1,027 research outputs found
Experimental proton-proton correlation function derived for the pp -> ppeta reaction
Based on the high statistics data from the pp -> ppX reaction measured by the
COSY-11 collaboration [1] we have derived a two-proton correlation function for
the production of the ppeta and pp+pions systems. The measured correlation
function normalized to the value simulated for a point-like source was compared
with a theoretical prediction in order to estimate the size of the reaction
volume.Comment: Talk given at the Symposium on Meson Physics at COSY-11 and
WASA-at-COSY Krakow, Poland, 17-22 June 200
Multimeson production in pp interactions as a background for eta and eta' decays
Multimeson production in pp interactions comprises important background for
eta, omega and eta' mesons production experiments and for the studies of their
decays planned with WASA detector at COSY. The available information about the
reactions is summarized and the need for efforts to describe the processes is
stressed.Comment: Proceedings of MENU07 Conference Julich, Germany 200
Two-proton correlation function: a gentle introduction
The recent COSY-11 collaboration measurement of the two-proton correlation
function in the pp -> ppeta reaction, reported at this meeting [1], arouse some
interest in a simple theoretical description of the correlation function. In
these notes we present a pedagogical introduction to the practical methods that
can be used for calculating the correlation function.Comment: Prepared for the proceedings of the Symposium on Meson Physics at
COSY-11 and WASA-at-COSY, Krakow, Poland, 17-22 June 200
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
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.
Controlled exchange interaction for quantum logic operations with spin qubits in coupled quantum dots
A two-electron system confined in two coupled semiconductor quantum dots is
investigated as a candidate for performing quantum logic operations on spin
qubits. We study different processes of swapping the electron spins by
controlled switching on/off the exchange interaction. The resulting spin swap
corresponds to an elementary operation in quantum information processing. We
perform a direct time evolution simulations of the time-dependent Schroedinger
equation. Our results show that -- in order to obtain the full interchange of
spins -- the exchange interaction should change smoothly in time. The presence
of jumps and spikes in the corresponding time characteristics leads to a
considerable increase of the spin swap time. We propose several mechanisms to
modify the exchange interaction by changing the confinement potential profile
and discuss their advantages and disadvantages
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Scoring Rubric Development: Validity and Reliability
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Drift chamber with a c-shaped frame
We present the construction of a planar drift chamber with wires stretched
between two arms of a c-shaped aluminium frame. The special shape of the frame
allows to extendthe momentum acceptance of the COSY-11 detection system towards
lower momenta without suppressing the high momentum particles. The proposed
design allows for construction of tracking detectors covering small angles with
respect to the beam, which can be installed and removed without dismounting the
beam-pipe. For a three-dimensional track reconstruction a computer code was
developed using a simple algorithm of hit preselection.Comment: submitted to Nucl. Instr. & Meth
Eta physics at threshold
The production of eta and eta-prime mesons in elementary nucleon-nucleon
collisions has been investigated at the synchrotrons CELSIUS, COSY and SATURNE.
The magnitude and energy dependence of the total cross section as well as the
occupation distribution of the phase space serve as observables for
investigating the mechanisms underlying the production processes and the
interaction of mesons with nucleons. The precise data on the eta and eta-prime
creation via the pp --> pp eta(eta-prime) reactions allowed to settle the
general features of the eta and eta-prime meson production and revealed the
sensitivity of the mentioned observables to the nucleon-nucleon-meson final
state interaction. The particular production properties, like for example the
determination of the dominating exchange processes which lead to the excitation
of the S_11 nucleon isobar in the case of eta creation, must be established by
confrontation with other observables. The present status of this investigation
with an emphasis on the results of the COSY-11 collaboration is briefly
presented. The available data are interpreted in view of the production
mechanism and the meson-nucleon interaction.Comment: 3 pages, 3 figures, Presented at Conference on Quarks and Nuclear
Physics (QNP 2002), Julich, Germany, 9-14 Jun 200
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