312 research outputs found
Determination of the eta'-proton scattering length in free space
Taking advantage of both the high mass resolution of the COSY-11 detector and
the high energy resolution of the low-emittance proton-beam of the Cooler
Synchrotron COSY we determine the excitation function for the pp --> pp eta'
reaction close-to-threshold. Combining these data with previous results we
extract the scattering length for the eta'-proton potential in free space to be
Re(a_{p eta'}) = 0+-0.43 fm and Im(a_{p eta'}) = 0.37(+0.40)(-0.16) fm.Comment: 5 pages, 3 figures, accepted for publication in Phys. Rev. Let
Dynamics of the near threshold eta meson production in proton-proton interaction
We present the results of measurements of the analysing power for the p(pol)p
--> pp eta reaction at the excess energies of Q=10 and 36 MeV, and interpret
these results within the framework of the meson exchange models. The determined
values of the analysing power at both excess energies are consistent with zero
implying that the eta meson is produced predominantly in s-wave.Comment: 3 pages, 3 figures, Presented at the Workshop on the physics of
excited nucleons (NSTAR 2007), 5-8 September 2007, Bonn, German
General thoughts to the Kaon pair production in the threshold region
Simple--minded thoughts about the cross sections for the reactions
pp-->ppK+K- and pp-->ppK0K0 are presented, which certainly do not account for
the complex coupled channel problem but rather provide some ideas into the
mutual reaction dynamics.Comment: Talk given at 9th International Workshop on Meson Production,
Properties and Interaction, Cracow, Poland, 9-13 June 2006. 3 pages, 2
figure
Associated strangeness production in pp collisions near threshold
Motivated by the ongoing discussion concerning the nature of the scalar
resonances f0(980) and a0(980), the COSY-11 collaboration has taken exclusive
data on the pp->ppK+K- reaction near the production threshold. A first total
cross section sigma=(1.80+-0.27+0.28-0.35)nb for the excess energy Q=17 MeV has
been determined. In contrary to the eta, omega and eta' single meson production
studies which clearly show the strong pp final state interaction (FSI), the
cross section values obtained at COSY-11 and DISTO can be both described by a
fit with a four-body phase space including the proton-proton final state
interaction as well as with one-meson exchange calculations neglecting FSI
effects. Therefore, one might think about a compensation of the strong pp
interaction through a pK- FSI effect or an additional degree of freedom caused
by the four-body final state. In the latter case, strong FSI effects can be
expected at Q-values very close to the K+K- production threshold. Such a
motivation triggered -- in combination with the investigation of the
kaon-Antikaon interaction being relevant to the structure of the f0(980) --
further measurements at the excess energies Q=10 and Q=28 MeV at COSY-11.Comment: 5 pages, 4 figures, Presented at X. International Conference On
Hadron Spectroscopy (Hadron 2003), Aschaffenburg, Germany, 31 Aug - 6 Sep
200
Production of eta and eta-prime mesons via the quasi-free proton-neutron interaction
A comparison of the close-to-threshold total cross sections for the eta-prime
meson production in both the pp --> pp eta-prime and pn --> pn eta-prime
reactions should provide insight into the flavour-singlet (perhaps also into
gluonium) content of the eta-prime meson and the relevance of quark-gluon or
hadronic degrees of freedom in the creation process. The excitation function
for the reaction pp --> pp eta-prime has been already established. At present,
experimental investigations of the quasi-free pn --> pn X reactions are carried
out at the COSY-11 facility using a beam of stochastically cooled protons and
the deuteron cluster target. A method of measurement and preliminary results
from the test experiments of the pn --> pn eta reaction are presented in this
report.Comment: 5 pages, 5 figures, Presented at X. International Conference On
Hadron Spectroscopy (Hadron 2003), Aschaffenburg, Germany, 31 Aug - 6 Sep
200
IFT proteins interact with HSET to promote supernumerary centrosome clustering in mitosis.
Centrosome amplification is a hallmark of cancer, and centrosome clustering is essential for cancer cell survival. The mitotic kinesin HSET is an essential contributor to this process. Recent studies have highlighted novel functions for intraflagellar transport (IFT) proteins in regulating motors and mitotic processes. Here, using siRNA knock-down of various IFT proteins or AID-inducible degradation of endogenous IFT88 in combination with small-molecule inhibition of HSET, we show that IFT proteins together with HSET are required for efficient centrosome clustering. We identify a direct interaction between the kinesin HSET and IFT proteins, and we define how IFT proteins contribute to clustering dynamics during mitosis using high-resolution live imaging of centrosomes. Finally, we demonstrate the requirement of IFT88 for efficient centrosome clustering in a variety of cancer cell lines naturally harboring supernumerary centrosomes and its importance for cancer cell proliferation. Overall, our data unravel a novel role for the IFT machinery in centrosome clustering during mitosis in cells harboring supernumerary centrosomes
First close-to-threshold measurement of the analyzing power Ay in the reaction p(pol)p -> pp eta
At the internal facility COSY-11 a first measurement of the reaction p(pol)p
-> pp eta near the production threshold has been performed. Results for the
analysing power will be presented and a comparison with one meson exchange
models will be discussed.Comment: 3 pages, 3 figures, Presented at Conference on Quarks and Nuclear
Physics (QNP 2002), Julich, Germany, 9-14 Jun 200
Additive Manufacturing Under Lunar Gravity and Microgravity
Mankind is setting to colonize space, for which the manufacturing of habitats, tools, spare parts and other infrastructure is required. Commercial manufacturing processes are already well engineered under standard conditions on Earth, which means under Earth’s gravity and atmosphere. Based on the literature review, additive manufacturing under lunar and other space gravitational conditions have only been researched to a very limited extent. Especially, additive manufacturing offers many advantages, as it can produce complex structures while saving resources. The materials used do not have to be taken along on the mission, they can even be mined and processed on-site. The Einstein-Elevator offers a unique test environment for experiments under different gravitational conditions. Laser experiments on selectively melting regolith simulant are successfully conducted under lunar gravity and microgravity. The created samples are characterized in terms of their geometry, mass and porosity. These experiments are the first additive manufacturing tests under lunar gravity worldwide
Total and Differential Cross Sections for the pp-->pp eta-prime Reaction Near Threshold
The eta-prime meson production in the reaction pp-->pp eta-prime has been
studied at excess energies of Q = 26.5, 32.5 and 46.6 MeV using the internal
beam facility COSY-11 at the cooler synchrotron COSY. The total cross sections
as well as one angular distribution for the highest Q-value are presented. The
excitation function of the near threshold data can be described by a pure
s-wave phase space distribution with the inclusion of the proton-proton final
state interaction and Coulomb effects. The obtained angular distribution of the
eta-prime mesons is also consistent with pure s-wave production.Comment: 6 pages, 5 figures, submitted to Eur. Phys. J.
Generalized Dalitz Plot analysis of the near threshold pp-->ppK+K- reaction in view of the K+K- final state interaction
The excitation function for the reaction revealed a
significant enhancement close to threshold which may plausibly be assigned to
the influence of the and final state interactions. In an
improved reanalysis of COSY-11 data for the reaction at excess
energies of Q = 10 MeV and 28 MeV including the proton-K- interaction the
enhancement is confirmed. Invariant mass distributions for the two- and
three-particle subsystems allow to test at low excess energies the ansatz and
parameters for the description of the interaction in the ppK+K- system as
derived from the COSY-ANKE data. Finally, based for the first time on the low
energy K+K- invariant mass distributions and the generalized Dalitz plot
analysis, we estimate the scattering length for the K+K- interaction to be
|Re(a_K^+K^-)| = 0.5 + 4.0 -0.5 fm and Im(a_K^+K^-) = 3.0 +- 3.0 fm.Comment: 8 pages, 7 figures, to be published in Phys. Rev.
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