1,102 research outputs found
A polarized version of the CCFM equation for gluons
A derivation for a polarized CCFM evolution equation which is suitable to
describe the scaling behavior of the the unintegrated polarized gluon density
is given. We discuss the properties of this polarized CCFM equation and compare
it to the standard CCFM equation in the unpolarized case.Comment: 15 pages, 6 figures, RevTeX, some minor typos corrected, version to
appear in Phys. Rev.
A nonlocal, covariant generalisation of the NJL model
We solve a nonlocal generalisation of the NJL model in the Hartree
approximation. This model has a separable interaction, as suggested by
instanton models of the QCD vacuum. The choice of form factor in this
interaction is motivated by the confining nature of the vacuum. A conserved
axial current is constructed in the chiral limit of the model and the pion
properties are shown to satisfy the Gell-Mann--Oakes--Renner relation. For
reasonable values of the parameters the model exhibits quark confinement.Comment: 13 pages (RevTeX), MC/TH 94/1
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Experimental cross-correlation Nitrogen Q-branch CARS Thermometry in a Spark Ignition Engine
A purely experimental technique was employed to derive temperatures from nitrogen Q-branch Coherent Anti-Stokes Raman Scattering (CARS) spectra, obtained in a high pressure, high temperature environment (spark ignition Otto engine). This was in order to obviate any errors arising from deficiencies in the spectral scaling laws which are commonly used to represent nitrogen Q-branch CARS spectra at high pressure. The spectra obtained in the engine were compared with spectra obtained in a calibrated high pressure, high temperature cell, using direct cross-correlation in place of the minimisation of sums of squares of residuals. The technique is demonstrated through the measurement of air temperature as a function of crankshaft angle inside the cylinder of a motored single-cylinder Ricardo E6 research engine, followed by the measurement of fuel-air mixture temperatures obtained during the compression stroke in a knocking Ricardo E6 engine. A standard CARS program (SANDIAâs CARSFIT) was employed to calibrate the altered non-resonant background contribution to the CARS spectra that was caused by the alteration to the mole fraction of nitrogen in the unburned fuel-air mixture. The compression temperature profiles were extrapolated in order to predict the auto-ignition temperatures
Preasymptotic nature of hadron scattering vs small-x HERA Data
We emphasize that recently observed regularities in hadron interactions and
deep-inelastic scattering are of preasymptotic nature and it is impossible to
make conclusions on the true asymptotic behavior of observables without
unitarization procedure. Unitarization is important and changes scattering
picture drastically.Comment: LaTeX file, 9 pages; 4 tarred, gzipped and uuencoded figures in a
separate fil
Low--Energy Behavior of Two--Point Functions of Quark Currents
We discuss vector, axial-vector, scalar and pseudoscalar two-point functions
at low and intermediate energies. We first review what is known from chiral
perturbation theory, as well as from a heat kernel expansion within the context
of the extended Nambu-Jona-Lasinio (ENJL) model of ref. \cite{12}. In this work
we derive then these two-point functions to all orders in the momenta and to
leading order in . We find an improved high-energy behaviour and a
general way of parametrizing them that shows relations between some of the
two-point functions, which are also valid in the presence of gluonic
interactions. The similarity between the shape of the experimentally known
spectral functions and the ones we derive, is greatly improved with respect to
those predicted by the usual constituent quark like models. We also obtain the
scalar mass independent of the regularization scheme. In the end,
we calculate fully an example of a nonleptonic matrix element in the
ENJL--model, the electromagnetic mass difference and find good
agreement with the measured value.Comment: 37 pages + 6 uuencoded figures, CERN TH 6924/93, CPT-93/P.2917,
NORDITA 93/43-N,
Capitals and commitment. The case of a local learning and employment network.
This article draws on research undertaken with a Local Learning and Employment Network (LLEN) in the state of Victoria, Australia. LLEN are networks that were implemented by the state government in 2001 to undertake community capacity building through which the outcomes of young people aged 15-19 in education, training and employment would be enhanced. In 2008, in the context
of an enhanced federal commitment to social inclusion through âjoining-upâ, the Victorian experience provides insights on the implications of such policy initiatives. Drawing on Bourdieuâs discussion of the forms of capital and
Granovetterâs notion of the strength of weak ties, I argue that stores of economic, cultural and social capital as outlined by Bourdieu were necessary, but insufficient, for LLEN to achieve the objectives with which they were charged
given the failure of government to follow through on the implications of its policies. I argue for a commitment on the part of all stakeholders to realise the potential of âjoining-upâ
Rare Kaon Decays in the -Expansion
We study the unknown coupling constants that appear at order in the
Chiral Perturbation Theory analysis of ,
and decays. To that
end, we compute the chiral realization of the Hamiltonian
in the framework of the -expansion of the low-energy action. The
phenomenological implications are also discussed.Comment: 18 pages, LaTeX, CPT-92/P.279
Lattice Study of the Decay B^0-bar -> rho^+ l^- nu_l-bar: Model-Independent Determination of |V_{ub}|
We present results of a lattice computation of the vector and axial-vector
current matrix elements relevant for the semileptonic decay B^0-bar -> rho^+
l^- nu_l-bar. The computations are performed in the quenched approximation of
lattice QCD on a 24^3 x 48 lattice at beta = 6.2, using an O(a) improved
fermionic action. Our principal result is for the differential decay rate,
dGamma/dq^2, for the decay B^0-bar -> rho^+ l^- nu_l-bar in a region beyond the
charm threshold, allowing a model-independent extraction of |V_{ub}| from
experimental measurements. Heavy quark symmetry relations between radiative and
semileptonic decays of B-bar mesons into light vector mesons are also
discussed.Comment: 22 pages LaTeX-209 (dependent on settings in a4.sty), 23 PostScript
figures included with epsf.sty. Complete PostScript file including figures
available at http://wwwhep.phys.soton.ac.uk/hepwww/papers/shep9518
The Jacobi Polynomials QCD analysis for the polarized structure function
We present the results of our QCD analysis for polarized quark distribution
and structure function . We use very recently experimental data
to parameterize our model. New parameterizations are derived for the quark and
gluon distributions for the kinematic range , GeV^2. The analysis is based on the Jacobi polynomials
expansion of the polarized structure functions. Our calculations for polarized
parton distribution functions based on the Jacobi polynomials method are in
good agreement with the other theoretical models. The values of
and are determined.Comment: 23 pages, 8 figures and 4 table
Evaluation of the Strong Coupling Constant alpha_s Using the ATLAS Inclusive Jet Cross-Section Data
We perform a determination of the strong coupling constant using the latest
ATLAS inclusive jet cross section data, from proton-proton collisions at
sqrt{s}=7 TeV, and their full information on the bin-to-bin correlations.
Several procedures for combining the statistical information from the different
data inputs are studied and compared. The theoretical prediction is obtained
using NLO QCD, and it also includes non-perturbative corrections. Our
determination uses inputs with transverse momenta between 45 and 600 GeV, the
running of the strong coupling being also tested in this range. Good agreement
is observed when comparing our result with the world average at the Z-boson
scale, as well as with the most recent results from the Tevatron.Comment: 15 pages, 6 figures. Extended discussion of non-perturbative
corrections. Matches version published in EPJ
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