4,956 research outputs found
Production of a Prompt Photon in Association with Charm at Next-to-Leading Order in QCD
A second order, , calculation in perturbative quantum
chromodynamics of the two particle inclusive cross section is presented for the
reaction for large values of the
transverse momentum of the prompt photon and charm quark. The combination of
analytic and Monte Carlo integration methods used here to perform phase-space
integrations facilitates imposition of photon isolation restrictions and other
selections of relevance in experiments. Differential distributions are provided
for various observables. Positive correlations in rapidity are predicted.Comment: 27 pages in RevTex plus 14 figures in one compressed PS fil
Spin Dependence of Massive Lepton Pair Production in Proton-Proton Collisions
We calculate the transverse momentum distribution for the production of
massive lepton-pairs in longitudinally polarized proton-proton reactions at
collider energies within the context of perturbative quantum chromodynamics.
For values of the transverse momentum Q_T greater than roughly half the pair
mass Q, Q_T > Q/2, we show that the differential cross section is dominated by
subprocesses initiated by incident gluons, provided that the polarized gluon
density is not too small. Massive lepton-pair differential cross sections
should be a good source of independent constraints on the polarized gluon
density, free from the experimental and theoretical complications of photon
isolation that beset studies of prompt photon production. We provide
predictions for the spin-averaged and spin-dependent differential cross
sections as a function of Q_T at energies relevant for the Relativistic Heavy
Ion Collider (RHIC) at Brookhaven, and we compare these with predictions for
real prompt photon production.Comment: 34 pages, RevTeX including 17 figures in .ps file
Analytic Calculation of Prompt Photon plus Associated Heavy Flavor at Next-to-Leading Order in QCD
Contributions through second order, , in perturbative quantum
chromodynamics are calculated analytically for inclusive associated production
of a prompt photon and a charm quark at large values of transverse momentum in
high energy hadron-hadron collisions. Seven partonic subprocesses contribute at
order . We find important corrections to the lowest order,
, subprocess . We demonstrate to what
extent data from may serve to measure
the charm quark density in the nucleon.Comment: 34 pages RevTex plus 9 figures submitted as uuencoded ps files;
figures replaced and text revised to include one additional referenc
Massive Lepton Pairs as a Prompt Photon Surrogate
We discuss the transverse momentum distribution for the production of massive
lepton-pairs in hadron reactions at fixed target and collider energies within
the context of next-to-leading order perturbative quantum chromodynamics. For
values of the transverse momentum greater than the pair mass , , we show that the differential cross section is dominated by subprocesses
initiated by incident gluons. Massive lepton-pair differential cross sections
are an advantageous source of constraints on the gluon density, free from the
experimental and theoretical complications of photon isolation that beset
studies of prompt photon production. We compare calculations with data and
provide predictions for the differential cross section as a function of
in proton-antiproton reactions at center-of-mass energies of 1.8 TeV, and in
proton-nucleon reactions at fixed target and LHC energies.Comment: 36 pages, RevTeX, including 16 ps files of figures; minor changes in
wording; one reference added. Version to appear in Phys Rev
Representation theory of super Yang-Mills algebras
We study in this article the representation theory of a family of super
algebras, called the \emph{super Yang-Mills algebras}, by exploiting the
Kirillov orbit method \textit{\`a la Dixmier} for nilpotent super Lie algebras.
These super algebras are a generalization of the so-called \emph{Yang-Mills
algebras}, introduced by A. Connes and M. Dubois-Violette in \cite{CD02}, but
in fact they appear as a "background independent" formulation of supersymmetric
gauge theory considered in physics, in a similar way as Yang-Mills algebras do
the same for the usual gauge theory. Our main result states that, under certain
hypotheses, all Clifford-Weyl super algebras \Cliff_{q}(k) \otimes A_{p}(k),
for , or and , appear as a quotient of all super
Yang-Mills algebras, for and . This provides thus a family
of representations of the super Yang-Mills algebras
Spin Dependence of Associated Production of a Prompt Photon and a Charm Quark at Next-to-Leading Order in QCD
A second order, , calculation in perturbative quantum
chromodynamics is presented of the longitudinal spin dependence of the cross
section for the two particle inclusive reaction for
large values of the transverse momentum of the prompt photon and charm quark.
Differential distributions are provided for the spin-averaged cross section and
for the two-spin longitudinal polarization asymmetry at the energy of
the Brookhaven Relativistic Heavy Ion Collider. An assessment is given of the
prospects for determination of the spin dependence of the charm quark density.Comment: 27 pages, RevTex, and 10 figure
Isolated Prompt Photon Production in Hadronic Final States of Annihilation
We provide complete analytic expressions for the isolated prompt photon
production cross section in annihilation reactions through one-loop
order in quantum chromodynamics (QCD) perturbation theory. Functional
dependences on the isolation cone size and isolation energy parameter
are derived. The energy dependence as well as the full angular
dependence of the cross section on are displayed, where
specifies the direction of the photon with respect to the
collision axis. We point out that conventional perturbative QCD
factorization breaks down for isolated photon production in
annihilation reactions in a specific region of phase space. We discuss the
implications of this breakdown for the extraction of fragmentation functions
from annihilation data and for computations of prompt photon
production in hadron-hadron reactions.Comment: 54 pages RevTeX plus 19 postscript figures submitted together in one
compressed fil
Integration of Nanostructures into Microsensor Devices on Whole Wafers
Chemical sensors are used in a wide variety of applications, such as environmental monitoring, fire detection, emission monitoring, and health monitoring. The fabrication of chemical sensors involving nanostructured materials holds the potential for the development of sensor systems with unique properties and improved performance. However, the fabrication and processing of nanostructures for sensor applications currently are limited in the ability to control their location on the sensor, which in turn hinders the progress for batch fabrication. This report discusses the advantages of using nanomaterials in sensor designs, some of the challenges encountered with the integration of nanostructures into microsensor / devices, and then briefly describes different methods attempted by other groups to address this issue. Finally, this report will describe how our approach for the controlled alignment of nanostructures onto a sensor platform was applied to demonstrate an approach for the mass production of sensors with nanostructures
An unusual interplay among disorder, Kondo-effect and spin-glass behavior in the Kondo lattices, CeAuCoSi
We report the results of magnetic measurements for the solid solution
CeAuCoSi. The results reveal that this solid solution is
characterized by a magnetic phase diagram (plot of magnetic transition
temperature versus ) unusual for Kondo lattices. In particular, the
spin-glass freezing induced by disorder is observed only for the compositions
at the weak coupling limit; as one approaches the quantum critical point by a
gradual replacement of Au by Co, this disorder effect is surprisingly
suppressed in favor of long range antiferro-magnetic ordering in contrast to
expectations. This unusual interplay between disorder, spin-glass freezing and
the Kondo-effect calls for further refinement of theories on competition
between magnetism and the Kondo effect.Comment: 4 pages, 3 figure
Partons and QCD in high-energy polarized pp collisions
We present and use a technique for implementing in a fast way, and without
any approximations, higher-order calculations of partonic cross sections into
global analyses of parton distribution functions. The approach, which is set up
in Mellin-moment space, is particularly suited for analyses of future data from
polarized proton-proton collisions at RHIC, but not limited to this case. We
also briefly discuss the effects of soft-gluon resummations on spin
asymmetries.Comment: 6 pages, LaTeX, 5 eps figures, Invited talk presented by W. Vogelsang
at the ``International Workshop on the Spin Structure of the Proton and
Polarized Collider Physics'', ECT*, Trento, Italy, July 23-28, 200
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