646 research outputs found
The B_s and D_s decay constants in 3 flavor lattice QCD
Capitalizing on recent advances in lattice QCD, we present a calculation of
the leptonic decay constants f_{B_s} and f_{D_s} that includes effects of one
strange sea quark and two light sea quarks. The discretization errors of
improved staggered fermion actions are small enough to simulate with 3
dynamical flavors on lattices with spacings around 0.1 fm using present
computer resources. By shedding the quenched approximation and the associated
lattice scale ambiguity, lattice QCD greatly increases its predictive power.
NRQCD is used to simulate heavy quarks with masses between 1.5 m_c and m_b. We
arrive at the following results: f_{B_s} = 260 \pm 7 \pm 26 \pm 8 \pm 5 MeV and
f_{D_s} = 290 \pm 20 \pm 29 \pm 29 \pm 6 MeV. The first quoted error is the
statistical uncertainty, and the rest estimate the sizes of higher order terms
neglected in this calculation. All of these uncertainties are systematically
improvable by including another order in the weak coupling expansion, the
nonrelativistic expansion, or the Symanzik improvement program.Comment: 4 page
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Barriers and facilitators to adherence to group exercise in institutionalized older people living with dementia: a systematic review
Objectives
Research suggests targeted exercise is important for people living with dementia, especially those living in residential care. The aim of this review was to collect and synthesize evidence on the known barriers and facilitators to adherence to group exercise of institutionalized older people living with dementia.
Methods
We searched all available electronic databases. Additionally, we searched trial registries (clinicaltrial.gov, and WHO ICTRP) for ongoing studies. We searched for and included papers from January 1990 until September 2017 in any language. We included randomized, non-randomized trials. Studies were not eligible if participants were either healthy older people or people suffering from dementia but not living in an institution. Studies were also excluded if they were not focused on barriers and facilitators to adherence to group exercise.
Results
Using narrative analysis, we identified the following themes for barriers: bio-medical reasons and mental wellbeing and physical ability, relationships dynamics, and socioeconomic reasons. The facilitators were grouped under the following thematic frames: bio-medical benefits and benefits related to physical ability, feelings and emotions and confidence improvements, therapist and group relationships dynamics and activity related reasons.
Conclusions
We conclude that institutionalized older people living with dementia, even those who are physically frail, incontinent and/or have mild dementia can demonstrate certain level of exercise adherence, and therefore can respond positively to exercise programs. Tailored, individually-adjusted and supported physical activity, led by a knowledgeable, engaging and well communicating therapist/facilitator improves the adherence to group exercise interventions of institutionalized older people living with dementia
Plans and Speculated Actions
In the last decades, much design research around “future-focused thinking” has come to prominence in relation to changes in human behaviour, at different scales, from the Quantified Self, to visions of smart cities, to Transition Design. The design of products, services, environments and systems plays an important role in affecting what people do, now and in the future: what has become known in recent years as design for behaviour change. Our Conversation is motivated by three, interlinked questions: on designers’ agency; on sense-making; and on complexity. We will collectively explore considerations of people, and people’s behaviour, in design, particularly in the ways visions of futures are drafted
Hadronic B Decays Involving Even Parity Charmed Mesons
Hadronic B decays containing an parity-even charmed meson in the final state
are studied. Specifically we focus on the Cabibbo-allowed decays and , where denotes generically a p-wave charmed meson.
The transition form factors are studied in the improved version
of the Isgur-Scora-Grinstein-Wise quark model. We apply heavy quark effective
theory and chiral symmetry to study the strong decays of p-wave charmed mesons
and determine the magnitude of the mixing angle. Except
the decay to the predictions for agree
with experiment. The sign of mixing angle is found to be
positive in order to avoid a severe suppression on the production of
. The interference between color-allowed and color-suppressed
tree amplitudes is expected to be destructive in the decay . Hence, an observation of the ratio
can be used to test the relative signs of
various form factors as implied by heavy quark symmetry. Although the predicted
at the level of exceeds the
present upper limit, it leads to the ratio
as expected from the factorization
approach and from the ratio . Therefore, it is
crucial to have a measurement of this mode to test the factorization
hypothesis. For decays, it is expected that \bar
D_{s0}^*D\gsim \bar D_{s1}D as the decay constants of the multiplet
become the same in the heavy quark limit.Comment: 27 pages, Belle's new data on DD_s^{**} productions in B decays and
on the radiative decay D_{s1}-> D_s\gamma are updated and discussed. Add two
reference
Covariant Light-Front Approach for s-wave and p-wave Mesons: Its Application to Decay Constants and Form Factors
We study the decay constants and form factors of the ground-state s-wave and
low-lying p-wave mesons within a covariant light-front approach. Numerical
results of the form factors for transitions between a heavy pseudoscalar meson
and an s-wave or p-wave meson and their momentum dependence are presented in
detail. In particular, form factors for heavy-to-light and B to D**
transitions, where D** denotes generically a p-wave charmed meson, are compared
with other model calculations. The experimental measurements of the decays B^-
to D** pi^- and B to D D**_s are employed to test the decay constants of D**_s
and the B to D** transition form factors. The heavy quark limit behavior of the
decay constants and form factors is examined and it is found that the
requirement of heavy quark symmetry is satisfied. The universal Isgur-Wise (IW)
functions, one for s-wave to s-wave and two for s-wave to p-wave transitions,
are obtained. The values of IW functions at zero recoil and their slope
parameters can be used to test the Bjorken and Uraltsev sum rules.Comment: 59 pages, 6 figures. Version to appear in Phys. Rev. D. Changes are:
(i) D_s to phi transition form factors are discussed and compared with the
recent FOCUS measurements and (ii) zero mode effects are clarifie
Heavy Quarkonium Physics
This report is the result of the collaboration and research effort of the
Quarkonium Working Group over the last three years. It provides a comprehensive
overview of the state of the art in heavy-quarkonium theory and experiment,
covering quarkonium spectroscopy, decay, and production, the determination of
QCD parameters from quarkonium observables, quarkonia in media, and the effects
on quarkonia of physics beyond the Standard Model. An introduction to common
theoretical and experimental tools is included. Future opportunities for
research in quarkonium physics are also discussed.Comment: xviii + 487 pages, 260 figures. The full text is also available at
the Quarkonium Working Group web page: http://www.qwg.to.infn.i
Measurement of B(Ds+ -->ell+ nu) and the Decay Constant fDs From 600/pb of e+e- Annihilation Data Near 4170 MeV
We examine e+e- --> Ds^-D_s^{*+} and Ds^{*-}Ds^{+} interactions at 4170 MeV
using the CLEO-c detector in order to measure the decay constant fDs with good
precision. Previously our measurements were substantially higher than the most
precise lattice based QCD calculation of (241 +/- 3) MeV. Here we use the D_s^+
--> ell^+ nu channel, where the ell^+ designates either a mu^+ or a tau^+, when
the tau^+ --> pi^+ anti-nu. Analyzing both modes independently, we determine
B(D_s^+ --> mu^+ nu)= 0.565 +/- 0.045 +/- 0.017)%, and B(D_s^+ --> mu^+ nu)=
(6.42 +/- 0.81 +/- 0.18)%. We also analyze them simultaneously to find an
effective value of B^{eff}(D_s^+ --> mu^+ nu)= (0.591 +/- 0.037 +/- 0.018)% and
fDs=(263.3 +/- 8.2 +/- 3.9) MeV. Combining with the CLEO-c value determined
independently using D_s^+ --> tau^+ nu, tau^+ --> e^+ nu anti-nu decays, we
extract fDs=(259.5 +/- 6.6 +/- 3.1) MeV. Combining with our previous
determination of B(D^+ --> mu^+ nu), we extract the ratio fDs/fD+=1.26 +/- 0.06
+/- 0.02. No evidence is found for a CP asymmetry between Gamma(D_s^+ -->
mu^+\nu) and \Gamma(D_s^- --> mu^- nu); specifically the fractional difference
in rates is measured to be (4.8 +/- 6.1)%. Finally, we find B(D_s^+ --> e^+ nu)
< 1.2x10^{-4} at 90% confidence level.Comment: 26 pages, 16 figure
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