Performance of the CMS precision electromagnetic calorimeter at the LHC Run II and prospects for high-luminosity LHC

doi:10.1016/j.nima.2017.10.079

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Volume 912, 21 December 2018, Pages 105-109

https://doi.org/10.1016/j.nima.2017.10.079 Get rights and content

Highlights

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The high-performance CMS electromagnetic calorimeter will operate at the High Luminosity LHC.
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Strategies employed to maintain the excellent performance of the CMS ECAL are described.
•
Status and plans for the upgraded ECAL barrel electronics for the HL-LHC are presented.

Abstract

The Compact Muon Solenoid (CMS) electromagnetic calorimeter (ECAL) is a high-performance calorimeter which will operate also at the High Luminosity Large Hadron Collider (HL-LHC). This talk will describe the strategies that have been employed to maintain the excellent performance of the CMS ECAL throughout Run 2. Performance results from the 2015–2016 data taking periods will be shown and an outlook on the expected Run 2 performance in the years to come will be provided. The status and plans for the upgraded ECAL barrel electronics for the HL-LHC will be presented, based on recent results from simulations, laboratory tests, and test beam measurements of prototype devices.

Introduction

The electromagnetic calorimeter (ECAL) of the Compact Muon Solenoid (CMS) experiment [1] is a high-resolution, hermetic, homogeneous and compact detector made of 75 848 lead tungstate ( $P b W O_{4}$ ) scintillating crystals arranged in a cylindrical structure around the LHC [2] interaction point.

The lead tungstate crystals are radiation tolerant, have fast scintillation ( $\sim 75 %$ in 25 ns), density $ρ = 8.28$ g/cm $^{3}$ , short radiation length ( $X_{0} = 0.89$ cm) and small Moliere radius ( $R_{M} = 2.2$ cm).

In the barrel (EB) covering the region $| η | < 1.48$ , the scintillation light from the crystals is read out by avalanche photodiodes (APDs) while in the two endcaps (EE) extending the coverage to $1.48 < | η | < 3.0$ , it is read out by vacuum phototriodes (VPTs). The pre-shower (ES) region with $1.65 < | η | < 2.6$ is instead made of 2 layers of $P b ∕ S i$ strips, with about 140 000 read-out channels.

Section snippets

ECAL at the LHC Run 2

The ECAL occupies an important role in many CMS physics analyses at the LHC. The excellent ECAL energy resolution played a key role in the discovery of the Higgs boson in LHC Run 1 through the $H \to γ γ$ decay channel and in the measurement of its couplings to other particles [3]. An high performance electromagnetic calorimetry is crucial also for many analyses of physics beyond the Standard Model (BSM), such as high-mass resonances or detection of final states with energetic photons or electrons [4

ECAL current performance

New techniques have been developed to maintain the ECAL energy resolution and trigger performance at higher pileup, like a more efficient electromagnetic trigger algorithm and a new method for pulse shape reconstruction.

The new multifit pulse shape reconstruction mitigate the effect of out-of-time (OOT) pile-up events, under the high luminosity conditions of Run 2. The pulse shape is modeled as the sum of one in-time signal amplitude and up to 9 OOT amplitudes (one per bunch crossing),

ECAL barrel upgrade for the HL-LHC

The LHC program foresees a high-luminosity phase (HL-LHC) [6] starting from 2026. The proposed operating scenario for the HL-LHC is to provide collisions with an instantaneous luminosity of at least $5 \times 1 0^{34}$ cm⁻² s⁻¹ and to accumulate a total dataset of about 3000 fb⁻¹ over a further 10 years of operation. The expected pileup is a factor of four larger than the current Run 2 values, and unprecedented levels of radiation, up to six times higher than for LHC, will be experienced. The HL-LHC will

Conclusions

The CMS electromagnetic calorimeter has been giving excellent performance throughout LHC Run 2 data taking. It is crucial for many CMS physics analyses at the LHC thanks to its precise measurements of electrons and photons energies. In the future years, an upgrade of the detector will be needed for the High Luminosity LHC to maintain performance comparable to Run 2 in an environment with unprecedented levels of pileup and radiation. Test beam measurements of prototype devices are being carried

References (9)

The CMS experiment at the CERN LHC
JINST
(2008)
EvansL. et al.
LHC machine
JINST
(2008)
Observation of the diphoton decay of the Higgs boson and measurement of its properties
Eur. Phys. J. C
(2014)
Search for narrow resonances in dilepton mass spectra in proton–proton collisions at $\sqrt{s} = 13$ TeV and combination with 8 TeV data
Phys. Lett. B
(2017)

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Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Performance of the CMS precision electromagnetic calorimeter at the LHC Run II and prospects for high-luminosity LHC

Highlights

Abstract

Introduction

Section snippets

ECAL at the LHC Run 2

ECAL current performance

ECAL barrel upgrade for the HL-LHC

Conclusions

The CMS experiment at the CERN LHC

JINST

LHC machine

JINST

Observation of the diphoton decay of the Higgs boson and measurement of its properties

Eur. Phys. J. C

Search for narrow resonances in dilepton mass spectra in proton–proton collisions at s=13 TeV and combination with 8 TeV data

Phys. Lett. B

Search for narrow resonances in dilepton mass spectra in proton–proton collisions at $\sqrt{s} = 13$ TeV and combination with 8 TeV data