286 research outputs found
Simulations of cubic-tetragonal ferroelastics
We study domain patterns in cubic-tetragonal ferroelastics by solving
numerically equations of motion derived from a Landau model of the phase
transition, including dissipative stresses. Our system sizes, of up to 256^3
points, are large enough to reveal many structures observed experimentally.
Most patterns found at late stages in the relaxation are multiply banded; all
three tetragonal variants appear, but inequivalently. Two of the variants form
broad primary bands; the third intrudes into the others to form narrow
secondary bands with the hosts. On colliding with walls between the primary
variants, the third either terminates or forms a chevron. The multipy banded
patterns, with the two domain sizes, the chevrons and the terminations, are
seen in the microscopy of zirconia and other cubic-tetragonal ferroelastics. We
examine also transient structures obtained much earlier in the relaxation;
these show the above features and others also observed in experiment.Comment: 7 pages, 6 colour figures not embedded in text. Major revisions in
conten
Co-evolution, opportunity seeking and institutional change: Entrepreneurship and the Indian telecommunications industry 1923-2009
"This is an Author's Original Manuscript of an article submitted for consideration in Business History [copyright Taylor & Francis]; Business History is available online at http://www.tandfonline.com/." 10.1080/00076791.2012.687538In this paper, we demonstrate the importance for entrepreneurship of historical contexts and processes, and the co-evolution of institutions, practices, discourses and cultural norms. Drawing on discourse and institutional theories, we develop a model of the entrepreneurial field, and apply this in analysing the rise to global prominence of the Indian telecommunications industry. We draw on entrepreneurial life histories to show how various discourses and discursive processes ultimately worked to generate change and the creation of new business opportunities. We propose that entrepreneurship involves more than individual acts of business creation, but also implies collective endeavours to shape the future direction of the entrepreneurial field
Search for single top quarks in the tau+jets channel using 4.8 fb of collision data
We present the first direct search for single top quark production using tau
leptons. The search is based on 4.8 fb of integrated luminosity
collected in collisions at =1.96 TeV with the D0 detector
at the Fermilab Tevatron Collider. We select events with a final state
including an isolated tau lepton, missing transverse energy, two or three jets,
one or two of them tagged. We use a multivariate technique to discriminate
signal from background. The number of events observed in data in this final
state is consistent with the signal plus background expectation. We set in the
tau+jets channel an upper limit on the single top quark cross section of
\TauLimObs pb at the 95% C.L. This measurement allows a gain of 4% in expected
sensitivity for the observation of single top production when combining it with
electron+jets and muon+jets channels already published by the D0 collaboration
with 2.3 fb of data. We measure a combined cross section of
\SuperCombineXSall pb, which is the most precise measurement to date.Comment: 12 pages, 5 figure
Search for the standard model Higgs boson in tau final states
We present a search for the standard model Higgs boson using hadronically
decaying tau leptons, in 1 inverse femtobarn of data collected with the D0
detector at the Fermilab Tevatron ppbar collider. We select two final states:
tau plus missing transverse energy and b jets, and tau+ tau- plus jets. These
final states are sensitive to a combination of associated W/Z boson plus Higgs
boson, vector boson fusion and gluon-gluon fusion production processes. The
observed ratio of the combined limit on the Higgs production cross section at
the 95% C.L. to the standard model expectation is 29 for a Higgs boson mass of
115 GeV.Comment: publication versio
Measurement of the p-pbar -> Wgamma + X cross section at sqrt(s) = 1.96 TeV and WWgamma anomalous coupling limits
The WWgamma triple gauge boson coupling parameters are studied using p-pbar
-> l nu gamma + X (l = e,mu) events at sqrt(s) = 1.96 TeV. The data were
collected with the DO detector from an integrated luminosity of 162 pb^{-1}
delivered by the Fermilab Tevatron Collider. The cross section times branching
fraction for p-pbar -> W(gamma) + X -> l nu gamma + X with E_T^{gamma} > 8 GeV
and Delta R_{l gamma} > 0.7 is 14.8 +/- 1.6 (stat) +/- 1.0 (syst) +/- 1.0 (lum)
pb. The one-dimensional 95% confidence level limits on anomalous couplings are
-0.88 < Delta kappa_{gamma} < 0.96 and -0.20 < lambda_{gamma} < 0.20.Comment: Submitted to Phys. Rev. D Rapid Communication
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s} = 1.96 TeV using Kinematic Characteristics of Lepton + Jets Events
We present a measurement of the top quark pair ttbar production cross section
in ppbar collisions at a center-of-mass energy of 1.96 TeV using 230 pb**{-1}
of data collected by the DO detector at the Fermilab Tevatron Collider. We
select events with one charged lepton (electron or muon), large missing
transverse energy, and at least four jets, and extract the ttbar content of the
sample based on the kinematic characteristics of the events. For a top quark
mass of 175 GeV, we measure sigma(ttbar) = 6.7 {+1.4-1.3} (stat) {+1.6- 1.1}
(syst) +/-0.4 (lumi) pb, in good agreement with the standard model prediction.Comment: submitted to Phys.Rev.Let
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Lepton + Jets Events with Lifetime b-tagging
We present a measurement of the top quark pair () production cross
section () in collisions at TeV
using 230 pb of data collected by the D0 experiment at the Fermilab
Tevatron Collider. We select events with one charged lepton (electron or muon),
missing transverse energy, and jets in the final state. We employ
lifetime-based b-jet identification techniques to further enhance the
purity of the selected sample. For a top quark mass of 175 GeV, we
measure pb, in
agreement with the standard model expectation.Comment: 7 pages, 2 figures, 3 tables Submitted to Phys.Rev.Let
Search for W' bosons decaying to an electron and a neutrino with the D0 detector
This Letter describes the search for a new heavy charged gauge boson W'
decaying into an electron and a neutrino. The data were collected with the D0
detector at the Fermilab Tevatron proton-antiproton Collider at a
center-of-mass energy of 1.96 TeV, and correspond to an integrated luminosity
of about 1 inverse femtobarn. Lacking any significant excess in the data in
comparison with known processes, an upper limit is set on the production cross
section times branching fraction, and a W' boson with mass below 1.00 TeV can
be excluded at the 95% C.L., assuming standard-model-like couplings to
fermions. This result significantly improves upon previous limits, and is the
most stringent to date.Comment: submitted to Phys. Rev. Let
Search for a scalar or vector particle decaying into Zgamma in ppbar collisions at sqrt(s) = 1.96 TeV
We present a search for a narrow scalar or vector resonance decaying into
Zgamma with a subsequent Z decay into a pair of electrons or muons. The data
for this search were collected with the D0 detector at the Fermilab Tevatron
ppbar collider at a center of mass energy sqrt(s) = 1.96 TeV. Using 1.1 (1.0)
fb-1 of data, we observe 49 (50) candidate events in the electron (muon)
channel, in good agreement with the standard model prediction. From the
combination of both channels, we derive 95% C.L. upper limits on the cross
section times branching fraction (sigma x B) into Zgamma. These limits range
from 0.19 (0.20) pb for a scalar (vector) resonance mass of 600 GeV/c^2 to 2.5
(3.1) pb for a mass of 140 GeV/c^2.Comment: Published by Phys. Lett.
Measurement of the Isolated Photon Cross Section in p-pbar Collisions at sqrt{s}=1.96 TeV
The cross section for the inclusive production of isolated photons has been
measured in p anti-p collisions at sqrt{s}=1.96 TeV with the D0 detector at the
Fermilab Tevatron Collider. The photons span transverse momenta 23 to 300 GeV
and have pseudorapidity |eta|<0.9. The cross section is compared with the
results from two next-to-leading order perturbative QCD calculations. The
theoretical predictions agree with the measurement within uncertainties.Comment: 7 pages, 5 figures, submitted to Phys.Lett.
- âŠ