566 research outputs found
Excitated state properties of 20-chloro-chlorophyll a
The excited-state and lasing properties of 20-chloro-chlorophyll a in ether solution were compared to those of chlorophyll a. Desactivation parameters and cross-sections were obtained from non-linear absorption spectroscopy in combination with a physico-mathematical methods package. The Cl substituent at C-20 (1) increases both intersystem crossing and internal conversion, (2) produces a blue-shift of the S1 absorption spectrum, and (3) leads to pronounced photochemistry
Information on the structure of the rho meson from the pion form-factor
The electromagnetic pion form-factor is calculated in a Bethe-Salpeter
approach which accounts for pion rescattering. In the scattering kernel the
pion-pion contact interaction from lowest-order chiral perturbation theory is
considered together with an optional vector meson in the s-channel.
Correspondingly the virtual photon couples to a two-pion state and optionally
to the vector meson. It is shown that for reasonable ranges of input parameters
the experimentally observed pion form-factor cannot be described by the
iterated pion-pion contact interaction alone, i.e. without an elementary vector
meson. The inclusion of an elementary vector meson allows for an excellent
description. This completes a recent study (``Information on the structure of
the a_1 from tau decay'') where it has been shown that the a_1 meson can be
well understood as a rescattering process of rho meson and pion. Here it is
demonstrated that within the same formalism the rho meson cannot be understood
as a pion-pion rescattering process. This suggests that the chiral partners a_1
and rho are not only different in mass, but also different in nature.Comment: 12 page
Modelling Drell-Yan pair production in pbar-p
We predict the triple differential cross section of the unpolarized Drell-Yan
process at sqrt(S)=6 GeV. The model incorporates primordial parton transverse
momentum and quark off-shellness effects caused by the initial state
interaction.Comment: 4 pages, AIP style, talk given at the conference LEAP'05 (Low Energy
Antiproton Physics
Electromagnetic Transition Form Factors of Mesons
Using a counting scheme which treats pseudoscalar and vector mesons on equal
footing, the decays of the narrow light vector mesons omega and phi into a
dilepton and a pseudoscalar pi-meson or eta-meson, respectively, are
calculated. Thereby, all required parameters could be determined by other
reactions so that one has predictive power for the considered decays. The
calculated partial decay widths are in very good agreement with the
experimental data.Comment: Talk given at the 33rd International School of Nuclear Physics (From
Quarks and Gluons to Hadrons and Nuclei) in Erice (Italy
Hadronic three-body decays of light vector mesons
The decays of light vector mesons into three pseudoscalar mesons are
calculated to leading order in the recently proposed counting scheme that is
based on the hadrogenesis conjecture. Fully differential as well as integrated
decay widths are presented. Since the required parameters have been fixed by
other processes, the considered three-body decays are predictions of the
presented approach. The decay width of the omega meson into three pions agrees
very well with experiment. The partial decay widths of the K^* into its three
K-pi-pi channels are predicted.Comment: 7 page
Nuclear shadowing and in-medium properties of the rho^0
We explain the early onset of shadowing in nuclear photoabsorption within a
multiple scattering approach and discuss its relation to in-medium
modifications of the rho^0.Comment: 4 pages, 2 figures, to appear in the proceedings of the 9th
International Conference on the Structure of Baryons, Newport News, VA, USA,
3-8 Mar 200
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