A. Ventura

The KLOE electromagnetic calorimeter

Abstract The KLOE calorimeter is a fine lead-scintillating fiber sampling calorimeter. We describe in the following the calibration procedures and the calorimeter performances obtained after 3 years of data taking. We get an energy resolution for electromagnetic showers of 5.4%/ E (GeV) and a time resolution of 56 ps/ E (GeV) . We also present a measurement of efficiency for low-energy photons.

Data handling, reconstruction, and simulation for the KLOE experiment

Abstract The broad physics program of the KLOE experiment is based on the high event rate at the Frascati φxa0factory, and calls for an up-to-date system for data acquisition and processing. In this review of the KLOE offline environment, the architecture of the data-processing system and the programs developed for data reconstruction and Monte Carlo simulation are described, as well as the various procedures used for data handling and transfer between the different components of the system.

Measurement of the KL meson lifetime with the KLOE detector

We present a measurement of the KL lifetime using the KLOE detector. From a sample of 4 x 10^8 KS KL pairs following the reaction e+ e- ->phi ->KS KL we select 15 x 10^6 KL ->p0 p0 p0 decays tagged by KS ->pi+ pi- events. From a fit of the proper time distribution we find tau_L = (50.92 +- 0.17{stat} +- 0.25{syst})

Overview of the high-level trigger electron and photon selection for the ATLAS experiment at the LHC

ns. This is the most precise measurement of the KL lifetime performed to date.

Implementation and performance of the seeded reconstruction for the ATLAS event filter

The ATLAS experiment is one of two general purpose experiments to start running at the Large Hadron Collider in 2007. The short bunch crossing period of 25 ns and the large background of soft-scattering events overlapped in each bunch crossing pose serious challenges that the ATLAS trigger must overcome in order to efficiently select interesting events. The ATLAS trigger consists of a hardware-based first-level trigger and of a software-based high-level trigger, which can be further divided into the second-level trigger and the event filter. This paper presents the current state of development of methods to be used in the high-level trigger to select events containing electrons or photons with high transverse momentum. The performance of these methods is presented, resulting from both simulation studies, timing measurements, and test beam studies.

The ATLAS Muon Trigger Slice

ATLAS is one of the four major Large Hadron Collider (LHC) experiments that will start data taking in 2007. It is designed to cover a wide range of physics topics. The ATLAS trigger system has to be able to reduce an initial 40 MHz event rate, corresponding to an average of 23 proton-proton inelastic interactions per every 25 ns bunch crossing, to 200 Hz admissible by the Data Acquisition System. The ATLAS trigger is divided in three different levels. The first one provides a signal describing an event signature using dedicated custom hardware. This signature must be confirmed by the High Level Trigger (HLT) which using commercial computing farms performs an event reconstruction by running a sequence of algorithms. The validity of a signature is checked after every algorithm execution. A main characteristic of the ATLAS HLT is that only the data in a certain window around the position flagged by the first level trigger are analyzed. In this work, the performance of one sequence that runs at the Event Filter level (third level) is demonstrated. The goal of this sequence is to reconstruct and identify high transverse momentum electrons by performing cluster reconstruction at the electromagnetic calorimeter, track reconstruction at the Inner Detector, and cluster track matching.

The ATLAS Muon Trigger "Slice"

The ATLAS experiment at the LHC will face the challenge of selecting interesting candidate events in proton-proton collisions at 14 TeV center of mass energy, while rejecting the enormous number of background events. The trigger system architecture is organized in three levels. From a bunch crossing rate of 40 MHz the First level trigger, hardware implemented, will reduce this rate to around ~75 kHz. Then the software based high level trigger (HLT), composed by the second level trigger and the event filter reduces the rate to ~ 200 Hz. HLT is implemented on commercial CPUs using a framework built on the common ATLAS object oriented software architecture. Inclusive trigger selections are used to collect events for the ATLAS physics program; final states with muons are crucial for electroweak precision measurements as well as Higgs and SUSY searches. In this paper we will present the implementation of the muon slice, signal efficiencies, background rejection rates and system performances (execution time,...) for online muon selection based on Monte Carlo simulations and results obtained on real events collected during cosmic data taking runs.

Implementation and performance of the third level muon trigger of the ATLAS experiment at LHC

The ATLAS experiment at the Large Hadron Collider (LHC) will face the challenge of selecting interesting candidate events in proton-proton collisions at 14 TeV center of mass energy, while rejecting the enormous number of background events. The trigger system architecture is organized in three levels. From a bunch crossing rate of 40 MHz, the First Level trigger, hardware implemented, will reduce this rate to around ~75 kHz. Then the software based High Level Trigger (HLT), composed by the Second Level Trigger and the Event Filter reduces the rate to 200 Hz. In this paper, we will present the implementation of the muon trigger ldquoslice,rdquo signal efficiencies, background rejection rates, and system performances (execution time, memory consumption, etc.) for online muon selection based on Monte Carlo simulations and results obtained on real events collected during cosmic data taking runs.

Data acquisition and monitoring for the KLOE detector

The trigger system of the ATLAS experiment at the LHC aims at a high selectivity in order to keep the full physics potential while reducing the 40 MHz initial event rate imposed by the LHC bunch crossing down to /spl sim/100 Hz, as required by the data acquisition system. Algorithms working in the final stage of the trigger environment (Event Filter) are implemented to run both in a wrapped mode (reconstructing tracks in the entire Muon Spectrometer) and in a seeded mode (according to a dedicated strategy that performs pattern recognition only in regions of the detector where trigger hypotheses have been produced at earlier stages). The working principles of the offline muon reconstruction and identification algorithms (MOORE and MuId) implemented and used in the framework of the Event Filter are discussed in this paper. The reconstruction performance of these algorithms is presented for both modes in terms of efficiency, momentum resolution, rejection power and execution times on several samples of simulated single muon events, also taking into account the high background environment expected for ATLAS.