1,705 research outputs found
Quantum Hamilton-Jacobi analysis of PT symmetric Hamiltonians
We apply the quantum Hamilton-Jacobi formalism, naturally defined in the
complex domain, to a number of complex Hamiltonians, characterized by discrete
parity and time reversal (PT) symmetries and obtain their eigenvalues and
eigenfunctions. Examples of both quasi-exactly and exactly solvable potentials
are analyzed and the subtle differences, in the singularity structures of their
quantum momentum functions, are pointed out. The role of the PT symmetry in the
complex domain is also illustrated.Comment: 11 page
Enhanced Room Temperature Coefficient of Resistance and Magneto-resistance of Ag-added La0.7Ca0.3-xBaxMnO3 Composites
In this paper we report an enhanced temperature coefficient of resistance
(TCR) close to room temperature in La0.7Ca0.3-xBaxMnO3 + Agy (x = 0.10, 0.15
and y = 0.0 to 0.40) (LCBMO+Ag) composite manganites. The observed enhancement
of TCR is attributed to the grain growth and opening of new conducting channels
in the composites. Ag addition has also been found to enhance intra-granular
magneto-resistance. Inter-granular MR, however, is seen to decrease with Ag
addition. The enhanced TCR and MR at / near room temperature open up the
possibility of the use of such materials as infrared bolometric and magnetic
field sensors respectively.Comment: 22 pages of Text +
Figs:comments/suggestions([email protected]
Interferometry of Direct Photons in Central 280Pb+208Pb Collisions at 158A GeV
Two-particle correlations of direct photons were measured in central
208Pb+208Pb collisions at 158 AGeV. The invariant interferometric radii were
extracted for 100<K_T<300 MeV/c and compared to radii extracted from charged
pion correlations. The yield of soft direct photons, K_T<300 MeV/c, was
extracted from the correlation strength and compared to theoretical
calculations.Comment: 5 pages, 4 figure
Event-by-Event Fluctuations in Particle Multiplicities and Transverse Energy Produced in 158.A GeV Pb+Pb collisions
Event-by-event fluctuations in the multiplicities of charged particles and
photons, and the total transverse energy in 158 GeV Pb+Pb collisions
are studied for a wide range of centralities. For narrow centrality bins the
multiplicity and transverse energy distributions are found to be near perfect
Gaussians. The effect of detector acceptance on the multiplicity fluctuations
has been studied and demonstrated to follow statistical considerations. The
centrality dependence of the charged particle multiplicity fluctuations in the
measured data has been found to agree reasonably well with those obtained from
a participant model. However for photons the multiplicity fluctuations has been
found to be lower compared to those obtained from a participant model. The
multiplicity and transverse energy fluctuations have also been compared to
those obtained from the VENUS event generator.Comment: To appear in Physical Review C; changes : more detailed discussion on
errors and few figures modifie
Centrality Dependence of Neutral Pion Production in 158 A GeV Pb + Pb Collisions
The production of neutral pions in 158AGeV Pb+Pb collisions has been studied
in the WA98 experiment at the CERN SPS. Transverse momentum spectra are studied
for the range 0.3 GeV/c < mT-m0 < 4.0 GeV/c. The results for central collisions
are compared to various models. The centrality dependence of the neutral pion
spectral shape and yield is investigated. An invariance of the spectral shape
and a simple scaling of the yield with the number of participating nucleons is
observed for centralities with greater than about 30 participating nucleons
which is most naturally explained by assuming an equilibrated system.Comment: 5 pages, Latex, including 3 eps figures, submitted to Phys.Rev.Lett;
updated pQCD comparison due to new input from the author, updated references,
corrected plotting error in figure
Systematics of Inclusive Photon Production in 158 AGeV Pb Induced Reactions on Ni, Nb, and Pb Targets
The multiplicity of inclusive photons has been measured on an event-by-event
basis for 158 AGeV Pb induced reactions on Ni, Nb, and Pb targets. The
systematics of the pseudorapidity densities at midrapidity (rho_max) and the
width of the pseudorapidity distributions have been studied for varying
centralities for these collisions. A power law fit to the photon yield as a
function of the number of participating nucleons gives a value of 1.13+-0.03
for the exponent. The mean transverse momentum, , of photons determined
from the ratio of the measured electromagnetic transverse energy and photon
multiplicity, remains almost constant with increasing rho_max. Results are
compared with model predictions.Comment: 16 pages including 4 figure
A Preshower Photon Multiplicity Detector for the WA98 Experiment
A high granularity preshower detector has been fabricated and installed in the WA98 Experiment at the CERN SPS for measuring the spatial distribution of photons produced in the forward region in lead ion induced interactions. Photons are counted by detecting the preshower signal in plastic scintillator pads placed behind a 3 radiation length thick lead converter and applying a threshold on the scintillator signal to reject the minimum ionizing particles. Techniques to improve the imaging of the fibre and performance of the detector in the high multiplicity environment of lead-lead collisions are described. Using Monte-Carlo simulation methods and test beam data of pi- and e- at various energies the photon counting efficiency is estimated to be 68% for central and 73% for peripheral Pb+Pb collisions
Scaling of Particle and Transverse Energy Production in 208Pb+208Pb collisions at 158 A GeV
Transverse energy, charged particle pseudorapidity distributions and photon
transverse momentum spectra have been studied as a function of the number of
participants (N_{part}) and the number of binary nucleon-nucleon collisions
(N_{coll}) in 158 A GeV Pb+Pb collisions over a wide impact parameter range. A
scaling of the transverse energy pseudorapidity density at midrapidity as
N_{part}^{1.08 \pm 0.06} and N_{coll}^{0.83 \pm 0.05} is observed. For the
charged particle pseudorapidity density at midrapidity we find a scaling as
N_{part}^{1.07 \pm 0.04} and N_{coll}^{0.82 \pm 0.03}. This faster than linear
scaling with N_{part} indicates a violation of the naive Wounded Nucleon Model.Comment: 13 pages, 16 figures, submitted to European Physical Journal C
(revised results for scaling exponents
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