11,834 research outputs found
Dynamical Generation of Linear model SU(3) Lagrangian and Meson Nonet Mixing
This paper is the SU(3) extension of the dynamically generated SU(2) linear
model Lagrangian worked out previously using dimensional
regularization. After discussing the quark-level Goldberger-Treiman relations
for SU(3) and the related gap equations, we dynamically generate the meson
cubic and quartic couplings. This also constrains the meson-quark coupling
constant to and determines the SU(3) scalar meson masses in a
Nambu-Jona-Lasinio fashion. Finally we dynamically induce the U(3) pseudoscalar
and scalar mixing angles in a manner compatible with data.Comment: 19 printed pages, requires plain Tex, now published in IJMPA 13, 657
(1998
Does Magnetic Charge Imply a Massive Photon ?
In Abelian theories of monopoles the magnetic charge is required to be
enormous. Using the electric-magnetic duality of electromagnetism it is argued
that the existence of such a large, non-perturbative magnetic coupling should
lead to a phase transition where magnetic charge is permanently confined and
the photon becomes massive. The apparent masslessness of the photon could then
be used as an argument against the existence of such a large, non-perturbative
magnetic charge. Finally it is shown that even in the presence of this
dynamical mass generation the Cabbibo-Ferrari formulation of magnetic charge
gives a consistent theory.Comment: 10 pages LaTe
Multi-label classification using ensembles of pruned sets
This paper presents a Pruned Sets method (PS) for multi-label classification. It is centred on the concept of treating sets of labels as single labels. This allows the classification process to inherently take into account correlations between labels. By pruning these sets, PS focuses only on the most important correlations, which reduces complexity and improves accuracy. By combining pruned sets in an ensemble scheme (EPS), new label sets can be formed to adapt to irregular or complex data. The results from experimental evaluation on a variety of multi-label datasets show that [E]PS can achieve better performance and train much faster than other multi-label methods
Cosmological implications of the Higgs mass measurement
We assume the validity of the Standard Model up to an arbitrary high-energy
scale and discuss what information on the early stages of the Universe can be
extracted from a measurement of the Higgs mass. For Mh < 130 GeV, the Higgs
potential can develop an instability at large field values. From the absence of
excessive thermal Higgs field fluctuations we derive a bound on the reheat
temperature after inflation as a function of the Higgs and top masses. Then we
discuss the interplay between the quantum Higgs fluctuations generated during
the primordial stage of inflation and the cosmological perturbations, in the
context of landscape scenarios in which the inflationary parameters scan. We
show that, within the large-field models of inflation, it is highly improbable
to obtain the observed cosmological perturbations in a Universe with a light
Higgs. Moreover, independently of the inflationary model, the detection of
primordial tensor perturbations through the B-mode of CMB polarization and the
discovery of a light Higgs can simultaneously occur only with exponentially
small probability, unless there is new physics beyond the Standard Model.Comment: 28 LaTeX pages, 6 figure
Search for Flavoured Multiquarks in a Simple Bag Model
We use a bag model to study flavoured mesonic and baryonic
states, where one heavy quark is associated with
light quarks or antiquarks, and search for possible stable multiquarks. No
bound state is found. However some states lie not too high above their
dissociation threshold, suggesting the possibility of resonances, or perhaps
bound states in improved models.Comment: REVTEX, VERSION 3.
The Unseen Face of E-Business Project Development
The purpose of this paper is intent on identify and analyze the unseen factors of successful or failure of e-business project development. The IT managers must take into account both all costs involved in e-business development and all phases (analysis, design, testing, implementation, maintenance and operation) according to principle of project management for software/systems life cycle development. There are many solutions to exceed these factors of failure among could be counted outsourcing, a good project management, involvement of senior management, a real cost estimation etc.Zadanie pt. „Digitalizacja i udostępnienie w Cyfrowym Repozytorium Uniwersytetu Łódzkiego kolekcji czasopism naukowych wydawanych przez Uniwersytet Łódzki” nr 885/P-DUN/2014 zostało dofinansowane ze środków MNiSW w ramach działalności upowszechniającej nauk
Standard Model Higgs boson production in association with a top anti-top pair at NLO with parton showering
We present predictions for the production cross section of a Standard Model
Higgs boson in association with a top-antitop pair at next-to-leading order
accuracy using matrix elements obtained from the HELAC-Oneloop package. The NLO
prediction was interfaced to the PYTHIA and HERWIG shower Monte Carlo programs
with the help of POWHEG-Box, allowing for decays of massive particles,
showering and hadronization, thus leading to final results at the hadron level.Comment: 14 pages, 9 figure
A comprehensive description of multiple observables in heavy-ion collisions at SPS
Combining and expanding on work from previous publications, a model for the
evolution of ultrarelativistic heavy-ion collisions at the CERN SPS for 158
AGeV beam energy is presented. Based on the assumption of thermalization and a
parametrization of the space-time expansion of the produced matter, this model
is able to describe a large set of observables including hadronic momentum
spectra, correlations and abundancies, the emission of real photons, dilepton
radiation and the suppression pattern of charmonia. Each of these obervables
provides unique capabilities to study the reaction dynamics and taken together
they form a strong and consistent picture of the evolving system. Based on the
emission of hard photons, we argue that a strongly interacting, hot and dense
system with temperatures above 250 MeV has to be created early in the reaction.
Such a system is bound to be different from hadronic matter and likely to be a
quark-gluon plasma, and we find that this assumption is in line with the
subsequent evolution of the system that is reflected in other observables.Comment: 21 pages, 10 figures, submitted to J. Phys.
Nonthermal Particles and Radiation Produced by Cluster Merger Shocks
We have developed a numerical model for the temporal evolution of particle
and photon spectra resulting from nonthermal processes at the shock fronts
formed in merging clusters of galaxies. Fermi acceleration is approximated by
injecting power-law distributions of particles during a merger event, subject
to constraints on maximum particle energies. We consider synchrotron,
bremsstrahlung, Compton, and Coulomb processes for the electrons, nuclear,
photomeson, and Coulomb processes for the protons, and knock-on electron
production during the merging process. The broadband radio through gamma-ray
emission radiated by nonthermal protons and primary and secondary electrons is
calculated both during and after the merger event. Using ROSAT observations to
establish typical parameters for the matter density profile of clusters of
galaxies, we find that typical merger shocks are weak and accelerate particles
with relatively soft spectra. We consider the prospects for detecting
nonthermal radio and gamma-ray emission from clusters of galaxies and
implications for the origin of ultra-high energy cosmic rays and the diffuse
gamma-ray background. Our results suggest that only a few of the
isotropically-distributed unidentified EGRET sources are due to shocks formed
in cluster mergers, and that only a minor contribution to the diffuse
extragalactic gamma-ray background can originate from cluster merger shocks.
Cluster merger shocks can accelerate protons to eV for the
standard parameters considered here. We predict that {\it GLAST} will detect
several cluster mergers and, depending on the mean magnetic fields in the
intracluster medium, the Low Frequency Array could detect anywhere from several
to several hundred.Comment: 51 pages, 11 figures. Submitted to The Astrophysical Journal.
accepted for publication in the Astrophysical Journa
Polarizing the Dipoles
We extend the massless dipole formalism of Catani and Seymour, as well as its
massive version as developed by Catani, Dittmaier, Seymour and Trocsanyi, to
arbitrary helicity eigenstates of the external partons. We modify the real
radiation subtraction terms only, the primary aim being an improved efficiency
of the numerical Monte Carlo integration of this contribution as part of a
complete next-to-leading order calculation. In consequence, our extension is
only applicable to unpolarized scattering. Upon summation over the helicities
of the emitter pairs, our formulae trivially reduce to their original form. We
implement our extension within the framework of Helac-Phegas, and give some
examples of results pertinent to recent studies of backgrounds for the LHC. The
code is publicly available. Since the integrated dipole contributions do not
require any modifications, we do not discuss them, but they are implemented in
the software.Comment: 20 pages, 4 figures, Integrated dipoles implemented for massless and
massive case
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