Abstract
Traditionally, EM and HAD compartments are thought to be separate and are often optimized individually. However, it is possible to optimize a robust and economical combined calorimeter system for myriad physics objectives. By employing event-by-event compensation afforded by the dual-readout technique, we have shown that excellent jet performance can be attained with a longitudinally un-segmented calorimeter that is calibrated only with electrons. In addition, the linear hadronic energy scale renders complex off-line correction schemes unnecessary. The proposed replacement of the CMS EE and HE calorimeters with a single Combined Forward Calorimeter (CFC) shows excellent jet performance complemented by good EM object detection. In this paper, we give brief snapshots on basic design criteria, timing characteristics of Cherenkov and scintillation pulses, trigger generation criteria and performance under high radiation fields. Although CMS has recently chosen different technologies for its endcap calorimetry in Phase II, the concepts developed here are likely to remain valuable for some time to come.
Highlights
The Combined Forward Calorimeter (CFC) can be thought of as two independent calorimeters occupying the same volume that provide complementary information
We have shown that excellent performance can be attained with a longitudinally un-segmented calorimeter that is calibrated only with electrons in beam tests [1, 2, 3, 4] and in standalone simulations [5]
The second path is for a detailed analysis of the Cherenkov signal using a multi-GHz pulse-shape sampler
Summary
The Combined Forward Calorimeter (CFC) can be thought of as two independent calorimeters occupying the same volume (the clear and scintillator fibers as two active media in a single absorber) that provide complementary information. The Cherenkov (Q) part originating in the clear fibers provides information on the EM content as well as the fast timing signal, whereas the scintillation (S) part predominantly gives information on ionization (dE/dx) losses. The ratio of the two signals enables us to measure the EM fraction (fem) of a shower event-by-event and to remove the source of one of the larger fluctuations in energy measurement. The proposed calorimeter gives excellent energy measurement and it is likely to help mitigate pile-up effects because of its fast (Cherenkov) response and fine transverse granularity. It is possible to optimize a robust and economical combined calorimeter (ECAL+HCAL) system for myriad physics objectives. Our studies targeted optimization of crucial design aspects: the absorber (tungsten vs brass), tower orientation
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