340 research outputs found
Kinematic sensitivity to the Fierz term of -decay differential spectra
The current most stringent constraints on exotic scalar or tensor couplings
in neutron and nuclear decay, involving left-handed neutrinos, are
obtained from the Fierz interference term. The sensitivity to this term in a
correlation coefficient is usually driven by an energy-averaged kinematic
factor that increases monotonically toward smaller values of the
endpoint energies. We first point out here that this property does not hold for
certain differential observables that are directly sensitive to the Fierz term,
such as the or the recoil energy spectrum. This observation is relevant
for the selection of sensitive transitions in searches for exotic couplings
through spectrum shape measurements. We then point out previous errors in the
exploitation of measurements of the angular correlation coefficient
and discuss their impact on the extraction of constraints on exotic couplings.Comment: 7 pages, 5 figure
Determination of |Vud| from nuclear mirror transitions
The Vud element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix has
traditionally been determined from the analysis of data in nuclear superallowed
0+ to 0+ transitions, neutron decay and pion beta decay. We show here that this
element can independently be determined from nuclear mirror transitions. The
extracted value, |Vud| = 0.9719 +- 0.0017, is at 1.2 combined standard
deviations from the value obtained in superallowed 0+ to 0+ transitions and has
a similar precision than the value obtained from neutron decay experiments. We
discuss some prospects to improve its precision through experiments in nuclear
mirror transitions.Comment: 4 pages, 2 figure
Precision measurements in nuclear {\beta}-decay with LPCTrap
The experimental achievements and the current program with the LPCTrap device
installed at the LIRAT beam line of the SPIRAL1-GANIL facility are presented.
The device is dedicated to the study of the weak interaction at low energy by
means of precise measurements of the {\beta}-{\nu} angular correlation
parameter. Technical aspects as well as the main results are reviewed. The
future program with new available beams is briefly discussed.Comment: Annalen der Physik (2013
Tests of the standard electroweak model in beta decay
We review the current status of precision measurements in allowed nuclear beta decay, including neutron decay, with emphasis on their potential to look for new physics beyond the standard electroweak model. The experimental results are interpreted in the framework of phenomenological model-independent descriptions of nuclear beta decay as well as in some specific extensions of the standard model. The values of the standard couplings and the constraints on the exotic couplings of the general beta decay Hamiltonian are updated. For the ratio between the axial and the vector couplings we obtain C_A/C_V = -1.26992(69) under the standard model assumptions. Particular attention is devoted to the discussion of the sensitivity and complementarity of different precision experiments in direct beta decay. The prospects and the impact of recent developments of precision tools and of high intensity low energy beams are also addressed
Modification of an OSCE format to enhance patient continuity in a high-stakes assessment of clinical performance
<p>Abstract</p> <p>Background</p> <p>Traditional Objective Structured Clinical Examinations (OSCEs) are psychometrically sound but have the limitation of fragmenting complex clinical cases into brief stations. We describe a pilot study of a modified OSCE that attempts to balance a typical OSCE format with a semblance of a continuous, complex, patient case.</p> <p>Methods</p> <p>Two OSCE scenarios were developed. Each scenario involved a single standardized patient and was subdivided into three sequential 10 minute sections that assessed separate content areas and competencies. Twenty Canadian PGY-4 internal medicine trainees were assessed by trained examiner pairs during each OSCE scenario. Paired examiners rated participant performance independent of each other, on each section of each scenario using a validated global rating scale. Inter-rater reliabilities and Pearson correlations between ratings of the 3 sections of each scenario were calculated. A generalizability study was conducted. Participant and examiner satisfaction was surveyed.</p> <p>Results</p> <p>There was no main effect of section or scenario. Inter-rater reliability was acceptable. The g-coefficient was 0.68; four scenarios would achieve 0.80. Moderate correlations between sections of a scenario suggest a possible halo effect. The majority of examiners and participants felt that the modified OSCE provided a sense of patient continuity.</p> <p>Conclusions</p> <p>The modified OSCE provides another approach to the assessment of clinical performance. It attempts to balance the advantages of a traditional OSCE with a sense of patient continuity.</p
Measurement of the Michel Parameter xi" in Polarized Muon Decay and Implications on Exotic Couplings of the Leptonic Weak Interaction
The Michel parameter xi" has been determined from a measurement of the
longitudinal polarization of positrons emitted in the decay of polarized and
depolarized muons. The result, xi" = 0.981 +- 0.045stat +- 0.003syst, is
consistent with the Standard Model prediction of unity, and provides an order
of magnitude improvement in the relative precision of this parameter. This
value sets new constraints on exotic couplings beyond the dominant V-A
description of the leptonic weak interaction.Comment: 15 pages, 16 figures, 3 tables; submitted to Phys. Rev.
Measurement of the Transverse Polarization of Electrons Emitted in Free Neutron Decay
Both components of the transverse polarization of electrons emitted in the
beta-decay of polarized, free neutrons have been measured. The T-odd, P-odd
correlation coefficient quantifying the component perpendicular to the decay
plane defined by neutron polarization and electron momentum, was found to be
R=0.008 +/- 0.015 +/-0.005. This value is consistent with time reversal
invariance, and significantly improves limits on the relative strength of
imaginary scalar couplings in the weak interaction. The value obtained for the
correlation coefficient associated with the electron polarization component
contained within the decay plane N=0.056 +/- 0.011 +/- 0.005, agrees with the
Standard Model expectation, providing an important sensitivity test of the
experimental setup.Comment: 4 pages, 4 figure
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