1,878 research outputs found
K-matrix analysis of the (IJ^{PC}=00^{++})-wave in the mass region below 1900 MeV
We present the results of the current analysis of the partial wave
IJ^{PC}=00^{++} based on the available data for meson spectra (pi-pi, K\bar K,
eta-eta, eta-eta', pi-pi-pi-pi). In the framework of the K-matrix approach, the
analytical amplitude has been restored in the mass region 280 MeV< \sqrt s
<1900 MeV. The following scalar-isoscalar states are seen: comparatively narrow
resonances f_0(980), f_0(1300), f_0(1500), f_0(1750) and the broad state
f_0(1200-1600). The positions of the amplitude poles (masses and total widths
of the resonances) are determined as well as pole residues (partial widths to
meson channels pi-pi, K\bar K, eta-eta, eta-eta', pi-pi-pi-pi). The fitted
amplitude gives us the positions of the K-matrix poles (bare states) and the
values of bare-state couplings to meson channels thus allowing the
quark-antiquark nonet classification of bare states. On the basis of the
obtained partial widths to the channels pi-pi, K\bar K, eta-eta, eta-eta', we
estimate the quark/gluonium content of f_0(980), f_0(1300), f_0(1500),
f_0(1750), f_0(1200-1600). For f_0(980), f_0(1300), f_0(1500) and f_0(1750),
their partial widths testify the q\bar q origin of these mesons though being
unable to provide precise evaluation of the possible admixture of the gluonium
component in these resonances. The ratios of the decay coupling constants for
the f_0(1200-1600) support the idea about gluonium nature of this broad state.Comment: 59 pages, 18 figures, epsfig, references are adde
Polarization degrees of freedom in near-threshold photoproduction of omega mesons in the pi^0 gamma decay channel
We study polarization variables in the photoproduction of omega-mesons with
subsequent omega to gamma pi^0 decay. Single and double polarization
observables are calculated as a function of different final-state angles.
Reaction models include pomeron (natural parity) and pi^0 (unnatural parity)
exchange in the t-channel. In addition, the contribution of s-channel
resonances is considered. The sensitivity of the polarization observables to
the reaction dynamics is discussed.Comment: 10 pages, 10 figures, explicit reference to sign of decay asymmetry
adde
A Rosetta Stone Relating Conventions In Photo-Meson Partial Wave Analyses
A new generation of complete experiments in pseudoscalar meson
photo-production is being pursued at several laboratories. While new data are
emerging, there is some confusion regarding definitions of asymmetries and the
conventions used in partial wave analyses (PWA). We present expressions for
constructing asymmetries as coordinate-system independent ratios of cross
sections, along with the names used for these ratios by different PWA groups.
(This update reflects a recent change in the definition of an asymmetry as used
by one group.)Comment: v2: This update reflects a recent change in the definition of an
asymmetry as used by one PWA group -see Table 1. v1: 4 pages. Contribution to
the proceedings of the 8th International Workshop on the Physics of Excited
Nucleons (NSTAR2011), Newport News, VA, USA, May 17-20, 201
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