251 research outputs found
The unit of electric charge and the mass hierarchy of heavy particles
We propose some empirical formulae relating the masses of the heaviest
particles in the standard model (the W,Z,H bosons and the t quark) to the
charge of the positron and the Higgs condensate v. The relations for the
masses of gauge bosons m_W = (1+e)v/4 and m_Z=sqrt{(1+e^2)/2}*(v/2) are in
excellent agreement with experimental values. By requiring the electroweak
standard model to be free from quadratic divergencies at the one-loop level, we
find: m_t=v/sqrt{2} and m_H=v/sqrt{2e}, or the very simple ratio (m_t/m_H)^2=e.Comment: 6 page
Resonance Propagation and Threshold Singularities
We consider the problem of propagation of an unstable particle in the
framework of Quantum Field Theory. Using unitarity, we show that a real
renormalization constant free of threshold singularities naturally arises.Comment: 5 pages, no figures, revte
Explaining Africa’s public consumption procyclicality : revisiting old evidence
This paper compiles a novel dataset of time-varying measures of government consumption cyclicality for a panel of 46 African economies between 1960 and 2014. Government consumption has, generally, been highly procyclical over time in this group of countries. However, sample averages hide serious heterogeneity across countries with the majority of them showing procyclical behavior despite some positive signs of graduation from the “procyclicality trap” in a few cases. By means of weighted least squares regressions, we find that more developed African economies tend to have a smaller degree of government consumption procyclicality. Countries with higher social fragmentation and those are more reliant on foreign aid inflows tend to have a more procyclical government consumption policy. Better governance promotes counter- cyclical fiscal policy whileincreased democracy dampens it. Finally, some fiscal rules are important in curbing the procyclical behavior of government consumption.info:eu-repo/semantics/publishedVersio
Pion-proton scattering and isospin breaking in the system
We determine the mass and width of the resonance
from data on scattering both, in the pole of the
-matrix and conventional Breit-Wigner approaches to the scattering
amplitude. We provide a simple formula that relates the two definitions for the
parameters of the . Isospin symmetry breaking in the \d0-\dm system
depends on the definition of the resonant properties: we find in
the pole approach while $\wt{M}_0-\wt{M}_{++} = 2.25 \pm 0.68\ {\rm MeV},\
\wt{\Gamma}_0 - \wt{\Gamma}_{++} = 8.45 \pm 1.11\ {\rm MeV}$ in the
conventional approach.Comment: Latex, 23 pages, two figures upon reques
Retirement Incentives in Belgium: Estimations and Simulations Using SHARE Data
peer reviewedThe paper studies retirement behavior of wage‐earners in Belgium – for the first time using
a rich survey dataset to analyze retirement incentives as faced by individuals. Specifically,
we use SHARE data to estimate a model à la Stock and Wise (1990). Exploring the data on
individual life‐histories from SHARELIFE, we construct a measure of financial incentive to
retire. Our analysis explicitly takes into account the different take‐up rates of the various
early retirement exit paths across time and ages. The results show that financial incentives
play a strong role. Health and education also matter, as do regional differences. Against the
general background of the 2020 strategy, we perform a set of policy simulations and
illustrate the scope but also the limits associated with selective parametric reforms
Gluon Polarization from QCD Sum Rules
The gluon polarization in a nucleon can be defined in a gauge
invariant way as the integral over the Ioffe-time distribution of polarized
gluons. We argue that for sufficiently regular polarized gluon distributions
is dominated by contributions from small and moderate values of the
Ioffe-time z < 10. As a consequence can be estimated with 20%
accuracy from the first two even moments of the polarized gluon distribution,
and its behavior at small values of Bjorken x or, equivalently, at large
Ioffe-times z. We employ this idea and compute the first two moments of the
polarized gluon distribution within the framework of QCD sum rules. Combined
with the color coherence hypothesis we obtain an upper limit for at a typical scale .Comment: 12 pages, Latex, 2 figures include
Ioffe-time distributions instead of parton momentum distributions in description of deep inelastic scattering
We argue that parton distributions in coordinate space provide a more natural
object for nonperturbative methods compared to the usual momentum distributions
in which the physics of different longitudinal distances is being mixed. To
illustrate the advantages of the coordinate space formulation, we calculate the
coordinate space distributions for valence quarks in the proton using the QCD
sum rule approach. A remarkable agreement is found between the calculated and
the experimentally measured u-quark distribution up to light-cone distances
of order fm in the proton rest frame.
The calculation for valence d quarks gives much worse results; the reasons for
this discrepancy are discussed.Comment: 24 pages plus 13 pages with figures, requires epsf.sty, revised
version to appear in Phys.Rev.
Gauge invariance and finite width effects in radiative two-pion tau lepton decay
The contribution of the rho^{\pm} vector meson to the tau -> pi pi nu gamma
decay is considered as a potential source for the determination of the magnetic
dipole moment of this light vector meson. In order to keep gauge-invariance of
the whole decay amplitude, a procedure similar to the fermion loop-scheme for
charged gauge bosons is implemented to incorporate the finite width effects of
the rho^{\pm} vector meson. The absorptive pieces of the one-loop corrections
to the propagators and electromagnetic vertices of the rho^{\pm} meson and
W^{\pm} gauge boson have identical forms in the limit of massless particles in
the loops, suggesting this to be a universal feature of spin-one unstable
particles. Model-dependent contributions to the tau -> pi pi nu gamma decay are
suppressed by fixing the two-pion invariant mass distribution at the rho meson
mass value. The resulting photon energy and angular distribution is relatively
sensitive to the effects of the rho magnetic dipole moment.Comment: 22 pages, 4 postscript figures, references and comments on relevance
of perturbative treatment of rho electromagnetic vertex are added, accepted
for pub. in Phys. Rev.
S-matrix approach to two-pion production in e^+e^- annihilation and tau decay
Based on the S-matrix approach, we introduce a modified formula for the
electromagnetic form factor which describes very well the
experimental data in the energy region GeV.
Using the CVC hypothesis we predict B(\tpp) = (24.75 \pm 0.38)\% , in
excellent agreement with recent experiments.Comment: Latex, 10 pages, submitted to Phys. Rev.
Ioffe-time distribution of quarks in the photon
We have analysed the Ioffe-time distribution of quarks in virtual photons
using Operator Product Expansion of the correlation function that determines
the matrix element of the corresponding quark string operator. The distribution
for a transversally polarised photon admits a spectral representation which can
be continued to the on-shell region . The resulting model Ioffe-time
distribution turns out to be larger than parametrisations of the available
data. This result is linked to the slope of the quark
distribution at the origin, which comes out too large as well.Comment: 12 pages, LaTex, one uuencoded figur
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