6,561 research outputs found
Neutral Kaon Production From One-prong Tau Decays
The branching ratio for the decay of the tau lepton into at least one neutral kaon meson was measured from a sample of 201850 tau decays recorded by the OPAL detector from 1991 to 1995. The selection yielded 305 t-→X- K0 Lnt candidates (the charge conjugate is implied for all reactions), where X- is any charged hadron possibly accompanied by a neutral particle, giving a branching ratio of B&parl0;t-→X- K 0Lnt&parr0;=&parl0; 10.01±0.79±0.64&parr0;×10- 3, where the first error is statistical and the second is systematic. From the sample of t-→X- K0 Lnt decays, three exclusive decay modes were identified and their branching ratios were measured to be B&parl0;t-→p- K0nt&parr0; =9.1±0.9± 0.6×10-3, B&parl0;t-→p- K0≥1p0n t&parr0;=3.6± 1.3±1.0×10-3, B&parl0;t-→K- K 0≥0p0nt&parr0; =3.3±0.9±0.7 ×10-3, where the first error is statistical and the second is systematic. The t- →K*892 -nt branching ratio was determined to be 0.0140 ± 0.0013 using the t- →p-K 0nt branching ratio and assuming isospin conservation. Finally, the ratio of the non-strange decay constant fr to the strange decay constant fK* was measured to be 0.93 ± 0.05
Activities of \gamma-ray emitting isotopes in rainwater from Greater Sudbury, Canada following the Fukushima incident
We report the activity measured in rainwater samples collected in the Greater
Sudbury area of eastern Canada on 3, 16, 20, and 26 April 2011. The samples
were gamma-ray counted in a germanium detector and the isotopes 131I and 137Cs,
produced by the fission of 235U, and 134Cs, produced by neutron capture on
133Cs, were observed at elevated levels compared to a reference sample of
ice-water. These elevated activities are ascribed to the accident at the
Fukushima Dai-ichi nuclear reactor complex in Japan that followed the 11 March
earthquake and tsunami. The activity levels observed at no time presented
health concerns.Comment: 4 pages, 8 figure
A mapping approach to synchronization in the "Zajfman trap". II: the observed bunch
We extend a recently introduced mapping model, which explains the bunching
phenomenon in an ion beam resonator for two ions [Geyer, Tannor, J. Phys. B 37
(2004) 73], to describe the dynamics of the whole ion bunch. We calculate the
time delay of the ions from a model of the bunch geometry and find that the
bunch takes on a spherical form at the turning points in the electrostatic
mirrors. From this condition we derive how the observed bunch length depends on
the experimental parameters. We give an interpretation of the criteria for the
existence of the bunch, which were derived from the experimental observations
by Pedersen et al [Pedersen etal, Phys. Rev. A 65 042704].Comment: 25 pages, 6 figures; added new section 5 and clarified text;
submitted to J. Phys.
Fermionic Symmetries: Extension of the two to one Relationship Between the Spectra of Even-Even and Neighbouring Odd mass Nuclei
In the single j shell there is a two to one relationship between the spectra
of certain even-even and neighbouring odd mass nuclei e.g. the calculated
energy levels of J=0^+ states in ^{44}Ti are at twice the energies of
corresponding levels in ^{43}Ti(^{43}Sc) with J=j=7/2. Here an approximate
extension of the relationship is made by adopting a truncated seniority scheme
i.e. for ^{46}Ti and ^{45}Sc we get the relationship if we do not allow the
seniority v=4 states to mix with the v=0 and v=2 states. Better than that, we
get very close to the two to one relationship if seniority v=4 states are
admixed perturbatively. In addition, it is shown that the higher isospin states
do not contain seniority 4 admixtures.Comment: 11 pages, RevTex file and no figures, typos added, references changed
and changed content
Isoscalar monopole excitations in O: -cluster states at low energy and mean-field-type states at higher energy
Isoscalar monopole strength function in O up to MeV is
discussed. We found that the fine structures at the low energy region up to
MeV in the experimental monopole strength function obtained
by the O reaction can be rather satisfactorily
reproduced within the framework of the cluster model, while the gross
three bump structures observed at the higher energy region ( MeV) look likely to be approximately reconciled by the mean-field
calculations such as RPA and QRPA. In this paper, it is emphasized that two
different types of monopole excitations exist in O; one is the monopole
excitation to cluster states which is dominant in the lower energy part ( MeV), and the other is the monopole excitation of the mean-field
type such as one-particle one-hole () which {is attributed} mainly to the
higher energy part ( MeV). It is found that this
character of the monopole excitations originates from the fact that the ground
state of O with the dominant doubly closed shell structure has a duality
of the mean-field-type {as well as} -clustering {character}. This dual
nature of the ground state seems to be a common feature in light nuclei.Comment: 35 pages, 5 figure
Wrist-worn physical activity trackers progressively underestimate steps with increasing walking speeds
Generalised -manifolds
We define new Riemannian structures on 7-manifolds by a differential form of
mixed degree which is the critical point of a (possibly constrained)
variational problem over a fixed cohomology class. The unconstrained critical
points generalise the notion of a manifold of holonomy , while the
constrained ones give rise to a new geometry without a classical counterpart.
We characterise these structures by the means of spinors and show the
integrability conditions to be equivalent to the supersymmetry equations on
spinors in supergravity theory of type IIA/B with bosonic background fields. In
particular, this geometry can be described by two linear metric connections
with skew torsion. Finally, we construct explicit examples by using the device
of T-duality.Comment: 27 pages. v2: references added. v3: wrong argument (Theorem 3.3) and
example (Section 4.1) removed, further examples added, notation simplified,
all comments appreciated. v4:computation of Ricci tensor corrected, various
minor changes, final version of the paper to appear in Comm. Math. Phy
Nitrogen and phosphorus limitation of oceanic microbial growth during spring in the Gulf of Aqaba
Bioassay experiments were performed to identify how growth of key groups within the microbial community was simultaneously limited by nutrient (nitrogen and phosphorus) availability during spring in the Gulf of Aqaba's oceanic waters. Measurements of chlorophyll a (chl a) concentration and fast repetition rate (FRR) fluorescence generally demonstrated that growth of obligate phototrophic phytoplankton was co-limited by N and P and growth of facultative aerobic anoxygenic photoheterotropic (AAP) bacteria was limited by N. Phytoplankton exhibited an increase in chl a biomass over 24 to 48 h upon relief of nutrient limitation. This response coincided with an increase in photosystem II (PSII) photochemical efficiency (F v /F m), but was preceded (within 24 h) by a decrease in effective absorption crosssection (σPSII) and electron turnover time (τ). A similar response for τ and bacterio-chl a was observed for the AAPs. Consistent with the up-regulation of PSII activity with FRR fluorescence were observations of newly synthesized PSII reaction centers via low temperature (77K) fluorescence spectroscopy for addition of N (and N + P). Flow cytometry revealed that the chl a and thus FRR fluorescence responses were partly driven by the picophytoplankton (æ10 μm) community, and in particular Synechococcus. Productivity of obligate heterotrophic bacteria exhibited the greatest increase in response to a natural (deep water) treatment, but only a small increase in response to N and P addition, demonstrating the importance of additional substrates (most likely dissolved organic carbon) in moderating the heterotrophs. These data support previous observations that the microbial community response (autotrophy relative to heterotrophy) is critically dependent upon the nature of transient nutrient enrichment. © Inter-Research 2009
Spin-Orbit Pendulum: the Microscopic Stern-Gerlach Effect
The motion of a particle with a spin in spherical harmonic oscillator
potential with spin-orbit interaction is studied. We have focus our attention
on spatial motion of wave packets, giving a description complementary to motion
of spin discussed already in [1]. The particular initial conditions studied
here lead to the most transparent formulas and can be treated analytically. A
strong analogy with the Stern-Gerlach experiment is suggested. [1] R.Arvieu and
P.Rozmej, Phys.Rev.A50 (1994) 4376.Comment: 4 pages, LaTeX (precisely RevTeX), attached 4 complicated Postscript
figures , Paper submitted to Phys.Rev.
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