991 research outputs found
Etaprime and Eta Mesons with Connection to Anomalous Glue
We review the present understanding of etaprime and eta meson physics and
these mesons as a probe of gluon dynamics in low-energy QCD. Recent highlights
include the production mechanism of eta and etaprime mesons in proton-nucleon
collisions from threshold to high-energy, the etaprime effective mass shift in
the nuclear medium, searches for possible eta and etaprime bound states in
nuclei as well as precision measurements of eta decays as a probe of
light-quark masses. We discuss recent experimental data, theoretical
interpretation of the different measurements and the open questions and
challenges for future investigation.Comment: Review, 25 pages, 11 figures, to appear in Reviews of Modern Physic
On Quasibound N* Nuclei
The possibility for the existence of unstable bound states of the S11 nucleon
resonance N(1535) and nuclei is investigated. These quasibound states are
speculated to be closely related to the existence of the quasibound states of
the eta mesons and nuclei. Within a simple model for the N N interaction
involving a pion and eta meson exchange, N-nucleus potentials for N*-He
and N*-Mg are evaluated and found to be of a Woods-Saxon like form which
supports two to three bound states. In case of N*-He, one state bound by
only a few keV and another by 4 MeV is found. The results are however quite
sensitive to the N N and N N vertex parameters. A rough
estimate of the width of these states, based on the mean free path of the
exchanged mesons in the nuclei leads to very broad states with 80
and 110 MeV for N*-He and N*-Mg respectively.Comment: Presented at the Jagiellonian Symposium on Fundamental and Applied
Subatomic Physics, Cracow, Poland, June 2015; to be published in Acta Physica
Polonica B (2016
Proton spin structure and the axial U(1) problem
We emphasise the relation between the spin structure of the proton and the
axial U(1) problem. New experiments motivated by the proton spin problem which
could shed light on the nature of U(1) symmetry breaking in QCD are discussed.Comment: Invited talk at the Workshop on the Spin Structure of the Proton and
Polarized Collider Physics, Trento (July 23-28, 2001), 6 pages, 1 figur
Project of the underwater system for chemical threat detection
In this article we describe a novel method for the detection of explosives
and other hazardous substances in the marine environment using neutron
activation. Unlike the other considered methods based on this technique we
propose to use guides forneutron and gamma quanta which speeds up and
simplifies identification. Moreover, it may provide a determination of the
density distribution of a dangerous substance. First preliminary results of
Monte Carlo simulations dedicated for design of a device exploiting this method
are also presented.Comment: 9 pages, 6 figure
Summary of the COSY-11 Measurements of Hyperon Production
The studies of hyperon production performed at COSY-11 are summarized. The
results of the experiments in the reaction channels pp-->pK+Lambda,
pp-->pK+Sigma0, and pp-->nK+Sigma+ are shown. Excitation functions
fromthreshold up to about 90MeV excess energies have been evaluated with high
precision for the Lambda and Sigma0 production. The Lambdap and Sigma0p final
state interactions were extracted. The Sigma+ production was measured at 13 and
60 MeV excess energies.Comment: 8 pages, 4 figures, Talk given at Symposium on Meson Physics at
COSY-11 and WASA-at-COSY, Cracow, Poland, 17-22 Jun 200
Design of the SABAT system for underwater detection of dangerous substances
We present status of simulations used to design a novel device for the
detection of hazardous substances in the aquatic environment using neutron
activation. Unlike the other considered methods based on this technique we
propose to use guides for neutron and gamma quanta which speeds up and
simplifies identification. First preliminary results show that both the neutron
guide and the ray guide increase the performance of underwater threats
detection.Comment: Presented at the Jagiellonian Symposium of Fundamental and Applied
Subatomic Physics, Krak{\o}w, 11.06.201
Measurement of the invariant mass distributions for the pp -> ppeta' reaction at excess energy of Q = 16.4 MeV
The proton-proton and proton-eta' invariant mass distributions have been
determined for the pp -> ppeta' reaction at an excess energy of Q = 16.4 MeV.
The measurement was carried out using the COSY-11 detector setup and the proton
beam of the cooler synchrotron COSY. The shapes of the determined invariant
mass distributions are similar to those of the pp -> ppeta reaction and reveal
an enhancement for large relative proton-proton momenta. This result, together
with the fact that the proton-eta interaction is much stronger that the
proton-eta' interaction, excludes the hypothesis that the observed enhancement
is caused by the interaction between the proton and the meson
Study of the Low Energy Dynamics in the ppK+K- System with the Cosy-11 Magnetic Spectrometer
The near threshold production of K+K- pairs in proton-proton collisions has
been investigated at the cooler synchrotron COSY below and above the threshold
for the \phi meson production. The experimental excitation function determined
for the pp-->ppK+K- reaction differs from theoretical expectations including
proton-proton final state interaction. The discrepancy may be assigned to the
influence of K+K- or pK interaction. In this article we present distributions
of the cross section for the pp-->ppK+K- reaction as a function of the
invariant masses of two and three particle subsystems at excess energies of
Q=10 MeV and 28 MeV.Comment: Presented at the Symposium on Meson Physics, Cracow, 01-04 October
200
Heavy Hyperon--Antihyperon Production
Based on the experience from the production of anti-Lambda Lambda and
anti-Sigma Sigma pairs at LEAR (experiment PS185) it is suggested to continue
the investigations towards the heavier antihyperon--hyperon pairs anti-Xi Xi
and anti-Omega Omega in view of: (1) the production dynamics of the heavier
antihyperon--hyperon out of the anti-p p annihilation (2) a comparison of the
(3s 3anti-s quark system) anti-Omega Omega to the (3 (anti-s s)) 3 phi meson
production, where both systems have similar masses (3.345 and 3.057,
respectively) and identical valence quark content. A systematic study of the
antihyperon--hyperon production with increasing strangeness content is
interesting for the following reasons: The anti-Omega Omega production is the
creation of two spin 3/2 objects out of the two spin 1/2 anti-p p particles.
Results of the PS185 experiments prove a clear dominance of the spin triplet
anti-s s dissociation. In the Omega anti-Omega the three s-quarks (three anti-s
quarks) are aligned to spin 3/2 each. If the three anti-s s pairs are now all
in spin triplet configurations when created out of the gluonic interaction they
should have spin parity quantum number as 3^- as long as Omega anti-Omega is
created with relative L=0 angular momentum. The comparison of the Omega
anti-Omega baryon pair to the phi phi phi three meson production (where the
three anti-s s quark pairs might not but can be produced without relative
correlation) would provide a unique determination of the intermediate matter
state. Measurements of excitation functions and polarization transfers should
be used to examine these gluon rich anti-p p --> anti-Omega Omega and anti-p p
--> phi phi phi reaction channels. Such experiments should be performed at the
PANDA detector at the FAIR facility of the GSI.Comment: 4 pages, 2 figures, Presented at LEAP05: International Conference on
Low Energy Antiproton Physics, Bonn - Juelich, Germany, May 16-22, 200
Kaon pair production close to threshold
The total cross section of the reaction pp->ppK+K- has been measured at
excess energies Q=10 MeV and 28 MeV with the magnetic spectrometer COSY-11. The
new data show a significant enhancement of the total cross section compared to
pure phase space expectations or calculations within a one boson exchange
model. In addition, we present invariant mass spectra of two particle
subsystems. While the K+K- system is rather constant for different invariant
masses, there is an enhancement in the pK- system towards lower masses which
could at least be partially connected to the influence of the Lambda(1405)
resonance.Comment: accepted for publication in Phys. Lett.
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