1,295 research outputs found
Is strong CP invariance due to a massless up quark?
A standing mystery in the Standard Model is the unnatural smallness of the
strong CP violating phase. A massless up quark has long been proposed as one
potential solution. A lattice calculation of the constants of the chiral
Lagrangian essential for the determination of the up quark mass, 2 alpha_8 -
alpha_5, is presented. We find 2 alpha_8 - alpha_5 = 0.29 +/- 0.18, which
corresponds to m_u / m_d = 0.410 +/- 0.036. This is the first such calculation
using a physical number of dynamical light quarks, N_f = 3.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Lett., corrected small
normalization error in f_pi (conclusions were unaffected), improved lattice
spacing analysis, improved finite volume analysi
Chiral perturbation theory for electroweak reactions on deuterium
I summarize two recent applications of chiral perturbation theory to
electromagnetic reactions on deuterium: elastic electron-deuteron scattering,
and Compton scattering on deuterium. Both calculations have now been carried
out to three orders in the chiral expansion. The expansion shows good
convergence and is able to reproduce data for q < 600 MeV in e-d and for
omega=55-95 MeV in gamma-d. These results demonstrate that ChiPT can be used to
reliably compute operators and wave functions for low-momentum-transfer
reactions in light nuclear systems.Comment: 10 pages, 6 figures. Write-up of invited talk at INT Workshop on
"Nuclear Forces and the Quantum Many-Body Problem", October 4-8, 200
Testing the Unitarity of the CKM Matrix with a Space-Based Neutron Decay Experiment
If the Standard Model is correct, and fundamental fermions exist only in the
three generations, then the CKM matrix should be unitary. However, there
remains a question over a deviation from unitarity from the value of the
neutron lifetime. We discuss a simple space-based experiment that, at an orbit
height of 500 km above Earth, would measure the kinetic-energy, solid-angle,
flux spectrum of gravitationally bound neutrons (kinetic energy K<0.606 eV at
this altitude). The difference between the energy spectrum of neutrons that
come up from the Earth's atmosphere and that of the undecayed neutrons that
return back down to the Earth would yield a measurement of the neutron
lifetime. This measurement would be free of the systematics of laboratory
experiments. A package of mass kg could provide a 10^{-3} precision in
two years.Comment: 10 pages, 4 figures. Revised and updated for publicatio
Exploring formalized elite coach mentoring programmes in the UK: âWeâve had to play the gameâ
Formalized mentoring programmes have been implemented increasingly have been implemented by UK sporting institutions as a central coach development tool, yet claims supporting formal mentoring as an effective learning strategy are often speculative, scarce, ill-defined and accepted without verification. The aim of this study, therefore, was to explore some of the realities of formalized elite sports coaching mentoring programmes. Data were collected using semi-structured interviews with 15 mentors of elite coaches on formal programmes, across a range of sports. The findings were read through a Bourdieusian lens and revealed the importance of understanding the complexities of elite sports coaching environments, that elite sports coach development is highly specific and, therefore, should not be over-formalized, and how current elite sport coach mentoring programmes may be better conceptualized as a form of social control rather than being driven by pedagogical concerns. Following this empirically based analysis of practice, a number of implications for Governing Bodies (GBs), mentors and mentees were considered
An analysis of the value of multiple mentors in formalised elite coach mentoring programmes
Background: Within the context of sports coaching and coach education, formalised mentoring relationships are often depicted as a mentorâmentee dyad. Thus, mentoring within sports coaching is typically conceptualised as a one-dimensional relationship, where the mentor is seen as the powerful member of the dyad, with greater age and/or experience (Colley 2003). Aim: The aim of this study was to explore the concept of a multiple mentor system in an attempt to advance our theoretical and empirical understanding of sports coach mentoring. In doing so, this paper builds upon the suggestion of Jones, Harris and Miles (2009) who highlight the importance of generating empirical research to explore current mentoring approaches in sport, which in turn can inform meaningful formal coach education enhancement. The significance of this work therefore lies in opening up both a practical and a theoretical space for dialogue within sports coach education in order to challenge the traditional dyadic conceptualisation of mentoring and move towards an understanding of âmentoring in practiceâ. Method: Drawing upon Kramâs (1985) foundational mentoring theory to underpin a multiple mentoring support system, 15 elite coach mentors across a range of sports were interviewed in an attempt to explore their mentoring experiences. Subsequently, an inductive thematic analysis endeavoured to further investigate the realities and practicalities of employing a multiple mentoring system in the context of elite coach development. Results: The participants advocated support for the utilisation of a multiple mentor system to address some of the inherent problems and complexities within elite sports coaching mentoring. Specifically, the results suggested that mentees sourced different mentors for specific knowledge acquisition, skills and attributes. For example, within a multiple mentor approach, mentors recommended that mentees use a variety of mentors, including cross-sports and non-sport mentors. Conclusion: Tentative recommendations for the future employment of a multiple mentoring framework were considered, with particular reference to cross-sports or non-sport mentoring experiences
Neutral Pions and Eta Mesons as Probes of the Hadronic Fireball in Nucleus-Nucleus Collisions around 1A GeV
Chemical and thermal freeze-out of the hadronic fireball formed in symmetric
collisions of light, intermediate-mass, and heavy nuclei at beam energies
between 0.8A GeV and 2.0A GeV are discussed in terms of an equilibrated,
isospin-symmetric ideal hadron gas with grand-canonical baryon-number
conservation. For each collision system the baryochemical potential mu_B and
the chemical freeze-out temperature T_c are deduced from the inclusive neutral
pion and eta yields which are augmented by interpolated data on deuteron
production. With increasing beam energy mu_B drops from 800 MeV to 650 MeV,
while T_c rises from 55 MeV to 90 MeV. For given beam energy mu_B grows with
system size, whereas T_c remains constant. The centrality dependence of the
freeze-out parameters is weak as exemplified by the system Au+Au at 0.8A GeV.
For the highest beam energies the fraction of nucleons excited to resonance
states reaches freeze-out values of nearly 15 %, suggesting resonance densities
close to normal nuclear density at maximum compression. In contrast to the
particle yields, which convey the status at chemical freeze-out, the shapes of
the related transverse-mass spectra do reflect thermal freeze-out. The observed
thermal freeze-out temperatures T_th are equal to or slightly lower than T_c,
indicative of nearly simultaneous chemical and thermal freeze-out.Comment: 42 pages, 12 figure
Mirror matter admixtures and isospin breaking in the \Delta I=1/2 rule in \Omega^- two body non-leptonic decays
We discuss a description of \Omega^- two body non-leptonic decays based on
possible, albeit tiny, admixtures of mirror matter in ordinary hadrons. The
\Delta I=1/2 rule enhancement is obtained as a result of isospin symmetry and,
more importantly, the rather large observed deviations from this rule result
from small isospin breaking. This analysis lends support to the possibility
that the enhancement phenomenon observed in low energy weak interactions may be
systematically described by mirror matter admixtures in ordinary hadrons.Comment: Changed conten
Large Electric Dipole Moments of Heavy Leptons
In many models of CP violation, the electric dipole moments (EDMs) of leptons
scale as the cube of the lepton mass. In these models, the EDM of a 100 GeV
heavy lepton would be a billion times greater than that of the muon, and could
be as large as a 0.01 e-fermi. In other models, in which the heavy leptons have
different properties from the lighter generations, a similarly large EDM can be
obtained. A large EDM could dominate the electromagnetic properties of heavy
leptons. The angular distribution and production cross-section of both charged
and neutral heavy leptons with large dipole moments is calculated and
discussed. The interesting possibility that a heavy neutrino with a large EDM
could leave an ionization track in a drift chamber is investigated.Comment: Discussion expanded extensively to include model-dependence of
results. Calculations unchanged. Note Added To Acknowledgments: This paper is
dedicated to the memory of Nathan Isgu
A New 5 Flavour NLO Analysis and Parametrizations of Parton Distributions of the Real Photon
New, radiatively generated, NLO quark (u,d,s,c,b) and gluon densities in a
real, unpolarized photon are presented. We perform three global fits, based on
the NLO DGLAP evolution equations for Q^2>1 GeV^2, to all the available
structure function F_2^gamma(x,Q^2) data. As in our previous LO analysis we
utilize two theoretical approaches. Two models, denoted as FFNS_{CJK}1 & 2 NLO,
adopt the so-called Fixed Flavour-Number Scheme for calculation of the
heavy-quark contributions to F_2^gamma(x,Q^2), the CJK NLO model applies the
ACOT(chi) scheme. We examine the results of our fits by a comparison with the
LEP data for the Q^2 dependence of the F_2^gamma, averaged over various
x-regions, and the F_2,c^gamma. Grid parametrizations of the parton densities
for all fits are provided.Comment: 49 pages, 27 postscript figures; FORTRAN programs available at
http://www.fuw.edu.pl/~pjank/param.htm
- âŠ