352 research outputs found
The stratigraphic sequence of volcanic and sedimentary units in the north polar region of Mars
Based on photogeologic mapping of Viking orbiter images of Mars, four distinct informal stratigraphic units are defined for the region north of 70 degrees N latitude. They are: (a) bulbous plains, (b) mantled plains, (c) dune deposits, and (d) layered deposits/perennial ice. Background information on the Martian polar caps is provided from telescopic observation, Mariner mission results, and Viking mission results (August 1976-November 1978). A description, and an interpretation and distribution of the stratigraphic units are presented. Surface winds, which were determined from dune orientations, and discussed and implications for the source of circumpolar dune materials are delineated. A list of the Viking Orbiter imagery used in the research, the computer programs for crater size frequency distributions, and the crater size frequency data are presented
Large Transverse Momentum Jet Production and DIS Distributions of the Proton
We have calculated the single jet inclusive cross section as measured at
Fermilab in next-to-leading order QCD using recent parton distributions of the
CTEQ collaboration. We studied the scheme dependence of the jet cross section
by employing the \overline{\mbox{MS}} and DIS factorization schemes
consistently. For GeV, we find that the cross section in the DIS
scheme is larger than in the \overline{\mbox{MS}} scheme yielding a
satisfactory description of the CDF data over the whole range in the DIS
scheme.Comment: 7 pages, latex, 2 figures include
Extracting the Strange Density from
We present a QCD analysis of the strange and charm contributions to the
neutrino deep inelastic structure function . We show that next-to-leading
order effects, which are relatively important for , play a lesser role in
the case of . The neutrino--antineutrino difference provides a new determination of the strange density, which
exhibits some advantages with respect to other traditional methods.Comment: 12 page
Vector-pseudoscalar two-meson distribution amplitudes in three-body meson decays
We study three-body nonleptonic decays by introducing two-meson
distribution amplitudes for the vector-pseudoscalar pair, such that the
analysis is simplified into the one for two-body decays. The twist-2 and
twist-3 two-meson distribution amplitudes, associated with
longitudinally and transversely polarized mesons, are constrained by the
experimental data of the and branching
ratios. We then predict the and decay
spectra in the invariant mass. Since the resonant contribution in the
channel is negligible, the above decay spectra provide a clean test
for the application of two-meson distribution amplitudes to three-body
meson decays.Comment: 9 pages, 1 figure, Revtex4, version to appear in PR
Multivariate Fitting and the Error Matrix in Global Analysis of Data
When a large body of data from diverse experiments is analyzed using a
theoretical model with many parameters, the standard error matrix method and
the general tools for evaluating errors may become inadequate. We present an
iterative method that significantly improves the reliability of the error
matrix calculation. To obtain even better estimates of the uncertainties on
predictions of physical observables, we also present a Lagrange multiplier
method that explores the entire parameter space and avoids the linear
approximations assumed in conventional error propagation calculations. These
methods are illustrated by an example from the global analysis of parton
distribution functions.Comment: 13 pages, 5 figures, Latex; minor clarifications, fortran program
made available; Normalization of Hessian matrix changed to HEP standar
Scheme and Scale Dependence of Charm Production in Neutrino Scattering
We discuss some theoretical uncertainties in the calculation of the cross
section for charm production in charged current deep inelastic neutrino
scattering related to ambiguities in the treatment of terms which are singular
in the limit of a vanishing charm mass. In particular we compare the so-called
variable flavour scheme where these terms are absorbed in the parton
distribution functions containing the charm as an active flavour, with the
so-called fixed flavour scheme with no charm mass subtraction where the charm
appears only in the final state of fixed-order scattering matrix elements.
Using available parametrizations of parton distribution functions we find that
the two schemes lead to largely differing results for separate structure
functions whereas the differences cancel to a large extent in the total cross
section in that kinematical region which has been measured so far.Comment: 20pages, uuencoded postscript, figures include
Consistent Analysis of the Transition Form Factor in the Whole Physical Region
In the paper, we show that the transition form factor can be
calculated by using the different approach in the different regions and
they are consistent with each other in the whole physical region. For the
transition form factor in the large recoil regions, one can apply the
PQCD approach, where the transverse momentum dependence for both the hard
scattering part and the non-perturbative wavefunction, the Sudakov effects and
the threshold effects are included to regulate the endpoint singularity and to
derive a more reliable PQCD result. Pionic twist-3 contributions are carefully
studied with a better endpoint behavior wavefunction for and we find
that its contribution is less than the leading twist contribution. Both the two
wavefunctions and of the B meson can give sizable
contributions to the transition form factor and should be kept for a
better understanding of the B decays. The present obtained PQCD results can
match with both the QCD light-cone sum rule results and the extrapolated
lattice QCD results in the large recoil regions.Comment: 18pages, 6 figure
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