The muon spectrometer of the ATLAS detector for the Large Hadron Collider is designed to provide a muon transverse momentum resolution of 2%–10% for momenta between 6
GeV and 1
TeV over a ...pseudo-rapidity range of |
η|⩽2.7. This required the development of precision drift chambers with a track position resolution of
40
μ
m, the Monitored Drift Tube (MDT) chambers. We report about the construction of the three main types of MDT chambers for ATLAS, test results and the first production experience.
The Monitored Drift Tube (MDT) chambers for the muon spectrometer of the ATLAS detector at the Large Hadron Collider (LHC) consist of 3-4 layers of pressurised drift tubes on either side of a space ...frame carrying an optical deformation monitoring system. The chambers have to provide a track position resolution of 40 microns with a single-tube resolution of at least 80 microns and a sense wire positioning accu- racy of 20 ?microns (rms). The feasibility was demonstrated with the full-scale prototype of one of the largest MDT chambers with 432 drift tubes of 3.8 m length. For the ATLAS muon spectrometer, 88 chambers of this type have to be built. The first chamber has been completed with a wire positioning accuracy of 14 microns (rms).
The Monitored Drift Tube (MDT) chambers for the muon spectrometer of the AT- LAS detector at the Large Hadron Collider (LHC) consist of 3-4 layers of pressurized drift tubes on either side of a space ...frame carrying an optical monitoring system to correct for deformations. The full-scale prototype of a large MDT chamber has been constructed with methods suitable for large-scale production. X-ray measurements at CERN showed a positioning accuracy of the sense wires in the chamber of better than the required 20 ?microns (rms). The performance of the chamber was studied in a muon beam at CERN. Chamber production for ATLAS now has started.
A search for pair-production of long-lived, heavy, singly-charged particles has been performed with data collected by the ALEPH detector at a centre-of-mass energy of 172 GeV. Data at
s
=161, 136
and ...130
GeV
are also included to improve the sensitivity to lower masses. No candidate is found in the data. A model-independent 95% confidence level upper limit on the production cross section at 172 GeV of 0.2–0.4 pb is derived for masses between 45 and 86 GeV/
c
2. This cross section limit implies, assuming the MSSM, a lower limit of 67 (69) GeV/
c
2 on the mass of right- (left-) handed long-lived scalar taus or scalar muons and of 86 GeV/
c
2 on the mass of long-lived charginos.
A search for events with a photon pair arising from the decay of a Higgs boson produced in association with a fermion pair, is performed in 893 pb−1 of data recorded by the ALEPH detector at LEP at ...centre-of-mass energies up to 209 GeV. No excess of such events is found over the expected background. An upper limit is derived on the product of the e+e−→HZ cross section and the H→γγ branching fraction as a function of the Higgs boson mass. A fermiophobic Higgs boson produced with the Standard Model cross section is excluded at 95% confidence level for all masses below 105.4 GeV/c2.
Single top production via the flavour changing neutral current reactions e+e−→t̄c,t̄u is searched for within the 214 pb−1 of data collected by ALEPH at centre-of-mass energies between 204 and ...209 GeV. No deviation from the Standard Model expectation is observed and upper limits on the single top production cross sections are derived. The combination with data collected at lower centre-of-mass energies yields an upper limit on the branching ratio BR(t→Zc)+BR(t→Zu)<14%, for BR(t→γc)+BR(t→γu)=0 and mt=174 GeV/c2.
A search for charged Higgs bosons produced in pairs is performed with data collected at centre-of-mass energies ranging from 189 to 209 GeV by ALEPH at LEP, corresponding to a total luminosity of ...629 pb
−1. The three final states
τ
+ν
ττ
−
ν
̄
τ
,
c
s
̄
τ
−
ν
̄
τ
and
c
s
̄
s
c
̄
are considered. No evidence for a signal is found and lower limits are set on the mass
m
H
±
as a function of the branching fraction
B(
H
+→τ
+ν
τ
)
. In the framework of a two-Higgs-doublet model, and assuming
B(
H
+→τ
+ν
τ
)+
B(
H
+→c
s
̄
)=1
, charged Higgs bosons with masses below 79.3 GeV/
c
2 are excluded at 95% confidence level independently of the branching ratios.
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