80,161 research outputs found
Measurement of the fraction of t-tbar production via gluon-gluon fusion in p-pbar collisions at sqrt(s)=1.96 TeV
We present a measurement of the ratio of t-tbar production cross section via
gluon-gluon fusion to the total t-tbar production cross section in p-pbar
collisions at sqrt{s}=1.96 TeV at the Tevatron. Using a data sample with an
integrated luminosity of 955/pb recorded by the CDF II detector at Fermilab, we
select events based on the t-tbar decay to lepton+jets. Using an artificial
neural network technique we discriminate between t-tbar events produced via
q-qbar annihilation and gluon-gluon fusion, and find
Cf=(gg->ttbar)/(pp->ttbar)<0.33 at the 68% confidence level. This result is
combined with a previous measurement to obtain the most precise measurement of
this quantity, Cf=0.07+0.15-0.07.Comment: submitted to Phys. Rev.
Measurement of Resonance Parameters of Orbitally Excited Narrow B^0 Mesons
We report a measurement of resonance parameters of the orbitally excited
(L=1) narrow B^0 mesons in decays to B^{(*)+}\pi^- using 1.7/fb of data
collected by the CDF II detector at the Fermilab Tevatron. The mass and width
of the B^{*0}_2 state are measured to be m(B^{*0}_2) =
5740.2^{+1.7}_{-1.8}(stat.) ^{+0.9}_{-0.8}(syst.) MeV/c^2 and \Gamma(B^{*0}_2)
= 22.7^{+3.8}_{-3.2}(stat.) ^{+3.2}_{-10.2}(syst.) MeV/c^2. The mass difference
between the B^{*0}_2 and B^0_1 states is measured to be
14.9^{+2.2}_{-2.5}(stat.) ^{+1.2}_{-1.4}(syst.) MeV/c^2, resulting in a B^0_1
mass of 5725.3^{+1.6}_{-2.2}(stat.) ^{+1.4}_{-1.5}(syst.) MeV/c^2. This is
currently the most precise measurement of the masses of these states and the
first measurement of the B^{*0}_2 width.Comment: 7 pages, 1 figure, 1 table. Submitted to Phys.Rev.Let
Confined One Dimensional Harmonic Oscillator as a Two-Mode System
The one-dimensional harmonic oscillator in a box problem is possibly the
simplest example of a two-mode system. This system has two exactly solvable
limits, the harmonic oscillator and a particle in a (one-dimensional) box. Each
of the two limits has a characteristic spectral structure describing the two
different excitation modes of the system. Near each of these limits, one can
use perturbation theory to achieve an accurate description of the eigenstates.
Away from the exact limits, however, one has to carry out a matrix
diagonalization because the basis-state mixing that occurs is typically too
large to be reproduced in any other way. An alternative to casting the problem
in terms of one or the other basis set consists of using an "oblique" basis
that uses both sets. Through a study of this alternative in this
one-dimensional problem, we are able to illustrate practical solutions and
infer the applicability of the concept for more complex systems, such as in the
study of complex nuclei where oblique-basis calculations have been successful.
Keywords: one-dimensional harmonic oscillator, particle in a box, exactly
solvable models, two-mode system, oblique basis states, perturbation theory,
coherent states, adiabatic mixing.Comment: 11 pages and 9 figures; Submitted to American Journal of Physic
Search for lepton flavor violating decays of a heavy neutral particle in p-pbar collisions at root(s)=1.8 TeV
We report on a search for a high mass, narrow width particle that decays
directly to e+mu, e+tau, or mu+tau. We use approximately 110 pb^-1 of data
collected with the Collider Detector at Fermilab from 1992 to 1995. No evidence
of lepton flavor violating decays is found. Limits are set on the production
and decay of sneutrinos with R-parity violating interactions.Comment: Figure 2 fixed. Reference 4 fixed. Minor changes to tex
Propositional Dynamic Logic for Message-Passing Systems
We examine a bidirectional propositional dynamic logic (PDL) for finite and
infinite message sequence charts (MSCs) extending LTL and TLC-. By this kind of
multi-modal logic we can express properties both in the entire future and in
the past of an event. Path expressions strengthen the classical until operator
of temporal logic. For every formula defining an MSC language, we construct a
communicating finite-state machine (CFM) accepting the same language. The CFM
obtained has size exponential in the size of the formula. This synthesis
problem is solved in full generality, i.e., also for MSCs with unbounded
channels. The model checking problem for CFMs and HMSCs turns out to be in
PSPACE for existentially bounded MSCs. Finally, we show that, for PDL with
intersection, the semantics of a formula cannot be captured by a CFM anymore
Sobolev Metrics on Diffeomorphism Groups and the Derived Geometry of Spaces of Submanifolds
Given a finite dimensional manifold , the group
of diffeomorphism of which fall
suitably rapidly to the identity, acts on the manifold of submanifolds
on of diffeomorphism type where is a compact manifold with . For a right invariant weak Riemannian metric on
induced by a quite general operator
, we
consider the induced weak Riemannian metric on and we compute its
geodesics and sectional curvature. For that we derive a covariant formula for
curvature in finite and infinite dimensions, we show how it makes O'Neill's
formula very transparent, and we use it finally to compute sectional curvature
on .Comment: 28 pages. In this version some misprints correcte
Bounded Arithmetic in Free Logic
One of the central open questions in bounded arithmetic is whether Buss'
hierarchy of theories of bounded arithmetic collapses or not. In this paper, we
reformulate Buss' theories using free logic and conjecture that such theories
are easier to handle. To show this, we first prove that Buss' theories prove
consistencies of induction-free fragments of our theories whose formulae have
bounded complexity. Next, we prove that although our theories are based on an
apparently weaker logic, we can interpret theories in Buss' hierarchy by our
theories using a simple translation. Finally, we investigate finitistic G\"odel
sentences in our systems in the hope of proving that a theory in a lower level
of Buss' hierarchy cannot prove consistency of induction-free fragments of our
theories whose formulae have higher complexity
Target company cross-border effects in acquisitions into the UK
We analyse the abnormal returns to target shareholders in crossborder and domestic acquisitions of UK companies. The crossborder effect during the bid month is small (0.84%), although crossborder targets gain significantly more than domestic targets during the months surrounding the bid. We find no evidence for the level of abnormal returns in crossborder acquisitions to be associated with market access or exchange rate effects, and only limited support for an international diversification effect. However, the crossborder effect appears to be associated with significant payment effects, and there is no significant residual crossborder effect once various bid characteristics are controlled for
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Electrodiffusion Method of Near-Wall Flow Diagnostics in Microfluidic Systems
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The electrodiffusion technique has been mostly used for the near-wall flow diagnostics on large
scales. A novel technique for fabrication of plastic microfluidic systems with integrated metal
microelectrodes (called technique of sacrificed substrate) enables us to produce microfluidic devices with
precisely shaped sensors for wall shear stress measurements. Several micrometer thick gold sensors built-in a
plastic substrate exhibit good mechanical resistance and smoothness. Proper functioning of prepared chips
with microsensors has been first tested in various calibration experiments (polarization curve, sensor
response to polarization set-up, steady flow calibration, temperature dependence of diffusivity). Our first
results obtained for separating/reattaching flow behind a backward-facing step and for gas-liquid Taylor flow
in microchannels then demonstrate its applicability for the detection of near-wall flow reversal, the
delimitation of flow-recirculation zones, and the determination of wall shear stress response to moving
bubbles. Other applications of these sensors in microfluidics (e.g. characterization of liquid films, capillary
waves, bubbles or drops) can be also envisaged
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