94 research outputs found
QCD and QED Corrections to Higgs Boson Production in Charged Current Scattering
First order QCD and leading QED corrections to Higgs boson production in the
channel are calculated for the
kinematical conditions at LEP LHC (\sqrt{s} = 1360 \GeV) and the
interesting mass range 80 < M_H < 150 \GeV. In the DIS scheme the QCD
corrections (not including the corrections to the branching ratio, which are
well-known) are found to be about 1\% for the total cross section and
to for the observable cross section as defined by appropriate cuts. The
latter results depend on the definition of these cuts. The QED corrections
amount to about . Also obtainable with anonymous ftp from
gluon.hep.physik.uni-muenchen.de.Comment: latex, 16 pages + 9 pages figures in PostScript (included
Generalized scaling of the transverse mass spectrum at the Relativistic Heavy-Ion Collider
We argue that the transverse mass spectra of identified hadrons as measured
in gold-gold collisions at BNL's Relativistic Heavy-Ion Collider (RHIC) follows
a generalized scaling law. Such a scaling behavior is motivated by the idea of
a Color Glass Condensate, or more generally, saturation of the gluon density.
In particular, we describe the shapes of transverse mass spectra as a function
of centrality. This scaling of the transverse mass spectrum is shown to be
consistent with previously observed scaling of multiplicity with centrality.Comment: 15 pages, 6 figures, refs. updated, version to appear in Nucl. Phys.
Glueball spectrum and the Pomeron in the Wilson loop approach
Using a nonperturbative method based on asymptotic behaviour of Wilson loops
we calculate masses of glueballs and corresponding Regge-trajectories. The only
input is string tension fixed by meson Regge slope, while perturbative
contributions to spin splittings are defined by standard alpha_s values. The
masses of lowest glueball states are in a perfect agreement with lattice
results. The leading glueball trajectory which is associated with Pomeron is
discussed in details and its mixing with f and f' trajectories is taken into
account.Comment: LaTeX2e, 49 pages, 2 figure
Model-based specification of safety compliance needs for critical systems : A holistic generic metamodel
Abstract Context: Many critical systems must comply with safety standards as a way of providing assurance that they do not pose undue risks to people, property, or the environment. Safety compliance is a very demanding activity, as the standards can consist of hundreds of pages and practitioners typically have to show the fulfilment of thousands of safety-related criteria. Furthermore, the text of the standards can be ambiguous, inconsistent, and hard to understand, making it difficult to determine how to effectively structure and manage safety compliance information. These issues become even more challenging when a system is intended to be reused in another application domain with different applicable standards. Objective: This paper aims to resolve these issues by providing a metamodel for the specification of safety compliance needs for critical systems. Method: The metamodel is holistic and generic, and abstracts common concepts for demonstrating safety compliance from different standards and application domains. Its application results in the specification of “reference assurance frameworks” for safety-critical systems, which correspond to a model of the safety criteria of a given standard. For validating the metamodel with safety standards, parts of several standards have been modelled by both academic and industry personnel, and other standards have been analysed. We further augment this with feedback from practitioners, including feedback during a workshop. Results: The results from the validation show that the metamodel can be used to specify safety compliance needs for aerospace, automotive, avionics, defence, healthcare, machinery, maritime, oil and gas, process industry, railway, and robotics. Practitioners consider that the metamodel can meet their needs and find benefits in its use. Conclusion: The metamodel supports the specification of safety compliance needs for most critical computer-based and software-intensive systems. The resulting models can provide an effective means of structuring and managing safety compliance information
An SU(3) model for octet baryon and meson fragmentation
The production of the octet of baryons and mesons in e^+ e^- collisions is
analysed, based on considerations of SU(3) symmetry and a simple model for
SU(3) symmetry breaking in fragmentation functions. All fragmentation
functions, D_q^h(x, Q^2), describing the fragmentation of quarks into a member
of the baryon octet (and similarly for fragmentation into members of the meson
octet) are expressed in terms of three SU(3) symmetric functions, \alpha(x,
Q^2), \beta(x, Q^2), and \gamma(x, Q^2). With the introduction of an SU(3)
breaking parameter, \lambda, the model is successful in describing
hadroproduction data at the Z pole. The fragmentation functions are then
evolved using leading order evolution equations and good fits to currently
available data at 34 GeV and at 161 GeV are obtained.Comment: 24 pages LaTeX file including 11 postscript figure file
Computer-assisted methods for molecular structure elucidation: realizing a spectroscopist's dream
CGC, QCD Saturation and RHIC data (Kharzeev-Levin-McLerran-Nardi point of view)
This is the talk given at the Workshop:"Focus on Multiplicitioes", Bari,
Italy, 17-19 June,2004.. In this talk, we are going to discuss ion-ion and
deuteron - nucleus RHIC data and show that they support, if not more, the idea
of the new QCD phase: colour glass condensate with saturated parton density. .Comment: 26 pages with 33 figure
The high energy neutrino cross-section in the Standard Model and its uncertainty
Updated predictions are presented for high energy neutrino and antineutrino
charged and neutral current cross-sections within the conventional DGLAP
formalism of NLO QCD using modern PDF fits. PDF uncertainties from model
assumptions and parametrization bias are considered in addition to the
experimental uncertainties. Particular attention is paid to assumptions and
biases which could signal the need for extension of the conventional formalism
to include effects such as ln(1/x) resummation or non-linear effects of high
gluon density.Comment: 15 pages, 13 figures, 2 tables (REVTeX4); clarifying comments and
link to tabulated cross sections at
http://www-pnp.physics.ox.ac.uk/~cooper/neutrino/ added; to appear in JHE
Experimental and Theoretical Challenges in the Search for the Quark Gluon Plasma: The STAR Collaboration's Critical Assessment of the Evidence from RHIC Collisions
We review the most important experimental results from the first three years
of nucleus-nucleus collision studies at RHIC, with emphasis on results from the
STAR experiment, and we assess their interpretation and comparison to theory.
The theory-experiment comparison suggests that central Au+Au collisions at RHIC
produce dense, rapidly thermalizing matter characterized by: (1) initial energy
densities above the critical values predicted by lattice QCD for establishment
of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by
constituent interactions of very short mean free path, established most
probably at a stage preceding hadron formation; and (3) opacity to jets. Many
of the observations are consistent with models incorporating QGP formation in
the early collision stages, and have not found ready explanation in a hadronic
framework. However, the measurements themselves do not yet establish
unequivocal evidence for a transition to this new form of matter. The
theoretical treatment of the collision evolution, despite impressive successes,
invokes a suite of distinct models, degrees of freedom and assumptions of as
yet unknown quantitative consequence. We pose a set of important open
questions, and suggest additional measurements, at least some of which should
be addressed in order to establish a compelling basis to conclude definitively
that thermalized, deconfined quark-gluon matter has been produced at RHIC.Comment: 101 pages, 37 figures; revised version to Nucl. Phys.
Multi-machine analysis of termination scenarios, providing the specifications for controlled shutdown of ITER discharges
The task is to show that the specific ITER design features allow a stable well-controlled termination. This is a joint effort in control, exception handling development and physics modelling. Relevant for ITER is to maintain vertical, radial position, and shape control during the termination, especially at the time of the relatively fast H-L transition. The analysis of a database, built using a selected set of experimental termination cases, is performed
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