353 research outputs found
Collecting data on leisure travel: The link between leisure contacts and social interactions
The aim of a new survey project is to collect data on the link between leisure contacts and leisure activities. The paper introduces briefly into former studies that applied the methods of social network analysis in transport planning. Using these projects as starting points the methodology and background of the new project are presented in detail. This is followed by first descriptive analyses checking how representative the data are for the Swiss population. The paper finishes by giving an outlook on further work and next steps to analyze the data
Hadroproduction of the Chi1 and Chi2 States of Charmonium in 800 GeV/c Proton-Silicon Interactions
The cross sections for the hadroproduction of the Chi1 and Chi2 states of
charmonium in proton-silicon collisions at sqrt{s}=38.8 GeV have been measured
in Fermilab fixed target Experiment 771. The Chi states were observed via their
radiative decay to J/psi+gamma, where the photon converted to e+e- in the
material of the spectrometer. The measured values for the Chi1 and Chi2 cross
sections for x_F>0 are 263+-69(stat)+-32(syst) and 498+-143(stat)+-67(syst) nb
per nucleon respectively. The resulting sigma(Chi1}/sigma(Chi2) ratio of
0.53+-0.20(stat)+-0.07(syst), although somewhat larger than most theoretical
expectations, can be accomodated by the latest theoretical estimates.Comment: 4 pages, 4 figure
Interferometric imaging with the 32 element Murchison Wide-field Array
The Murchison Wide-field Array (MWA) is a low frequency radio telescope,
currently under construction, intended to search for the spectral signature of
the epoch of re-ionisation (EOR) and to probe the structure of the solar
corona. Sited in Western Australia, the full MWA will comprise 8192 dipoles
grouped into 512 tiles, and be capable of imaging the sky south of 40 degree
declination, from 80 MHz to 300 MHz with an instantaneous field of view that is
tens of degrees wide and a resolution of a few arcminutes. A 32-station
prototype of the MWA has been recently commissioned and a set of observations
taken that exercise the whole acquisition and processing pipeline. We present
Stokes I, Q, and U images from two ~4 hour integrations of a field 20 degrees
wide centered on Pictoris A. These images demonstrate the capacity and
stability of a real-time calibration and imaging technique employing the
weighted addition of warped snapshots to counter extreme wide field imaging
distortions.Comment: Accepted for publication in PASP. This is the draft before journal
typesetting corrections and proofs so does contain formatting and journal
style errors, also has with lower quality figures for space requirement
Virus Replication as a Phenotypic Version of Polynucleotide Evolution
In this paper we revisit and adapt to viral evolution an approach based on
the theory of branching process advanced by Demetrius, Schuster and Sigmund
("Polynucleotide evolution and branching processes", Bull. Math. Biol. 46
(1985) 239-262), in their study of polynucleotide evolution. By taking into
account beneficial effects we obtain a non-trivial multivariate generalization
of their single-type branching process model. Perturbative techniques allows us
to obtain analytical asymptotic expressions for the main global parameters of
the model which lead to the following rigorous results: (i) a new criterion for
"no sure extinction", (ii) a generalization and proof, for this particular
class of models, of the lethal mutagenesis criterion proposed by Bull,
Sanju\'an and Wilke ("Theory of lethal mutagenesis for viruses", J. Virology 18
(2007) 2930-2939), (iii) a new proposal for the notion of relaxation time with
a quantitative prescription for its evaluation, (iv) the quantitative
description of the evolution of the expected values in in four distinct
"stages": extinction threshold, lethal mutagenesis, stationary "equilibrium"
and transient. Finally, based on these quantitative results we are able to draw
some qualitative conclusions.Comment: 23 pages, 1 figure, 2 tables. arXiv admin note: substantial text
overlap with arXiv:1110.336
The Murchison Widefield Array
It is shown that the excellent Murchison Radio-astronomy Observatory site
allows the Murchison Widefield Array to employ a simple RFI blanking scheme and
still calibrate visibilities and form images in the FM radio band. The
techniques described are running autonomously in our calibration and imaging
software, which is currently being used to process an FM-band survey of the
entire southern sky.Comment: Accepted for publication in Proceedings of Science [PoS(RFI2010)016].
6 pages and 3 figures. Presented at RFI2010, the Third Workshop on RFI
Mitigation in Radio Astronomy, 29-31 March 2010, Groningen, The Netherland
Search for charged Higgs decays of the top quark using hadronic tau decays
We present the result of a search for charged Higgs decays of the top quark,
produced in collisions at 1.8 TeV. When the charged
Higgs is heavy and decays to a tau lepton, which subsequently decays
hadronically, the resulting events have a unique signature: large missing
transverse energy and the low-charged-multiplicity tau. Data collected in the
period 1992-1993 at the Collider Detector at Fermilab, corresponding to
18.70.7~pb, exclude new regions of combined top quark and charged
Higgs mass, in extensions to the standard model with two Higgs doublets.Comment: uuencoded, gzipped tar file of LaTeX and 6 Postscript figures; 11 pp;
submitted to Phys. Rev.
Inclusive jet cross section in collisions at TeV
The inclusive jet differential cross section has been measured for jet
transverse energies, , from 15 to 440 GeV, in the pseudorapidity region
0.10.7. The results are based on 19.5 pb of data
collected by the CDF collaboration at the Fermilab Tevatron collider. The data
are compared with QCD predictions for various sets of parton distribution
functions. The cross section for jets with GeV is significantly
higher than current predictions based on O() perturbative QCD
calculations. Various possible explanations for the high- excess are
discussed.Comment: 8 pages with 2 eps uu-encoded figures Submitted to Physical Review
Letter
Measurement of the lepton charge asymmetry in W-boson decays produced in p-pbar collisions
We describe a measurement of the charge asymmetry of leptons from W boson
decays in the rapidity range 0 enu, munu events from
110+/-7 pb^{-1}of data collected by the CDF detector during 1992-95. The
asymmetry data constrain the ratio of d and u quark momentum distributions in
the proton over the x range of 0.006 to 0.34 at Q2 \approx M_W^2. The asymmetry
predictions that use parton distribution functions obtained from previously
published CDF data in the central rapidity region (0.0<|y_l|<1.1) do not agree
with the new data in the large rapidity region (|y_l|>1.1).Comment: 13 pages, 3 tables, 1 figur
Measurement of Dijet Angular Distributions at CDF
We have used 106 pb^-1 of data collected in proton-antiproton collisions at
sqrt(s)=1.8 TeV by the Collider Detector at Fermilab to measure jet angular
distributions in events with two jets in the final state. The angular
distributions agree with next to leading order (NLO) predictions of Quantum
Chromodynamics (QCD) in all dijet invariant mass regions. The data exclude at
95% confidence level (CL) a model of quark substructure in which only up and
down quarks are composite and the contact interaction scale is Lambda_ud(+) <
1.6 TeV or Lambda_ud(-) < 1.4 TeV. For a model in which all quarks are
composite the excluded regions are Lambda(+) < 1.8 TeV and Lambda(-) < 1. 6
TeV.Comment: 16 pages, 2 figures, 2 tables, LaTex, using epsf.sty. Submitted to
Physical Review Letters on September 17, 1996. Postscript file of full paper
available at http://www-cdf.fnal.gov/physics/pub96/cdf3773_dijet_angle_prl.p
Observation of Hadronic W Decays in t-tbar Events with the Collider Detector at Fermilab
We observe hadronic W decays in t-tbar -> W (-> l nu) + >= 4 jet events using
a 109 pb-1 data sample of p-pbar collisions at sqrt{s} = 1.8 TeV collected with
the Collider Detector at Fermilab (CDF). A peak in the dijet invariant mass
distribution is obtained that is consistent with W decay and inconsistent with
the background prediction by 3.3 standard deviations. From this peak we measure
the W mass to be 77.2 +- 4.6 (stat+syst) GeV/c^2. This result demonstrates the
presence of two W bosons in t-tbar candidates in the W (-> l nu) + >= 4 jet
channel.Comment: 20 pages, 4 figures, submitted to PR
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