Precision Timing with the CMS MIP Timing Detector

Cristián H Peña,Cms Collaboration

doi:10.1088/1742-6596/1162/1/012035

Abstract

The Compact Muon Solenoid (CMS) detector at the CERN Large Hadron Collider (LHC) is undergoing an extensive Phase II upgrade program to prepare for the challenging conditions of the High Luminosity LHC (HL-LHC). A new timing layer is designed to measure minimum ionizing particles (MIPs) with a time resolution of 30 ps and hermetic coverage up to a pseudo-rapidity of |η|=3. This MIP Timing Detector (MTD) will consist of a central barrel region based on LYSO:Ce crystals read out with SiPMs and two end-caps instrumented with radiation-tolerant Low Gain Avalanche Detectors (LGADs). The precision time information from the MTD will reduce the effects of the high levels of pile-up expected at the HL-LHC and will bring new and unique capabilities to the CMS detector. The time information assigned to each track will enable the use of 4D-vertexing which will render a 5-fold pile-up reduction thus recovering the current conditions. Precision timing will also enable new time-based isolations and improved b-tagging algorithms. All of this translates into a 20% gain in effective luminosity when looking at di-Higgs boson events decaying to a pair of b-quarks and two photons. We present the current status and ongoing R&D of the MTD, including implications on the physics reach at the HL-LHC and test beam results.

Highlights

The primary goal of the Phase-2 upgrade for the High-Luminosity Large Hadron Collider (LHC) (HL-LHC) is to maintain the excellent performance of the Compact Muon Solenoid (CMS) detector in efficiency, resolution, and background rejection for all final state particles and physical quantities used in data analyses
A new timing layer is designed to measure minimum ionizing particles (MIPs) with a time resolution of 30 ps and hermetic coverage up to a pseudo-rapidity of |η|=3. This MIP Timing Detector (MTD) will consist of a central barrel region based on LYSO:Ce crystals read out with silicon photomultipliers (SiPMs) and two end-caps instrumented with radiationtolerant Low Gain Avalanche Detectors (LGADs)
Barrel Timing Layer For the barrel timing layer (BTL), we propose to adapt the present Tracker Support Tube (TST) design by instrumenting the current location of the thermal screen with a thin, actively cooled, standalone detector, based on lutetium-yttrium orthosilicate crystals activated with cerium (LYSO:Ce) read out with SiPMs

Summary

Introduction

The primary goal of the Phase-2 upgrade for the High-Luminosity LHC (HL-LHC) is to maintain the excellent performance of the CMS detector in efficiency, resolution, and background rejection for all final state particles and physical quantities used in data analyses. The timing upgrade of the CMS detector will improve the particle-flow performance at high pileup to a level comparable to the Phase-1 CMS detector, exploiting the additional information provided by the precision timing of both tracks and energy deposits in the calorimeters. Instances of vertex merging are reduced from 15% in space to 1% in spacetime Another quantitative measure of the performance improvement is shown in the right panel of Fig. 1, showing the rate of tracks from pileup vertices incorrectly associated with the hard interaction vertex as a function of the line density of vertices.

Detector requirement

Findings

Endcap Timing Only