Searches for supersymmetric partners of top and bottom quarks are presented using data taken by the DELPHI experiment at LEP in 1997 and 1998. No deviations from standard model expectations are ...observed in these data sets, which are taken at centre-of-mass energies of 183 GeV and 189 GeV and correspond to integrated luminosities of 54 pb
−1 and 158 pb
−1. These results are used in combination with those obtained by DELPHI at lower centre-of-mass energies to exclude regions in the squark–neutralino mass plane at 95% confidence level.
A test of the QED process
e
+
e
−→
γγ(
γ) is reported. The data analysed were collected with the DELPHI detector in 1998 and 1999 at the highest energies achieved at LEP, reaching 202 GeV in the ...centre-of-mass. The total integrated luminosity amounts to 375.7 pb
−1. The differential and total cross-sections for the process
e
+
e
−→
γγ were measured, and found to be in agreement with the QED prediction. 95% confidence level (C.L.) lower limits on the QED cut-off parameters of
Λ
+>330 GeV and
Λ
−>320 GeV were derived. A 95% C.L. lower bound on the mass of an excited electron of 311 GeV/
c
2 (for
λ
γ
=1) was obtained. s-channel virtual graviton exchange was searched for, resulting in 95% C.L. lower limits on the string mass scale,
M
S
:
M
S
>713 GeV/
c
2 (
λ=1) and
M
S
>691 GeV/
c
2 (
λ=−1).
The muon spectrometer of the LHC detector ATLAS provides an independent and precise muon track measurement using three layers of precision drift tube chambers in a toroidal magnetic field with a ...bending power
∫
B
d
l
of
2
T
m
to
8
T
m
. Muon tracks are reconstructed with 97% efficiency and a momentum resolution about 3% for most of the range and better than 10% for transverse momenta up to 1 TeV/c. The latter requires the knowledge of the magnetic field with 1% accuracy and misalignment corrections of the track curvature with an accuracy of about
30
μ
m
. The magnetic field is measured by Hall probes on each chamber with sufficient precision. The misalignment corrections are given by a system of optical sensors. We present methods which allow us to measure the performance of the muon spectrometer during the operation of the ATLAS detector. The alignment of the chambers can be verified with single muon tracks by making use of redundant momentum measurements in the spectrometer. The muon reconstruction efficiency and the momentum resolution can be determined with muons from Z decays.
To analyse quantitatively a coronary arterial segment from a cineangiogram, an end-diastolic or neighbouring frame is usually selected. However, different cardiologists may select other (although ...usually neighbouring) frames, even when the same selection criteria are followed. It is also possible that the frames are selected from different cardiac cycles. In this study the effects of such phase shifts on the reproducibility of the quantitative measurements were studied. In a total of 38 consecutive patient films obtained at a filmspeed of 25 frames s-1, the frame phi demonstrating the severity of a lesion optimally as judged by a senior cardiologist, the three preceding frames, the three following frames and one frame exactly one cycle prior to or following frame phi were selected; frame phi was always chosen in the end-diastolic phase of the cardiac cycle. In each film one coronary arterial segment with a focal lesion was analysed quantitatively in these total of 8 frames with the Cardiovascular Angiography Analysis System (CAAS). No significant differences were found in the mean difference and the standard deviations of the differences (variabilities) in the obstruction diameter, interpolated reference diameter, percent diameter stenosis, extent of the obstruction and area of atherosclerotic plaque obtained in the various frames with respect to frame phi. Therefore, it may be concluded that the selection of a cineframe for quantitative analysis in the end-diastolic phase of the cardiac cycle is not very critical.
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