34,823 research outputs found
Complementarity of Semileptonic to and Decays in the Standard Model with Fourth Generation
The decays are
analyzed in the Standard Model extended to fourth generation of quarks (SM4).
The decay rate, forward-backward asymmetry, lepton polarization asymmetries and
the helicity fractions of the final state meson are obtained
using the form factors calculated in the light cone sum rules (LCSR) approach.
We have utilized the constraints on different fourth generation parameters
obtained from the experimental information on , and decays and from
the electroweak precision data to explore their impact on the decay. We find that the values of above mentioned
physical observables deviate deviate significantly from their minimal SM
predications. We also identify a number of correlations between various
observables in and decays. Therefore a combined analysis of these two
decays will compliment each other in the searches of SM4 effects in flavor
physics.Comment: 28 pages, 12 figure
Detection of Minimum-Ionizing Particles and Nuclear Counter Effect with Pure BGO and BSO Crystals with Photodiode Read-out
Long BGO (Bismuth Germanate) and BSO (Bismuth Silicate) crystals coupled with
silicon photodiodes have been used to detect minimum-ionizing particles(MIP).
With a low noise amplifier customized for this purpose, the crystals can detect
MIPs with an excellent signal-to-noise ratio. The NCE(Nuclear Counter Effect}
is also clearly observed and measured. Effect of full and partial wrapping of a
reflector around the crystal on light collection is also studied.Comment: 18 pages, including 5 figures; LaTeX and EP
The development of the Silurian trilobite Aulacopleura koninckii reconstructed by applying inferred growth and segmentation dynamics: A case study in paleo-evo-devo
Fossilized growth series provide rare glimpses into the development of ancient organisms, illustrating descriptively how size and shape changed through ontogeny. Occasionally fossil preservation is such that it is feasible to test alternative possibilities about how ancient development was regulated. Here we apply inferred developmental parameters pertaining to size, shape, and segmentation in the abundant and well-preserved 429 Myr old trilobite Aulacopleura koninckii that we have investigated previously to reconstruct the post-embryonic ontogeny of this ancient arthropod. Our published morphometric analyses associated with model testing have shown that: specification of the adult number of trunk segments (polymorphic in this species) was determined precociously in ontogeny; that growth regulation was targeted (i.e., compensatory), such that each developmental stage exhibited comparable variance in size and shape; and that growth gradients operating along the main body axis, both during juvenile and adult ontogeny, resulted from a form of growth control based on positional specification. While such developmental features are common among extant organisms, our results represent the oldest evidence for them within Metazoa. Herein, the novel reconstruction of the development of Aulacopleura koninckii permits visualization of patterns of relative and absolute growth and segmentation as never before possible for a fossilized arthropod ontogeny. By conducting morphometric analysis of appropriate data sets it is thus possible to move beyond descriptive ontogenetic studies and to address questions of high interest for evolutionary developmental biology using data from fossils, which can help elucidate both how developmental processes themselves evolve and how they affect the evolution of organismal body patterning. By extending similar analyses to other cases of exceptional preservation of fossilized ontogeny, we can anticipate beginning to realize the research program of “paleo-evo-devo.
Implications for and Modes from Observed Large
The unexpectedly large branching ratios for decays
could be of gluonic origin. We study the implications for and , where is the pseudoscalar glueball. In the
mechanism proposed by Fritzsch, large branching ratios are predicted for these
modes. The rate is barely within the experimental limit, and
, could be at the 0.1% and 1% level, respectively. Smaller but
less definite results are found for the mechanism of via the
gluon anomaly.Comment: 11 pages, revtex, no fig
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