11,691 research outputs found
System integration report
Several areas that arise from the system integration issue were examined. Intersystem analysis is discussed as it relates to software development, shared data bases and interfaces between TEMPUS and PLAID, shaded graphics rendering systems, object design (BUILD), the TEMPUS animation system, anthropometric lab integration, ongoing TEMPUS support and maintenance, and the impact of UNIX and local workstations on the OSDS environment
Control System for the LEDA 6.7-MeV Proton Beam Halo Experiment
Measurement of high-power proton beam-halo formation is the ongoing
scientific experiment for the Low Energy Demonstration Accelerator (LEDA)
facility. To attain this measurement goal, a 52-magnet beam line containing
several types of beam diagnostic instrumentation is being installed. The
Experimental Physics and Industrial Control System (EPICS) and commercial
software applications are presently being integrated to provide a real-time,
synchronous data acquisition and control system. This system is comprised of
magnet control, vacuum control, motor control, data acquisition, and data
analysis. Unique requirements led to the development and integration of
customized software and hardware. EPICS real-time databases, Interactive Data
Language (IDL) programs, LabVIEW Virtual Instruments (VI), and State Notation
Language (SNL) sequences are hosted on VXI, PC, and UNIX-based platforms which
interact using the EPICS Channel Access (CA) communication protocol.
Acquisition and control hardware technology ranges from DSP-based diagnostic
instrumentation to the PLC-controlled vacuum system. This paper describes the
control system hardware and software design, and implementation.Comment: LINAC2000 Conference, 4 pg
Supersymmetric particle mass measurement with the boost-corrected contransverse mass
A modification to the contransverse mass (MCT) technique for measuring the
masses of pair-produced semi-invisibly decaying heavy particles is proposed in
which MCT is corrected for non-zero boosts of the centre-of-momentum (CoM)
frame of the heavy states in the laboratory transverse plane. Lack of knowledge
of the mass of the CoM frame prevents exact correction for this boost, however
it is shown that a conservative correction can nevertheless be derived which
always generates an MCT value which is less than or equal to the true value of
MCT in the CoM frame. The new technique is demonstrated with case studies of
mass measurement with fully leptonic ttbar events and with SUSY events
possessing a similar final state.Comment: 33 pages, 33 .eps figures, JHEP3 styl
Reducing combinatorial uncertainties: A new technique based on MT2 variables
We propose a new method to resolve combinatorial ambiguities in hadron
collider events involving two invisible particles in the final state. This
method is based on the kinematic variable MT2 and on the MT2-assisted-on-shell
reconstruction of invisible momenta, that are reformulated as `test' variables
Ti of the correct combination against the incorrect ones. We show how the
efficiency of the single Ti in providing the correct answer can be
systematically improved by combining the different Ti and/or by introducing
cuts on suitable, combination-insensitive kinematic variables. We illustrate
our whole approach in the specific example of top anti-top production, followed
by a leptonic decay of the W on both sides. However, by construction, our
method is also directly applicable to many topologies of interest for new
physics, in particular events producing a pair of undetected particles, that
are potential dark-matter candidates. We finally emphasize that our method is
apt to several generalizations, that we outline in the last sections of the
paper.Comment: 1+23 pages, 8 figures. Main changes in v3: (1) discussion at the end
of sec. 2 improved; (2) added sec. 4.2 about the method's dependence on mass
information. Matches journal versio
Simple supersymmetric solution to the strong CP problem
It is shown that the minimal supersymmetric left-right model can provide a
natural solution to the strong {\it CP} problem without the need for an axion,
nor any additional symmetries beyond supersymmetry and parity.Comment: Plain Latex. 10 pages, including two figures which are part of the
Latex file. Shortened version, to appear in Phys. Rev. Lett. 7
Eliminating the d=5 proton decay operators from SUSY GUTs
A general analysis is made of the question whether the d=5 proton decay
operators coming from exchange of colored Higgsinos can be completely
eliminated in a natural way in supersymmetric grand unified models. It is shown
that they can indeed be in SO(10) while at the same time naturally solving the
doublet-triplet splitting problem, having only two light Higgs doublets, and
using no more than a single adjoint Higgs field. Accomplishing all of this
requires that the vacuum expectation value of the adjoint Higgs field be
proportional to the generator I_{3R} rather than to B-L, as is usually assumed.
It is shown that such models can give realistic quark and lepton masses. We
also point out a new mechanism for solving the \mu problem in the context of
SO(10) SUSY GUTs.Comment: 24 pages in LaTeX, with 3 figure
Polynomials, Riemann surfaces, and reconstructing missing-energy events
We consider the problem of reconstructing energies, momenta, and masses in
collider events with missing energy, along with the complications introduced by
combinatorial ambiguities and measurement errors. Typically, one reconstructs
more than one value and we show how the wrong values may be correlated with the
right ones. The problem has a natural formulation in terms of the theory of
Riemann surfaces. We discuss examples including top quark decays in the
Standard Model (relevant for top quark mass measurements and tests of spin
correlation), cascade decays in models of new physics containing dark matter
candidates, decays of third-generation leptoquarks in composite models of
electroweak symmetry breaking, and Higgs boson decay into two tau leptons.Comment: 28 pages, 6 figures; version accepted for publication, with
discussion of Higgs to tau tau deca
Ecosystem carbon 7 dioxide fluxes after disturbance in forests of North America
Disturbances are important for renewal of North American forests. Here we summarize more than 180 site years of eddy covariance measurements of carbon dioxide flux made at forest chronosequences in North America. The disturbances included stand-replacing fire (Alaska, Arizona, Manitoba, and Saskatchewan) and harvest (British Columbia, Florida, New Brunswick, Oregon, Quebec, Saskatchewan, and Wisconsin) events, insect infestations (gypsy moth, forest tent caterpillar, and mountain pine beetle), Hurricane Wilma, and silvicultural thinning (Arizona, California, and New Brunswick). Net ecosystem production (NEP) showed a carbon loss from all ecosystems following a stand-replacing disturbance, becoming a carbon sink by 20 years for all ecosystems and by 10 years for most. Maximum carbon losses following disturbance (g C m−2y−1) ranged from 1270 in Florida to 200 in boreal ecosystems. Similarly, for forests less than 100 years old, maximum uptake (g C m−2y−1) was 1180 in Florida mangroves and 210 in boreal ecosystems. More temperate forests had intermediate fluxes. Boreal ecosystems were relatively time invariant after 20 years, whereas western ecosystems tended to increase in carbon gain over time. This was driven mostly by gross photosynthetic production (GPP) because total ecosystem respiration (ER) and heterotrophic respiration were relatively invariant with age. GPP/ER was as low as 0.2 immediately following stand-replacing disturbance reaching a constant value of 1.2 after 20 years. NEP following insect defoliations and silvicultural thinning showed lesser changes than stand-replacing events, with decreases in the year of disturbance followed by rapid recovery. NEP decreased in a mangrove ecosystem following Hurricane Wilma because of a decrease in GPP and an increase in ER
The Stability of the Gauge Hierarchy in
It has been shown that the Dimopoulos-Wilczek (or missing-VEV) mechanism for
doublet-triplet splitting can be implemented in models,
which requires no adjoint Higgs fields. This is an advantage from the point of
view of string theory construction. Here the stability of the gauge hierarchy
is examined in detail, and it is shown that it can be guaranteed much more
simply than in . In fact a symmetry ensures the stability of the
DW form of the expectation values to all orders in GUT-scale VEVs. It is also
shown that models based on have the advantages of while permitting complete quark-lepton unification as in
.Comment: 13 pages, LaTe
Constraint on the heavy sterile neutrino mixing angles in the SO(10) model with double see-saw mechanism
Constraints on the heavy sterile neutrino mixing angles are studied in the
framework of a minimal supersymmetric model with {\it double
see-saw mechanism}. A new singlet matter in addition to the right-handed
neutrinos is introduced to realize the double see-saw mechanism. The minimal
model gives an unambiguous Dirac neutrino mass matrix, which
enables us to predict the masses and the mixing angles in the enlarged neutrino mass matrix. Mixing angles between the light Majorana
neutrinos and the heavy sterile neutrinos are shown to be within the LEP
experimental bound on all ranges of the Majorana phases.Comment: 16 pages, 4 figures; the version to be published in Eur. Phys. J.
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