7,752 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: Structure–activity 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 gamma‐carboxylation of the vitamin K‐dependent bone proteins. We therefore tested the hypothesis that vitamin K catabolites, 5‐carbon (CAN5C) and 7‐carbon carboxylic acid (CAN7C) aliphatic side‐chain derivatives of the naphthoquinone moiety exert an osteotrophic role consistent with the treatment of osteoporosis
Child’s 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
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
On the origin of the decrease in the torsional oscillator period of solid He4
A decrease in the rotational period observed in torsional oscillator
measurements was recently taken as a possible indication of a supersolid state
of helium. We reexamine this interpretation and note that the decrease in the
rotation period is also consistent with a solidification of a small liquid-like
component into a low-temperature glass. Such a solidification may occur by a
low-temperature quench of topological defects (e.g., grain boundaries or
dislocations) which we examined in an earlier work. The low-temperature glass
can account for not only a monotonic decrease in the rotation period as the
temperature is lowered but also explains the peak in the dissipation occurring
near the transition point. Unlike the non-classical rotational inertia
scenario, which depends on the supersolid fraction, the dependence of the
rotational period on external parameters, e.g., the oscillator velocity,
provides an alternate interpretation of the oscillator experiments. Future
experiments might explore this effect.Comment: 10 pages, 3 figures; to appear in Phys. Rev.
Extracting Weak Phase Information from B -> V_1 V_2 Decays
We describe a new method for extracting weak, CP-violating phase information,
with no hadronic uncertainties, from an angular analysis of B -> V_1 V_2
decays, where V_1 and V_2 are vector mesons. The quantity can be cleanly obtained from the study of decays such as B_d^0(t) ->
D^{*\pm} \rho^\mp, D^{*\pm} a_1^{\mp}, D^{*0} K^{*0}, etc. Similarly, one can
use B_s^0(t) -> D_s^{*\pm} K^{*\mp} to extract . There are no
penguin contributions to these decays. It is possible that will be the second function of CP phases, after , to be
measured at B-factories.Comment: 4 pages, RevTeX, no figure
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