403 research outputs found
Charm as a domain wall fermion in quenched lattice QCD
We report a study describing the charm quark by a domain-wall fermion (DWF)
in lattice quantum chromodynamics (QCD). Our study uses a quenched gauge
ensemble with the DBW2 rectangle-improved gauge action at a lattice cutoff of
GeV. We calculate masses of heavy-light (charmed) and
heavy-heavy (charmonium) mesons with spin-parity and ,
leptonic decay constants of the charmed pseudoscalar mesons ( and ),
and the - mixing parameter. The charm quark mass is found to be
GeV. The mass splittings in
charmed-meson parity partners and are
degenerate within statistical errors, in accord with experiment, and they
satisfy a relation , also consistent with
experiment. A C-odd axial vector charmonium state, \chi_{c1}m_{h_{c}} = 3533(11)_{\rm stat.}\chi_{c1}) mass. However, in this regard, we emphasize
significant discrepancies in the calculation of hyperfine splittings on the
lattice. The leptonic decay constants of and mesons are found to be
MeV and
,
where the first error is statistical, the second a systematic due to chiral
extrapolation and the third error combination of other known systematics. The
- mixing bag parameter, which enters the
transition amplitude, is found to be .Comment: 49 pages, 15 figure
Heavy-Quark Symmetry and the Electromagnetic Decays of Excited Charmed Strange Mesons
Heavy-hadron chiral perturbation theory (HHPT) is applied to the decays
of the even-parity charmed strange mesons, D_{s0}(2317) and D_{s1}(2460).
Heavy-quark spin symmetry predicts the branching fractions for the three
electromagnetic decays of these states to the ground states D_s and D_s^* in
terms of a single parameter. The resulting predictions for two of the branching
fractions are significantly higher than current upper limits from the CLEO
experiment. Leading corrections to the branching ratios from chiral loop
diagrams and spin-symmetry violating operators in the HHPT Lagrangian can
naturally account for this discrepancy. Finally the proposal that the
D_{s0}(2317) (D_{s1}(2460)) is a hadronic bound state of a D (D^*) meson and a
kaon is considered. Leading order predictions for electromagnetic branching
ratios in this molecular scenario are in very poor agreement with existing
data.Comment: 25 pages, 3 figure
An estimate of the flavour singlet contributions to the hyperfine splitting in charmonium
We explore the splitting between flavour singlet and non-singlet mesons in
charmonium. This has implications for the hyperfine splitting in charmonium
Exact Absorption Probability in the Extremal Six-Dimensional Dyonic String Background
We show that the minimally coupled massless scalar wave equation in the
background of an six-dimensional extremal dyonic string (or D1-D5 brane
intersection) is exactly solvable, in terms of Mathieu functions. Using this
fact, we calculate absorption probabilities for these scalar waves, and present
the explicit results for the first few low energy corrections to the
leading-order expressions. For a specific tuning of the dyonic charges one can
reach a domain where the low energy absorption probability goes to zero with
inverse powers of the logarithm of the energy. This is a dividing domain
between the regime where the low energy absorption probability approaches zero
with positive powers of energy and the regime where the probability is an
oscillatory function of the logarithm of the energy. By the conjectured AdS/CFT
correspondence, these results shed novel light on the strongly coupled
two-dimensional field theory away from its infrared conformally invariant fixed
point (the strongly coupled ``non-critical'' string).Comment: Latex (3 times), 23 page
Excited Charmed Mesons: Observations, Analyses and Puzzles
We review the status of recently observed positive parity charmed resonances,
both in the non-strange and in the strange sector. We describe the experimental
findings, the main theoretical analyses and the open problems deserving further
investigations.Comment: LaTeX, 25 pages, 5 figures. Invited revie
Waiting for Precise Measurements of K^+->pi^+ nu nu and K_L->pi^0 nu nu
In view of future plans for accurate measurements of the theoretically clean
branching ratios Br(K+ -> pi+ nu nu) and Br(KL -> pi0 nu nu), that should take
place in the next decade, we collect the relevant formulae for quantities of
interest and analyze their theoretical and parametric uncertainties. We point
out that in addition to the angle beta in the unitarity triangle (UT) also the
angle gamma can in principle be determined from these decays with respectable
precision and emphasize in this context the importance of the recent NNLO QCD
calculation of the charm contribution to K+ -> pi+ nu nu and of the improved
estimate of the long distance contribution by means of chiral perturbation
theory. In addition to known expressions we present several new ones that
should allow transparent tests of the Standard Model (SM) and of its
extensions. While our presentation is centered around the SM, we also discuss
models with minimal flavour violation and scenarios with new complex phases in
decay amplitudes and meson mixing. We give a brief review of existing results
within specific extensions of the SM, in particular the Littlest Higgs Model
with T-parity, Z' models, the MSSM and a model with one universal extra
dimension. We derive a new "golden" relation between B and K systems that
involves (beta,gamma) and Br(KL -> pi0 nu nu) and investigate the virtues of
(R_t,beta), (R_b,gamma), (beta,gamma) and (etabar,gamma) strategies for the UT
in the context of K -> pi nu nu decays with the goal of testing the SM and its
extensions.Comment: 56 pages, 18 figures, Section on Long Distance Contributions, 2
Figures and few References added, Uses Rev Mod Phys Style; Includes new
results of NNLO calculation as well as matrix elements, extended and modified
sections on new physic
A survey of prolapse practice in UK women’s health physiotherapists: what has changed in the last decade?
INTRODUCTION AND HYPOTHESIS: Prolapse is a common female problem, and conservative treatments such as pelvic floor muscle training (PFMT) are important options for women. Evidence supporting the effectiveness of PFMT for prolapse has grown over the last decade, and it was hypothesised that practice and practice guidelines would have developed in line with the evidence. To assess this, up-to-date information about the practice of physiotherapists working in women’s health regarding their treatment of prolapse was required. METHODS: An online survey sent to members of the Association of Chartered Physiotherapists in Women’s Health and the Chartered Physiotherapists Promoting Continence. Results were compared with those of an earlier survey undertaken in 2002. RESULTS: A 49 % response rate was achieved. The majority of respondents were senior physiotherapists (55 %) and had worked in women’s health for more than 10 years. Respondents were treating significantly more women with prolapse than a decade before: 36 % vs 14 % treated more than 50 women per year in 2002 and 2013 respectively (p < 0.001). Individualised PFMT (93 %), lifestyle advice (92 %) and biofeedback-assisted PFMT (83 %) were the most common treatment elements, with four being the average number of appointments. Forty-eight percent had changed their practice as a result of recent research; however, scepticism amongst medics, the referral of women directly for surgery, and constraints on resources were thought to be barriers to wider implementation of the evidence of PFMT for prolapse. CONCLUSIONS: There has been uptake of evidence-based prolapse practice by UK specialist physiotherapists in the last decade. Further research targeting the implementation of this evidence would be valuable in addressing potential barriers, and in supporting the need for physiotherapy in the treatment of prolapse
The establishment of a WHO Reference Reagent for anti-malaria (Plasmodium falciparum) human serum
BACKGROUND: At a World Health Organization (WHO) sponsored
meeting it was concluded that there is an urgent need for a
reference preparation that contains antibodies against malaria
antigens in order to support serology studies and vaccine
development. It was proposed that this reference would take the
form of a lyophilized serum or plasma pool from a
malaria-endemic area. In response, an immunoassay standard,
comprising defibrinated human plasma has been prepared and
evaluated in a collaborative study. RESULTS: A pool of human
plasma from a malaria endemic region was collected from 140
single plasma donations selected for reactivity to Plasmodium
falciparum apical membrane antigen-1 (AMA-1) and merozoite
surface proteins (MSP-119, MSP-142, MSP-2 and MSP-3). This pool
was defibrinated, filled and freeze dried into a single batch of
ampoules to yield a stable source of naturally occurring
antibodies to P. falciparum. The preparation was evaluated by an
enzyme-linked immunosorbent assay (ELISA) in a collaborative
study with sixteen participants from twelve different countries.
This anti-malaria human serum preparation (NIBSC Code: 10/198)
was adopted by the WHO Expert Committee on Biological
Standardization (ECBS) in October 2014, as the first WHO
reference reagent for anti-malaria (Plasmodium falciparum) human
serum with an assigned arbitrary unitage of 100 units (U) per
ampoule. CONCLUSION: Analysis of the reference reagent in a
collaborative study has demonstrated the benefit of this
preparation for the reduction in inter- and intra-laboratory
variability in ELISA. Whilst locally sourced pools are regularly
use for harmonization both within and between a few
laboratories, the presence of a WHO-endorsed reference reagent
should enable optimal harmonization of malaria serological
assays either by direct use of the reference reagent or
calibration of local standards against this WHO reference. The
intended uses of this reference reagent, a multivalent
preparation, are (1) to allow cross-comparisons of results of
vaccine trials performed in different centres/with different
products; (2) to facilitate standardization and harmonization of
immunological assays used in epidemiology research; and (3) to
allow optimization and validation of immunological assays used
in malaria vaccine development
Study of DJ meson decays to D+π−, D0π+ and D∗+π− final states in pp collisions
A study of D+π−, D0π+ and D∗+π− final states is performed using pp collision data, corresponding to an integrated luminosity of 1.0 fb−1, collected at a centre-of-mass energy of 7 TeV with the LHCb detector. The D1(2420)0 resonance is observed in the D∗+π− final state and the D∗2(2460) resonance is observed in the D+π−, D0π+ and D∗+π− final states. For both resonances, their properties and spin-parity assignments are obtained. In addition, two natural parity and two unnatural parity resonances are observed in the mass region between 2500 and 2800 MeV. Further structures in the region around 3000 MeV are observed in all the D∗+π−, D+π− and D0π+ final states
Enhanced Protective Efficacy of a Chimeric Form of the Schistosomiasis Vaccine Antigen Sm-TSP-2
The large extracellular loop of the Schistosoma mansoni tetraspanin, Sm-TSP-2, when fused to a thioredoxin partner and formulated with Freund's adjuvants, has been shown to be an efficacious vaccine against murine schistosomiasis. Moreover, Sm-TSP-2 is uniquely recognised by IgG1 and IgG3 from putatively resistant individuals resident in S. mansoni endemic areas in Brazil. In the present study, we expressed Sm-TSP-2 at high yield and in soluble form in E. coli without the need for a solubility enhancing fusion partner. We also expressed in E. coli a chimera called Sm-TSP-2/5B, which consisted of Sm-TSP-2 fused to the immunogenic 5B region of the hookworm aspartic protease and vaccine antigen, Na-APR-1. Sm-TSP-2 formulated with alum/CpG showed significant reductions in adult worm and liver egg burdens in two separate murine schistosomiasis challenge studies. Sm-TSP-2/5B afforded significantly greater protection than Sm-TSP-2 alone when both antigens were formulated with alum/CpG. The enhanced protection obtained with the chimeric fusion protein was associated with increased production of anti-Sm-TSP-2 antibodies and IL-4, IL-10 and IFN-γ from spleen cells of vaccinated animals. Sera from 666 individuals from Brazil who were infected with S. mansoni were screened for potentially deleterious IgE responses to Sm-TSP-2. Anti-Sm-TSP-2 IgE to this protein was not detected (also shown previously for Na-APR-1), suggesting that the chimeric antigen Sm-TSP-2/5B could be used to safely and effectively vaccinate people in areas where schistosomes and hookworms are endemic
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