650 research outputs found
Roper excitation in reactions
We calculate differential cross sections and the spin transfer coefficient
in the reaction for proton
bombarding energies from 1 to 10 GeV and invariant masses spanning
the region of the N(1440) Roper resonance. Two processes --
excitation in the -particle and Roper excitation in the proton -- are
included in an effective reaction model which was shown previously to reproduce
existing inclusive spectra. The present calculations demonstrate that these two
contributions can be clearly distinguished via , even under kinematic
conditions where cross sections alone exhibit no clear peak structure due to
the excitation of the Roper.Comment: 12 pages, 11 ps figures, Late
Competition Between Gravitational and Scalar Field Radiation
Recent astrophysical observations have provided strong evidence that the
present expansion of the universe is accelerating, powered by the energy
density associated with a cosmological term. Assuming the latter to be not
simply a constant term but a "quintessence" field, we study the radiation of
quanta of such a "quintessence" field ("quintons") by binary systems of
different types and compare intensities to those of standard tensor
gravitational wave emission. We consider both the case in which the
quintessence field varies only over cosmological distances and the case in
which it is modified spatially by (strong) gravitational fields, a condition
that results in bounds on the gradient of the scalar field. We show that, in
both the first case and, because of a bound we derive from the Hulse-Taylor
pulsar, in the second, there is not sufficient quinton radiation to affect
expected LISA and LIGO gravity wave signals from binary systems. We show that,
in the second case, the Large Hadron Collider is capable of setting a bound
similar to that from the binary pulsar.Comment: 12 pages aastex, accepted for publication in the Astrophysical
Journal. Minor typographical errors and reference list correcte
IR Kuiper Belt Constraints
We compute the temperature and IR signal of particles of radius and
albedo at heliocentric distance , taking into account the
emissivity effect, and give an interpolating formula for the result. We compare
with analyses of COBE DIRBE data by others (including recent detection of the
cosmic IR background) for various values of heliocentric distance, ,
particle radius, , and particle albedo, . We then apply these
results to a recently-developed picture of the Kuiper belt as a two-sector disk
with a nearby, low-density sector (40<R<50-90 AU) and a more distant sector
with a higher density. We consider the case in which passage through a
molecular cloud essentially cleans the Solar System of dust. We apply a simple
model of dust production by comet collisions and removal by the
Poynting-Robertson effect to find limits on total and dust masses in the near
and far sectors as a function of time since such a passage. Finally we compare
Kuiper belt IR spectra for various parameter values.Comment: 34 pages, LaTeX, uses aasms4.sty, 11 PostScript figures not embedded.
A number of substantive comments by a particularly thoughtful referee have
been addresse
Plasma Energy Loss into Kaluza-Klein Modes
Recently, Barger {\em et al.} computed energy losses into Kaluza Klein modes
from astrophysical plasmas in the approximation of zero density for the
plasmas. We extend their work by considering the effects of finite density for
two plasmon processes. Our results show that, for fixed temperature, the energy
loss rate per cm is constant up to some critical density and then falls
exponentially. This is true for transverse and longitudinal plasmons in both
the direct and crossed channels over a wide range of temperature and density. A
difficulty in deriving the appropriate covariant interaction energy at finite
density and temperature is addressed. We find that, for the cases considered by
Barger {\em et al.}, the zero density approximation and the neglect of other
plasmon processes is justified to better than an order of magnitude.Comment: 17 pages, LaTeX2e, 4 figures, 11 table
Study of the (d->,6-Li) Reaction
This work was supported by National Science Foundation Grants PHY 76-84033A01, PHY 78-22774, and Indiana Universit
Systematics of the K X-Ray Multiplicity for (Li,xn) Products with 180 < A < 210
This work was supported by the National Science Foundation Grant NSF PHY 78-22774 A02 & A03 and by Indiana Universit
The Analyzing Power for p-p Scattering at 180 MeV
This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440
The Multiplicity of K X-Rays Emitted in (6-Li,xn) Reactions
This work was supported by National Science Foundation Grants PHY 76-84033A01, PHY 78-22774, and Indiana Universit
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