9,812 research outputs found
Reducing Penguin Pollution
The most common decay used for measuring 2beta_s, the phase of Bs-Bsbar
mixing, is Bs -> J/psi phi. This decay is dominated by the colour-suppressed
tree diagram, but there are other contributions due to gluonic and electroweak
penguin diagrams. These are often referred to as "penguin pollution" (PP)
because their inclusion in the amplitude leads to a theoretical error in the
extraction of 2beta_s from the data. In the standard model (SM), it is
estimated that the PP is negligible, but there is some uncertainty as to its
exact size. Now, phi_s^{c\bar{c}s} (the measured value of 2beta_s) is small, in
agreement with the SM, but still has significant experimental errors. When
these are reduced, if one hopes to be able to see clear evidence of new physics
(NP), it is crucial to have the theoretical error under control. In this paper,
we show that, using a modification of the angular analysis currently used to
measure phi_s^{c\bar{c}s} in Bs -> J/psi phi, one can reduce the theoretical
error due to PP. Theoretical input is still required, but it is much more
modest than entirely neglecting the PP. If phi_s^{c\bar{c}s} differs from the
SM prediction, this points to NP in the mixing. There is also enough
information to test for NP in the decay. This method can be applied to all
Bs/Bsbar -> V1 V2 decays.Comment: 17 pages, latex, extensive discussion of theoretical error added,
reference added. Further revision: even more detailed discussion of
theoretical error added, as well as an explanation of why the NP strong phase
is negligibl
Vitamin K catabolite inhibition of ovariectomy-induced bone loss: Structureâactivity relationship considerations
The potential benefit of vitamin K as a therapeutic in osteoporosis is controversial and the vitamin K regimen being used clinically (45 mg/day) employs doses that are many times higher than required to ensure maximal gammaâcarboxylation of the vitamin Kâdependent bone proteins. We therefore tested the hypothesis that vitamin K catabolites, 5âcarbon (CAN5C) and 7âcarbon carboxylic acid (CAN7C) aliphatic sideâchain derivatives of the naphthoquinone moiety exert an osteotrophic role consistent with the treatment of osteoporosis
Childâs play: Exposure to household pesticide use among children in rural, urban and informal areas of South Africa
Background. As part of a larger dermatological investigation undertaken in 1999 - 2001 involving the Department of Dermatology, Groote Schuur Hospital (Cape Town, South Africa) and Nottingham University (UK), household pesticide use was investigated among Xhosa-speaking families living in three areas in South Africa (a rural area, an urban township and an informal settlement).Objectives. The aim was to characterise pesticide use patternsand potential exposures through skin absorption, ingestion and inhalation for this group of South African children.Methods. A standardised questionnaire, which included a section investigating household pesticide use, was administered by four trained fieldworkers to the parents/guardians of the 740 children (25%) aged between 3 and 11 years identified as having atopic dermatitis either by clinical examination or according to the UK criteria (rural N=387,urban N=292, informal N=61).Results. Of the children with atopic dermatitis, 539 (73%) had been exposed to household pesticides. Most childhood exposure (89%) occurred in the informal settlements, followed by 78% in the urban area and 63% in the rural area.Conclusions. This research highlighted considerable home environment pesticide exposure of South African children in lower socio-economic groups in rural, urban and informal areas. As children are particularly vulnerable to the short- and long-term health effects of pesticide exposure, further indepth investigation is needed to ascertain and document the health effects associated with such exposure in the home
Bounds on New Physics from B -> V1 V2 Decays
We consider the possibility that physics beyond the standard model
contributes to the decays B -> V1 V2, where V1 and V2 are vector mesons. We
show that a time-dependent angular analysis of B -> V1 V2 decays provides many
tests for this new physics (NP). Furthermore, although one cannot solve for the
NP parameters, we show that this angular analysis allows one to put bounds on
these parameters. This can be useful in estimating the scale of NP, and can
tell us whether any NP found directly at future high-energy colliders can be
responsible for effects seen in B -> V1 V2 decays.Comment: 23 pages, plain LaTeX, 5 figures (included
Trends in Moderate-to-Vigorous Physical Activity among Veterans: Findings from the National Health Interview Survey 2011-2020
poste
Crystal Structure of the ZrO Phase at Zirconium/Zirconium Oxide Interfaces
Zirconium-based alloys are used in water-cooled nuclear reactors for both nuclear fuel cladding and structural components. Under this harsh environment, the main factor limiting the service life of zirconium cladding, and hence fuel burn-up efficiency, is water corrosion. This oxidation process has recently been linked to the presence of a sub-oxide phase with well-defined composition but unknown structure at the metalâoxide interface. In this paper, the combination of first-principles materials modeling and high-resolution electron microscopy is used to identify the structure of this sub-oxide phase, bringing us a step closer to developing strategies to mitigate aqueous oxidation in Zr alloys and prolong the operational lifetime of commercial fuel cladding alloys
Pair Production of Fourth Family Charged Sleptons at Colliders
We study the pair production of , which is the supersymmetric
partner of the fourth family charged lepton, at the colliders. It
is shown that the investigation of this process at ILC/CLIC will give
opportunity to differentiate the MSSM with three and four families.Comment: 6 pages, 2 figure
Observables in the Decays of B to Two Vector Mesons
In general there are nine observables in the decay of a B meson to two vector
mesons defined in terms of polarization correlations of these mesons. Only six
of these can be detected via the subsequent decay angular distributions because
of parity conservation in those decays. The remaining three require the
measurement of the spin polarization of one of the decay products.Comment: 12 pages, no figur
Finite size mean-field models
We characterize the two-site marginals of exchangeable states of a system of
quantum spins in terms of a simple positivity condition. This result is used in
two applications. We first show that the distance between two-site marginals of
permutation invariant states on N spins and exchangeable states is of order
1/N. The second application relates the mean ground state energy of a
mean-field model of composite spins interacting through a product pair
interaction with the mean ground state energies of the components.Comment: 20 page
The Influence of Veteran Status, Psychiatric Diagnosis, and Traumatic Brain Injury on Inadequate Sleep
Adequate sleep is essential for health, social participation, and wellbeing. We use 2010 and 2011 Behavioral Risk Factor Surveillance System data (N = 35,602) to examine differences in sleep adequacy between: non-veterans; non-combat veterans with no psychiatric diagnosis or traumatic brain injury (TBI); combat veterans with no psychiatric diagnosis or TBI; and veterans (non-combat and combat combined) with a psychiatric diagnosis and/or TBI. On average, respondents reported 9.28 days of inadequate sleep; veterans with a psychiatric diagnosis and/or TBI reported the mostâ12.25 days. Multivariate analyses indicated that veterans with a psychiatric diagnosis and/or TBI had significantly more days of inadequate sleep than all other groups. Findings contribute to a growing literature on the relevance of the military serviceâpsychiatric diagnosisâTBI nexus for sleep problems by using population-representative data and non-veteran and healthy veteran comparison groups. This research underscores the importance of screening and treating veterans for sleep problems, and can be used by social workers and health professionals to advocate for increased education and research about sleep problems among veterans with mental health problems and/or TBI
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