ATLAS Research

Higgs Analysis

The measurement of the properties of the Higgs boson has become the main focus of the ATLAS experiment since its discovery was announced on July 4th, 2012. Thought to be responsible for giving all other particles mass (and thus macroscopic matter like dirt, rocks, and people too) , this boson was theorized in 1964. Nearly 5 decades after it was theorized, a particle which matches all the qualities of the Higgs boson was discovered at the LHC. It now remains to the analyzers at ATLAS to measure its properties with great precision to determine if this is indeed the Standard Model Higgs, or some new particle requiring a new explanation from theorists.

 
 

Standard Model Physics

 The Standard Model of Particle Physics is the theoretical framework that attempts to encompass many of our observations on how the fundamental forces of nature interact with matter. This remarkably successful theory is consistently borne out by measurements. The W and Z bosons, the carriers of the weak force, appear in final states of many physics signatures, either as a significant background which must be well measured and subtracted or as genuine final states of very exciting physics processes. Understanding the abundance and properties of leptonically-decaying W and Z are of critical importance to the physics endeavours at the LHC: performance of the detector, full understanding the Standard Model in the kinematic regime of the LHC, Higgs, and exotic physics are a few examples.

 
HL-LHC image

R&D and construction of the new all-silicon inner tracker, ITk

Starting in 2024, the LHC will undergo major upgrades to obtain a substantially increased collision rate. The instantaneous luminosity will reach 7 × 1034 cm-2s-1, which is seven times the design luminosity. The number of proton-proton collisions per bunch crossing will be 140–200. This results in a significantly enhanced overall physics potential, but also a very harsh environment for the ATLAS detector. The entire current tracking detector will not be able to operate under these high radiation conditions, and will need to be replaced with an all-new silicon Inner Tracker detector (ITk) based on state-of-the-art thin silicon technology (130 nm). Carleton University is working in conjunction with eight other Canadian institutes towards the construction of a full ITk strip endcap detector for the ATLAS ITk project. We are specializing in mechanical and electrical tests of the silicon microstrip sensors that detect charge particles produced in the proton-proton collisions. We also participate in test beams and associated data analysis to study the performance of irradiated prototype sensors and DAQ loads, and aims to contribute to front-end-electronics/DAQ R&D. Our goal for 2016-2017 is to qualify the Eastern Canada site (Toronto, Carleton, Montreal & York universities) as an ITk module construction site, which means producing five silicon strip modules that meet design specifications. 

 

Top Analysis

The mass of the top is one of the fundamental parameters of the Standard Model of Particle Physics.  The vast number of top quarks produced in the centre of the ATLAS detector during data-taking will usher in a new era of precision measurements in top quark physics.  Some members of Carleton's ATLAS group are actively involved in making such a precision measurement - in this case a measurement of the top quark mass - using pairs of top quarks.

 
 

Muon Small Wheel  

After the LHC upgrade, higher luminosity will threaten to overwhelm the ATLAS forward muon triggers with higher fake rates. To avoid being forced to raise the forward muon trigger thresholds, which would damage analyses such as H->4 lepton, the New Small Wheel (NSW) project will replace the current small wheel with one capable of rejecting fakes by pointing back to the IP and matching to the Big Wheel.  To achieve the necessary combination of rapid response time and small (<1 mrad) angular resolution required, the New Small Wheel will use a new, high-precision version of the Thin Gap Chamber, the sTGC.  Carleton, together with TRIUMF and McGill, will be responsible for building one-third of the sTGC's for the NSW.  Achieving the necessary sTGC resolution, which is almost an order of magnitude less than previous TGCs, requires new, more precise, construction techniques, and Carleton is currently carrying out R+D efforts on these techniques, with sTGC production expected to start at the beginning of 2015.

 
 

Previous Analyses

Some of the previous (but important) contribution that Carleton has made include: Development of the diamond detector for upgrade phase of the ATLAS detector; Analysis and testing of the Forward Calorimeter (FCal)