4,186 research outputs found
A Remark on the Width
The width, , is analysed in conjunction with the
total and hadronic widths, and . Assuming,
tentatively, that the present 2 discrepancy in will
substantiate as time goes on, for large values of it will be sufficient
to modify the vertex only. In contrast, for small values of
, the theoretical predictions for both the width into light quarks
and leptons as well as the vertex will have to be modified.Comment: 8 pages uuencoded postscript including 2 figure
ATLAS Monitored Drift Tube Chambers in E = 11 MeV Neutron Background
The influence of fast neutrons on the occupancy and the single tube
resolution of ATLAS muon drift detectors was investigated by exposing a chamber
built out of 3 layers of 3 short standard drift tubes to neutron flux-densities
of up to 16 kHz/cm2 at a neutron energy of E=11 MeV. Pulse shape capable NE213
scintillaton detectors and a calibrated BF3 neutron detector provided
monitoring of the neutron flux-density and energy. The sensitivity of the drift
chamber to the neutrons was measured to be 4*10-4 by comparing data sets with
and without neutron background. For the investigation of tracks of cosmic muons
two silicon-strip detectors above and underneath the chamber allow to compare
measured drift-radii with reference tracks. Alternatively, the single tube
resolution was determined using the triple-sum method. The comparison between
data with and without neutron irradiation shows only a marginal effect on the
resolution and little influence on the muon track reconstruction.Comment: 4 pages, 11 figures, conferenc
High Rate Performance of Drift Tubes
This article describes calculations and measurements of space charge effects
due to high rate irradiation in high resolution drift tubes. Two main items are
studied: the reduction of the gas gain and changes of the drift time. Whereas
the gain reduction is similar for all gases and unavoidable, the drift time
changes depend on the kind of gas that is used. The loss in resolution due to
high particle rate can be minimized with a suitable gas. This behaviour is
calculable, allowing predictions for new gas mixtures.Comment: 20 pages, submitted to Nuclear Instruments and Methods
HIGGS BOSON PRODUCTION IN
The production of the Standard Model Higgs boson in the four-fermion reaction
is studied. The complete tree-level matrix
element, including signal and backgrounds in the standard electroweak theory,
is computed and initial state radiation is taken into account in the
leading-log approximation. A Monte Carlo event generator has been built and
numerical results for some distributions of experimental interest for the
search of the Higgs particle at future electron-positron colliders are shown,
compared with those existing in the literature and commented.Comment: 8 pages, 5 figures available via anonymous ftp at:
ftp://cobra1.pv.infn.it/pub/4f/, files fig#h.ps with #=1,...,5
A Search for Vector Diquarks at the CERN LHC
Resonant production of the first generation vector diquarks at the CERN Large
Hadron Collider (LHC) is investigated. It is shown that the LHC will be able to
discover vector diquarks with masses up to 9 TeV for quark-diquark-quark
coupling alpha_(D)=0.1 and 4 TeV for alpha_(D)=5x10^(-4).Comment: 9 pages, 4 tables, 4 figure
THE SENSITIVITY TO NEW PHYSICS OF A LEP SCAN IN 1995
We study the implications of possible off-peak measurements in the 1995 LEP
run, in regard to probing physics beyond the Standard Model. To do so, we
determine the accuracy with which various nonstandard couplings can be expected
to be measured in the three different scan scenarios recently discussed by
Clarke and Wyatt. We find that each scan scenario allows greater sensitivity to
a different set of new physics couplings. Oblique parameters are best measured
with the longest scan, while nonstandard fermion couplings to the Z tend to be
better constrained (albeit only marginally) if all of the 1995 LEP measurements
are taken on the Z peak.Comment: Plain TeX, 9 pages, no figures. We have streamlined our presentation
by omitting observables of our Class B. All else is completely unchanged
Z' Physics
The limits on extra neutral gauge bosons, which could be reached at LEP2, are
reviewed. Exclusion and discovery limits are discussed for f\bar f and WW
production.Comment: 20 pages Latex, 7 figures included by epsfig, Contribution to the
Proceedings the workshop "Physics at LEP2", Geneva, 199
Electron spin resonance and exchange paths in the orthorhombic dimer system Sr2VO4
We report on magnetization and electron spin resonance (ESR) measurements of
SrVO with orthorhombic symmetry. In this dimer system the
ions are in tetrahedral environment and are coupled by an antiferromagnetic
intra-dimer exchange constant 100 K to form a singlet ground
state without any phase transitions between room temperature and 2 K. Based on
an extended-H\"{u}ckel-Tight-Binding analysis we identify the strongest
exchange interaction to occur between two inequivalent vanadium sites via two
intermediate oxygen ions. The ESR absorption spectra can be well described by a
single Lorentzian line with an effective g-factor = 1.89. The temperature
dependence of the ESR intensity is well described by a dimer model in agreement
with the magnetization data. The temperature dependence of the ESR linewidth
can be modeled by a superposition of a linear increase with temperature with a
slope = 1.35 Oe/K and a thermally activated behavior with an
activation energy = 1418 K, both of which point to spin-phonon
coupling as the dominant relaxation mechanism in this compound.Comment: 5 pages, 4 figure
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