LHCb's Experiment Control System will handle the configuration, monitoring, and operation of all experimental equipment involved in the various activities of the experiment. A control framework ...(based on an industrial SCADA system) allowing the integration of the various devices into a coherent hierarchical system is being developed in common for the four Large Hadron Collider (LHC) experiments. The aim of this paper is to demonstrate that the same architecture and tools can be used to control and monitor all the different types of devices, from front-end electronics boards to temperature sensors to algorithms in an event filter farm, thus providing LHCb with a homogeneous control system and a coherent interface to all parts of the experiment.
The LHCb software trigger has two levels: a high-speed trigger running at 1 MHz with strictly limited latency and a second level running below 40 kHz without latency limitations. The trigger strategy ...requires full flexibility in the distribution of the installed CPU power to the two software trigger levels because of the unknown background levels and event topology distribution at the time the LHC accelerator will start its operation. This requirement suggests using a common CPU farm for both trigger levels fed by a common data acquisition (DAQ) infrastructure. The limited latency budget of the first level of software trigger has an impact on the organization of the CPU farm performing the trigger function for optimal usage of the installed CPU power. We will present the architecture and the design of the hardware infrastructure for the entire LHCb software triggering system based on Ethernet as link technology that fulfills these requirements. The performance of the event-building of the combined traffic of both software trigger levels, as well as the expected scale of the system will be presented.
A search is made for charged Higgs bosons predicted by Two-Higgs-Doublet extensions of the Standard Model (2HDM) using electron-positron collision data collected by the OPAL experiment at
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\begin{document}$\sqrt{s}=189\mbox{--}209\ \mbox{GeV}$\end{document}
, corresponding to an integrated luminosity of approximately 600 pb
−1
. Charged Higgs bosons are assumed to be pair-produced and to decay into
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\begin{document}$\mathrm{q} \bar{\mathrm{q}}$\end{document}
,
τν
τ
or AW
±
. No signal is observed. Model-independent limits on the charged Higgs-boson production cross section are derived by combining these results with previous searches at lower energies. Under the assumption
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\begin{document}$\mathrm{BR} (\mathrm{H}^{\pm} \to \tau\nu_{\tau}) + \mathrm{BR} (\mathrm{H}^{\pm} \to \mathrm{q} \bar{\mathrm{q}}) = 1$\end{document}
, motivated by general 2HDM type II models, excluded areas on the
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\begin{document}$m_{\mathrm{H}^{\pm}} , \mathrm{BR} (\mathrm {H}^{\pm} \to \tau\nu_{\tau})$\end{document}
plane are presented and charged Higgs bosons are excluded up to a mass of 76.3 GeV at 95 % confidence level, independent of the branching ratio BR(H
±
→
τν
τ
). A scan of the 2HDM type I model parameter space is performed and limits on the Higgs-boson masses
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\begin{document}$m_{\mathrm{H}^{\pm}}$\end{document}
and
m
A
are presented for different choices of tan
β
.
A search is performed for Higgs bosons decaying into invisible final states, produced in association with a Z0 boson in e+e− collisions at energies between 183 and 209 GeV. The search is based on ...data samples collected by the OPAL detector at LEP corresponding to an integrated luminosity of about 660 pb−1. The analysis aims to select events containing the hadronic decay products of the Z0 boson and large missing momentum, as expected from Higgs boson decay into a pair of stable weakly interacting neutral particles, such as the lightest neutralino in the Minimal Supersymmetric Standard Model. The same analysis is applied to a search for nearly invisible Higgs boson cascade decays into stable weakly interacting neutral particles. No excess over the expected background from Standard Model processes is observed. Limits on the production of invisibly decaying Higgs bosons produced in association with a Z0 boson are derived. Assuming a branching ratio BR(h0→invisible)=1, a lower limit of 108.2 GeV is placed on the Higgs boson mass at the 95% confidence level. Limits on the production of nearly invisibly decaying Higgs bosons are also obtained.
Inclusive jet production (e+e−→e+e−+jet+X) is studied in collisions of quasi-real photons radiated by the LEP beams at e+e− centre-of-mass energies see from 189 to 209 GeV. Jets are reconstructed ...using the k⊥ jet algorithm. The inclusive differential cross-section is measured as a function of the jet transverse momentum, pTjet, in the range 5<pTjet<40 GeV for pseudo-rapidities, ηjet, in the range −1.5<ηjet<1.5. The results are compared to predictions of perturbative QCD in next-to-leading order in the strong coupling constant.
Hadronic events produced in e+e- collisions by the LEP collider and recorded by the OPAL detector were used to form distributions based on the number of reconstructed jets. The data were collected ...between 1995 and 2000 and correspond to energies of 91 GeV, 130-136 GeV and 161-209 GeV. The jet rates were determined using four different jet-finding algorithms (Cone, JADE, Durham and Cambridge). The differential two-jet rate and the average jet rate with the Durham and Cambridge algorithms were used to measure in the LEP energy range by fitting an expression in which calculations were matched to a NLLA prediction and fitted to the data. Combining the measurements at different centre-of-mass energies, the value of () was determined to beαS(MZ) = 0.1177 ± 0.0006 (stat.) ± 0.0012 (expt.) ± 0.0010 (had.) ± 0.0032 (theo.).
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