The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for pair-produced charged Higgs bosons in the framework of Two Higgs Doublet Models (2HDMs). The data of the four experiments ...have been statistically combined. The results are interpreted within the 2HDM for Type I and Type II benchmark scenarios. No statistically significant excess has been observed when compared to the Standard Model background prediction, and the combined LEP data exclude large regions of the model parameter space. Charged Higgs bosons with mass below 80
(Type II scenario) or 72.5
(Type I scenario, for pseudo-scalar masses above 12
) are excluded at the 95 % confidence level.
The four LEP Collaborations, ALEPH, DELPHI, L3 and OPAL, have collected a total of 2461 pb−1 of e+e− collision data at centre-of-mass energies between 189 and 209 GeV. The data are used to search for ...the Standard Model Higgs boson. The search results of the four Collaborations are combined and examined in a likelihood test for their consistency with two hypotheses: the background hypothesis and the signal plus background hypothesis. The corresponding confidences have been computed as functions of the hypothetical Higgs boson mass. A lower bound of 114.4 GeV/c2 is established, at the 95% confidence level, on the mass of the Standard Model Higgs boson. The LEP data are also used to set upper bounds on the HZZ coupling for various assumptions concerning the decay of the Higgs boson.
The full LEP-1 data set collected with the ALEPH detector at the
Z pole during 1991–1995 is analysed in order to measure the
τ
decay branching fractions. The analysis follows the global method used ...in the published study based on 1991–1993 data, but several improvements are introduced, especially concerning the treatment of photons and
π
0
's. Extensive systematic studies are performed, in order to match the large statistics of the data sample corresponding to over 300
000 measured and identified
τ
decays. Branching fractions are obtained for the two leptonic channels and 11 hadronic channels defined by their respective numbers of charged particles and
π
0
's. Using previously published ALEPH results on final states with charged and neutral kaons, corrections are applied to the hadronic channels to derive branching ratios for exclusive final states without kaons. Thus the analyses of the full LEP-1 ALEPH data are combined to yield a complete description of
τ
decays, encompassing 22 non-strange and 11 strange hadronic modes. Some physics implications of the results are given, in particular related to universality in the leptonic charged weak current, isospin invariance in
a
1
decays, and the separation of vector and axial-vector components of the total hadronic rate. Finally, spectral functions are determined for the dominant hadronic modes and updates are given for several analyses. These include: tests of isospin invariance between the weak charged and electromagnetic hadronic currents, fits of the
ρ
resonance lineshape, and a QCD analysis of the non-strange hadronic decays using spectral moments, yielding the value
α
s
(
m
τ
2
)
=
0.340
±
0
.
005
exp
±
0
.
014
th
. The evolution to the
Z mass scale yields
α
s
(
M
Z
2
)
=
0.1209
±
0.0018
. This value agrees well with the direct determination from the
Z width and provides the most accurate test to date of asymptotic freedom in the QCD gauge theory.
An algorithm is presented, that provides a fast and robust reconstruction of neutrino induced upward-going muons and a discrimination of these events from downward-going atmospheric muon background ...in data collected by the ANTARES neutrino telescope. The algorithm consists of a hit merging and hit selection procedure followed by fitting steps for a track hypothesis and a point-like light source. It is particularly well-suited for real time applications such as online monitoring and fast triggering of optical follow-up observations for multi-messenger studies. The performance of the algorithm is evaluated with Monte Carlo simulations and various distributions are compared with that obtained in ANTARES data.
A search for a diffuse flux of astrophysical muon neutrinos, using data collected by the ANTARES neutrino telescope is presented. A (0.83×2π) sr sky was monitored for a total of 334 days of ...equivalent live time. The searched signal corresponds to an excess of events, produced by astrophysical sources, over the expected atmospheric neutrino background. The observed number of events is found compatible with the background expectation. Assuming an E−2 flux spectrum, a 90% c.l. upper limit on the diffuse νμ flux of E2Φ90%=5.3×10−8 GeVcm−2s−1sr−1 in the energy range 20 TeV–2.5 PeV is obtained. Other signal models with different energy spectra are also tested and some rejected.
The AMADEUS (ANTARES Modules for the Acoustic Detection Under the Sea) system which is described in this article aims at the investigation of techniques for acoustic detection of neutrinos in the ...deep sea. It is integrated into the ANTARES neutrino telescope in the Mediterranean Sea. Its acoustic sensors, installed at water depths between 2050 and 2300
m, employ piezo-electric elements for the broad-band recording of signals with frequencies ranging up to 125
kHz. The typical sensitivity of the sensors is around −145
dB
re
1
V/
μ
Pa
(including preamplifier). Completed in May 2008, AMADEUS consists of six “acoustic clusters”, each comprising six acoustic sensors that are arranged at distances of roughly 1
m from each other. Two vertical mechanical structures (so-called lines) of the ANTARES detector host three acoustic clusters each. Spacings between the clusters range from 14.5 to 340
m. Each cluster contains custom-designed electronics boards to amplify and digitise the acoustic signals from the sensors. An on-shore computer cluster is used to process and filter the data stream and store the selected events. The daily volume of recorded data is about 10
GB. The system is operating continuously and automatically, requiring only little human intervention. AMADEUS allows for extensive studies of both transient signals and ambient noise in the deep sea, as well as signal correlations on several length scales and localisation of acoustic point sources. Thus the system is excellently suited to assess the background conditions for the measurement of the bipolar pulses expected to originate from neutrino interactions.
► Magnetic monopoles are hypothetical particles predicted in unified theories. ► Relativistic monopoles could be detected in a neutrino telescope. ► A search for upgoing monopoles has been performed ...using 2008 ANTARES data. ► The obtained flux limits are stronger than limits from other experiments.
Magnetic monopoles are predicted in various unified gauge models and could be produced at intermediate mass scales. Their detection in a neutrino telescope is facilitated by the large amount of light emitted compared to that from muons. This paper reports on a search for upgoing relativistic magnetic monopoles with the ANTARES neutrino telescope using a data set of 116days of live time taken from December 2007 to December 2008. The one observed event is consistent with the expected atmospheric neutrino and muon background, leading to a 90% C.L. upper limit on the monopole flux between 1.3×10−17 and 8.9×10−17cm−2s−1sr−1 for monopoles with velocity β⩾0.625.
► A method to search for neutrinos from transient sources with ANTARES is presented. ► High energy single neutrinos or low energy multiplets can trigger alerts. ► Alerts are sent within a minute to a ...network of optical telescopes. ► A telescopes network can search for optical counterparts of neutrino alerts. ► ANTARES has a median angular precision of about 0.5 degrees above 10TeV.
The ANTARES telescope has the capability to detect neutrinos produced in astrophysical transient sources. Potential sources include gamma-ray bursts, core collapse supernovae, and flaring active galactic nuclei. To enhance the sensitivity of ANTARES to such sources, a new detection method based on coincident observations of neutrinos and optical signals has been developed. A fast online muon track reconstruction is used to trigger a network of small automatic optical telescopes. Such alerts are generated for special events, such as two or more neutrinos, coincident in time and direction, or single neutrinos of very high energy.
Results are presented of a search for cosmic sources of high-energy neutrinos with the ANTARES neutrino telescope. The data were collected during 2007 and 2008 using detector configurations ...containing between 5 and 12 detection lines. The integrated live time of the analyzed data is 304 days. Muon tracks are reconstructed using a likelihood-based algorithm. Studies of the detector timing indicate a median angular resolution of 0.5 ? 0.1 deg. The neutrino flux sensitivity is 7.5 X 10--8(E Delta *n/ GeV)--2 GeV--1 s--1 cm--2 for the part of the sky that is always visible ( Delta *d < --48 deg), which is better than limits obtained by previous experiments. No cosmic neutrino sources have been observed.
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