1,318 research outputs found
Contact interaction probes at the Linear Collider with polarized electron and positron beams
For contact-interaction searches at the Linear Collider, we discuss the
advantages of polarizing both the electron and the positron beams as compared
with polarizing only the electron beam. In particular, for the processes
e^+e^-\to \mu^+\mu^-, \tau^+\tau^-, b\bar{b} and c\bar{c} at a future e^+e^-
collider with \sqrt{s}=0.5 TeV we derive model-independent bounds on the
four-fermion contact interaction parameters from studies of the helicity cross
sections.Comment: 1+15 pages, LaTeX2e, including 7 figure
Primordial Bispectrum Information from CMB Polarization
After the precise observations of the Cosmic Microwave Background (CMB)
anisotropy power spectrum, attention is now being focused on the higher order
statistics of the CMB anisotropies. Since linear evolution preserves the
statistical properties of the initial conditions, observed non-Gaussianity of
the CMB will mirror primordial non-Gaussianity. Single field slow-roll
inflation robustly predicts negligible non-Gaussianity so an indication of
non-Gaussianity will suggest alternative scenarios need to be considered. In
this paper we calculate the information on primordial non-Gaussianity encoded
in the polarization of the CMB. After deriving the optimal weights for a cubic
estimator we evaluate the Signal-to-Noise ratio of the estimator for WMAP,
Planck and an ideal cosmic variance limited experiment. We find that when the
experiment can observe CMB polarization with good sensitivity, the sensitivity
to primordial non-Gaussianity increases by roughly a factor of two. We also
test the weakly non-Gaussian assumption used to derive the optimal weight
factor by calculating the degradation factor produced by the gravitational
lensing induced connected four-point function. The physical scales in the
radiative transfer functions are largely irrelevant for the constraints on the
primordial non-Gaussianity. We show that the total (S/N)^2 is simply
proportional to the number of observed pixels on the sky.Comment: To be submitted to PRD, 25 pages, 6 figure
New physics signatures at a Linear Collider: model-independent analysis from `conventional' polarized observables
We discuss four-fermion contact-interaction searches in the processes
e^+e^-\to\mu^+\mu^-, c{\bar c} and b{\bar b} at a future e^+e^- Linear Collider
with c.m. energy \sqrt{s}=0.5 TeV and with both beams longitudinally polarized.
Our analysis is based on the measurements of familiar polarized observables
such as the total cross section and the forward-backward/left-right
asymmetries, and accounts for the general set of contact interaction couplings
as independent, non-zero, parameters thus avoiding simplifying,
model-dependent, assumptions. We derive the corresponding model-independent
constraints on the above-mentioned coupling constants, and evaluate the
corresponding reach at the Linear Collider, emphasizing the role of beam
polarization. We compare the results with a model-dependent procedure where
only one coupling is varied at a time.Comment: 13 pages, including 3 figure
Consistency relation for single scalar inflation
Single scalar field inflation with a generic, non-quadratic in derivatives,
field Lagrangian is considered. It is shown that non-Gaussianity of curvature
perturbations is characterized by two dimensionless amplitudes. One of these
amplitudes can be expressed in terms of the usual inflationary observables --
the scalar power, the tensor power, and the tensor index. This consistency
relation provides an observational test for the single scalar inflation.Comment: 6 page
Experiences with the expansion of hospital accreditation into the developing world
Thesis (Ph.D.)--Boston UniversityMore developing countries are adopting hospital accreditation to improve the quality of their health systems, but it is uncertain whether accreditation standards and processes, largely borrowed from Western countries, are being adapted to fit each country's context. Three qualitative studies explore issues in assimilating hospital accreditation into developing countries, drawing mainly from experiences of two Southern African countries, Lesotho and Swaziland. Data sources included: archival records, documentary information, interviews, focus groups, expert panel surveys, and direct observations.
Study 1, Explaining the expansion of hospital accreditation in the developing world, investigates the proposition that institutional theory largely explains the adoption of hospital accreditation in developing countries and how this external motivation influences the innovation process. Adoption of accreditation in developing countries is associated with the perceived contribution of accreditation to quality care in developed countries, endorsement of accreditation by key international players, and substantial donor support for implementing accreditation. This can result in less adaptation of Western accreditation practices, and this lack of local adaptation can hinder true assimilation and sustainability.
Study 2, Connecting hospital accreditation with other quality improvement efforts in the developing world, explores the perceived connection between hospital accreditation and other quality improvement efforts and the effects of this com1ection on subsequent improvement efforts. This study found that hospital accreditation is laying important groundwork and establishing norms for future quality efforts, but is not being tied to more comprehensive national strategies for quality assurance and quality improvement.
Study 3, Considerations in implementing hospital accreditation in the developing world, examines perceived appropriateness of hospital accreditation standards and processes implemented in Lesotho and Swaziland according to stakeholders in those health systems. Standards were perceived to be of high importance, fairly strong relevance, and moderate feasibility due to limited financial and human resources. Perceptions of the appropriateness of accreditation processes were strongly influenced by how accreditation was introduced to hospital staff, its gradual implementation, inclusion of hospital staff in the process, clearly defined role responsibilities, leadership commitment to accreditation, and implementation support. Overall, lower perceived control over accreditation standards and processes was linked to lower perceptions of appropriateness among hospital staff
Contact interactions and polarized beams at a Linear Collider
We discuss contact-interaction searches in the processes e^+e^-\to
\mu^+\mu^-, b\bar{b} and c\bar{c} at an e^+e^- Linear Collider with c.m. energy
\sqrt{s}=0.5 TeV and with longitudinally polarized beams. The measurement of
polarized cross sections allows to study the individual helicity cross
sections, and consequently to derive separate, model-independent, constraints
on the four-fermion contact interaction couplings. We evaluate the reach on
those parameters foreseeable in the case of both electron and positron
polarization fixed at some reference values, and compare it with the situation
where only electron polarization is available. The analysis is based on
polarized integrated cross sections with optimal kinematical cuts that can
improve the sensitivity to the relevant couplings. While electron polarization
would by itself allow such an analysis, the additional positron polarization
(with no loss of beam intensity) and optimization can have a crucial role in
improving the sensitivity to the new interactions.Comment: 13 pages, LaTeX, including figure
Model-independent constraints on contact interactions from LEP2 data analysis
We derive model-independent constraints on four-fermion contact
interaction-type dynamics from the published preliminary LEP2 experimental data
on e^+e^- annihilation into \mu^+\mu^- and \tau^+\tau^- pairs, measured at
different energies between 130 and 207 GeV. The basic observables are chosen to
be the total cross section and the forward-backward asymmetry, and the analysis
realistically takes into account data uncertainties and correlations among
measurements at the various energies. The combination of data from different
energy points plays an important role in the determination of regions allowed
for the contact interaction coupling constants. In contrast to the more common
one-parameter analyses, we only obtain constraints on pairs of parameters
rather than limits on individual ones.Comment: 13 pages, LaTeX, including figures. v2: Included discussion of tau
data, version to appear in EPJ
Two-band superconductors: Extended Ginzburg-Landau formalism by a systematic expansion in small deviation from the critical temperature
We derive the extended Ginzburg-Landau (GL) formalism for a clean s-wave
two-band superconductor by employing a systematic expansion of the free-energy
functional and the corresponding matrix gap equation in powers of the small
deviation from the critical temperature tau = 1-T/T_c. The two lowest orders of
this expansion produce the equation for T_c and the GL theory. It is shown that
in agreement with previous studies, the two-band GL theory maps onto the
single-band GL model and thus fails to describe the difference in the spatial
profiles of the two band condensates. We prove that except for some very
special cases, this difference appears already in the leading correction to the
GL theory, which constitutes the extended GL formalism. We derive linear
differential equations that determine the leading corrections to the band order
parameters and magnetic field, discuss the validity of these equations, and
consider examples of an important interplay between the band condensates.
Finally, we present numerical results for the thermodynamic critical magnetic
field and temperature-dependent band gaps (at zero field), which are in a very
good agreement with those obtained from the full BCS approach in a wide
temperature range. To this end, we emphasize the advantages of our extended GL
theory in comparison with the often used two-component GL-like model based on
an unreconstructed two-band generalization of the Gor'kov derivation
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