J. P. Rutherfoord

Design, construction, and performance of the electromagnetic module of the DØ end calorimeter

Author(s): Aihara, H.; Arthur, A.A.; Dahl, O.I.; Eberhard, P.H.; Edwards, W.R.; Fulton, R.L.; Haughian, J.M.; Madaras, R.J.; Roe, N.A.; Shuman, D.B.; Spadafora, A.L.; Stevenson, M.L.; Taylor, J.D.; Wenzel, W.A.

Liquid ionization calorimetry with time-sampled signals☆

We present the results of a study of amplitude and timing measurements made in a liquid krypton electromagnetic calorimeter, using multiply sampled signals of the shaped waveform. The measurements were designed to emulate the type of data that will be available from a calorimeter operating at future hadron-hadron colliders with short (∼ 20 ns) spacing between bunch crossings. Data have been collected with 18 ns sample spacing on waveforms from individual calorimeter sections with a shaping time of 40 ns and from 5 × 5 tower analog sums with a shaping time of 50 ns. The amplitude was measured using the analog sum signal, and the timing was measured using the signal from the individual sections. The data were processed using the method of optimal filtering, and a reduction in the noise of about a factor of two over that for a single sample is seen when using multiple samples for determining the amplitude. We find an energy resolution of 6.7%E, in agreement with the resolution measured for the same calorimeter using a single sample measured at the peak of the waveform. The timing resolution for a section of a calorimeter tower with deposited energy ∈ can be expressed as (c∈)2 + σcal2, with a value of c of 0.38 GeV ns for the front section (the first 6 radiation lengths) and 0.70 GeV ns for the back section, and a value of 0.15 ns for σcal.

Precision timing with liquid ionization calorimeters

We present timing measurements performed with a liquid krypton electromagnetic accordion calorimeter, measured in an electron beam over an energy range of 5–20 GeV. A novel discriminator with an amplitude-independent timing response was used to extract the inherently accurate timing information from the calorimeter. As expected, the timing resolution στ is observed to vary inversely with the signal amplitude, which is proportional to the deposited energy E. We measure a resolution of στ = 4.15±0.06 GeV ns/E for a sum of 5×5 towers with dimensions 2.7×2.5 cm2 each. From this we deduce that the timing resolution for an individual tower is approximately 0.8 GeV ns/E.

Performance of an accordion electromagnetic calorimeter with liquid krypton and argon

Test results of a liquid krypton/argon electromagnetic calorimeter with accordion type electrode structure are presented. The test was carried out at the Brookhaven AGS in a negative beam with good electron identification at momenta 5, 10, 15, and 20 GeV/c. Results on energy resolution, linearity, pointing resolution, and muon response are presented. The results are in good agreement with Monte Carlo calculations. The energy resolution of 6.7%E was achieved using liquid krypton and 7.7%E with liquid argon, with a negligible constant term.

Relative luminosity measurement of the LHC with the ATLAS forward calorimeter

In this paper it is shown that a measurement of the relative luminosity changes at the LHC may be obtained by analysing the currents drawn from the high voltage power supplies of the electromagnetic section of the forward calorimeter of the ATLAS detector. The method was verified with a reproduction of a small section of the ATLAS forward calorimeter using proton beams of known beam energies and variable intensities at the U-70 accelerator at IHEP in Protvino, Russia. The experimental setup and the data taking during a test beam run in April 2008 are described in detail. A comparison of the measured high voltage currents with reference measurements from beam intensity monitors shows a linear dependence on the beam intensity. The non-linearities are measured to be less than 0.5% combining statistical and systematic uncertainties.

Electron testbeam results for the ATLAS liquid argon forward calorimeter prototype

Abstract A novel liquid argon calorimeter concept with thin cylindrical shell gaps, meeting the required physics performance for the forward region (/ vbη / vb > 3) in a high energy, high luminosity hadron collider experiment such as ATLAS, is described. A prototype for the electromagnetic section was built and tested in two electron testbeam runs at the Brookhaven AGS and at the CERN North Area in 1993, covering a total energy range from 2 to 200 GeV. Dependences of the signal on the impact angle and varying inactive material in front of the calorimeter have been studied. Important performance requirements such as signal linearity better than 2%, a sufficient energy resolution with a constant term of about 4% and a very good space resolution of about 0.6 mm have been demonstrated.

An accordion liquid argon electromagnetic calorimeter with absorber in all electrodes

Abstract A prototype electromagnetic liquid argon calorimeter with accordion geometry, using absorber material in all electrodes, has been constructed and tested. This construction results in twice the sampling frequency compared to the conventional accordion electrode structure. The energy resolution, measured with 15 GeV electrons, was found to be 6.3%/√E, in good agreement with the value expected from Monte Carlo simulations.

Performance of the ATLAS liquid argon forward calorimeter in beam tests

One of two ATLAS Forward Calorimeters, consisting of three modules, one behind the other, was exposed to particle beams of known energies in order to study the detector performance with and without the presence of upstream material in the beam, and at the inner edge of the acceptance where shower energy containment is incomplete. Data were taken in the H6 beamline at CERN using electron and hadron beams with energies from 10 to 200 GeV. Results related to the intrinsic detector calibration, based on data taken with a minimal amount of material in front of the detector, have been previously published, but are updated here. This paper focuses on studies of data taken with additional upstream material in place. The effects of this additional material on the linearity and resolution of the response are presented. The response at the inner edge of the acceptance is also investigated. For all analyses, results based on a GEANT4 simulation of the beam-test setup and detector response are also presented.