The reaction
γ
p
→
p
π
0
η
has been studied with the CBELSA/TAPS detector at the electron stretcher accelerator ELSA in Bonn for incident photon energies from threshold up to 3.1 GeV. This paper has ...been motivated by the recently claimed observation of a narrow structure in the
M
N
η
invariant mass distribution at a mass of
1678
MeV
/
c
2
. The existence of this structure cannot be confirmed in the present work. Instead, for
E
γ
= 1400–1500 MeV and the cut
M
p
π
0
≤
1190
MeV
/
c
2
a statistically significant structure in the
M
p
η
invariant mass distribution near 1700
MeV
/
c
2
is observed with a width of
Γ
≈
35
MeV
/
c
2
while the mass resolution is
σ
res
= 5
MeV
/
c
2
. Increasing the incident photon energy from 1420 to 1540 MeV this structure shifts in mass from
≈
1700
MeV
/
c
2
to
≈
1725
MeV
/
c
2
; the width increases to about 50
MeV
/
c
2
and decreases thereafter. The cross section associated with this structure reaches a maximum of
≈
100 nb around
E
γ
≈
1490 MeV (W
≈
1920 MeV), which coincides with the
p
a
0
threshold. Three scenarios are discussed which might be the origin of this structure in the
M
p
η
invariant mass distribution. The most likely interpretation is that it is due to a triangular singularity in the
γ
p
→
p
a
0
→
p
π
0
η
reaction.
Abstract
A measurement of the double-polarization observable
E
for the reaction
$$\gamma p\rightarrow \pi ^0 p$$
γ
p
→
π
0
p
is reported. The data were taken with the CBELSA/TAPS experiment at the ...ELSA facility in Bonn using the Bonn frozen-spin butanol (C
$$_4$$
4
H
$$_9$$
9
OH) target, which provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range from
$$E_\gamma =600$$
E
γ
=
600
to 2310 MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses.
A measurement of the double-polarization observable E for the reaction γp→π0p is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn using the Bonn frozen-spin ...butanol (C4H9OH) target, which provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range from Eγ=600 to 2310 MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses.
A measurement of the double-polarization observable
E
for the reaction
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\begin{document}$$\gamma p\rightarrow \pi ^0 p$$\end{document}
γ
p
→
π
0
p
is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn using the Bonn frozen-spin butanol (C
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4
H
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\begin{document}$$_9$$\end{document}
9
OH) target, which provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range from
\documentclass12pt{minimal}
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\begin{document}$$E_\gamma =600$$\end{document}
E
γ
=
600
to 2310 MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses.
A measurement of the double-polarization observable
E
for the reaction
γ
p
→
π
0
p
is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn using the Bonn ...frozen-spin butanol (C
4
H
9
OH) target, which provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range from
E
γ
=
600
to 2310 MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses.
.
This paper reports on a measurement of the double-polarization observable
G
in
π
0
photoproduction off the proton using the CBELSA/TAPS experiment at the ELSA accelerator in Bonn. The observable
G
...is determined from reactions of linearly polarized photons with longitudinally polarized protons. The polarized photons are produced by bremsstrahlung off a diamond radiator of well-defined orientation. A frozen spin butanol target provides the polarized protons. The data cover the photon energy range from 617 to 1325 MeV and a wide angular range. The experimental results for
G
are compared to predictions by the Bonn-Gatchina (BnGa), Jülich-Bonn (JüBo), MAID and SAID partial wave analyses. Implications of the new data for the pion photoproduction multipoles are discussed.
A measurement of the double-polarization observable
for the reaction
is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn using the Bonn frozen-spin butanol ...(C
H
OH) target, which provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range from
to 2310 MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses.
A discrete model for long time sintering Luding, Stefan; Manetsberger, Karsten; Müllers, Johannes
Journal of the mechanics and physics of solids,
02/2005, Letnik:
53, Številka:
2
Journal Article
Recenzirano
Odprti dostop
A discrete model for the sintering of polydisperse, inhomogeneous arrays of cylinders is presented with empirical contact force-laws, taking into account plastic deformations, cohesion, temperature ...dependence (melting), and long-time effects. Samples are prepared under constant isotropic load and are sintered for different sintering times. Increasing both external load and sintering time leads to a stronger, stiffer sample after cooling down. The material behavior is interpreted from both microscopic and macroscopic points of view.
Among the interesting results is the observation that the coordination number, even though it has the tendency to increase, sometimes slightly decreases, whereas the density continuously increases during sintering—this is interpreted as an indicator of reorganization effects in the packing. Another result of this study is the finding that strongly attractive contacts occur during cool-down of the sample and leave a sintered block of material with almost equally strong attractive and repulsive contact forces.
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