Located at the center of the ATLAS experiment, the tracker underpins the success of every physics analysis.

The tracker disentangles thousands of charged particles produced in each LHC event

Our group builds and operates silicon tracking detectors for the ATLAS experiment, and is pursuing cutting-edge tracker R&D for future colliders


The ATLAS Pixel Detector

Pixel Performance in Run 3

The ATLAS pixel detector is the innermost part of the ATLAS tracker. Located a few centimeters from the interaction point, the pixel detector consists of four layers of silicon with tens of millions of pixels in each layer. Each pixel is smaller than a grain of sand!

Charged particles produced in LHC collisions leave a small energy deposit in each layer of the pixel as they traverse the detector. The position of each energy deposit is measured with a precision of about 10 µm, and used to determine the origin and momentum of each particle.

The pixel detector must operate in the most intense radiation environment of any ATLAS subdetector. The detector's ability to collect and read out charge degrades as we collect more data. Our group studies low-level pixel performance to ensure the detector's successful operation throughout Run 3.

Pixel Run 3

Charge collection efficiency of the innermost layer of the pixel detector as a function of delivered LHC luminosity

High Luminosity LHC Upgrade

Pixel Module

Prototype Pixel module being prepared for testing

A new Pixel detector

The High-Luminosity LHC will deliver 5-7 times the design luminosity of the LHC. The increase in statistics will enable us to improve the precision of our measurements, and tease out potential rare or unconventional signatures of Beyond the Standard Model physics. However, the unprecedented luminosity requires a new fully silicon tracker with high-granularity and increased radiation-hardness.

The upgraded pixel detector will feature 60 times the number channels and introduce novel silicon sensor technologies to ATLAS. Thinner pixels, advanced powering schemes as well as mechanical supports, and inclined sections result in a significantly reduced material budget, improving tracking performance with respect to the current detector.

UChicago is working with the Argonne ATLAS group to construct pixel modules for the new detector. Modules are the most basic unit of the detector, consisting of the active detecting element, a roughly 4x4 cm2 silicon sensor, and custom readout electronics. Over the next few years, we'll build and test roughly 1000 modules to be assembled into the new pixel detector.

Next Generation Tracker R&D

Though the next collider may seem far away, the race to develop next generation trackers has already begun. Future discovery machines, such as a muon or hadron collider, will produce collisions with tremendous numbers of background particles.

To cope with this environment, the next generation of trackers must be 4D, disentangling particles in both space and time. The enormous amounts of data that will be generated per event will also require on-detector readout electronics that can rapidly differentiate between signals of interest and background.

At UChicago, we're pursuing cutting edge R&D for next generation trackers. Our work involves testing novel silicon sensor technologies and intelligent on-detector electronics.

3D integration
3D integrated sensor and 2-tier chip from Fermilab