347 research outputs found
Q^2-Dependence of the Drell-Hearn-Gerasimov integral
The energy and four-momentum (Q^2) dependence of the photo-absorption cross
section on the proton is calculated for helicity -1/2 and -3/2 states. An
effective Lagrangian model is used, formulated in terms of meson and baryon
degrees of freedom, which obeys crossing symmetry, unitarity, Lorentz and gauge
invariance. The difference in the cross sections for the two helicity states,
the Drell-Hearn-Gerasimov integral , is evaluated at different
. We find that at small momentum transfer the absolute value of
first increases to reach a maximum at
before decreasing at higher .Comment: 8 pages, 3 figures, revte
Angular distribution and forward-backward asymmetry of the Higgs-boson decay to photon and lepton pair
The Higgs-boson decay h -> gamma l+ l- for various lepton states l = (e, mu,
tau) is analyzed. The differential decay width and forward-backward asymmetry
are calculated as functions of the dilepton invariant mass in a model where the
Higgs boson interacts with leptons and quarks via a mixture of scalar and
pseudoscalar couplings. These couplings are partly constrained from data on the
decays to leptons, h -> l+ l-, and quarks h -> q \bar{q} (where q = (c, b)),
while the Higgs couplings to the top quark are chosen from the two-photon and
two-gluon decay rates. Nonzero values of the forward-backward asymmetry will
manifest effects of new physics in the Higgs sector. The decay width and
asymmetry integrated over the dilepton invariant mass are also presented.Comment: 9 pages, 4 figures, SVJour3 class; v2: minor changes in text,
references updated and extended, corresponds to journal versio
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