A. Hidvegi

The ATLAS Level-1 Calorimeter Trigger

The ATLAS Level-1 Calorimeter Trigger uses reduced-granularity information from all the ATLAS calorimeters to search for high transverse-energy electrons, photons, τ leptons and jets, as well as high missing and total transverse energy. The calorimeter trigger electronics has a fixed latency of about 1 μs, using programmable custom-built digital electronics. This paper describes the Calorimeter Trigger hardware, as installed in the ATLAS electronics cavern.

Measurement of the

First measurements of the W → ℓν and Z/γ*→ ℓℓ (ℓ = e, μ) production cross sections in proton-proton collisions at

W\to\ell\nu

\sqrt {s} = 7\;{\text{TeV}}

and

are presented using data recorded by the ATLAS experiment at the LHC. The results are based on 2250 W → ℓν and 179 Z/γ* → ℓℓ candidate events selected from a data set corresponding to an integrated luminosity of approximately 320 nb. The measured total W and Z/γ∗-boson production cross sections times the respective leptonic branching ratios for the combined electron and muon channels are

Z/gamma^\ast\to\ell\ell

\sigma_W^{\text{tot}}

Production Cross Sections in Proton-Proton Collisions at

. BR(W → ℓν) = 9.96 ± 0.23(stat) ± 0.50(syst) ± 1.10(lumi) nb and

\sqrt{s}=7

\sigma_{{{Z} \left/ {\gamma } \right.}}^{\text{tot}}

TeV with the ATLAS Detector

BR(Z/γ∗ → ℓℓ) = 0.82 ± 0.06 (stat) ± 0.05 (syst) ± 0.09(lumi) nb (within the invariant mass window 66 < mℓℓ< 116GeV). The W/Z cross-section ratio is measured to be 11.7 ± 0.9(stat) ± 0.4(syst). In addition, measurements of the W+ and W− production cross sections and of the lepton charge asymmetry are reported. Theoretical predictions based on NNLO QCD calculations are found to agree with the measurements.First measurements of the W ->lnu and Z/gamma* ->ll (l = e, mu) production cross sections in proton-proton collisions at sqrt(s) = 7 TeV are presented using data recorded by the ATLAS experiment at the LHC. The results are based on 2250 W ->lnu and 179 Z/gamma* ->ll candidate events selected from a data set corresponding to an integrated luminosity of approximately 320 nb-1. The measured total W and Z/gamma*-boson production cross sections times the respective leptonic branching ratios for the combined electron and muon channels are

The ATLAS level-1 calorimeter trigger architecture

\stotW

Timing and triggering system prototype for the XFEL project

* BR(W ->lnu) = 9.96 +- 0.23(stat) +- 0.50(syst) +- 1.10(lumi) nb and