Calibration of the CMS Pixel Detector at the Large Hadron Collider

Tamas Almos Vami

doi:10.1016/j.nuclphysbps.2015.09.447

Abstract

The Compact Muon Solenoid (CMS) detector is one of two general-purpose detectors that reconstruct the products of high energy particle interactions at the Large Hadron Collider (LHC) at CERN. The silicon pixel detector is the innermost component of the CMS tracking system. It determines the trajectories of charged particles originating from the interaction region in three points with high resolution enabling precise momentum and impact parameter measurements in the tracker. The pixel detector is exposed to intense ionizing radiation generated by particle collisions in the LHC. This irradiation could result in temporary or permanent malfunctions of the sensors and could decrease the efficiency of the detector. We have developed procedures in order to correct for these effects. In this paper, we present the types of malfunctions and the offline calibration procedures. We will also show the efficiency and the resolution of the detector in 2012.

Highlights

The Compact Muon Solenoid (CMS) detector is a general-purpose detector at the Large Hadron Collider (LHC) at CERN [1]
The Compact Muon Solenoid (CMS) detector is one of two general-purpose detectors that reconstruct the products of high energy particle interactions at the Large Hadron Collider (LHC) at CERN
The silicon pixel detector is the innermost component of the CMS tracking system

Summary

Introduction

The CMS detector is a general-purpose detector at the LHC at CERN [1]. The task of the CMS Tracker [2] is to measure the trajectories of charged particles with high accuracy and reconstruction efficiency [3]. The pixel detector is constructed in hybrid pixel technology. The barrel pixel detector (BPIX) consists of three cylindric layers of pixel modules oriented coaxially with respect to the beamline and centred around the collision point. The forward pixel detector (FPIX) includes a pair of disks per side composed of pixel modules, which are situated orthogonally to the beamline on each side of BPIX. The sensors of the pixel detector are segmented into a total of 66 million pixels, each with the size of 100 μm × 150 μm. A 52 × 80 pixel array is processed by one read-out chip

Track reconstruction

Detector calibration

Hit resolution

Lorentz angle measurement