1,084 research outputs found
Flight investigation to evaluate the roll-rate stabilization system of the Naval Ordnance Test Station Sidewinder missile at Mach numbers from 0.9 to 2.3
QCD in e+e- collisions at 2 TeV
We discuss some topics in QCD studies at 2 TeV. Particular emphasis is given
to the separation of pure QCD events from the WW and the t-tbar backgroundsComment: 10 pages, Latex, epsfig, 7 figures To appear in the Proceedings of
the 1995 "Workshop on Physics with e+e- Linear Colliders", Annecy-Gran
Sasso-DES
The Resummation of Soft Gluon in Hadronic Collisions
We compute the effects of soft gluon resummation for the production of high
mass systems in hadronic collisions. We carefully analyse the growth of the
perturbative expansion coefficients of the resummation formula. We propose an
expression consistent with the known leading and next-to-leading resummation
results, in which the coefficients grow much less than factorially. We apply
our formula to Drell--Yan pair production, heavy flavour production, and the
production of high invariant mass jet pairs in hadronic collisions. We find
that, with our formula, resummation effects become important only fairly close
to the threshold region. In the case of heavy flavour production we find that
resummation effects are small in the experimental configurations of practical
interest.Comment: 45 pages, Latex, epsfig, 10 figures. Minor corrections to text,
notation and references. The previously quoted HERAb NLO bottom production
cross section was wrong, and it has been fixed. Accepted for Publication on
Nucl. Phys.
Missing heavy flavor backgrounds to Higgs boson production
We investigate characteristics of the signal and backgrounds for Higgs boson
decay into WW at the Fermilab Tevatron and CERN Large Hadron Collider. In the
the lepton-pair-plus-missing-energy final state, we show that the background
receives an important contribution from semileptonic decays of heavy flavors.
Lepton isolation cuts provide too little suppression of these heavy flavor
contributions, and an additional 4 to 8 orders-of-magnitude suppression must
come from physics cuts. We demonstrate that an increase of the minimum
transverse momentum of nonleading leptons in multilepton events is one
effective way to achieve the needed suppression, without appreciable loss of
the Higgs boson signal. Such a cut would impact the efficiency of searches for
supersymmetry as well. We emphasize the importance of direct measurement of the
lepton background from heavy flavor production.Comment: 23 pgs., 10 figs, revtex4, 1 Ref. added, minor typos corrected, to
appear in Phys. Rev.
Phenomenological study of charm photoproduction at HERA
We present predictions for single inclusive distributions of charmed mesons,
relevant to the HERA experiments. Our results are based upon a computation that
correctly incorporates mass effects up to the next-to-leading order level, and
the resummation of transverse momentum logarithms up to
next-to-leading-logarithmic level. We apply the same acceptance cuts as the H1
and Zeus experiments, and compare our results to their data. We perform a study
of the sensitivity of our predictions on the charm mass, \LambdaQCD,
factorization scale, renormalization scale, and fragmentation parameters.Comment: 15 pages Latex; 25 figures include
Standard Model Top Quark Asymmetry at the Fermilab Tevatron
Top quark pair production at proton-antiproton colliders is known to exhibit
a forward-backward asymmetry due to higher-order QCD effects. We explore how
this asymmetry might be studied at the Fermilab Tevatron, including how the
asymmetry depends on the kinematics of extra hard partons. We consider results
for top quark pair events with one and two additional hard jets. We further
note that a similar asymmetry, correlated with the presence of jets, arises in
specific models for parton showers in Monte Carlo simulations. We conclude that
the measurement of this asymmetry at the Tevatron will be challenging, but
important both for our understanding of QCD and for our efforts to model it.Comment: 26 p., 10 embedded figs., comment added, version to appear in PR
Next-to-next-to-leading soft-gluon corrections for the top quark cross section and transverse momentum distribution
I present results for top quark production in hadronic collisions at LHC and
Tevatron energies. The soft-gluon corrections to the differential cross section
are resummed at next-to-next-to-leading-logarithm (NNLL) accuracy via the
two-loop soft anomalous dimension matrices. Approximate
next-to-next-to-leading-order (NNLO) differential and total cross sections are
calculated. Detailed theoretical predictions are shown for the t tbar cross
section and the top quark p_T distribution at the Tevatron and the LHC.Comment: 23 pages, 14 figures; additional results and figure
Design of an air-flow microchamber for microparticles detec
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.A novel device, able to funnel a suspension of micrometric particles in air into a microchamber
equipped with a capacitive sensor, has been designed for the detection and characterization of particulate
matter (PM) in air. Numerical simulations have been performed to predict the trajectory of the microparticles
through the PDMS microchamber where the sensor is located. The feasibility of detecting single PM10
particles has been demonstrated by our experiments, where sequences of single industrial talc particles
(average diameter of 8 ÎĽm) have been detected and counted by a capacitive sensor. Our results indicate that
radical miniaturization of air quality monitors is possible and, therefore, pervasive monitoring of air
pollution will be soon feasible
J/psi Production via Fragmentation at the Tevatron
The production of \jpsi at large transverse momenta (\pt > M_\jpsi) in
collisions is considered by including the mechanism of fragmentation.
Both contributions of fragmentation to \jpsi and of fragmentation to
states followed by radiative decay to \jpsi are taken into account. The
latter is found to be dominant and larger than direct production. The overall
theoretical estimate is shown to be nearly consistent with the experimental
observation.Comment: LaTeX, 7 pages. Preprint FNT/T-94/13, LNF-94/024(P). Data taken from
a reference were incorrect and have been changed. Complete postscript file
available via anonymous ftp at cobra1.pv.infn.it, as pub/jpsi.ps(.Z)(.gz
Heavy-Quark Production
We review the present theoretical and experimental status of heavy quark
production in high-energy collisions. In particular, we cover hadro- and
photoproduction at fixed target experiments, at HERA and at the hadron
colliders, as well as aspects of heavy quark production in e+e- collisions at
the Z0 peak.Comment: 100 pages, Latex, epsfig, 48 figures. To appear in "Heavy Flavours
II", eds. A.J. Buras and M. Lindner, Advanced Series on Directions in High
Energy Physics, World Scientific Publishing Co., Singapore. Few typos have
been fixed, figs. 4(left) and 27(left) have been update
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