4,175 research outputs found
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
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
A Cosmic Ray Measurement Facility for ATLAS Muon Chambers
Monitored Drift Tube (MDT) chambers will constitute the large majority of
precision detectors in the Muon Spectrometer of the ATLAS experiment at the
Large Hadron Collider at CERN. For commissioning and calibration of MDT
chambers, a Cosmic Ray Measurement Facility is in operation at Munich
University. The objectives of this facility are to test the chambers and
on-chamber electronics, to map the positions of the anode wires within the
chambers with the precision needed for standalone muon momentum measurement in
ATLAS, and to gain experience in the operation of the chambers and on-line
calibration procedures.
Until the start of muon chamber installation in ATLAS, 88 chambers built at
the Max Planck Institute for Physics in Munich have to be commissioned and
calibrated. With a data taking period of one day individual wire positions can
be measured with an accuracy of 8.3 micrometers in the chamber plane and 27
micrometers in the direction perpendicular to that plane.Comment: 14+1 pages, 11 figures, contributed paper to the EPS2003 conference,
Aache
Temperature Studies for ATLAS MDT BOS Chambers
Data sets with high statistics taken at the cosmic ray facility, equipped
with 3 ATLAS BOS MDT chambers, in Garching (Munich) have been used to study
temperature and pressure effects on gas gain and drifttime. The deformation of
a thermally expanded chamber was reconstructed using the internal RasNik
alignment monitoring system and the tracks from cosmic data. For these studies
a heating system was designed to increase the temperature of the middle chamber
by up to 20 Kelvins over room temperature. For comparison the temperature
effects on gas properties have been simulated with Garfield. The maximum
drifttime decreased under temperature raise by -2.21 +- 0.08 ns/K, in agreement
with the results of pressure variations and the Garfield simulation. The
increased temperatures led to a linear increase of the gas gain of about 2.1%
1/K. The chamber deformation has been analyzed with the help of reconstructed
tracks. By the comparison of the tracks through the reference chambers with
these through the test chamber the thermal expansion has been reconstructed and
the result shows agreement with the theoretical expansion coefficient. As the
wires are fixed at the end of the chamber, the wire position calculation can
not provide a conclusion for the chamber middle. The complete deformation has
been identified with the analysis of the monitoring system RasNik, whose
measured values have shown a homogeneous expansion of the whole chamber,
overlayed by a shift and a rotation of the chamber middle with respect to the
outer part of the chamber. The established results of both methods are in
agreement. We present as well a model for the position-drifttime correction as
function of temperature.Comment: 4 pages, 12 figures, conferenc
First identification of large electric monopole strength in well-deformed rare earth nuclei
Excited states in the well-deformed rare earth isotopes Sm and
Er were populated via ``safe'' Coulomb excitation at the Munich MLL
Tandem accelerator. Conversion electrons were registered in a cooled Si(Li)
detector in conjunction with a magnetic transport and filter system, the
Mini-Orange spectrometer. For the first excited state in Sm at
1099 keV a large value of the monopole strength for the transition to the
ground state of could be extracted. This confirms the interpretation of the lowest
excited state in Sm as the collective -vibrational
excitation of the ground state. In Er the measured large electric
monopole strength of clearly identifies the state at 1934 keV to be the
-vibrational excitation of the ground state.Comment: submitted to Physics Letters
Single Top Quark Production as a Probe for Anomalous Moments at Hadron Colliders
Single production of top quarks at hadron colliders via fusion is
examined as a probe of possible anomalous chromomagnetic and/or chromoelectric
moment type couplings between the top and gluons. We find that this channel is
far less sensitive to the existence of anomalous couplings of this kind than is
the usual production of top pairs by or fusion. This result is
found to hold at both the Tevatron as well as the LHC although somewhat greater
sensitivity for anomalous couplings in this channel is found at the higher
energy machine.Comment: New discussion and 10 new figures added. uuencoded postscript fil
An analytical program for fermion pair production in e+e- annihilation
We describe how to use {\tt ZFITTER}, a program based on a semi-analytical approach to fermion pair production in e^+ e^- annihilation and Bhabha scattering. A flexible treatment of complete {\cal O}(\alpha) QED corrections, also including higher orders, allows for three calculational {\bf chains} with different realistic sets of restrictions in the photon phase space. {\tt ZFITTER} consists of several {\bf branches} with varying assumptions on the underlying hard scattering process. One includes complete {\cal O}(\alpha) weak loop corrections with a resummation of leading higher-order terms. Alternatively, an ansatz inspired from S-matrix theory, or several model-independent effective Born cross sections may be convoluted. The program calculates cross sections, forward-backward asymmetries, and for \tau~pair production also the final-state polarization. Various {\bf interfaces} allow fits to be performed with different sets of free parameters
Can We Observe Weak Anomalous Couplings of Heavy Quarks Through Three Jet Events?
The rates and corresponding jet distributions for the decay
and the process may be sensitive to anomalous dipole-like
couplings of heavy quarks to the photon and . In the -quark case, after
updating our previous analysis on the constraints imposed by current
experiments on anomalous couplings, we show that the variation of
these couplings within their presently allowed ranges leads to rather minor
modifications to the Standard Model expectations for
observables. In the -quark case, significant deviations from the Standard
Model predictions for production at the Next Linear Collider are
possible.Comment: 26 pages with 9 embedded figures; gzipped, uuencoded postscript file.
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