11 research outputs found
Near threshold eta production in proton-proton collisions
The total cross section for the near threshold eta production in
proton-proton collisions has been investigated with the assumption that the
production mechanism is due to the emission of a meson x (pi, eta, sigma) from
one of the nucleons followed by a x N --> eta N transition on the second one.
The x N --> eta N amplitudes are generated from the unitary multi-channel
multi-resonance model which has recently been constructed in analyzing the pi N
scattering and pi N --> eta N reaction. The initial and final pp distortions
are calculated from a coupled-channel pi-NN model which describes the NN
scattering data up to about 2 GeV. With the x-NN vertex functions taken from
the Bonn potential, the predicted total cross sections of threshold pp --> eta
pp reaction are in good agreement with the data. In contrast to previous works,
we find that the eta-exchange plays an important role. The effect of the
two-pion exchange, simulated by sigma- exchange, is found to be significant but
not as dominant as the vector meson-exchange introduced in previous works.Comment: 9 pages (latex: elsart.sty) + 3 figures (PostScript gzip+uuencode)
Submitted to Phys.Lett.
Mechanisms of the reaction pi^-p --> a^0_0(980)n --> p-^0 eta n at high energies
The main dynamical mechanisms of the reaction at high energies, currently investigated at
Serpukhov and Brookhaven, are considered in detail. It is shown that the
observed forward peak in its differential cross section can be explained within
the framework of the Regge pole model only by the conspiring Regge
pole exchange. The tentative estimates of the absolute reaction cross section at GeV/c are obtained: nb and, in the forward direction,
nb/GeV. The contribution of the one pion exchange,
which is forbidden by -parity and which can rise owing to the
mixing, is also estimate. A role of the Regge cuts in
the non-flip helicity amplitude is briefly examined and a conclusion is made
that the contributions of the cuts have to be inessential in comparison with
the conspiring Regge pole exchange.Comment: 14 pages, Latex, 2 ps figure
An investigation of the emc effect using antineutrino interactions in deuterium and neon
A local control system for the test masses of the Virgo gravitational wave detector
The mirrors of interferometric detectors of gravitational waves (GW) are suspended in order to be isolated from external disturbances. A local control system able to keep them correctly aligned and to damp the angular modes of the suspension is necessary. In this paper we present the solution adopted for Virgo based on a CCD camera sensor and on digital controls. With this solution the mirrors are kept aligned at the level of less than 1 murad rms, enough to lock the interferometer and start the automatic alignment system. (C) 2003 Elsevier B.V. All rights reserved
First locking of the Virgo central area interferometer with suspension hierarchical control
Operation of the central portion of Virgo as a simple 6 in Michelson interferometer has given the first demonstration of the possibility to control an interferometer suspended from Virgo full scale multistage seismic attenuators using information derived from the interferometer locking signal. A special role in the control is played by the first stage of these suspensions, an inverted pendulum: besides its seismic preisolation action, this stage has positioning dynamics of several mm, and it allows to exert a very low frequency control at the tipper level of the suspension using the interferometer fringe signal. The application of this feedback to the top-stage of the suspension allows corrections of drifts, such as tidal ones, at a stage of the suspension where a large dynamic range in displacements is available, without introducing noise at the level of the mirror, resulting in a significant reduction of the lock keeping force applied directly on the mirror at the lowest stage of the attenuator. (C) 2003 Elsevier B.V. All rights reserved