134 research outputs found
Higgs Boson Flavor-Changing Neutral Decays into Bottom Quarks in Supersymmetry
We analyze the maximum branching ratios for the Flavor Changing Neutral
Current (FCNC) decays of the neutral Higgs bosons of the Minimal Supersymmetric
Standard Model (MSSM) into bottom quarks, h -> b\bar{s} (h=h^0,H^0,A^0). We
consistently correlate these decays with the radiative B-meson decays (b->
s\gamma). A full-fledged combined numerical analysis is performed of these
high-energy and low-energy FCNC decay modes in the MSSM parameter space. Our
calculation shows that the available data on B(b->s \gamma) severely restricts
the allowed values of B(h->b\bar{s}). While the latter could reach a few
percent level in fine-tuned scenarios, the requirement of naturalness reduces
these FCNC rates into the modest range B(h->b\bar{s}) ~ 10^{-4}-10^{-3}. We
find that the bulk of the MSSM contribution to B(h->b\bar{s}) could originate
from the strong supersymmetric sector. The maximum value of the FCNC rates
obtained in this paper disagree significantly with recent (over-)estimates
existing in the literature. Our results are still encouraging because they show
that the FCNC modes h->b\bar{s} can be competitive with other Higgs boson
signatures and could play a helpful complementary role to identify the
supersymmetric Higgs bosons, particularly the lightest CP-even state in the
critical LHC mass region m_{h^0} ~= 90-130 GeV.Comment: LaTeX, 19 pages, 4 tables, 7 figures. Clarifications and discussions
added, references added. Slight changes in Figs2b,6b and 7b. Version accepted
in JHE
Non-universal gaugino masses: a signal-based analysis for the Large Hadron Collider
We discuss the signals at the Large Hadron Collider (LHC) for scenarios with
non-universal gaugino masses in supersymmetric (SUSY) theories. We perform a
multichannel analysis, and consider the ratios of event rates in different
channels such as , - and -
, as well as and final states
together with . Low-energy SUSY spectra corresponding to
high-scale gaugino non-universality arising from different breaking schemes of
SU(5) as well as SO(10) Grand Unified (GUT) SUSY models are considered, with
both degenerate low-energy sfermion masses and those arising from a
supergravity scenario. We present the numerical predictions over a wide range
of the parameter space using the event generator {\tt Pythia}, specifying the
event selection criteria and pointing out regions where signals are likely to
be beset with backgrounds. Certain broad features emerge from the study, which
may be useful in identifying the signatures of different GUT breaking schemes
and distinguishing them from a situation with a universal gaugino mass at high
scale. The absolute values of the predicted event rates for different scenarios
are presented together with the various event ratios, so that these can also be
used whenever necessary.Comment: 54 pages, 18 figure
Supergauge interactions and electroweak baryogenesis
We present a complete treatment of the diffusion processes for supersymmetric
electroweak baryogenesis that characterizes transport dynamics ahead of the
phase transition bubble wall within the symmetric phase. In particular, we
generalize existing approaches to distinguish between chemical potentials of
particles and their superpartners. This allows us to test the assumption of
superequilibrium (equal chemical potentials for particles and sparticles) that
has usually been made in earlier studies. We show that in the Minimal
Supersymmetric Standard Model, superequilibrium is generically maintained --
even in the absence of fast supergauge interactions -- due to the presence of
Yukawa interactions. We provide both analytic arguments as well as illustrative
numerical examples. We also extend the latter to regions where analytical
approximations are not available since down-type Yukawa couplings or supergauge
interactions only incompletely equilibrate. We further comment on cases of
broken superequilibrium wherein a heavy superpartner decouples from the
electroweak plasma, causing a kinematic bottleneck in the chain of
equilibrating reactions. Such situations may be relevant for baryogenesis
within extensions of the MSSM. We also provide a compendium of inputs required
to characterize the symmetric phase transport dynamics.Comment: 49 pages, 9 figure
Fermionic decays of sfermions: a complete discussion at one-loop order
We present a definition of an on-shell renormalization scheme for the
sfermion and chargino-neutralino sector of the Minimal Supersymmetric Standard
Model (MSSM). Then, apply this renormalization framework to the interaction
between charginos/neutralinos and sfermions. A kind of universal corrections is
identified, which allow to define effective chargino/neutralino coupling
matrices. In turn, these interactions generate (universal) non-decoupling terms
that grow as the logarithm of the heavy mass. Therefore the full MSSM spectrum
must be taken into account in the computation of radiative corrections to
observables involving these interactions. As an application we analyze the full
one-loop electroweak radiative corrections to the partial decay widths
\Gamma(\tilde{f} -> f\neut) and \Gamma(\tilde{f} -> f'\cplus) for all sfermion
flavours and generations. These are combined with the QCD corrections to
compute the corrected branching ratios of sfermions. It turns out that the
electroweak corrections can have an important impact on the partial decay
widths, as well as the branching ratios, in wide regions of the parameter
space. The precise value of the corrections is strongly dependent on the
correlation between the different particle masses.Comment: LaTeX 53 pages, 22 figures, 3 tables. Typos correcte
Early childhood feeding practices and dental caries in preschool children: a multi-centre birth cohort study
Extent: 7p.Background Dental caries (decay) is an international public health challenge, especially amongst young children. Early Childhood Caries is a rapidly progressing disease leading to severe pain, anxiety, sepsis and sleep loss, and is a major health problem particularly for disadvantaged populations. There is currently a lack of research exploring the interactions between risk and protective factors in the development of early childhood caries, in particular the effects of infant feeding practises. Methods/Design This is an observational cohort study and involves the recruitment of a birth cohort from disadvantaged communities in South Western Sydney. Mothers will be invited to join the study soon after the birth of their child at the time of the first home visit by Child and Family Health Nurses. Data on feeding practices and dental health behaviours will be gathered utilizing a telephone interview at 4, 8 and 12 months, and thereafter at 6 monthly intervals until the child is aged 5 years. Information collected will include a) initiation and duration of breastfeeding, b) introduction of solid food, c) intake of cariogenic and non-cariogenic foods, d) fluoride exposure, and e) oral hygiene practices. Children will have a dental and anthropometric examination at 2 and 5 years of age and the main outcome measures will be oral health quality of life, caries prevalence and caries incidence. Discussion This study will provide evidence of the association of early childhood feeding practices and the oral health of preschool children. In addition, information will be collected on breastfeeding practices and the oral health concerns of mothers living in disadvantaged areas in South Western Sydney.Amit Arora, Jane A Scott, Sameer Bhole, Loc Do, Eli Schwarz and Anthony S Blinkhor
Plasma–liquid interactions: a review and roadmap
Plasma–liquid interactions represent a growing interdisciplinary area of research involving plasma science, fluid dynamics, heat and mass transfer, photolysis, multiphase chemistry and aerosol science. This review provides an assessment of the state-of-the-art of this multidisciplinary area and identifies the key research challenges. The developments in diagnostics, modeling and further extensions of cross section and reaction rate databases that are necessary to address these challenges are discussed. The review focusses on non-equilibrium plasmas
Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.
Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability
Restructuring UK local government employment relations: pay determination and employee participation in tough times
The Conservative-led coalition government has been committed to shrinking the state and this has had a major impact on local government. This article examines the consequences of austerity measures for staff participation and pay determination in UK local government. Local government has been particularly hard hit by austerity measures and this has encouraged employers to change terms and conditions, review forms of staff participation and cut jobs. The implications for the institutional resilience of systems of employment regulation and employee involvement in the sector are considered
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