of photons emitted in two-pseudoscalar decays of
charged vector mesons. By choosing a kinematical configuration appropriate to
isolate these effects from model-dependent and dominant bremsstrahlung
contributions, we show that this method can provide a valid alternative for a
measurement of the unknown magnetic dipole moments of charged vector mesons.Comment: Latex, 11 pages incl. 3 .ps figures, to appear in Phys. Rev.
Arithmetic and the standard electroweak theory
We propose the relations 1/e - e =3 and tan(2theta_W)=3/2, where e is the
positron charge and theta_W is the weak angle. Present experimental data
support these relations to a very high accuracy. We suggest that some duality
relates the weak isospin and hypercharge gauge groups of the standard
electroweak theory.Comment: Latex, 6 page
Tests for the asymptotic behaviour of the gamma^* --> gamma pi^0 form factor
The gamma^* --> gamma pi^0 transition measured at different photon
virtualities already provides us with a clean test for the behaviour of the
pi^0 gamma^* gamma off-shell axial anomaly at large time-like squared momenta.
It also allows reliable predictions for the branching ratio of heavy quarkonium
decays into omega pi^0.Comment: Latex, 7 pages + 1 .ps figure, comments on the Brodsky-Lepage limit
and 5 new references adde
Binding energy corrections in positronium decays
Positronium annihilation amplitudes that are computed by assuming a
factorization approximation with on-shell intermediate leptons, do not exhibit
good analytical behavior. We propose an ansatz which allows to include binding
energy corrections and obtain the correct analytical and gauge invariance
behavior of these QED amplitudes. As a consequence of these non-perturbative
corrections, the parapositronium and orthopositronium decay rates receive
corrections of order alpha^4 and alpha^2, respectively. These new corrections
for orthopositronium are relevant in view of a precise comparison between
recent theoretical and experimental developments. Implications are pointed out
for analogous decays of quarkonia .Comment: 11 pages, 1 .ps figure, submitted for publicatio
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