Experimental Particle Physics
Table of Contents
ATLAS
ATLAS statistical data analysis
Dag Gillberg
Project 1: Jet calibration using the 'forward folding' technique. The most common fundamental particles produced at the Large Hadron Colliders are quarks and gluons. However, as a high energetic quark or gluon emerges from the collision point, it will undergo so-called hadronization and produce a collimated spray of particles known as a jet. Jets are hence extremely common at the Large Hadron Collider and very important for most of the physics analyses. This project is about investigating the potential of using a new technique called ‘forward folding’ to measure the ATLAS detector's response to jets. The two key quantities to be extracted are the mean jet detector response and the associated resolution. The forward folding technique is based on convolution. The aim of the project would be to investigate the use of this technique with ALTAS Z+jets data and simulation, which is something that has not been done before.
Project 2: Visualization and statistical compatibility tests of unbinned data. Most analyses at ATLAS that measure distributions provide and analyse these as histograms. However, new machine learning-based techniques have started to produce unbinned measurements, provided as event-datasets. Presenting such measurements as histograms does not do them justice: it would be better to construct a smooth function based on the unbinned data, which is possible using Gaussian Kernels, and perhaps other similar techniques. This project would be to investigate easy to visualize unbinned measurements, and quantify the uncertainties. In part it would include a literature review - looking if this problem already has been encountered in other fields. The goal would be to find a good way to visualize unbinned data for particle physics applications, and if times permit, investigate how to compare two different spectra to see if they are compatible or not within uncertainty.
The EXO Experiment
Razvan Gornea
Noble liquid time projection chambers (TPC) are excellent detectors for rare event searches in neutrino physics. For example, the EXO-200 detector employs a 200 kg liquid xenon (LXe) with a TPC configuration which allows the collection of the electric charge produced by ionizing particles. When energy is deposited in a noble liquid, pairs of electron/hole are formed and can be collected by applying an external electric field. The amount of electrons collected is proportional to the initial energy of the ionizing particle.
During their drift in the TPC, electrons may encounter impurities with a large electron affinity and, therefore, part of the initial electric charge could be lost. When the noble liquid in a TPC is of low purity a large amount of charge is lost and then accurate event energy reconstruction becomes challenging. The average time for the electron to get captured is called the "electron lifetime". Experimentally, it often occurs that a LXe TPC can easily suffer from a short electron lifetime or, equivalently, a large concentration of impurities. On the other hand, the accurate measurement of a very long electron lifetime is challenging when using a compact device.
In this project, the student will design, optimize and build a compact purity monitoring device able to measure both short and long electron lifetimes using a custom pulsed VUV-LED-based electron source previously developed at Carleton. SIMION simulations will be employed to design and optimize a compact drift volume able to recycle the probing electron cloud. Hardware development, construction and testing will also be part of the project. Elements of front-end electronics, computer control and system programing using LabVIEW complete the program. A full year commitment is better suited for this project.
Gaseous Particle Detector Research and Development
Jesse Heilman
Recent advances in design and manufacture of pixelized silicon-based sensors, known as GridPix sensors, have opened up an avenue for innovation in the development of Pixelized Time Projection Chambers based on this technology. Based on the TimePix CMOS sensor developed by the MediPix collaboration at CERN, a GridPix leverages an amplification mesh grown on the sensor’s surface to increase the number of electrons incident on an individual pixel in a similar fashion to a MicroMegas detector. By amplifying the electron signal immediately before detection on the sensor, a GridPix TPC can then leverage the low multiple scattering of gaseous detectors with the high granularity of solid-state technologies to track the passage of ionizing radiation to extremely high levels of precision. A TPC based on GridPix sensors is a candidate technology for future particle physics experiments.
Interested students would work on the design and construction of a small GridPix based TPC for R&D purposes. Students would gain experience with the design and operation of gaseous particle detectors, high voltage systems, gas distribution systems, electronics readout technologies, and a working knowledge of particle physics concepts.