12,912 research outputs found
On the stability constraints and oscillatory behavior of coupled systems
Stability constraints for two general forms of coupled systems of second order nonlinear differential equation
Photon Multiplicity Measurements : From SPS to RHIC and LHC
Results from the photon multiplicity measurements using a fine granularity
preshower photon multiplicity detector (PMD) at CERN SPS are discussed. These
include study of pseudo-rapidity distributions of photons, scaling of photon
multiplicity with number of participating nucleons, centrality dependence of
mean transverse momentum of photons, event-by-event fluctuations in photon
multiplicity and localised charged-neutral fluctuations. Basic features of the
PMD to be used in STAR experiment at RHIC and in ALICE experiment at LHC are
also discussed.Comment: 12 pages, Invited talk at the 4th International Conference on the
Physcis and Astrophysics of the Quark-Gluon-Plasma, November 2001, Jaipur,
India, to appear in Praman
Optimal control of linear time delay systems
Obtaining optimal control for linear time varying system with time dela
Electron Impact Excitation Cross Sections for Hydrogen-Like Ions
We present cross sections for electron-impact-induced transitions n --> n' in
hydrogen-like ions C 5+, Ne 9+, Al 12+, and Ar 17+. The cross sections are
computed by Coulomb-Born with exchange and normalization (CBE) method for all
transitions with n < n' < 7 and by convergent close-coupling (CCC) method for
transitions with n 2s and 1s
--> 2p are presented as well. The CCC and CBE cross sections agree to better
than 10% with each other and with earlier close-coupling results (available for
transition 1 --> 2 only). Analytical expression for n --> n' cross sections and
semiempirical formulae are discussed.Comment: RevTeX, 5 pages, 13 PostScript figures, submitted to Phys. Rev.
Event-by-Event Search for Charged Neutral Fluctuations in Pb - Pb Collisions at 158-A-GeV
Results from the analysis of data obtained from the WA98 experiment at the
CERN SPS have been presented. Some events have been filtered which show photon
excess in limited zones within the overlap region of the charged
particle and photon multiplicity detectors.Comment: 6 pages, 4 figure
On fixed linear systems with a generalized performance criteria
Fixed linear systems with generalized performance criteri
The effect of ionization on the populations of excited levels of C IV and C V in tokamak edge plasmas
The main populating and depopulating mechanisms of the excited energy levels
of ions in plasmas with densities <1023-1024 m-3 are electron collisional
excitation from the ion's ground state and radiative decay, respectively, with
the majority of the electron population being in the ground state of the
ionization stage. Electron collisional ionization is predominately expected to
take place from one ground state to that of the next higher ionization stage.
However, the question arises as to whether, in some cases, ionization can also
affect the excited level populations. This would apply particularly to those
cases involving transient events such as impurity influxes in a laboratory
plasma. An analysis of the importance of ionization in populating the excited
levels of ions in plasmas typical of those found in the edge of tokamaks is
undertaken for the C IV and C V ionization stages. The emphasis is on those
energy levels giving rise to transitions of most use for diagnostic purposes.
Carbon is chosen since it is an important contaminant of JET plasmas; it was
the dominant low Z impurity before the installation of the ITER-like wall and
is still present in the plasma after its installation. Direct electron
collisional ionization both from and to excited levels is considered.
Distorted-wave Flexible Atomic Code calculations are performed to generate the
required ionization cross sections, due to a lack of atomic data in the
literature.Comment: 29 pages, 5 figures. This is an author-created, un-copyedited version
of an article accepted for publication in Journal of Physics B. IOP
Publishing Ltd is not responsible for any errors or omissions in this version
of the manuscript or any version derived from i
Experimental Signatures of Anomaly Induced DCC Formation
We discuss characteristic experimental signatures related to the formation of
domains of disoriented chiral condensate (DCC) triggered by the axial anomaly
in relativistic heavy ion collisions. We predict that the enhancement of the
fraction of neutral pions compared to all pions depends on the angle of
emission with respect to the scattering plane and is concentrated at small
transverse momentum and small rapidity in the center-of-mass frame. The
anisotropy with respect to the reaction plane is also observable in the
inclusive photon distribution.Comment: 11 pages, 4 figures, REVTEX, discussion on photon distribution added,
one figure adde
- …