983 research outputs found
Integrated optical directional coupler biosensor
We present measurements on biomolecular binding reactions, using a new type of integrated optical biosensor based on a planar directional coupler structure. The device is fabricated by Ag+-Na+ ion-exchange in glass and definition of the sensing region is achieved by use of transparent fluoropolymer isolation layers formed by thermal evaporation. The suitability of the sensor for application to the detection of environmental pollutants is considered
D^* production from e^+e^- to ep collisions in NLO QCD
Fragmentation functions for D mesons, based on the convolution of a
perturbative part, related to the heavy quark perturbative showering, and a
non-perturbative model for its hadronization into the meson, are used to
describe D^* production in e^+e^- and ep collisions. The non-perturbative part
is determined by fitting the e^+e^- data taken by ARGUS and OPAL at 10.6 and
91.2 GeV respectively. When fitting with a non perturbative Peterson
fragmentation function and using next-to-leading evolution for the perturbative
part, we find an epsilon parameter sensibly different from the one commonly
used, which is instead found with a leading order fit. The use of this new
value is shown to increase considerably the cross section for D^* production at
HERA, suggesting a possible reconciliation between the next-to-leading order
theoretical predictions and the experimental data.Comment: 20 pages, LaTeX2e, 8 Postscript figure
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
The t-tbar cross-section at 1.8 and 1.96 TeV: a study of the systematics due to parton densities and scale dependence
We update the theoretical predictions for the t-tbar production cross-section
at the Tevatron, taking into account the most recent determinations of
systematic uncertainties in the extraction of the proton parton densities.Comment: 12 pages, 1 figure, Late
Prospects of Open Charm Production at GSI-FAIR and J-PARC
We present a detailed phenomenological study of the prospects of open charm
physics at the future and facilities GSI-FAIR and J-PARC,
respectively. In particular, we concentrate on differential cross sections and
the charge and longitudinal double-spin asymmetries at next-to-leading order
accuracy. Theoretical uncertainties for the proposed observables are estimated
by varying the charm quark mass and the renormalization and factorization
scales.Comment: 11 pages, 13 figure
Low-Energy Supersymmetry and the Tevatron Bottom-Quark Cross Section
A long-standing discrepancy between the bottom-quark production cross section
and predictions of perturbative quantum chromodynamics is addressed. We show
that pair production of light gluinos, of mass 12 to 16 GeV, with two-body
decays into bottom quarks and light bottom squarks, yields a bottom-quark
production rate in agreement with hadron collider data. We examine constraints
on this scenario from low-energy data and make predictions that may be tested
at the next run of the Fermilab Tevatron Collider.Comment: Version in Phys. Rev. Lett., 4 pp., 1 ps fig., uses RevTeX, added why
moderate gluino masses are not ruled out, updated reference
Inclusive J/psi and psi(2S) Production from B Decay in p p-bar Collisions
Using information on B-meson fragmentation functions from CERN LEP 1 and
adopting the nonrelativistic QCD factorization formalism proposed by Bodwin,
Braaten, and Lepage, we predict the transverse-momentum distribution of J/psi
mesons originating from the inclusive decays of b hadrons produced in p p-bar
collisions at the Fermilab Tevatron. We determine the relevant colour-octet
charmonium matrix elements from fits to CDF data on prompt charmonium
hadroproduction and to CLEO data on charmonium production from B-meson decay.
Our predictions are found to agree well with recent CDF and D0 data.Comment: 27 pages (Latex), 9 figures (Postscript
Analytic Calculation of Prompt Photon plus Associated Heavy Flavor at Next-to-Leading Order in QCD
Contributions through second order, , in perturbative quantum
chromodynamics are calculated analytically for inclusive associated production
of a prompt photon and a charm quark at large values of transverse momentum in
high energy hadron-hadron collisions. Seven partonic subprocesses contribute at
order . We find important corrections to the lowest order,
, subprocess . We demonstrate to what
extent data from may serve to measure
the charm quark density in the nucleon.Comment: 34 pages RevTex plus 9 figures submitted as uuencoded ps files;
figures replaced and text revised to include one additional referenc
Hard-scattering factorization with heavy quarks: A general treatment
A detailed proof of hard scattering factorization is given with the inclusion
of heavy quark masses. Although the proof is explicitly given for
deep-inelastic scattering, the methods apply more generally The
power-suppressed corrections to the factorization formula are uniformly
suppressed by a power of \Lambda/Q, independently of the size of heavy quark
masses, M, relative to Q.Comment: 52 pages. Version as published plus correction of misprint in Eq.
(45
Relating parton model and color dipole formulation of heavy quark hadroproduction
At high center of mass energies, hadroproduction of heavy quarks can be
expressed in terms of the same color dipole cross section as low Bjorken-x deep
inelastic scattering. We show analytically that at leading order, the dipole
formulation is equivalent to the gluon-gluon fusion mechanism of the
conventional parton model. In phenomenological application, we employ a
parameterization of the dipole cross section which also includes higher order
and saturation effects, thereby going beyond the parton model. Numerical
calculations in the dipole approach agree well with experimental data on open
charm production over a wide range of energy. Dipole approach and next to
leading order parton model yield similar values for open charm production, but
for open bottom production, the dipole approach tends to predict somewhat
higher cross sections than the parton model.Comment: 16 pages, 4 figure
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