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High Energy Physics


Cambridge Linear Collider Group - CALICE

CALICE - Calorimetry for an ILC detector

Maurice Goodrick, Bart Hommels, Mark Thomson, David Ward

The CALICE collaboration was formed to coordinate various R&D efforts aimed at developing technologies for particle flow calorimetry, motivated originally by the needs of future ILC experiments. The Cambridge group joined the CALICE collaboration in 2002. CALICE is an umbrella for several strands of R&D projects. Electromagnetic and hadronic calorimeters have been tested both separately and together, using different choices of absorber material (Iron, Tungsten). Several detector technologies are also under consideration -- silicon pads, scintillator tiles, large area resistive plate chambers (RPCs), MicroMegas and GEMs.

prototype calorimeters

The activities of CALICE have been focussed on a series of beam tests being performed since 2006 in which a series of prototype calorimeter modules were exposed to a variety of hadron and electron beams. The prototypes are all directed towards the construction of calorimeters with high granularity, dictated by the requirements of particle flow.

The first prototype electromagnetic calorimeter was a silicon-tungsten sampling calorimeter, with readout through 1x1cm2 silicon pads. The 18x18x18cm3 prototype has approximately 104 readout channels. See this paper for details. In parallel, a calorimeter is being tested in which small scintillator strips, of dimensions 1x4 cm, are used instead of the silicon.

prototype ECAL

The first hadronic calorimeter prototype was of the iron-scintillator sampling type, with dimensions 1x1x1m3 and sampling using 3x3cm2 tiles in the shower core. Later, the scintillator will be replaced by RPCs and GEMs with digital readout in pads of size 1x1cm2. The electromagnetic and hadronic calorimeters were tested together in CERN in 2006-7, and in Fermilab from 2008.

As well as yielding information about various detector technologies, the beam tests are playing a crucial role in validating the Monte Carlo simulation programs which will be used to optimise the design of a full detector. In particular, simulations of hadronic shower processes in calorimeters are notoriously problematic, and good data are essential before credible simulation results can be delivered.

Dif card

More recent activities have centred on developing prototype technologies which can be directly scaled to a full-size detector, with very low power consumption and extreme compactness in the readout.

Cambridge and CALICE

The Cambridge group played a leading role in the CALICE data analysis and simulation effort in the UK, though our level of involvement has reduced since 2010. This involved technical studies, comparing the simulation of key physics processes in various Monte Carlo packages, which then led into comparisons with test beam data. The latest version of GEANT4 was found to give satisfactory agreement with the electron beam data, while older versions were not acceptable.

For example, extensive studies of pion interactions in the CALICE Si-W ECAL were made in Cambridge. These provided novel tests of GEANT, since the fine granularity of the ECAL allowed excellent resolution of the longitudinal shower structure, which yielded sensitivity to the various particle components in the hadronic showers.

We also provided monitoring software for use in the CALICE test beam runs.

We have carried out longer term electronics R&D for granular calorimeters. The physics requirements demand that the calorimeter be very compact. Signals from tens of millions of sensors have to be read out in minimal space, with minimal power dissipation. This forms the basis for a challenging R&D programme. The main outcome of this work has been the provision of detector interface cards (DIFs) for the second generation CALICE Si-W ECAL, under the aegis of the EUDET project, and the development of techniques for the interconnection of modules into long detector slabs.