491 research outputs found
Threshold meson production and cosmic ray transport
An interesting accident of nature is that the peak of the cosmic ray
spectrum, for both protons and heavier nuclei, occurs near the pion production
threshold. The Boltzmann transport equation contains a term which is the cosmic
ray flux multiplied by the cross section. Therefore when considering pion and
kaon production from proton-proton reactions, small cross sections at low
energy can be as important as larger cross sections at higher energy. This is
also true for subthreshold kaon production in nuclear collisions, but not for
subthreshold pion production.Comment: 9 pages, 1 figur
Comparison of Space Radiation GCR Models to Recent AMS Data
This paper is the third in a series of comparisons of American (NASA) and Russian (ROSCOSMOS) space radiation calculations. The present work focuses on calculation of fluxes of galactic cosmic rays (GCR), which are a constant source of radiation that constitutes one of the major hazards during deep space exploration missions for both astronauts/cosmonauts and hardware. In this work, commonly used GCR models are compared with recently published measurements of cosmic ray Hydrogen, Helium, and the Boron-to-Carbon ratio from the Alpha Magnetic Spectrometer (AMS). All of the models were developed and calibrated prior to the publication of the AMS data, therefore this an opportunity to validate the models against an independent data set
Comparison of Space Radiation GCR Models to AMS Heavy Ion Data
Galactic cosmic rays (GCR) are a constant source of radiation that constitutes one of the major hazards during deep space exploration missions for both astronauts and hardware. In this work, GCR models commonly used by the space radiation protection community are compared with recently published high-precision, high- resolution measurements of cosmic ray lithium, beryllium, boron, carbon, nitrogen, and oxygen fluxes along with their ratios (Li/B, Li/C, Li/O, Be/B, Be/C, Be/O, B/C, B/O, C/O, N/B, N/O) from the Alpha Magnetic Spectrometer (AMS). All of the models were developed and calibrated prior to the publication of this AMS data, therefore this is an opportunity to validate the models against an independent data set. This paper is a compliment to the previously published comparison of GCR models with AMS hydrogen, helium, and the boron-to-carbon ratio
Relativistic Multiple Scattering Theory and the Relativistic Impulse Approximation
It is shown that a relativistic multiple scattering theory for hadron-nucleus
scattering can be consistently formulated in four-dimensions in the context of
meson exchange. We give a multiple scattering series for the optical potential
and discuss the differences between the relativistic and non-relativistic
versions. We develop the relativistic multiple scattering series by separating
out the one boson exchange term from the rest of the Feynman series. However
this particular separation is not absolutely necessary and we discuss how to
include other terms. We then show how to make a three-dimensional reduction for
hadron-nucleus scattering calculations and we find that the relative energy
prescription used in the elastic scattering equation should be consistent with
the one used in the free two-body t-matrix involved in the optical potential.
We also discuss what assumptions are involved in making a Dirac Relativistic
Impulse Approximation (RIA).Comment: 20 pages, 9 figures, Accepted for publication in Journal of Physics
Another exact inflationary solution
A new closed-form inflationary solution is given for a hyperbolic interaction
potential. The method used to arrive at this solution is outlined as it appears
possible to generate additional sets of equations which satisfy the model. In
addition a new form of decaying cosmological constant is presented.Comment: 10 pages, 0 figure
Working with simple machines
A set of examples is provided that illustrate the use of work as applied to
simple machines. The ramp, pulley, lever and hydraulic press are common
experiences in the life of a student and their theoretical analysis therefore
makes the abstract concept of work more real. The mechanical advantage of each
of these systems is also discussed so that students can evaluate their
usefulness as machines.Comment: 9 pages, 4 figure
Exclusive Production of Higgs Bosons in Hadron Colliders
We study the exclusive, double--diffractive production of the Standard Model
Higgs particle in hadronic collisions at LHC and FNAL (upgraded) energies. Such
a mechanism would provide an exceptionally clean signal for experimental
detection in which the usual penalty for triggering on the rare decays of the
Higgs could be avoided. In addition, because of the color singlet nature of the
hard interaction, factorization is expected to be preserved, allowing the
cross--section to be related to similar hard--diffractive events at HERA.
Starting from a Fock state expansion in perturbative QCD, we obtain an estimate
for the cross section in terms of the gluon structure functions squared of the
colliding hadrons. Unfortunately, our estimates yield a production rate well
below what is likely to be experimentally feasible.Comment: 17 pages, RevTeX file, four uufiled PostScript figures. UMPP #94-177.
(Revised version. Some mistakenly missing Feynman diagrams are now added.
Results do not change qualitatively. Paper reorganized.
Nonlinear Enhancement of the Multiphonon Coulomb Excitation in Relativistic Heavy Ion Collisions
We propose a soluble model to incorporate the nonlinear effects in the
transition probabilities of the multiphonon Giant Dipole Resonances based on
the SU(1,1) algebra. Analytical expressions for the multi-phonon transition
probabilities are derived. Enhancement of the Double Giant Resonance excitation
probabilities in relativistic ion collisions scales as for
the degree of nonlinearity and is able to reach values
compatible with experimental data. The enhancement factor is found to decrease
with increasing bombarding energy. [KEYWORDS: Relativistic Heavy Ion
Collisions,Double Giant Resonance]Comment: 12 pages, 2 figure
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