172 research outputs found
Search for Narrow NNpi Resonances in Exclusive p p -> p p pi+ pi- Measurements
Narrow structures in the range of a few MeV have been searched for in p p pi+
and p p pi- invariant mass spectra obtained from exclusive measurements of the
p p -> p p pi+ pi- reaction at Tp = 725, 750 and 775 MeV using the PROMICE/WASA
detector at CELSIUS. The selected reaction is particularily well suited for the
search for NN and / or N Delta decoupled dibaryon resonances. Except for a
possible fluctuation at 2087 MeV/c^2 in Mpppi- no narrow structures could be
identified neither in Mpppi+ nor in Mpppi- on the 3 sigma level of statistical
significance, giving an upper limit (95% C.L.) for dibaryon production in this
reaction of sigma < 20 nb for 2020 MeV/c^2 < m(dibaryon) < 2085 MeV/c^2Comment: 3 pages, 4 figure
Study of the p p -> p p pi+ pi- Reaction in the Low-Energy Tail of the Roper Resonance
Exclusive measurements of the p p -> p p pi+ pi- reaction have been carried
out at Tp = 775 MeV at CELSIUS using the PROMICE/WASA setup. Together with data
obtained at lower energy they point to a dominance of the Roper excitation in
this process. From the observed interference of its decay routes N* -> N sigma
and N* -> Delta pi -> N sigma their energy-dependent relative branching ratio
is determined
Three-body decay of the d* dibaryon
Under certain circumstances, a three-body decay width can be approximated by
an integral involving a product of two off-shell two-body decay widths. This
``angle-average'' approximation is used to calculate the decay width
of the dibaryon in a simple model for the most
important Feynman diagrams describing pion emissions with baryon-baryon recoil
and meson retardation. The decay width is found to be about 0.006 (0.07, 0.5)
MeV at the mass of 2065 (2100, 2150) MeV for input dynamics derived from
the Full Bonn potential. The smallness of this width is qualitatively
understood as the result of the three-body decay being ``third forbidden''. The
concept of forbiddenness and the threshold behavior of a three-body
decay are further studied in connection with the decay of the dibaryon
where the idea of unfavorness has to be introduced.
The implications of these results are briefly discussed.Comment: 15 pages, RevTeX, two-column journal style, six figure
The d' dibaryon in the quark-delocalization, color-screening model
We study the questions of the existence and mass of the proposed dibaryon in the quark-delocalization, color-screening model
(QDCSM). The transformation between physical and symmetry bases has been
extended to the cases beyond the SU(2) orbital symmetry. Using parameters fixed
by baryon properties and scattering, we find a mild attraction in the
channel, but it is not strong enough to form a deeply bound state
as proposed for the state. Nor does the (isospin) I=2 N
configuration have a deeply bound state. These results show that if a narrow
dibaryon state does exist, it must have a more complicated structure.Comment: 12 pp. latex, no figs., 2 tables, additional refs., Report-no was
adde
Observation of strong final-state effects in pi+ production in pp collisions at 400 MeV
Differential cross sections of the reactions and have been measured at MeV by detecting the charged
ejectiles in the angular range . The
deduced total cross sections agree well with those published previously for
neighbouring energies. The invariant mass spectra are observed to be strongly
affected by production and final-state interaction. The data are
well described by Monte Carlo simulations including both these effects. The
ratio of and cross sections also compares
favourably to a recent theoretical prediction which suggests a dominance of
-production in the relative -state.Comment: 17 pages, 5 figure
Higher Partial Waves in p+p->p+p+eta near Threshold
Exclusive measurements of the production of eta mesons in the p+p->p+p+eta
reaction have been carried out at excess energies of 16 and 37 MeV above
threshold. The deviations from phase space are dominated by the proton-proton
final state interaction and this influences particularly the energy
distribution of the eta meson. However, evidence is also presented at the
higher energy for the existence of an anisotropy in the angular distributions
of the eta meson and also of the final proton-proton pair, probably to be
associated with D-waves in this system interfering with the dominant S-wave
term. The sign of the eta angular anisotropy suggests that rho-exchange is
important for this reaction.Comment: 16 pages, LaTeX2e, 3 EPS Figures, Updated version, Accepted for
publication in Phys. Lett.
On the Production of Pairs in pp Collisions at 0.8 GeV
Data accumulated recently for the exclusive measurement of the reaction at a beam energy of 0.793 GeV using the COSY-TOF
spectrometer have been analyzed with respect to possible events from the reaction channel. The latter is expected to be the only
production channel, which contains no major contributions from
resonance excitation close to threshold and hence should be a good testing
ground for chiral dynamics in the production process. No single event
has been found, which meets all conditions for being a candidate for the reaction. This gives an upper limit for the cross section of
0.16 b (90% C.L.), which is more than an order of magnitude smaller than
the cross sections of the other two-pion production channels at the same
incident energy
Food processing and technology 1978: a summary of research
Evaluation of tomato cultivars for processing / W. A. Gould, W. Stone, J. Mount, L. Witt, Y. Yamada, and S. Z. Berry -- Geotrichum candidum in midwestern tomato processing plants and various methods of inhibiting its growth / James G. Fox and Wilbur A. Gould -- Effects of various qualities of raw tomatoes (subjective evaluation) on color of extractable juice (objective evaluation) / Yasunori Yamada and Wilbur A. Gould -- Protein content of seeds taken from tomatoes at various stages of ripeness / Daniel Brodowski and J. R. Geisman -- Effects of cultivar, break temperature, and extraction methods on the viscosity of tomato juice / Hashmy Bel-Haj and Wilbur A. Gould -- A study of some factors affecting the solid content of canned tomatoes / J. R. Mount and W. A. Gould -- Prediction of ascorbic acid stability in canned apple juice / Mohamed I. Mahmoud and Wilbur A. Gould -- Investigation of protein content of ohio grown soybeans / Girish N. Desai and Andrew C. Peng -- Recovery and functionality of soybean leaf proteins / Mohammed H. Ali and Andrew C. Peng -- Carotene content of green snap beans / H. Fenercioglu and D. E. Crean -- Effect of reconditioning on the ascorbic acid content of potato cultivars / I. S. Arkoudilos and D. E. Crean -- Kinetic studies of polyphenol oxidase from HiDri cabbage / Ling-May Chen and Andrew C. Peng -- Refinements in pickle brine recycling / T. Glares and J. R. Geisman -- Use of ultraviolet light to inhibit Staphylococcus aureus growth on the surface of baked pumpkin pie / Nicholas N. Kallas and Wilbur A. Gould -- Development of a nutritionally improved corn masa / Thomas H. Rieman and Wilbur A. Gould -- Mechanical deboning of Lake Erie freshwater drum / W. E. Stone and W. A. Gould -- Lake Erie freshwater drum fillet processing, storage, and evaluation / W. E. Stone and W. A. Goul
Exclusive Measurements of : the Effect Revisited
Exclusive measurements of the reactions and
have been carried out at GeV at the
CELSIUS storage ring using the WASA detector. The channel
evidences a pronounced enhancement at low invariant masses - as
anticipated from previous inclusive measurements of the ABC effect. This
enhancement is seen to be even much larger in the isoscalar
channel. The differential distributions prove this enhancement to be of
scalar-isoscalar nature. calculations give a good description of
the data, if a boundstate condition is imposed for the intermediate
system.Comment: extended version, 8 pages, 7 figures, theoretical model calculations
adde
The two pion decay of the Roper resonance
We evaluate the two pion decay of the Roper resonance in a model where
explicit re-scattering of the two final pions is accounted for by the use of
unitarized chiral perturbation theory. Our model does not include an explicit
or scalar-isoscalar meson decay mode, instead it
generates it dynamically by means of the pion re-scattering. The two ways,
explicit or dynamically generated, of introducing this decay channel have very
different amplitudes.
Nevertheless, through interference with the other terms of the model we are
able to reproduce the same phenomenology as models with explicit consideration
of the meson.Comment: 17 latex pages, 11 eps figures. A few misprints corrected. A few new
references. Version accepted for publication in Phys. Rev.
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