71 research outputs found
Dopaminergic modulation of appetitive trace conditioning: the role of D1 receptors in medial prefrontal cortex
Rationale: Trace conditioning may provide a behavioural model suitable to examine the maintenance of ‘on line’ information and its underlying neural substrates.
Objectives: Experiment la was run to establish trace conditioning in a shortened procedure which would be suitable to test the effects of dopamine (DA) D1 receptor agents administered by microinjection directly into the brain. Experiment lb examined the effects of the DA D1 agonist SKF81297 and the DA D1 antagonist SCH23390 following systemic administration in pre-trained animals. Experiment 2 went on to test the effects of systemically administered SKF81297 on the acquisition of trace conditioning. In experiment 3, SKF81297 was administered directly in prelimbic (PL) and infralimbic (IL) sub-regions of medial prefrontal cortex (mPFC) to compare the role of different mPFC sub-regions.
Results: Whilst treatment with SCH23390 impaired motor responding and/or motivation, SKF81297 had relatively little effect in the pre-trained animals tested in experiment 1b. However, systemic SKF81297 depressed the acquisition function at the 2-s trace interval in experiment 2. Similarly, in experiment 3, SKF81297 (0.1 μg in 1.0 μl) microinjected into either PL or IL mPFC impaired appetitive conditioning at the 2-s trace interval.
Conclusions: Impaired trace conditioning under SKF81297 is likely to be mediated in part (but not exclusively) within the IL and PL mPFC sub-regions. The finding that trace conditioning was impaired rather than enhanced under SKF81297 provides further evidence for the inverse U-function which has been suggested to be characteristic of mPFC DA function
Search for New Physics in e mu X Data at D0 Using Sleuth: A Quasi-Model-Independent Search Strategy for New Physics
We present a quasi-model-independent search for the physics responsible for
electroweak symmetry breaking. We define final states to be studied, and
construct a rule that identifies a set of relevant variables for any particular
final state. A new algorithm ("Sleuth") searches for regions of excess in those
variables and quantifies the significance of any detected excess. After
demonstrating the sensitivity of the method, we apply it to the semi-inclusive
channel e mu X collected in 108 pb^-1 of ppbar collisions at sqrt(s) = 1.8 TeV
at the D0 experiment during 1992-1996 at the Fermilab Tevatron. We find no
evidence of new high p_T physics in this sample.Comment: 23 pages, 12 figures. Submitted to Physical Review
Ratio of the Isolated Photon Cross Sections at \sqrt{s} = 630 and 1800 GeV
The inclusive cross section for production of isolated photons has been
measured in \pbarp collisions at GeV with the \D0 detector at
the Fermilab Tevatron Collider. The photons span a transverse energy ()
range from 7-49 GeV and have pseudorapidity . This measurement is
combined with to previous \D0 result at GeV to form a ratio
of the cross sections. Comparison of next-to-leading order QCD with the
measured cross section at 630 GeV and ratio of cross sections show satisfactory
agreement in most of the range.Comment: 7 pages. Published in Phys. Rev. Lett. 87, 251805, (2001
Quasi-model-independent search for new high physics at D0
We apply a quasi-model-independent strategy ("Sleuth") to search for new high p_T physics in approximately 100 pb^-1 of ppbar collisions at sqrt(s) = 1.8 TeV collected by the DZero experiment during 1992-1996 at the Fermilab Tevatron. We systematically analyze many exclusive final states and demonstrate sensitivity to a variety of models predicting new phenomena at the electroweak scale. No evidence of new high p_T physics is observed
Search for single top quark production at D0 using neural networks
We present a search for electroweak production of single top quarks in ~90 pb^-1 of data collected with the DZero detector at the Fermilab Tevatron collider. Using arrays of neural networks to separate signals from backgrounds, we set upper limits on the cross sections of 17 pb for the s-channel process ppbar->tb+X, and 22 pb for the t-channel process ppbar->tqb+X, both at the 95% confidence level
Cross Section for b Jet Production in pbar-p Collisions at sqrt(s) = 1.8 TeV
Bottom quark production in pbar-p collisions at sqrt(s)=1.8 TeV is studied
with 5 inverse picobarns of data collected in 1995 by the DO detector at the
Fermilab Tevatron Collider. The differential production cross section for b
jets in the central rapidity region (|y(b)| < 1) as a function of jet
transverse energy is extracted from a muon-tagged jet sample. Within
experimental and theoretical uncertainties, DO results are found to be higher
than, but compatible with, next-to-leading-order QCD predictions.Comment: 11 pages, 3 figure
Differential cross section for W boson production as a function of transverse momentum in proton-antiproton collisions at 1.8 TeV
We report a measurement of the differential cross section for W boson
production as a function of its transverse momentum in proton-antiproton
collisions at sqrt{s} = 1.8 TeV. The data were collected by the D0 experiment
at the Fermilab Tevatron Collider during 1994-1995 and correspond to an
integrated luminosity of 85 pb^{-1}. The results are in good agreement with
quantum chromodynamics over the entire range of transverse momentum.Comment: Accepted by Physics Letters
Measurement of the ratio of differential cross sections for W and Z boson production as a function of transverse momentum in pbar p collisions at sqrt(s)=1.8 TeV
We report on a measurement of the ratio of the differential cross sections
for W and Z boson production as a function of transverse momentum in
proton-antiproton collisions at sqrt(s) = 1.8 TeV. This measurement uses data
recorded by the D0 detector at the Fermilab Tevatron in 1994-1995. It
represents the first investigation of a proposal that ratios between W and Z
observables can be calculated reliably using perturbative QCD, even when the
individual observables are not. Using the ratio of differential cross sections
reduces both experimental and theoretical uncertainties, and can therefore
provide smaller overall uncertainties in the measured mass and width of the W
boson than current methods used at hadron colliders.Comment: 10 pages, 2 figures, to be published in Physics Letters
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