Abstract

The performance of the CMS electromagnetic calorimeter (ECAL) has been continuously monitored during LHC running. The evolution of this performance is a critical issue for the future, in particular for High-Luminosity LHC (HL-LHC) operation which is planned for 2022 and beyond. Work has started to assess the need for possible changes to the detector in order to maintain adequate performance in the high radiation environment of HL-LHC. In this paper, results from CMS running, beam tests and laboratory measurements on proton-irradiated crystals are combined to predict the performance of the current detector during the HL-LHC phase. Several options for the replacement of the CMS endcap calorimeters for HL-LHC running are presented.

Highlights

  • I N order to exploit the full potential of the Large H√adron Collider (LHC) at CERN a major upgrade will be carried out around 2022 to increase the instantaneous luminosity of the collider

  • This paper addresses the status of these studies, in order to carry out an optimum upgrade of the CMS electromagnetic calorimeter (ECAL) endcaps during the long LHC shutdown which is foreseen around 2022

  • It is of great importance to evaluate the future performance of the current calorimeter in the High-Luminosity LHC (HL-LHC) environment in order to assess the need for an eventual upgrade of some of its components

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Summary

INTRODUCTION

I N order to exploit the full potential of the LHC at CERN a major upgrade will be carried out around 2022 to increase the instantaneous luminosity of the collider. To understand whether the calorimeter will be able to maintain good performance during HL-LHC, several studies on Lead Tungstate (PbWO4) crystals have been performed, establishing that high-energy protons and pions cause a cumulative loss of light transmission in PbWO4 [2]–[5]. Test beam studies were used to measure the performance of 5×5 matrices of PbWO4 crystals following exposures to hadron fluences similar to those predicted at the end of HL-LHC These experimental data have been used to construct a simulation model in order to predict the detector performance in situ. This feature played an important role in the discovery of the Higgs boson with the CMS detector [7]

THE HIGH LUMINOSITY LHC ENVIRONMENT
RADIATION DAMAGE IN PBWO4 CRYSTALS
EVALUATION OF THE LONG TERM PERFORMANCE OF THE CMS ECAL
Test beam studies
Simulation predictions
POSSIBLE DESIGN OPTIONS FOR THE CALORIMETER
Upgrade Scenario 1
Upgrade Scenario 2
CONCLUSIONS

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