1,543 research outputs found
Measurement of the Permanent Electric Dipole Moment of the Xe Atom
We report on a new measurement of the CP-violating permanent Electric Dipole
Moment (EDM) of the neutral Xe atom. Our experimental approach is based
on the detection of the free precession of co-located nuclear spin-polarized
He and Xe samples. The EDM measurement sensitivity benefits
strongly from long spin coherence times of several hours achieved in diluted
gases and homogeneous weak magnetic fields of about 400~nT. A finite EDM is
indicated by a change in the precession frequency, as an electric field is
periodically reversed with respect to the magnetic guiding field. Our result,
ecm, is consistent with zero and is
used to place a new upper limit on the Xe EDM: ecm (95% C.L.). We also discuss the implications of this result for
various CP-violating observables as they relate to theories of physics beyond
the standard model
Precise Measurement of Magnetic Field Gradients from Free Spin Precession Signals of He and Xe Magnetometers
We report on precise measurements of magnetic field gradients extracted from
transverse relaxation rates of precessing spin samples. The experimental
approach is based on the free precession of gaseous, nuclear spin polarized
He and Xe atoms in a spherical cell inside a magnetic guiding field
of about 400 nT using LT SQUIDs as low-noise magnetic flux detectors. The
transverse relaxation rates of both spin species are simultaneously monitored
as magnetic field gradients are varied. For transverse relaxation times
reaching 100 h, the residual longitudinal field gradient across the spin sample
could be deduced to be pT/cm. The method takes
advantage of the high signal-to-noise ratio with which the decaying spin
precession signal can be monitored that finally leads to the exceptional
accuracy to determine magnetic field gradients at the sub pT/cm scale
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Planning at the neighbourhood scale: localism, dialogic politics and the modulation of community action
This paper builds upon literature examining the foreclosing of community interventions to show how a resident-led anti-road-noise campaign in South-Eastern England has been framed, managed and modulated by authorities. We situate the case within wider debates considering dialogical politics. For advocates, this offers the potential for empowerment through non-traditional forums (Beck, 1994; Giddens, 1994). Others view such trends, most recently expressed as part of the localism agenda, with suspicion (Haughton et al, 2013; Mouffe, 2005). The paper brings together these literatures to analyse the points at which modulation occurs in the community planning process. We describe the types of counter-tactics residents deployed to deflect the modulation of their demands, and the events that led to the outcome. We find that community planning offers a space - albeit one that is tightly circumscribed - within which (select) groups can effect change. The paper argues that the detail of neighbourhood-scale actions warrant further attention, especially as governmental enthusiasm for dialogical modes of politics shows no sign of abating
Divided we stand: institutional collaboration in tourism planning and development in the Central Region of Ghana
This research is an exploratory study that examines collaboration at the institutional level in the tourism sector of the Central Region, Ghana. The research begins with a review of the key issues related to collaboration in tourism planning and development followed by an extensive exploration of three main issues related to institutional collaboration in tourism in the Central Region. The three main issues are the vision of tourism development shared among stakeholders, collaboration and coordination within the public sector and between the public and private sectors and the factors that constrain and facilitate collaboration and coordination. Using extensive interviews with key stakeholders and reviewing policy documents, the research indicates low levels of collaboration between tourism institutions both within the public sector and across the public?private sectors. This is notwithstanding a shared awareness of the benefits of collaboration among all actors. The research thus contributes interesting insights into the politics of collaboration in tourism destinations. Given tourism's contribution to the Ghanaian economy, it is imperative that efforts are made towards improving the levels of collaboration and coordination between tourism agencies and institutions
On the problem of the justification of river rights
This article aims to work out the social conditions that determine whether the
communication of river rights finds success in society. Employing the context of
hydropower development in the Mekong region, the article finds that an essentialist
strategy which claims that river rights have unlimited âmoralâ validity regardless of any
of the decision consequences is unlikely to succeed. Instead, it is proposed that moral
conflicts over river rights may ultimately only be resolvable âunmorallyâ, that is, by
procedural legitimacy â and this is best captured by employing a methodological
framework composed of thematic, social and temporal dimension
Study of Leading Hadrons in Gluon and Quark Fragmentation
The study of quark jets in e+e- reactions at LEP has demonstrated that the
hadronisation process is reproduced well by the Lund string model. However, our
understanding of gluon fragmentation is less complete. In this study enriched
quark and gluon jet samples of different purities are selected in three-jet
events from hadronic decays of the Z collected by the DELPHI experiment in the
LEP runs during 1994 and 1995. The leading systems of the two kinds of jets are
defined by requiring a rapidity gap and their sum of charges is studied. An
excess of leading systems with total charge zero is found for gluon jets in all
cases, when compared to Monte Carlo Simulations with JETSET (with and without
Bose-Einstein correlations included) and ARIADNE. The corresponding leading
systems of quark jets do not exhibit such an excess. The influence of the gap
size and of the gluon purity on the effect is studied and a concentration of
the excess of neutral leading systems at low invariant masses (<~ 2 GeV/c^2) is
observed, indicating that gluon jets might have an additional hitherto
undetected fragmentation mode via a two-gluon system. This could be an
indication of a possible production of gluonic states as predicted by QCD.Comment: 19 pages, 6 figures, Accepted by Phys. Lett.
Determination of the b quark mass at the M_Z scale with the DELPHI detector at LEP
An experimental study of the normalized three-jet rate of b quark events with
respect to light quarks events (light= \ell \equiv u,d,s) has been performed
using the CAMBRIDGE and DURHAM jet algorithms. The data used were collected by
the DELPHI experiment at LEP on the Z peak from 1994 to 2000. The results are
found to agree with theoretical predictions treating mass corrections at
next-to-leading order. Measurements of the b quark mass have also been
performed for both the b pole mass: M_b and the b running mass: m_b(M_Z). Data
are found to be better described when using the running mass. The measurement
yields: m_b(M_Z) = 2.85 +/- 0.18 (stat) +/- 0.13 (exp) +/- 0.19 (had) +/- 0.12
(theo) GeV/c^2 for the CAMBRIDGE algorithm. This result is the most precise
measurement of the b mass derived from a high energy process. When compared to
other b mass determinations by experiments at lower energy scales, this value
agrees with the prediction of Quantum Chromodynamics for the energy evolution
of the running mass. The mass measurement is equivalent to a test of the
flavour independence of the strong coupling constant with an accuracy of 7
permil.Comment: 24 pages, 10 figures, Accepted by Eur. Phys. J.
Measurement and Interpretation of Fermion-Pair Production at LEP energies above the Z Resonance
This paper presents DELPHI measurements and interpretations of
cross-sections, forward-backward asymmetries, and angular distributions, for
the e+e- -> ffbar process for centre-of-mass energies above the Z resonance,
from sqrt(s) ~ 130 - 207 GeV at the LEP collider. The measurements are
consistent with the predictions of the Standard Model and are used to study a
variety of models including the S-Matrix ansatz for e+e- -> ffbar scattering
and several models which include physics beyond the Standard Model: the
exchange of Z' bosons, contact interactions between fermions, the exchange of
gravitons in large extra dimensions and the exchange of sneutrino in R-parity
violating supersymmetry.Comment: 79 pages, 16 figures, Accepted by Eur. Phys. J.
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