Data taken with the ALEPH detector at LEP1 have been used to search for
γγ production of the glueball candidates
f
0(1500) and
f
J
(1710) via their decay to
π
+
π
−. No signal is observed and upper ...limits to the product of
γγ width and
π
+
π
− branching ratio of the
f
0(1500) and the
f
J
(1710) have been measured to be
Γ(γγ→f
0(1500))·
B
R(f
0(1500)→π
+π
−)<0.31
keV
and
Γ(γγ→f
J(1710))·
B
R(f
J(1710)→π
+π
−)<0.55
keV
at 95% confidence level.
Hadronic Z decay data taken with the ALEPH detector at LEP1 are used to measure the three-jet rate as well as moments of various event-shape variables. The ratios of the observables obtained from ...b-tagged events and from an inclusive sample are determined. The mass of the b quark is extracted from a fit to the measured ratios using a next-to-leading order prediction including mass effects. Taking the first moment of the \(y_3\) distribution, which is the observable with the smallest hadronization corrections and systematic uncertainties, the result isThe measured ratio is alternatively employed to test the flavour independence of the strong coupling constant for b and light quarks.
Leptonic decays of the Ds meson Merle, E.; Boix, G.; Fernandez, E. ...
Physics letters. B,
02/2002, Letnik:
528, Številka:
1-2
Journal Article
Recenzirano
Odprti dostop
The purely leptonic decays Ds→τν and Ds→μν are studied in a sample of four million hadronic Z decays collected with the ALEPH detector at the LEP e+e− collider from 1991 to 1995. The branching ...fractions are extracted from a combination of two analyses, one optimized to select Ds→τν decays with τ→eνν̄ or μνν̄, and the other optimized for Ds→μν decays. The results are used to evaluate the Ds decay constant, within the Standard Model: fDs=285±19(stat)±40(syst) MeV.
The triple gauge-boson couplings involving the W are determined using data samples collected with the ALEPH detector at mean centre-of-mass energies of 183 GeV and 189 GeV, corresponding to ...integrated luminosities of 57 pb\(^{-1}\) and 174 pb\(^{-1}\), respectively. The couplings, \(g^Z_1\), \(\kappa_\gamma\) and \(\lambda_\gamma\), are measured using W-pair events, single-{\it W} production and single-\(\gamma\) production. Each coupling is measured individually with the other two couplings fixed at their standard model value. Including ALEPH results from lower energies, the 95% confidence level intervals for the deviation to the standard model are \(-0.087 <\Delta{g}^{Z}_1 < 0.141\), \(-0.200 < \Delta\kappa_\gamma < 0.258\), and \(-0.062 < \lambda_\gamma < 0.147\).Fits are also presented where two or all three couplings are allowed to vary. In addition, W-pair events are used to set limits on the C- or P-violating couplings \(g^V_4\), \(g^V_5\), \({\tilde{\kappa}_{V}}\), and \({\tilde{\lambda}_{V}}\), where V denotes either \(\gamma\) or Z. No deviations from the standard model expectations are observed.
A search for Higgs bosons produced in association with a fermion pair, and decaying to WW, is performed with the data collected by the ALEPH detector at centre-of-mass energies ranging from 191 to ...209 GeV. The data correspond to an integrated luminosity of 453.2 pb-1. Thirteen exclusive selections are developed according to the different final state topologies. No statistically significant evidence for a Higgs boson decaying into a WW pair has been found. An upper limit is derived, as a function of the Higgs boson mass, on the product of the e+e-→Hff̄ cross section and the H→WW branching ratio. The data on the search for H→WW are combined with previously published ALEPH results on the search for H→γγ, to significantly extend the limits on the mass of a fermiophobic Higgs boson.
The acoplanar photon pairs produced in the reaction
e
+
e
−
→
ν
ν
¯
γ
γ
are analysed in the 700 pb
−1 of data collected by the ALEPH detector at centre-of-mass energies between 183 and 209 GeV. No ...deviation from the Standard Model predictions is seen in any of the distributions examined. The resulting 95% C.L. limits set on the anomalous QGCs,
a
0
Z
,
a
c
Z
,
a
0
W
and
a
c
W
, are
−
0.012
<
a
0
Z
/
Λ
2
<
+
0.019
GeV
−
2
,
−
0.041
<
a
c
Z
/
Λ
2
<
+
0.044
GeV
−
2
,
−
0.060
<
a
0
W
/
Λ
2
<
+
0.055
GeV
−
2
,
−
0.099
<
a
c
W
/
Λ
2
<
+
0.093
GeV
−
2
, where
Λ is the energy scale of the new physics responsible for the anomalous couplings.
The cross sections for single vector boson production in the Weν and Zee channels are measured from the data collected by the ALEPH detector at LEP for centre-of-mass energies between 183 and 209 ...GeV. These data correspond to a total integratedluminosity of 683 pb−1. Single-W production is studied in both hadronic and leptonic decay channels. Hadronic and dimuon decays are used for single-Z production. The measured cross sections agree with the Standard Model predictions.
Search for neutral MSSM Higgs bosons at LEP De Bonis, I.; Tempesta, P.; Xue, S. ...
The European physical journal. C, Particles and fields,
07/2006, Letnik:
47, Številka:
7
Journal Article
Recenzirano
Odprti dostop
The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric standard model (MSSM). The data of the four ...collaborations are statistically combined and examined for their consistency with the background hypothesis and with a possible Higgs boson signal. The combined LEP data show no significant excess of events which would indicate the production of Higgs bosons. The search results are used to set upper bounds on the cross-sections of various Higgs-like event topologies. The results are interpreted within the MSSM in a number of “benchmark” models, including CP-conserving and CP-violating scenarios. These interpretations lead in all cases to large exclusions in the MSSM parameter space. Absolute limits are set on the parameter cosβ and, in some scenarios, on the masses of neutral Higgs bosons.
During 2006 and the first half of 2007, the installation, integration and commissioning of trigger and data acquisition (TDAQ) equipment in the ATLAS experimental area have progressed. There have ...been a series of technical runs using the final components of the system already installed in the experimental area. Various tests have been run including ones where level 1 preselected simulated proton-proton events have been processed in a loop mode through the trigger and dataflow chains. The system included the readout buffers containing the events, event building, level 2 and event filter trigger algorithms. The scalability of the system with respect to the number of event building nodes used has been studied and quantities critical for the final system, such as trigger rates and event processing times, have been measured using different trigger algorithms as well as different TDAQ components. This paper presents the TDAQ architecture, the current status of the installation and commissioning and highlights the main test results that validate the system.
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