450 research outputs found
Generalized wordlength patterns and strength
Xu and Wu (2001) defined the \emph{generalized wordlength pattern} of an arbitrary fractional factorial design (or orthogonal array) on
factors. They gave a coding-theoretic proof of the property that the design
has strength if and only if . The quantities are
defined in terms of characters of cyclic groups, and so one might seek a direct
character-theoretic proof of this result. We give such a proof, in which the
specific group structure (such as cyclicity) plays essentially no role.
Nonabelian groups can be used if the counting function of the design satisfies
one assumption, as illustrated by a couple of examples
Experimental Restrictions on Ne'eman's Fifth Interaction
Recently, Ne'eman has proposed a "fifth interaction" between the strangeness current and a neutral vector meson χ, for the purpose of breaking SU(3) symmetry. We show that a χ mass less than 2mπ would be inconsistent with a variety of experiments, including K-mesonic atoms, the long-range pp potential, K1 regeneration from a K2 beam, the Lamb shift, modern refinements of the Cavendish "ice-bucket" experiment, and the absence of π0→γ+χ and χ→e++e-. The remaining possibility, that mχ exceeds 2mπ, is discussed briefly
Relevance of the precautionary principle in water recycling
Presented at the International Conference on Integrated Concepts on Water Recycling, Wollongong, NSW, Australia, 14–17 February 2005.In an engineering context the precautionary principle is often perceived as an excuse to do nothing or a
substantial barrier to technical progress. The precautionary principle requires that remedial measures be
taken in situations of scientific uncertainty where evidence of harm cannot be proven but potential damage to
human or environmental health is significant.
In this paper the scope of the precautionary principle in water recycling is discussed. It is clear that
uncertainties and risks exist in many areas of water recycling. Those risks are closely linked to the risks of
sewage discharge.
Hence water recycling has two main areas of concern (i) the dilemma that minimising potential
environmental harm by reducing effluent discharge may increase potential harm through reducing the water
flow in receiving waters and (ii) the consequences of using recycled water of varying quality for a number of
applications.
The precautionary principle can be regarded as an opportunity to improve water recycling practice and in
fact increase the scope of ecologically sustainable water recycling. Hence the precautionary principle has an
important role to play as a guide in decision making and in dealing with the vast number of risks and
uncertainties in water recycling
On the pion electroproduction amplitude
We analyze amplitudes for the pion electroproduction on proton derived from
Lagrangians based on the local chiral SU(2) x SU(2) symmetries. We show that
such amplitudes do contain information on the nucleon axial form factor F_A in
both soft and hard pion regimes. This result invalidates recent Haberzettl's
claim that the pion electroproduction at threshold cannot be used to extract
any information regarding F_A.Comment: 14 pages, 6 figures, revised version, accepted for publication in
Phys. Rev.
Polarized photons in radiative muon capture
We discuss the measurement of polarized photons arising from radiative muon
capture. The spectrum of left circularly polarized photons or equivalently the
circular polarization of the photons emitted in radiative muon capture on
hydrogen is quite sensitive to the strength of the induced pseudoscalar
coupling constant . A measurement of either of these quantities, although
very difficult, might be sufficient to resolve the present puzzle resulting
from the disagreement between the theoretical prediction for and the
results of a recent experiment. This sensitivity results from the absence of
left-handed radiation from the muon line and from the fact that the leading
parts of the radiation from the hadronic lines, as determined from the chiral
power counting rules of heavy-baryon chiral perturbation theory, all contain
pion poles.Comment: 10 pages, 6 figure
Observation of double radiative capture on pionic hydrogen
We report the first observation of double radiative capture on pionic
hydrogen. The experiment was conducted at the TRIUMF cyclotron using the RMC
spectrometer, and detected --ray coincidences following stops
in liquid hydrogen. We found the branching ratio for double radiative capture
to be . The measured
branching ratio and angle-energy distributions support the theoretical
prediction of a dominant contribution from the
annihilation mechanism.Comment: 4 Pages, 4 Figures. accepted for publication in Phys. Rev. Let
Search for exotic baryons in double radiative capture on pionic hydrogen
We report a search for low-lying exotic baryons via double radiative capture
on pionic hydrogen. The data were collected at the TRIUMF cyclotron using the
RMC spectrometer by detecting gamma-ray pairs from pion stops in liquid
hydrogen. No evidence was found to support an earlier claim for exotic baryons
of masses 1004 and 1044 MeV/. We obtain upper limits on the branching
ratios for double radiative capture via these exotic states of and respectively.Comment: 13 pages, 4 figure
Muon capture by a proton in heavy baryon chiral perturbation theory
The matrix element for muon capture by a proton is calculated to O(p^3)
within heavy baryon chiral perturbation theory using the new O(p^3) Lagrangian
of Ecker and Mojzis. External nucleon fields are renormalized using the
appropriate definition of the wave function renormalization factor Z_N. Our
expression for Z_N differs somewhat from that found in existing literature, but
is the one which is consistent with the Lagrangian we use and the one which
ensures, within our approach, the nonrenormalization of the vector coupling as
required by the conserved vector current. Expressions for the standard muon
capture form factors are derived and compared to experimental data and we
determine three of the coefficients of the Ecker - Mojzis Lagrangian, namely,
b_7, b_{19}, and b_{23}.Comment: 14 pages, LaTeX, using revte
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