136 research outputs found
First Observation of the Rare Decay Mode K-long -> e+ e-
In an experiment designed to search for and study very rare two-body decay
modes of the K-long, we have observed four examples of the decay K-long -> e+
e-, where the expected background is 0.17+-0.10 events. This observation
translates into a branching fraction of 8.7^{+5.7}_{-4.1} X 10^{-12},
consistent with recent theoretical predictions. This result represents by far
the smallest branching fraction yet measured in particle physics.Comment: 9 pages, 3 figure
Second Generation Leptoquark Search in p\bar{p} Collisions at = 1.8 TeV
We report on a search for second generation leptoquarks with the D\O\
detector at the Fermilab Tevatron collider at = 1.8 TeV.
This search is based on 12.7 pb of data. Second generation leptoquarks
are assumed to be produced in pairs and to decay into a muon and quark with
branching ratio or to neutrino and quark with branching ratio
. We obtain cross section times branching ratio limits as a function
of leptoquark mass and set a lower limit on the leptoquark mass of 111
GeV/c for and 89 GeV/c for at the 95%\
confidence level.Comment: 18 pages, FERMILAB-PUB-95/185-
Jet Production via Strongly-Interacting Color-Singlet Exchange in Collisions
A study of the particle multiplicity between jets with large rapidity
separation has been performed using the D{\O}detector at the Fermilab Tevatron
Collider operating at TeV. A significant excess of
low-multiplicity events is observed above the expectation for color-exchange
processes. The measured fractional excess is , which is consistent with a strongly-interacting
color-singlet (colorless) exchange process and cannot be explained by
electroweak exchange alone. A lower limit of 0.80% (95% C.L.) is obtained on
the fraction of dijet events with color-singlet exchange, independent of the
rapidity gap survival probability.Comment: 15 pages (REVTeX), 3 PS figs (uuencoded/tar compressed, epsf.sty)
Complete postscript available at http://d0sgi0.fnal.gov/d0pubs/journals.html
Submitted to Physical Review Letter
Measurement of the and Couplings in Collisions at TeV
We have directly measured the ZZ-gamma and Z-gamma-gamma couplings by
studying p pbar --> l+ l- gamma + X, (l = e, mu) events at the CM energy of
1.813.3 pb^-1)
for the electron (muon) channel, yields the following 95% confidence level
limits on the anomalous CP-conserving ZZ-gamma couplings: -1.9 < h^Z_30 < 1.8
(h^Z_40 = 0), and -0.5 < h^Z_40 < 0.5 (h^Z_30 = 0), for a form-factor scale
Lambda = 500 GeV. Limits for the Z-gamma-gamma$ couplings and CP-violating
couplings are also discussed.Comment: 11 pages, 1 table, and 3 figure
Measurement of the gauge boson couplings in Collisions at TeV
The gauge boson couplings were measured using () events at TeV observed with the
{D\O} detector at the Fermilab Tevatron Collider. The signal, obtained from the
data corresponding to an integrated luminosity of , agrees
well with the Standard Model prediction. A fit to the photon transverse energy
spectrum yields limits at the 95% confidence level on the CP--conserving
anomalous coupling parameters of ( = 0) and
( = 0).Comment: 16pages (14pages + 2figure pages) Uses ReVTEX Two postscript files
for figures will follow immediatel
W and Z Boson Production in PbarP Collisions at Sqrt(s)=1.8 TeV
The inclusive cross sections times leptonic branching ratios for W and Z
boson production in PbarP collisions at Sqrt(s)=1.8 TeV were measured using the
D0 detector at the Fermilab Tevatron collider:
Sigma_W*B(W->e, nu) = 2.36 +/- 0.07 +/- 0.13 nb,
Sigma_W*B(W->mu,nu) = 2.09 +/- 0.23 +/- 0.11 nb,
Sigma_Z*B(Z-> e, e) = 0.218 +/- 0.011 +/- 0.012 nb,
Sigma_Z*B(Z->mu,mu) = 0.178 +/- 0.030 +/- 0.009 nb.
The first error is the combined statistical and systematic uncertainty, and
the second reflects the uncertainty in the luminosity. For the combined
electron and muon analyses we find:
[Sigma_W*B(W->l,nu)]/[Sigma_Z*B(Z->l,l)] = 10.90 +/- 0.49.
Assuming Standard Model couplings, this result is used to determine the width
of the W boson:
Gamma(W) = 2.044 +/- 0.093 GeV.Comment: 11 pages (including 2 figure pages), in REVTEX. Two PostScript
figures are appended in a UUencoded fil
Urban Biodiversity and Landscape Ecology: Patterns, Processes and Planning
Effective planning for biodiversity in cities and towns is increasingly important as urban areas and their human populations grow, both to achieve conservation goals and because ecological communities support services on which humans depend. Landscape ecology provides important frameworks for understanding and conserving urban biodiversity both within cities and considering whole cities in their regional context, and has played an important role in the development of a substantial and expanding body of knowledge about urban landscapes and communities. Characteristics of the whole city including size, overall amount of green space, age and regional context are important considerations for understanding and planning for biotic assemblages at the scale of entire cities, but have received relatively little research attention. Studies of biodiversity within cities are more abundant and show that longstanding principles regarding how patch size, configuration and composition influence biodiversity apply to urban areas as they do in other habitats. However, the fine spatial scales at which urban areas are fragmented and the altered temporal dynamics compared to non-urban areas indicate a need to apply hierarchical multi-scalar landscape ecology models to urban environments. Transferring results from landscape-scale urban biodiversity research into planning remains challenging, not least because of the requirements for urban green space to provide multiple functions. An increasing array of tools is available to meet this challenge and increasingly requires ecologists to work with planners to address biodiversity challenges. Biodiversity conservation and enhancement is just one strand in urban planning, but is increasingly important in a rapidly urbanising world
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