205 research outputs found
Helicity Analysis of Semileptonic Hyperon Decays Including Lepton Mass Effects
Using the helicity method we derive complete formulas for the joint angular
decay distributions occurring in semileptonic hyperon decays including lepton
mass and polarization effects. Compared to the traditional covariant
calculation the helicity method allows one to organize the calculation of the
angular decay distributions in a very compact and efficient way. In the
helicity method the angular analysis is of cascade type, i.e. each decay in the
decay chain is analyzed in the respective rest system of that particle. Such an
approach is ideally suited as input for a Monte Carlo event generation program.
As a specific example we take the decay () followed by the nonleptonic decay for which we show a few examples of decay distributions which are
generated from a Monte Carlo program based on the formulas presented in this
paper. All the results of this paper are also applicable to the semileptonic
and nonleptonic decays of ground state charm and bottom baryons, and to the
decays of the top quark.Comment: Published version. 40 pages, 11 figures included in the text. Typos
corrected, comments added, references added and update
Measurement of the branching ratio of the decay
From the 2002 data taking with a neutral kaon beam extracted from the
CERN-SPS, the NA48/1 experiment observed 97 candidates with a background contamination of events.
From this sample, the BR() is measured to be
Observation of the rare decay K_S -> pi^0mu^+mu^-
A search for the decay K_S -> pi^0mu^+mu^- has been made by the NA48/1
Collaboration at the CERN SPS accelerator. The data were collected during 2002
with a high-intensity K_S beam. Six events were found with a background
expectation of 0.22^+0.18_-0.11 event. Using a vector matrix element and unit
form factor, the measured branching ratio is B(K_S ->
pi^0mu^+mu^-)=[2.9^+1.5_-1.2(stat)+/-0.2(syst)]x10^{-9}.Comment: 19 pages, 8 figures, 4 tables. To be published in Physics Letters
First observation and branching fraction and decay parameter measurements of the weak radiative decay Xi0 --> Lambda e+e-
The weak radiative decay Xi0 --> Lambda e+e- has been detected for the first
time. We find 412 candidates in the signal region, with an estimated background
of 15 +/- 5 events. We determine the branching fraction B(Xi0 --> Lambda e+e-)
= [7.6 +/- 0.4(stat) +/- 0.4(syst) +/- 0.2(norm)] x 10^{-6}, consistent with an
internal bremsstrahlung process, and the decay asymmetry parameter
alpha_{XiLambdaee} = -0.8 +/- 0.2, consistent with that of Xi0 --> Lambda
gamma. The charge conjugate reaction Xi0_bar --> Lambda_bar e+e- has also been
observed.Comment: 20 pages, 5 figures, 4 tables; revised: 19 pages, 4 figures, 4
tables, after reviewers' comments: 1 figure removed, 1 figure corrected,
minor editorial changes; to be published in Phys. Lett.
First Observation and Measurement of the Decay K+- -> pi+- e+ e- gamma
Using the full data set of the NA48/2 experiment, the decay K+- -> pi+- e+ e-
gamma is observed for the first time, selecting 120 candidates with 7.3 +- 1.7
estimated background events. With K+- -> pi+- pi0D as normalisation channel,
the branching ratio is determined in a model-independent way to be Br(K+- ->
pi+- e+ e- gamma, m_eegamma > 260 MeV/c^2) = (1.19 +- 0.12_stat +- 0.04_syst) x
10^-8. This measured value and the spectrum of the e+ e- gamma invariant mass
allow a comparison with predictions of Chiral Perturbation Theory.Comment: 13 pages, 3 figures. Accepted for publication in Phys.Lett.
Empirical parameterization of the K+- -> pi+- pi0 pi0 decay Dalitz plot
As first observed by the NA48/2 experiment at the CERN SPS, the \p0p0
invariant mass (M00) distribution from \kcnn decay shows a cusp-like anomaly
at M00=2m+, where m+ is the charged pion mass. An analysis to extract the pi pi
scattering lengths in the isospin I=0 and I=2 states, a0 and a2, respectively,
has been recently reported. In the present work the Dalitz plot of this decay
is fitted to a new empirical parameterization suitable for practical purposes,
such as Monte Carlo simulations of K+- -> pi+- pi0 pi0 decays.Comment: 9 pages, 3 figures
Search for direct CP-violation in K+- --> pi+-pi0pi0 decays
A search for direct CP-violation in K+- --> pi+-pi0pi0 decays based on 47.14
million events has been performed by the NA48/2 experiment at the CERN SPS. The
asymmetry in the Dalitz plot linear slopes A_g=(g^+ - g^-)/(g^+ + g^-) is
measured to be A_g=(1.8 +- 2.6).10^{-4}. The design of the experiment and the
method of analysis provide good control of instrumental charge asymmetries in
this measurement. The precision of the result is limited by statistics and is
almost one order of magnitude better than that of previous measurements by
other experiments.Comment: 14 page
ChPT tests at the NA48 and NA62 experiments at CERN
The NA48/2 Collaboration at CERN has accumulated unprecedented statistics of
rare kaon decays in the Ke4 modes: Ke4(+-) ()
and Ke4(00) () with nearly one percent
background contamination. The detailed study of form factors and branching
rates, based on these data, has been completed recently. The results brings new
inputs to low energy strong interactions description and tests of Chiral
Perturbation Theory (ChPT) and lattice QCD calculations. In particular, new
data support the ChPT prediction for a cusp in the invariant mass
spectrum at the two charged pions threshold for Ke4(00) decay. New final
results from an analysis of about 400 rare
decay candidates collected by the NA48/2 and NA62 experiments at CERN during
low intensity runs with minimum bias trigger configurations are presented. The
results include a model-independent decay rate measurement and fits to ChPT
description.Comment: XIIth International Conference on Heavy Quarks and Leptons 2014,
Mainz, German
Recent NA48/2 and NA62 results
The NA48/2 Collaboration at CERN has accumulated and analysed unprecedented
statistics of rare kaon decays in the modes: () and ()
with nearly one percent background contamination. It leads to the improved
measurement of branching fractions and detailed form factor studies. New final
results from the analysis of 381 rare decay
candidates collected by the NA48/2 and NA62 experiments at CERN are presented.
The results include a decay rate measurement and fits to Chiral Perturbation
Theory (ChPT) description.Comment: Prepared for the Proceedings of "Moriond QCD and High Energy
Interactions. March 22-29 2014." conferenc
Blood glucose testing and primary prevention of diabetes mellitus type 2 - evaluation of the effect of evidence based patient information
<p>Abstract</p> <p>Background</p> <p>Evidence-based patient information (EBPI) has been recognised as important tool for informed choice in particular in the matter of preventive options. An objective, on the best scientific evidence-based consumer information about subthreshold elevated blood glucose levels (impaired fasting glucose and impaired glucose tolerance) and primary prevention of diabetes, is not available yet. Thus we developed a web-based EBPI and aim to evaluate its effects on informed decision making in people 50 years or older.</p> <p>Methods/Design</p> <p>We conduct a web-based randomised-controlled trial to evaluate the effect of information about elevated blood glucose levels and diabetes primary prevention on five specific outcomes: (i) knowledge of elevated blood glucose level-related issues (primary outcome); (ii) attitudes to a metabolic testing; (iii) intention to undergo a metabolic testing; (iv) decision conflict; (v) satisfaction with the information. The intervention group receives a specially developed EBPI about subthreshold elevated blood glucose levels and diabetes primary prevention, the control group information about this topic, available in the internet.</p> <p>The study population consists of people between 50 and 69 years of age without known diabetes. Participants will be recruited via the internet page of the cooperating health insurance company, Techniker Krankenkasse (TK), and the internet page of the German Diabetes Centre. Outcomes will be measured through online questionnaires. We expect better informed participants in the intervention group.</p> <p>Discussion</p> <p>The design of this study may be a prototype for other web-based prevention information and their evaluation.</p> <p>Trial registration</p> <p>Current Controlled Trial: ISRCTN22060616.</p
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