178 research outputs found
Limits on Associated Production of Visibly and Invisibly Decaying Higgs Bosons from Z Decays
Many extensions of the standard electroweak model Higgs sector suggest that
the main Higgs decay channel is "invisible", for example, where
denotes the majoron, a weakly interacting pseudoscalar Goldstone boson
associated to the spontaneous violation of lepton number. In many of these
models the Higgs boson may also be produced in association to a massive
pseudoscalar boson (HA), in addition to the standard Bjorken mechanism (HZ). We
describe a general strategy to determine limits from LEP data on the masses and
couplings of such Higgs bosons, using the existing data on acoplanar dijet
events as well as data on four and six jet event topologies. For the sake
of illustration, we present constraints that can be obtained for the ALEPH
data.Comment: FTUV/94-36, IFIC/94-31 TIFR/TH/94--25, 12 pages + 4 figures (included
as ps files at the end
The wool proteome and fibre characteristics of three distinct genetic ovine breeds from Portugal
Wool properties and commodity value vary considerably between breeds. In Portugal, three major ovine groups exist: Churros, Bordaleiros and Merinos. This work studies the effect of the ovine genotype on the wool proteome of such groups. Wool was collected from 15 ewes/breed and genetic groups: Churra da Terra Quente (CTQ) or Churro, Serra da Estrela (SE) or Bordaleiro and Merino Branco (MB) or Merino. Proteins were extracted and subjected to label-free proteomics analysis. A total of 50 keratinous protein groups were identified in all the samples, divided into type I and II keratins and the keratin associated proteins: high-glycine-tyrosine proteins, ultra-high sulphur proteins and high-sulphur proteins. Major differences were found between MB and CTQ with respect to K75 and K38, both medullar proteins and to a lesser extent between SE and CTQ suggesting that these might be good markers for this trait in wool. Partial least squares discriminatory analysis proved MB to be readily distinguishable from the other two breeds. Further differences were noted in keratin associated protein levels between the three breeds, normally an indicator of higher levels of orthocortex and also their relationship to high curvature, high crimp fibres like Merinoinfo:eu-repo/semantics/acceptedVersio
Back reaction in the formation of a straight cosmic string
A simple model for the formation of a straight cosmic string, wiggly or
unperturbed is considered. The gravitational field of such string is computed
in the linear approximation. The vacuum expectation value of the stress tensor
of a massless scalar quantum field coupled to the string gravitational field is
computed to the one loop order. Finally, the back-reaction effect on the
gravitational field of the string is obtained by solving perturbatively the
semiclassical Einstein's equations.Comment: 29 pages, LaTeX, no figures. A postcript version can be obtained from
anonymous ftp at ftp://ftp.ifae.es/preprint.f
Block Spin Density Matrix of the Inhomogeneous AKLT Model
We study the inhomogeneous generalization of a 1-dimensional AKLT spin chain
model. Spins at each lattice site could be different. Under certain conditions,
the ground state of this AKLT model is unique and is described by the
Valence-Bond-Solid (VBS) state. We calculate the density matrix of a contiguous
block of bulk spins in this ground state. The density matrix is independent of
spins outside the block. It is diagonalized and shown to be a projector onto a
subspace. We prove that for large block the density matrix behaves as the
identity in the subspace. The von Neumann entropy coincides with Renyi entropy
and is equal to the saturated value.Comment: 20 page
Probing a Supersymmetric Model for Neutrino Masses at Ultrahigh Energy Neutrino Telescopes
A bilinear R-Parity breaking SUSY model for neutrino mass and mixing predicts
the lightest superparticle to decay mainly into a pair of tau leptons or b
quarks along with a neutrino for relatively light SUSY spectra. This leads to a
distinctive triple bang signature of SUSY events at ultrahigh energy neutrino
telescopes like IceCube or Antares. While the expected signal size is only
marginal at IceCube, it will be promising for a future multi-km^3 size neutrino
telescope.Comment: 11 pages pdf including 2 figures. Discussion added. Final version to
appear in Physics Letters
Entanglement and Density Matrix of a Block of Spins in AKLT Model
We study a 1-dimensional AKLT spin chain, consisting of spins in the bulk
and at both ends. The unique ground state of this AKLT model is described
by the Valence-Bond-Solid (VBS) state. We investigate the density matrix of a
contiguous block of bulk spins in this ground state. It is shown that the
density matrix is a projector onto a subspace of dimension . This
subspace is described by non-zero eigenvalues and corresponding eigenvectors of
the density matrix. We prove that for large block the von Neumann entropy
coincides with Renyi entropy and is equal to .Comment: Revised version, typos corrected, references added, 31 page
Application of phasor measurement units for monitoring power system dynamic performance
This Working Group is a sequel to a previous working group on Wide Area Monitoring and Control for Transmission Capability Enhancement, which published the Technical Brochure 330 in 2007. Since then the synchrophasor technology has advanced rapidly and many utilities around the world have installed hundreds of PMUs in their networks. In this Technical Brochure, we look at the current state of the technology and the extent to which it has been used in the industry. As the technology has matured, it is also important to understand the communication protocols used in synchrophasor networks and their relevant cyber-security issues. These concerns are briefly discussed in the brochure. The applications of Phasor Measurement Units (PMU) measurements reported here are divided into three categories: (a) applications already installed in utility networks, (b) applications that are well-tested, but not yet installed, and (c) applications that are beneficial to the industry, but not fully developed yet. The most common and mature applications are wide area monitoring, state estimation, and model validation. Out of these three applications, wide area monitoring is well established in the industry. The protection and control applications are emerging as evident from the reported examples. The experience of using remote synchrophasor measurements as feedback control signals is not widely reported by the industry. In parallel to this Working Group, Study Committee B5 had a Working Group on “Wide area protection and control technologies.” The Technical Brochure 664 published by this Working Group in September 2016 reviews synchrophasor technology and discusses the industry experience with wide area protection and control. The North American synchrophasor Initiative (NASPI) is another technical group that has gathered and reported a wide range of PMU experiences of industry and researchers. In summary, the field-tested applications presented in this Technical Brochure are a testimony to the confidence of utilities in the synchrophasor technology. The progress in state estimation techniques indicates that synchrophasor measurements will become a standard part of energy management and security assessment systems in the near future
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