2,388 research outputs found
Conformality and Gauge Coupling Unification
It has been recently proposed to embed the standard model in a conformal
gauge theory to resolve the hierarchy problem, and to avoid assuming either
grand unification or low-energy supersymmetry. By model building based on
string-field duality we show how to maintain the successful prediction of an
electroweak mixing angle with in conformal gauge
theories with three chiral families.Comment: 8 pages LaTe
Present challenges in hadrontherapy techniques
Hadrontherapy is a high-precision technique in cancer radiation therapy, which allows obtaining a superior conformal treatment with respect to photons used in conventional radiation therapy. To reach this ambitious goal without reducing the patient throughput needed in a hospital-based environment, the physical and radiobiological properties of charged hadrons, protons and carbon ions in particular, have to be exploited at best, making use of the most modern technologies issued from research in nuclear and particle physics. In the present days, we are assisting to a continuous technological challenge, leading to the conception and to the development of innovative methods and instruments. In this paper, the most relevant challenges in dose delivery systems, gantries, imaging, quality assurance and particle accelerators are reviewe
Editorial: In use, in situ: extending field research methods
A case for evaluating in use and in-situ
Many authors have argued the need for a broader understanding of context and the situatedness of activity when approaching the evaluation of systems. However, prevailing practice often still tends towards attempting to understand the use of designed artefacts by focusing on a core set of tasks that are thought to define the system. A consequence of such focus is that other tasks are considered peripheral and outside the scope of design and evaluation activities. To illustrate the point, consider the experience, familiar to many of us, of being involved in an evaluation activity where participants provide unstructured qualitative feedback. Irrespective of whether the activity is carried out in a laboratory, in a high fidelity simulation or in a naturalistic setting, participants will frequently volunteer unsolicited feedback about tasks and goals that were not originally within the ambit of the design activity. This unprompted feedback, we suggest, is a cue for the evaluators to pay attention to the relationship between the tool and the practice in which it will be used. In other words a cue to consider the situations in which artefact will be used, the tasks and activities that may be affected by the new system, and so on. These are empirical questions that cannot be answered a priori by the development team, whether the evaluation is taking place in “artificial” or “natural” setting
High-power test results of a 3 GHz single-cell cavity
Compact, reliable and little consuming accelerators are required for the
treatment of tumours with ions. TERA proposes the "cyclinac", composed of a
high-frequency, fast-cycling linac which boosts the energy of the particles
previously accelerated in a cyclotron. The dimensions of the linac can be
reduced if high gradients are used. TERA initiated a high-gradient test program
to understand the operational limit of such structures. The program foresees
the design, prototyping and high-power test of several high-gradient structures
operating at 3 and 5.7 GHz. The high-power tests of the 3 GHz single-cell
cavity were completed in Winter 2012. The maximum BDR threshold measured for
Emax of 170 MV/m and RF pulses of 2.5 \mu s was 3 x 10-6 bpp/m
Phenomenological Analysis of and Elastic Scattering Data in the Impact Parameter Space
We use an almost model-independent analytical parameterization for and
elastic scattering data to analyze the eikonal, profile, and
inelastic overlap functions in the impact parameter space. Error propagation in
the fit parameters allows estimations of uncertainty regions, improving the
geometrical description of the hadron-hadron interaction. Several predictions
are shown and, in particular, the prediction for inelastic overlap
function at TeV shows the saturation of the Froissart-Martin
bound at LHC energies.Comment: 15 pages, 16 figure
Inclusive neutrino scattering off deuteron from threshold to GeV energies
Background: Neutrino-nucleus quasi-elastic scattering is crucial to interpret
the neutrino oscillation results in long baseline neutrino experiments. There
are rather large uncertainties in the cross section, due to insufficient
knowledge on the role of two-body weak currents. Purpose: Determine the role of
two-body weak currents in neutrino-deuteron quasi-elastic scattering up to GeV
energies. Methods: Calculate cross sections for inclusive neutrino scattering
off deuteron induced by neutral and charge-changing weak currents, from
threshold up to GeV energies, using the Argonne potential and
consistent nuclear electroweak currents with one- and two-body terms. Results:
Two-body contributions are found to be small, and increase the cross sections
obtained with one-body currents by less than 10% over the whole range of
energies. Total cross sections obtained by describing the final two-nucleon
states with plane waves differ negligibly, for neutrino energies
MeV, from those in which interaction effects in these states are fully
accounted for. The sensitivity of the calculated cross sections to different
models for the two-nucleon potential and/or two-body terms in the weak current
is found to be weak. Comparing cross sections to those obtained in a naive
model in which the deuteron is taken to consist of a free proton and neutron at
rest, nuclear structure effects are illustrated to be non-negligible.
Conclusion: Contributions of two-body currents in neutrino-deuteron
quasi-elastic scattering up to GeV are found to be smaller than 10%. Finally,
it should be stressed that the results reported in this work do not include
pion production channels.Comment: 30 pages, 17 figures; publishe
Comment On ``Grand Unification and Supersymmetric Threshold"
Barbieri and Hall have argued that threshold effects at the scale of
grand-unification wipe out predictions on the SUSY scale, M_S. Using triviality
arguments we give upper bounds on ultraheavy particles, while proton stability
gives lower bounds on the mass of the higgs color-triplet. We find no useful
lower bound on the supermultiplet, but if the strong coupling constant
is as large as recent experiments suggest, unification in the minimal SUSY
SU(5) model requires that the masses be and that the
color octet and weak triplet be split in mass by a factor of 100.Comment: 6 pages (revised
A Transient New Coherent Condition of Matter: The Signal for New Physics in Hadronic Diffractive Scattering
We demonstrate the existence of an anomalous structure in the data on the
diffractive elastic scattering of hadrons at high energies and small momentum
transfer. We analyze five sets of experimental data on
scattering from five different experiments with colliding beams, ranging from
the first-- and second--generation experiments at GeV to the
most recent experiments at 546 GeV and at 1800 GeV. All of the data sets
exhibit a localized anomalous structure in momentum transfer. We represent the
anomalous behavior by a phenomenological formula. This is based upon the idea
that a transient coherent condition of matter occurs in some of the
intermediate inelastic states which give rise, via unitarity, to diffractive
elastic scattering. The Fourier--Bessel transform into momentum--transfer space
of a spatial oscillatory behavior of matter in the impact--parameter plane
results in a small piece of the diffractive amplitude which exhibits a
localized anomalous behavior near a definite value of . In addition, we
emphasize possible signals coming directly from such a new condition of matter
that may be present in current experiments on inelastic processes.Comment: 25 pages, LaTeX (12 figures, not included). A complete postscript
file (except figures 1 and 11, which are available upon request) is available
via anonymous ftp at ttpux2.physik.uni-karlsruhe.de (129.13.102.139) as
/ttp94-03 /ttp94-03.ps, Local preprint# TTP94-03 (March 1994
RMT 555 - PERSEKITARAN PERUNDANGAN APRIL-MAY 06.
Abstract. We present a linear time algorithm for computing an implicit linear space representation of a minimum cycle basis (MCB) in weighted partial 2-trees, i.e., graphs of treewidth two. The implicit representation can be made explicit in a running time that is proportional to the size of the MCB. For planar graphs, Borradaile, Sankowski, and Wulff-Nilsen [Min st-cut Oracle for Planar Graphs with Near-Linear Preprocessing Time, FOCS 2010] showed how to compute an implicit O(n log n) space representation of an MCB in O(n log 5 n) time. For the special case of partial 2-trees, our algorithm improves this result to linear time and space. Such an improvement was achieved previously only for outerplanar graphs [Liu and Lu: Minimum Cycle Bases of Weighted Outerplanar Graphs, IPL 110:970–974, 2010]
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