1,423 research outputs found
Dispersive analysis of omega --> 3pi and phi --> 3pi decays
We study the three-pion decays of the lightest isoscalar vector mesons, omega
and phi, in a dispersive framework that allows for a consistent description of
final-state interactions between all three pions. Our results are solely
dependent on the phenomenological input for the pion-pion P-wave scattering
phase shift. We predict the Dalitz plot distributions for both decays and
compare our findings to recent measurements of the phi --> 3pi Dalitz plot by
the KLOE and CMD-2 collaborations. Dalitz plot parameters for future precision
measurements of omega --> 3pi are predicted. We also calculate the pi-pi P-wave
inelasticity contribution from omega-pi intermediate states.Comment: 23 pages, 18 figures; discussion extended, Appendix D added, matches
version published in EPJ
Dispersion relations for
We present a dispersive analysis of the decay amplitude for
that is based on the fundamental principles of analyticity
and unitarity. In this framework, final-state interactions are fully taken into
account. Our dispersive representation relies only on input for the
and scattering phase shifts. Isospin symmetry allows us to describe
both the charged and neutral decay channel in terms of the same function. The
dispersion relation contains subtraction constants that cannot be fixed by
unitarity. We determine these parameters by a fit to Dalitz-plot data from the
VES and BES-III experiments. We study the prediction of a low-energy theorem
and compare the dispersive fit to variants of chiral perturbation theory.Comment: 22 pages, 10 figures; v2: added footnote, version published in EPJ
Dispersive analysis of the pion transition form factor
We analyze the pion transition form factor using dispersion theory. We
calculate the singly-virtual form factor in the time-like region based on data
for the cross section, generalizing previous studies on
decays and scattering, and verify our
result by comparing to data. We perform the analytic
continuation to the space-like region, predicting the poorly-constrained
space-like transition form factor below 1 GeV, and extract the slope of the
form factor at vanishing momentum transfer .
We derive the dispersive formalism necessary for the extension of these results
to the doubly-virtual case, as required for the pion-pole contribution to
hadronic light-by-light scattering in the anomalous magnetic moment of the
muon.Comment: 13 pages, 5 figures, journal versio
omega --> pi0 gamma* and phi --> pi0 gamma* Transition form factors in dispersion theory
We calculate the omega --> pi0 gamma* and phi --> pi0 gamma* electromagnetic
transition form factors based on dispersion theory, relying solely on a
previous dispersive analysis of the corresponding three-pion decays and the
pion vector form factor. We compare our findings to recent measurements of the
omega --> pi0 mu+ mu- decay spectrum by the NA60 collaboration, and strongly
encourage experimental investigation of the Okubo-Zweig-Iizuka-forbidden phi
--> pi0 l+ l- decays in order to understand the strong deviations from
vector-meson dominance found in these transition form factors.Comment: 11 pages, 8 figures; references updated, version published in Phys.
Rev.
Bending Strength and Stiffness of Caribbean Pine from Trinidad and Tobago
Small samples of Caribbean pine wood grown in Trinidad were measured for specific gravity, modulus of elasticity, and modulus of rupture in bending. Core and outer wood and samples from along the length of the tree were studied. Mechanical properties and specific gravity varied along and across the trees. Linear relationships between specific gravity and mechanical properties were better for the outer wood than for the core wood. Core wood was weaker than outer wood. The bolts varied in properties along the tree, with a maximum in the second 2-m bolt
Ultrafast dynamics of a magnetic antivortex - Micromagnetic simulations
The antivortex is a fundamental magnetization structure which is the
topological counterpart of the well-known magnetic vortex. We study here the
ultrafast dynamic behavior of an isolated antivortex in a patterned Permalloy
thin-film element. Using micromagnetic simulations we predict that the
antivortex response to an ultrashort external field pulse is characterized by
the production of a new antivortex as well as of a temporary vortex, followed
by an annihilation process. These processes are complementary to the recently
reported response of a vortex and, like for the vortex, lead to the reversal of
the orientation of the antivortex core region. In addition to its fundamental
interest, this dynamic magnetization process could be used for the generation
and propagation of spin waves for novel logical circuits.Comment: 4 pages, 4 figures. To be published in Physical Review B (R
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