4,708 research outputs found
The energies and residues of the nucleon resonances N(1535) and N(1650)
We extract pole positions for the N(1535) and N(1650) resonances using two
different models. The positions are determined from fits to different subsets
of the existing , and data
and found to be 1515(10)--i85(15)MeV and 1660(10)--i65(10)MeV, when the data is
described in terms of two poles. Sensitivity to the choice of fitted data is
explored. The corresponding and residues of these poles
are also extracted.Comment: 9 page
Nucleon-Nucleon Optical Model for Energies to 3 GeV
Several nucleon-nucleon potentials, Paris, Nijmegen, Argonne, and those
derived by quantum inversion, which describe the NN interaction for T-lab below
300$ MeV are extended in their range of application as NN optical models.
Extensions are made in r-space using complex separable potentials definable
with a wide range of form factor options including those of boundary condition
models. We use the latest phase shift analyses SP00 (FA00, WI00) of Arndt et
al. from 300 MeV to 3 GeV to determine these extensions. The imaginary parts of
the optical model interactions account for loss of flux into direct or resonant
production processes. The optical potential approach is of particular value as
it permits one to visualize fusion, and subsequent fission, of nucleons when
T-lab above 2 GeV. We do so by calculating the scattering wave functions to
specify the energy and radial dependences of flux losses and of probability
distributions. Furthermore, half-off the energy shell t-matrices are presented
as they are readily deduced with this approach. Such t-matrices are required
for studies of few- and many-body nuclear reactions.Comment: Latex, 40 postscript pages including 17 figure
Diffraction of complex molecules by structures made of light
We demonstrate that structures made of light can be used to coherently
control the motion of complex molecules. In particular, we show diffraction of
the fullerenes C60 and C70 at a thin grating based on a standing light wave. We
prove experimentally that the principles of this effect, well known from atom
optics, can be successfully extended to massive and large molecules which are
internally in a thermodynamic mixed state and which do not exhibit narrow
optical resonances. Our results will be important for the observation of
quantum interference with even larger and more complex objects.Comment: 4 pages, 3 figure
Mechanism of Pion Production in p Scattering at 1 GeV/nucleon
The one-pion and two-pion production in the p(alpha, alpha prime)X reaction
at an energy of E{alpha} = 4.2 GeV has been studied by simultaneous
registration of the scattered alpha particles and the secondary pion or proton.
The obtained results demonstrate that the inelastic alpha-particle scattering
on the proton at the energy of the experiment proceeds either through
excitation and decay of Delta resonance in the projectile or through excitation
in the target proton of the Roper resonance, which decays mainly on a nucleon
and a pion or a nucleon and a sigma meson - system of two pions in the isospin
I = 0, S-wave.Comment: 16 pages, 10 figures. Submitted to Proceedings of the XX
International Baldin Seminar on High - Energy Physics Problems, Dubna,
October 4 - 9, 201
Phase transition in a non-conserving driven diffusive system
An asymmetric exclusion process comprising positive particles, negative
particles and vacancies is introduced. The model is defined on a ring and the
dynamics does not conserve the number of particles. We solve the steady state
exactly and show that it can exhibit a continuous phase transition in which the
density of vacancies decreases to zero. The model has no absorbing state and
furnishes an example of a one-dimensional phase transition in a homogeneous
non-conserving system which does not belong to the absorbing state universality
classes
Delayed Decision-making in Real-time Beatbox Percussion Classification
This is an electronic version of an article published in Journal of New Music Research, 39(3), 203-213, 2010. doi:10.1080/09298215.2010.512979. Journal of New Music Research is available online at: www.tandfonline.com/openurl?genre=article&issn=1744-5027&volume=39&issue=3&spage=20
Relaxation Processes in Clouds of Trapped Bosons above the Bose-Einstein Condensation Temperature
We present a unified account of damping of low-lying collective modes and of
relaxation of temperature anisotropies in a trapped Bose gas in the
collisionless regime. By means of variational techniques, we show that the
relaxation times for the two situations are closely related to the simplest
variational estimate of the viscous relaxation time. We derive rather precise
theoretical expressions for the characteristic relaxation times, and compare
our results with experiment.Comment: 4 pages, revte
Study of nucleon resonances with electromagnetic interactions
Recent developments in using electromagnetic meson production reactions to
study the structure of nucleon resonances are reviewed. Possible future works
are discussed.Comment: 25 pages, 19 figure
Differential cross sections for pion charge exchange on the proton at 27.5 MeV
We have measured pion single charge exchange differential cross sections on
the proton at 27.5 MeV incident kinetic energy in the center of
momentum angular range between and . The extracted cross
sections are compared with predictions of the standard pion-nucleon partial
wave analysis and found to be in excellent agreement.Comment: ReVTeX v3.0 with aps.sty, 23 pages in e-print format, 7 PostScript
Figures and 4 Tables, also available via anonymous ftp at
ftp://helena.phys.virginia.edu/pub/preprints/scx.p
Two-body Pion Absorption on at Threshold
It is shown that a satisfactory explanation of the ratio of the rates of the
reactions and for stopped pions is obtained
once the effect of the short range two-nucleon components of the axial charge
operator for the nuclear system is taken into account. By employing realistic
models for the nucleon-nucleon interaction in the construction of these
components of the axial charge operator, the predicted ratios agree with the
empirical value to within 10-20\%.Comment: 19, UHPHYDOR-94-
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