33,357 research outputs found
Inclusive Diffraction at HERA
New precision measurements of inclusive diffractive deep-inelastic ep
scattering interactions, performed by the H1 and ZEUS collaborations at the
HERA collider, are discussed. A new set of diffractive parton distributions,
determined from recent high precision H1 data, is presented.Comment: 5 pages, to appear in the proceedings of the 31st Intl. Conference on
High Energy Physics ICHEP 2002, Amsterdam, July 200
Relative distributions of W's and Z's at low transverse momenta
Despite large uncertainties in the and transverse momentum
() distributions for q_T\lsim 10 GeV, the ratio of the distributions
varys little. The uncertainty in the ratio of to distributions is
on the order of a few percent, independent of the details of the
nonperturbative parameterization.Comment: 13 pages in revtex, 5 postscript figures available upon request,
UIOWA-94-0
Design of prototype charged particle fog dispersal unit
The unit was designed to be easily modified so that certain features that influence the output current and particle size distribution could be examined. An experimental program was designed to measure the performance of the unit. The program described includes measurements in a fog chamber and in the field. Features of the nozzle and estimated nozzle characteristics are presented
Resolving the plasma profile via differential single inclusive suppression
The ability of experimental signatures to resolve the spatio-temporal profile
of an expanding quark gluon plasma is studied. In particular, the single
inclusive suppression of high momentum hadrons versus the centrality of a
heavy-ion collision and with respect to the reaction plane in non-central
collisions is critically examined. Calculations are performed in the higher
twist formalism for the modification of the fragmentation functions. Radically
different nuclear geometries are used. The influence of different initial gluon
distributions as well as different temporal evolution scenarios on the single
inclusive suppression of high momentum pions are outlined. It is demonstrated
that the modification versus the reaction plane is quite sensitive to the
initial spatial density. Such sensitivity remains even in the presence of a
strong elliptic flow.Comment: 5 pages, 4 figures, RevTex
Single spin asymmetries in hadron-hadron collisions
We study weighted azimuthal single spin asymmetries in hadron-hadron
scattering using the diagrammatic approach at leading order and assuming
factorization. The effects of the intrinsic transverse momenta of the partons
are taken into account. We show that the way in which -odd functions, such
as the Sivers function, appear in these processes does not merely involve a
sign flip when compared with semi-inclusive deep inelastic scattering, such as
in the case of the Drell-Yan process. Expressions for the weighted scattering
cross sections in terms of distribution and fragmentation functions folded with
hard cross sections are obtained by introducing modified hard cross sections,
referred to as gluonic pole cross sections.Comment: 22 pages, 4 figures; minor text modifications and some additional
reference
An evaluation of the suitability of ERTS data for the purposes of petroleum exploration
This experiment was designed to determine the types and amounts of information valuable to petroleum exploration extractable from ERTS data and the cost of obtaining the information using traditional or conventional means. It was desired that an evaluation of this new petroleum exploration tool be made in a geologically well known area in order to assess its usefulness in an unknown area. The Anadarko Basin lies in western Oklahoma and the panhandle of Texas. It was chosen as a test site because there is a great deal of published information available on the surface and subsurface geology of the area, and there are many known structures that act as traps for hydrocarbons. This basin is similar to several other large epicontinental sedimentary basins. It was found that ERTS imagery is an excellent tool for reconnaissance exploration of large sedimentary basins or new exploration provinces. For the first time, small and medium size oil companies can rapidly and effectively analyze exploration provinces as a whole
Hard-scattering factorization with heavy quarks: A general treatment
A detailed proof of hard scattering factorization is given with the inclusion
of heavy quark masses. Although the proof is explicitly given for
deep-inelastic scattering, the methods apply more generally The
power-suppressed corrections to the factorization formula are uniformly
suppressed by a power of \Lambda/Q, independently of the size of heavy quark
masses, M, relative to Q.Comment: 52 pages. Version as published plus correction of misprint in Eq.
(45
Nonstationary Stochastic Resonance in a Single Neuron-Like System
Stochastic resonance holds much promise for the detection of weak signals in
the presence of relatively loud noise. Following the discovery of nondynamical
and of aperiodic stochastic resonance, it was recently shown that the
phenomenon can manifest itself even in the presence of nonstationary signals.
This was found in a composite system of differentiated trigger mechanisms
mounted in parallel, which suggests that it could be realized in some
elementary neural networks or nonlinear electronic circuits. Here, we find that
even an individual trigger system may be able to detect weak nonstationary
signals using stochastic resonance. The very simple modification to the trigger
mechanism that makes this possible is reminiscent of some aspects of actual
neuron physics. Stochastic resonance may thus become relevant to more types of
biological or electronic systems injected with an ever broader class of
realistic signals.Comment: Plain Latex, 7 figure
Applying machine learning to the problem of choosing a heuristic to select the variable ordering for cylindrical algebraic decomposition
Cylindrical algebraic decomposition(CAD) is a key tool in computational
algebraic geometry, particularly for quantifier elimination over real-closed
fields. When using CAD, there is often a choice for the ordering placed on the
variables. This can be important, with some problems infeasible with one
variable ordering but easy with another. Machine learning is the process of
fitting a computer model to a complex function based on properties learned from
measured data. In this paper we use machine learning (specifically a support
vector machine) to select between heuristics for choosing a variable ordering,
outperforming each of the separate heuristics.Comment: 16 page
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