5,802 research outputs found
A Comparative Study of the Decays in Standard Model and Supersymmetric Theories
Using improved theoretical calculations of the decay form factors in the
Light Cone-QCD sum rule approach, we investigate the decay rates, dilepton
invariant mass spectra and the forward-backward (FB) asymmetry in the decays () in the standard
model (SM) and a number of popular variants of the supersymmetric (SUSY)
models. Theoretical precision on the differential decay rates and FB-asymmetry
is estimated in these theories taking into account various parametric
uncertainties. We show that existing data on and the
experimental upper limit on the branching ratio provide interesting bounds on the coefficients of the underlying
effective theory. We argue that the FB-asymmetry in
constitutes a precision test of the SM and its measurement in forthcoming
experiments may reveal new physics. In particular, the presently allowed
large- solutions in SUGRA models, as well as more general
flavor-violating SUSY models, yield FB-asymmetries which are characteristically
different from the corresponding ones in the SM.Comment: 36 pages, 12 figures (require epsfig.sty), 8 Tables, LaTeX2e;
subsection 6.4 corrected, minor changes in numerical results, Figures 3 and 9
to 12 modified; submitted to Physical Review
Subtleties in the beta function calculation of N=1 supersymmetric gauge theories
We investigate some peculiarities in the calculation of the two-loop
beta-function of supersymmetric models which are intimately related to
the so-called "Anomaly Puzzle". There is an apparent paradox when the
computation is performed in the framework of the covariant derivative
background field method. In this formalism, it is obtained a finite two-loop
effective action, although a non-null coefficient for the beta-function is
achieved by means of the renormalized two-point function in the background
field. We show that if the standard background field method is used, this
two-point function has a divergent part which allows for the calculation of the
beta-function via the renormalization constants, as usual. Therefore, we
conjecture that this paradox has its origin in the covariant supergraph
formalism itself, possibly being an artifact of the rescaling anomaly.Comment: Few misprintings corrected and comments added. To meet the version to
be published at European Physical Journal
Age, Sex, and Nest Success of Translocated Mountain Quail in Oregon, 2001–2010
We trapped mountain quail (Oreortyx pictus) from relatively abundant populations in southwestern Oregon for re-introduction or augmentation in areas of central and eastern Oregon where they were rare or extirpated. We captured 2,596 mountain quail during 2001–2010 using treadle-style traps, of which 1,430 were released in Oregon; the remaining birds were transferred to Idaho, Nevada, and Washington. Yearlings (hatch-year) comprised 69.6% of the total (n 1⁄4 2,596). Analysis of nuclear DNA from 850 captured quail revealed 50.5% were male. We radiomarked 800 (55.9%) of the quail released in Oregon and monitored them to estimate reproductive success. We located 150 nests in Oregon; at least 1 egg hatched in 110 (73.3%) nests. Average (6 SE) clutch size was 10.2 6 0.2 eggs and average number of chicks hatched from successful nests was 8.3 6 0.3. Sixty-eight nests (45.3%) were incubated exclusively by males, 78 (52.0%) exclusively by females, and 4 (2.7%) by birds of unknown gender. Males incubated slightly larger clutches (11.0 6 0.3) and hatched more eggs than females (5.5 6 0.5). Males also regularly contributed to brood-rearing. The reproductive effort and nest success of translocated mountain quail was comparable to native populations in Oregon. Translocations may be an effective means of restoring mountain quail populations that have been extirpated or augmenting populations that have substantially declined
Predictions for decays
We present a phenomenological study of the rare double radiative decay in the Standard Model (SM) and beyond. Using the operator
product expansion (OPE) technique, we estimate the short-distance (SD)
contribution to the decay amplitude in a region of the phase space which is
around the point where all decay products have energy in the rest
frame of the -meson. At lowest order in 1/Q, where is of order ,
the matrix element is then expressed in terms of the
usual form factors known from semileptonic rare decays. The integrated
SD branching ratio in the SM in the OPE region turns out to be . We work
out the di-photon invariant mass distribution with and without the resonant
background through . In the SM,
the resonance contribution is dominant in the region of phase space where the
OPE is valid. The present experimental upper limit on
decays, which constrains the scalar/pseudoscalar Four-Fermi operators with
, leaves considerable room for new physics in the
one-particle-irreducible contribution to decays. In this
case, we find that the SD branching ratio can be
enhanced by one order of magnitude with respect to its SM value and the SD
contribution can lie outside of the resonance peaks.Comment: 17 pages, 4 figures; Note added on Schouten identity and 2 references
added; v4: typos in Eqs (8), (44) and erroneous statement on mixing before Eq
(44) fixed. All results and conclusions unchange
Symmetries and Ambiguities in the linear sigma model with light quarks
We investigate the role of undetermined finite contributions generated by
radiative corrections in a linear sigma model with quarks.
Although some of such terms can be absorbed in the renormalization procedure,
one such contribution is left in the expression for the pion decay constant.
This arbitrariness is eliminated by chiral symmetry.Comment: 9 pages. Added references through the text; an author was added due
to an important contribution; corrected typos; the title also was changed.
Submitted to Modern Physics Letter
Sonoluminescing air bubbles rectify argon
The dynamics of single bubble sonoluminescence (SBSL) strongly depends on the
percentage of inert gas within the bubble. We propose a theory for this
dependence, based on a combination of principles from sonochemistry and
hydrodynamic stability. The nitrogen and oxygen dissociation and subsequent
reaction to water soluble gases implies that strongly forced air bubbles
eventually consist of pure argon. Thus it is the partial argon (or any other
inert gas) pressure which is relevant for stability. The theory provides
quantitative explanations for many aspects of SBSL.Comment: 4 page
Infusing Environmental Sustainability into Textile and Apparel Curriculum: Professional Development Needs for a Discipline in Transition
In recent years there is evidence that apparel industry firms are beginning to acknowledge the environmental impacts of their products and processes. For example, the Sustainable Apparel Coalition (SAC) was founded by a group of apparel industry, trade, governmental, and non-profit organizations as a collaborative initiative to reduce the environmental consequences of the soft goods industry (i.e., water use and quality; energy and emissions; waste; chemicals and toxicity) as well as social and labor issues (www.apparelcoalition.org/desired-outcomes). As these and other industry leaders invest in and support change toward greater sustainability, the educational programs that prepare young textile and apparel (TA) professionals must evolve as well. Incorporating environmental sustainability competencies and learning outcomes into textile and apparel curriculum is becoming an imperative
Mechanisms for Stable Sonoluminescence
A gas bubble trapped in water by an oscillating acoustic field is expected to
either shrink or grow on a diffusive timescale, depending on the forcing
strength and the bubble size. At high ambient gas concentration this has long
been observed in experiments. However, recent sonoluminescence experiments show
that in certain circumstances when the ambient gas concentration is low the
bubble can be stable for days. This paper presents mechanisms leading to
stability which predict parameter dependences in agreement with the
sonoluminescence experiments.Comment: 4 pages, 3 figures on request (2 as .ps files
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