1,005 research outputs found
B decays dominated by omega-phi mixing
Recently Belle has established the 90% confidence level (CL) upper limit \b
< 9.4 \times 10^{-7} for the branching ratio for , a
process expected to be suppressed by the Okubo-Zweig-Iizuka (OZI) rule
disfavoring disconnected quark diagrams. We use information on --
mixing to establish likely lower bounds on this and related processes. We find
that the Belle result is about a factor of five above our limit, while other
decays such as and , for which
upper limits have been obtained by BaBar, could be observable with similar
improvements in data. We argue that a significant enhancement of our predicted
decay rates by rescattering is unlikely.Comment: paragraph added, submitted to Physics Letters
CP violation in B meson decays
Recent CP asymmetry measurements in tree-dominated processes, , and in
penguin-dominated decays, , are
interpreted in the framework of the Kobayashi-Maskawa (KM) mechanism of CP
violation. The KM phase emerges as the dominant source of CP violation in
tree-dominated decays, which are beginning to constrain the unitarity triangle
beyond other constraints. Improving precision of CP asymmetry measurements in
penguin-dominated decays may indicate the need for new physics.Comment: Talk presented at the Sixth International Conference on Hyperons,
Charm and Beauty Hadrons, IIT, Chicago, June 27--July 3 200
The Universal Aspect Ratio of Vortices in Rotating Stratifi?ed Flows: Experiments and Observations
We validate a new law for the aspect ratio of vortices in a
rotating, stratified flow, where and are the vertical half-height and
horizontal length scale of the vortices. The aspect ratio depends not only on
the Coriolis parameter f and buoyancy (or Brunt-Vaisala) frequency of
the background flow, but also on the buoyancy frequency within the vortex
and on the Rossby number of the vortex such that . This law for is obeyed precisely by the
exact equilibrium solution of the inviscid Boussinesq equations that we show to
be a useful model of our laboratory vortices. The law is valid for both
cyclones and anticyclones. Our anticyclones are generated by injecting fluid
into a rotating tank filled with linearly-stratified salt water. The vortices
are far from the top and bottom boundaries of the tank, so there is no Ekman
circulation. In one set of experiments, the vortices viscously decay, but as
they do, they continue to obey our law for , which decreases over time.
In a second set of experiments, the vortices are sustained by a slow continuous
injection after they form, so they evolve more slowly and have larger |Ro|, but
they also obey our law for . The law for is not only validated
by our experiments, but is also shown to be consistent with observations of the
aspect ratios of Atlantic meddies and Jupiter's Great Red Spot and Oval BA. The
relationship for is derived and examined numerically in a companion
paper by Hassanzadeh et al. (2012).Comment: Submitted to the Journal of Fluid Mechanics. Also see the companion
paper by Hassanzadeh et al. "The Universal Aspect Ratio of Vortices in
Rotating Stratifi?ed Flows: Theory and Simulation" 201
Origin and fluxes of atmospheric REE entering an ombrotrophic peat bog in Black Forest (SW Germany): Evidence from snow, lichens and mosses
The fate of the Rare Earth Elements (REE) were investigated in different types of archives of atmospheric deposition in the Black Forest, Southern Germany: (1) a 70 cm snow pack collected on the domed part of a raised bog and representing 2 months of snow accumulation, (2) a snow sample collected close to the road about 500 m from the peat bog, (3) two species of lichens and (4) a peat profile representing 400 years of peat accumulation as well as a “preanthropogenic” sample and the living moss layer from the top of the core. REE concentrations in peat are significantly correlated to Ti which is a lithogenic conservative element suggesting that REE are immobile in peat bog environments. Snow, lichens and peat samples show similar PAAS (Post Archean Australian Shale) normalized REE distributions suggesting that the complete atmospheric REE signal is preserved in the peat profile. However, the annual flux of REE accumulated by the peat is ca. 10 times greater than that of the bulk winter flux of REE. This difference probably indicates that the REE concentrations in the snowpack are not representative of the average REE flux over the whole year. Despite the pronounced geological differences between this site (granite host-rock) and a previously studied peat bog in Switzerland (limestone host-rock) similar REE distribution patterns and accumulation rates were found at both sites. Given that both sites confirm an Upper Continental Crust signature, the data suggests both sites are influenced by regional and not local, soil-derived lithogenic aerosols
Enhanced effects on extracting \gamma from untagged B^0 and B_s decays
The weak phase \gamma can be determined using untagged B^0\to DK_S or B_s\to
D\phi, D\eta^{(')} decays. In the past, the small lifetime difference y\equiv
\Delta\Gamma/(2\Gamma) has been neglected in B^0, while the CP violating
parameter \epsilon\equiv 1-|q/p|^2 has been neglected in both B^0-\bar B^0 and
B_s-\bar B_s mixing. We estimate the effect of neglecting y and \epsilon. We
find that in D decays to flavor states this introduces a systematic error,
which is enhanced by a large ratio of Cabibbo-allowed to doubly
Cabibbo-suppressed D decay amplitudes.Comment: one reference added, to be submitted for publication in Physics
Letters
Improving Bounds on Penguin Pollution in B -> pi pi
In the presence of penguin contributions, the indirect CP asymmetry in B0(t)
-> pi+ pi- measures sin(2\alpha + 2\theta), where 2\theta parametrizes the size
of the penguin ``pollution.'' We derive a new upper bound on |2\theta|,
requiring the measurement of of BR(B+ -> pi+ pi0) and an upper bound on B00
\equiv {1\over 2} [BR(B0 -> pi0 pi0) + BR(B0bar -> pi0 pi0)]. The new bound is
stronger than those previously discussed in the literature. We also present a
lower bound on B00. Current data may suggest that it is not very small, in
which case \theta can be determined using a complete isospin analysis.Comment: 10 pages, LaTeX, 3 figures. Abstract modified slightly. Submitted to
Physics Letter
Recent atmospheric Pb deposition at a rural site in southern Germany assessed using a peat core and snowpack, and comparison with other archives
In a peat bog from Black Forest, Southern Germany, the rate of atmospheric Pb accumulation was quantified using a peat core dated by 210Pb and 14C. The most recent Pb accumulation rate (2.5 mg m−2 y−1) is similar to that obtained from a snowpack on the bog surface, which was sampled during the winter 2002 (1 to 4 mg m−2 y−1). The Pb accumulation rates recorded by the peat during the last 25 yr are also in agreement with published values of direct atmospheric fluxes in Black Forest. These values are 50 to 200 times greater than the “natural” average background rate of atmospheric Pb accumulation (20 μg m−2 y−1) obtained using peat samples from the same bog dating from 3300 to 1300 cal. yr B.C. The isotopic composition of Pb was measured in both the modern and ancient peat samples as well as in the snow samples, and clearly shows that recent inputs are dominated by anthropogenic Pb. The chronology and isotopic composition of atmospheric Pb accumulation recorded by the peat from the Black Forest is similar to the chronologies reported earlier using peat cores from various peat bogs as well as herbarium samples of Sphagnum and point to a common Pb source to the region for the past 150 years. In contrast, Pb contamination occurring before 1850 in southwestern Germany, differs from the record published for Switzerland mainly due to the mining activity in Black Forest. Taken together, the results show that peat cores from ombrotrophic bogs can yield accurate records of atmospheric Pb deposition, provided that the cores are carefully collected, handled, prepared, and analysed using appropriate methods
Implications for CP asymmetries of improved data on
The decay , dominated by a penguin amplitude,
holds the potential for exhibiting new physics in this amplitude. In the pure
QCD penguin limit one expects \ckp = 0 and \skp = \sin 2 \beta for the
coefficients of and in the time-dependent
CP asymmetry. Small non-penguin contributions lead to corrections to these
expressions which are calculated in terms of isospin-related rates
and asymmetries, using information about strong phases from experiment. We
study the prospects for incisive tests of the Standard Model through
examination of these corrections. We update a prediction \ckp=0.15\pm 0.04,
pointing out the sensitivity of a prediction \skp\approx 1 to the measured
branching ratio for and to other observables.Comment: Note added, to be published in Physics Letters
Light dark matter in the singlet-extended MSSM
We discuss the possibility of light dark matter in a general singlet
extension of the MSSM. Singlino LSPs with masses of a few GeV can explain the
signals reported by the CRESST, CoGeNT and possibly also DAMA experiments. The
interactions between singlinos and nuclei are mediated by a scalar whose
properties coincide with those of the SM Higgs up to two crucial differences:
the scalar has a mass of a few GeV and its interaction strengths are suppressed
by a universal factor. We show that such a scalar can be consistent with
current experimental constraints, and that annihilation of singlinos into such
scalars in the early universe can naturally lead to a relic abundance
consistent with the observed density of cold dark matter.Comment: 11 pages, 3 figure
Lattice gauge theory: A retrospective
I discuss some of the historical circumstances that drove us to use the
lattice as a non-perturbative regulator. This approach has had immense success,
convincingly demonstrating quark confinement and obtaining crucial properties
of the strong interactions from first principles. I wrap up with some
challenges for the future.Comment: Lattice 2000 (Plenary), 9 pages, 7 figure
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