Earth-like exoplanets are ten orders of magnitude fainter than their host stars, but planned space missions will nonetheless be able to directly image these these planets using high contrast imaging techniques (e.g., HabEx and LUVOIR). An unresolved problem is how to most efficiently identify true Earth twins based on one or two images of such a "pale blue dot". This project entails an analytic effort to estimate the posterior probability of a planet's Keplerian orbital elements based on a single image. In other words, given an image of a planet at some projected distance from its star, what is the probability distribution for that planet's semi-major axis and other orbital parameters? A successful solution to this problem will provide an analytic expression to estimate the orbital separation of a newly-discovered planet and hence to prioritize follow-up of certain planets (e.g., those orbiting in their star's habitable zone).

The student will use probability theory (including Bayes), Jacobians, and literature review to set up a multi-dimensional integral for the marginalized posterior probability for various orbital parameters. In cases where closed form solutions are not possible, the student will Taylor series expand the integrand for low-ish eccentricity to obtain an approximate solution. The work will be reported in impeccable LaTeX.

For more information contact: Nicolas Cowan (cowan at physics dot mcgill dot ca).

Posted on 2020/01/03

Earth-like exoplanets are ten orders of magnitude fainter than their host stars, but planned space missions will nonetheless be able to directly image these these planets using high contrast imaging techniques (e.g., HabEx and LUVOIR). An unresolved problem is how to most efficiently identify true Earth twins based on one or two images of such a "pale blue dot". This project entails a numerical effort to estimate the posterior probability of a planet's Keplerian orbital elements based on 2-3 images, including the brightness of the planet. In other words, if a planet's location and brightness relative to its host star change with time, is the probability distribution for that planet's semi-major axis and other orbital parameters? A successful solution to this problem will provide a numerical framework to estimate the orbital separation of a newly-discovered planet and hence to prioritize follow-up of certain planets (e.g., those orbiting in their star's habitable zone).

The student will first write Python code to produce synthetic images of directly imaged exoplanets, including realistic errors. They will then use a Markov chain Monte Carlo to retrieve the posteriors on the Keplerian orbital parameters. They will test under what circumstances the brightness of the planet is a useful constraint on its orbit. The work will be described in LaTeX with informative and intuitive figures.

For more information contact: Nicolas Cowan (cowan at physics dot mcgill dot ca).

Posted on 2020/01/03

The Belle II electron-positron collider experiment at the KEK laboratory in Japan began collecting physics-quality data over a period of several months in 2019. The Belle II experiment is designed to record data at SuperKEKB, an upgraded accelerator constructed to achieve collision luminosities 40 times higher than those previously attained, with the aim of amassing vast data sets to probe the limits of the Standard Model of particle physics while searching for evidence of new physical phenomena. The goal for 2020 is to take an order of magnitude more data than the 2019 sample, with the extraction of physics from the 2020 samples requiring an improved understanding of the performance of the new Belle II detector under severe and unprecedented background conditions.

The student will develop basic familiarity with Belle II software tools in order to conduct an analysis of a sample of 2019 data to examine the reconstruction and identification of a reference particle or particle decay process. The study will help to improve understanding of the Belle II detector's performance and could lay the groundwork for future performance improvements, thereby sharpening the experiment's capacity to detect New Physics more quickly. The student will be based at McGill, meeting at least weekly with the supervisor and working within the McGill Belle II group, which also meets on a weekly basis. This role could potentially be held in conjunction with an IPP CERN Summer Student position; for details about the IPP CERN Summer Student program, please refer to https://particlephysics.ca/research-activities/undergrad-program-cern/.

For more information contact: Andreas Warburton (awarburt at physics dot mcgill dot ca).

Posted on 2020/01/07

The student will study the neural ODE method, perform numerical analysis using this method as well as numerical simulations of biophysical networks. She/he will then combine those tools to infer models. The student will have daily interactions with the supervisor and a senior post-doc, and will participate in all group related activities (group meeting, hackathons).

For more information contact: Paul François (paulf at physics dot mcgill dot ca).

Posted on 2020/01/15

Non-linear oscillators are at the core of many processes in biology, including spine formation. Several models have been proposed to account for those oscillations, including delayed oscillator. There are now more and more data on how real oscillators synchronize and build non-linear waves not only within biological tissue but also in synthetic in-vitro systems. The goal of this project will be to figure out what kind of delayed oscillators are compatible with the experimentally measured synchronization properties, using tools from non-linear dynamics.

The student will develop numerical and analytical models of coupled delayed differential equations. She/he will then test various scenarios for coupling, first through numerical simulations and then with simple analytical models. Those analyses will be compared to available data provided by the supervisor. The student will have daily interactions with the supervisor and a senior graduate student, and will participate in all group related activities (group meeting, hackathons)

For more information contact: Paul François (paulf at physics dot mcgill dot ca).

Posted on 2020/01/15

At TRIUMF, in Vancouver, beams of exotic isotopes are produced by proton-induced nuclear reactions, sent through a series of ion guides, and finally collected in an ion trap system called TITAN (TRIUMF Atom Trap for Atomic and Nuclear Science). Our laser spectroscopy group has developed a technique to pulse ions out of the TITAN trap, and to overlap these pulsed beams with a laser beam. Tuning the laser frequency or changing the ion velocity allows us to collect a high-resolution spectrum of atomic transitions. The hyperfine splitting of these atomic levels is used to deduce changes in nuclear radii, to measure nuclear magnetic dipole and electric quadrupole moments and to probe the variation of nuclear shape and size over a series of isotopes.

To be successful, the frequency of the laser beam must be stable during experiments that may last for many hours. Currently this is done by comparing the laser frequency to that of a stabilized helium-neon laser. An improved system would instead lock the laser to a known atomic transition using a technique called saturation spectroscopy. In principle, the improved system's stability would be unaffected by changes in temperature, air pressure or local magnetic fields. In this project, a student will assemble the new system and test its short and long-term stability. He or she will be assisted by an experienced group of TRIUMF staff, PDFs, and other McGill graduate students. McGill staff members (Crawford, Buchinger) regularly visit TRIUMF to participate in experiments. On-site supervision will be done by Dr. Matthew Pearson, an adjunct McGill professor.

For more information contact: John Crawford (crawford at physics dot mcgill dot ca).

Posted on 2020/01/20

In this project the Reisner and Gervais groups will collaborate to explore the physics of He flow through a nanometric scale hole in a silicon nitride membrane. While nanopore sensing in electrolytes is a powerful technology in the biophysical domain, the mass-flow analogy to ionic transport is less well-understood. In particular, one important question is how statistical fluctuations in the He flow, analogous to fluctuations in current, depend on applied pressure and pore size.

The student will learn how to setup a room temperature mass-flow system and perform measurements of conductance and conductance fluctuations over a range of pressures and pore sizes. In addition, the student will be trained on TEM based pore-making techniques. The expected quality of training is expected to be very high as the student will be exposed to a diverse range of expertise in the Reisner and Gervais groups including (1) nanofabrication approaches, (2) experience with vacuum techniques and gas handling systems and (3) gain theoretical background in statistical mechanics such as fluctuation-dissipation theorem. Prof. Reisner and Gervais will jointly supervise the project with meetings taking place on a bi-weekly basis.

For more information contact: Walter Reisner (reisner at physics dot mcgill dot ca) or Guillaume Gervais (gervaisnbsp;at physics dot mcgill dot ca).

Posted on 2020/01/24

The CRISPR/Cas9 gene editing tool has become an important platform for genome editing and imaging. This approach has been the basis of genome- and drug target screening, but off-target binding is a major roadblock in these efforts and could result in unintended mutations. An important question is how Cas9 searches through millions of base pairs in a genome to locate specific base pair targets.

For this project, a student will work with a physics graduate student who uses confinement microscopy to examine the DNA-Cas9/RNA interactions at the single-molecule level. The student will implement and refine data analysis tools to investigate the interactions between Cas9, RNA, and DNA.

Weekly meetings with Professor Leslie and biochemistry collaborators, and daily interactions with members of our interdisciplinary research group, will support and guide the project. In addition to gaining hands-on research experience, anticipated outcomes of this summer research project include presentations at local conferences and workshops, providing key training in writing and oral communication.

For more information contact: Sabrina Leslie (sleslie at physics dot mcgill dot ca).

Posted on 2020/01/28

DNA-DNA and protein-DNA interactions are crucial to cellular processes, with errors in these reactions sometimes leading to genetic diseases such as cancer. Emerging single-molecule microscopy techniques allow for multiple, independent interactions to be imaged at once, allowing for measurements of both the expected behaviour, as well as deviations from the norm. Single-molecule imaging, however, suffers from limitations in signal-to-background. This presents an opportunity to develop computer-vision algorithms to extract salient information about the molecules.

For this project, the student will develop image analysis tools to study the interactions between fluorescent probe molecules and supercoiled DNA trapped in microwell arrays. Statistical mechanics theory predicts the probability of specific DNA structural transitions. As background to this project, PhD students have collected fluorescence images of mixtures of DNA molecules and probe molecules (oligonucleotides, proteins). This computational project focuses on implementing computer vision and principal component analysis (PCA) algorithms to improve measurements of binding kinetic rates and stoichiometries, and on running simulations to test the analysis methods.

The student will receive training in quantitative data analysis as well as theory, and work closely with a graduate student on this project. Weekly meetings with Professor Leslie and biochemistry collaborators, and daily interactions with members of our interdisciplinary research group, will support and guide the project. In addition to gaining hands-on research experience, anticipated outcomes of this summer research project include presentations at local conferences and workshops, providing key training in writing and oral communication.

For more information contact: Sabrina Leslie (sleslie at physics dot mcgill dot ca).

Posted on 2020/01/28

Supercoiled DNA exists in all cells, however the impact of DNA supercoiling on local structure, and thus on gene regulation, is not fully understood. Statistical mechanics theory predicts changes to local DNA structure driven by the torsional strain created through supercoiling. These structural changes can have important implications in gene regulation.

For this project, the student will perform microscopy and bulk experiments to study supercoil-driven structural transitions, in partnership with PhD students. Students will learn how to culture cells, extract DNA and supercoil the DNA. They will learn several gel electrophoresis techniques used to quantify DNA secondary structure (including 2D-gel electrophoresis and DNA fingerprinting). And they will compare their results to microscopy data taken in the lab and to statistical mechanical models. An ideal candidate is a student in one of the biophysics streams or the quantitative biology program.

The student will receive hands-on training in sample design and preparation, and work closely with two graduate students on this project. Weekly meetings with Professor Leslie and biochemistry collaborators, and daily interactions with members of the research group, will support and guide the project. Anticipated outcomes of the summer research project include presentations at local conferences and workshops, providing the student with key training in writing and oral communication.

For more information contact: Sabrina Leslie (sleslie at physics dot mcgill dot ca).

Posted on 2020/01/28

Nanoparticles are increasingly used in pharmaceutical applications. This research project will use single-particle confinement microscopy to investigate the biophysical properties, stoichiometry and kinetics of nanoparticle assemblies and their interactions. This technique entraps particles in femto-liter reaction wells and allows prolonged monitoring of reactions. It also enables direct visualization of interactions between chemical species and nanoparticles.

For this project, the student will develop image analysis approaches to quantify probe-nanoparticle interactions. For example, particle tracking algorithms can be used to extract valuable information such as binding/unbinding kinetics, encapsulation dynamics and adsorption kinetics.

The student will receive training in quantitative image analysis (Matlab) as well as hands-on training in confinement microscopy and will work closely with a research fellow and graduate student. Weekly meetings with Professor Leslie and collaborators, and daily interactions with members of our interdisciplinary research group, will support and guide the project. In addition to gaining hands-on research experience, anticipated outcomes of this summer research project include presentations at local conferences and workshops, providing key training in writing and oral communication.

For more information contact: Sabrina Leslie (sleslie at physics dot mcgill dot ca).

Posted on 2020/01/28

Single-molecule microscopy experiments to visualize freely diffusing and interacting molecules are complex, with many factors influencing biomolecule behavior. We apply theory and simulations to model molecular behavior and corresponding microscopy images, which then helps guide and define the imaging parameters for future experiments. A candidate student for this project has strong interest and proficiency in mathematical modeling and computational simulations to adapt and develop existing models to our experiments.

In this summer research project, the student will help refine and implement in Matlab existing models to accurately simulate our experimental data. Simulated data will be analyzed and compared to experimental data to validate the model and drive its evolution. By comparing results to theoretical models, the student will extract meaningful system parameters such as binding and unbinding rates and diffusivity. Validated models will also be applied to determine the imaging parameters for future experiments.

The student will receive training in quantitative data analysis (Matlab) as well as theory and programming interact with experimentalists and an analysis team on this project. Weekly meetings with Professor Leslie and collaborators including Professor Mark Sutton, and daily interactions with members of our interdisciplinary research group, will support and guide the project. In addition to gaining hands-on research experience, anticipated outcomes of this summer research project include presentations at local conferences and workshops, providing key training in writing and oral communication.

For more information contact: Sabrina Leslie (sleslie at physics dot mcgill dot ca).

Posted on 2020/01/29

At the TRIUMF facility in Vancouver, we use atomic spectroscopy techniques to study the properties of exotic nuclei. Interactions between the nucleus and the electrons split the atomic levels into hyperfine structure components. We overlap ion and atomic beams of isotopes produced by TRIUMF with a probe laser that excites these hyperfine states. Scanning the beam velocity and keeping the laser frequency fixed allows us to produce the hyperfine spectrum. To keep the laser frequency very stable during a scan we compare its frequency with that of a very stable helium neon (He:Ne) laser. Since the He:Ne's frequency may be very far from that of our probe laser we produce interference fringes by passing both the laser beams through a Fabry- Perot interferometer- essentially two silvered parallel plates. This project is to construct and test a new interferometer of high finesse (fringe sharpness) that will be suitable for the frequencies we use to study different isotopes. A student in this project will be assisted by an experienced group of TRIUMF staff, PDFs, and other McGill graduate students. McGill staff members (Crawford, Buchinger) regularly visit TRIUMF to participate in experiments. On-site supervision will be done by Dr. Matthew Pearson, an adjunct McGill professor.

For more information contact: John Crawford (crawford at physics dot mcgill dot ca).

Posted on 2020/01/29

The first stars to form in the Universe are expected to be much more massive than the average star today. Those that explode as supernovae inject tremendous amounts of energy and heavy elements into their host galaxy, and thus may fundamentally alter the conditions for subsequent star formation. Other stars may not explode at all, instead collapsing directly to black holes (BHs). These BHs may be the progenitors of those living in the centers of nearly all galaxies today, but also accrete material and irradiate their environments with X-rays, which can affect how stars and BHs form and grow. These effects result in complicated feedback loops, in which stars and BHs regulate the formation of additional stars and black holes, which makes modeling the star and BH formation histories of early galaxies very difficult. The goal of this project is to better understand how upcoming observations can be used to infer the formation histories of the first galaxies, and so to constrain the properties of the first stars and BHs themselves.

The primary role of the student working on this project is to use the results of sophisticated numerical simulations of galaxy formation to guide the development of simpler, more efficient models, which are fast enough to be used directly in the analysis of real data. Part of the work will be in mining the publicly available simulation data provided by the Renaissance Simulations collaboration and part will be in comparing with (and extending) pre-existing semi-analytic models of galaxy formation developed by co-supervisor Dr. Mirocha and collaborators.

For more information contact: Adrian Liu (acliu at physics dot mcgill dot ca).

Posted on 2020/01/30

Progress in understanding galaxy formation is driven in large part by surveys of distant galaxies. Such surveys conducted using the Hubble Space Telescope, and soon the James Webb Space Telescope, all suffer from biases of one sort or another due to their adopted survey strategy. For example, surveys targeting a large area of sky will spend less time on each sky region, and so will only be able to detect the brightest galaxies, while the distances of galaxies that are detected cannot even be precisely determined in photometric surveys. These effects are generally neglected when interpreting galaxy survey results in the context of galaxy evolution models, i.e., the observed population is assumed to perfectly reflect the "true" underlying galaxy population. The goal of this project is to generate forward models of galaxies and conduct mock surveys of them, so as to more carefully compare with observations. Such improvements may help to distinguish between viable galaxy evolution models, which can make the same predictions for the entire galaxy population, but different predictions for the observed galaxy population due to selection effects and biases.

The primary role of the student working on this project is to build a mock galaxy survey interface in a pre-existing galaxy formation model. This essentially means designing an intermediate step, in which model galaxies are "observed" via different surveys before the model is compared with the data. Then, with this extension in place, students will fit the new model to existing observational data, and quantify the effect of survey strategy on inferred properties of galaxies, such as the star formation efficiency and dust contents. This will provide important guidance for future surveys, and allow us to more accurately infer the properties of galaxies detected in them.

For more information contact: Adrian Liu (acliu at physics dot mcgill dot ca).

Posted on 2020/01/30

In recent years, radio astronomers have assembled maps of our Milky Way galaxy with increasing levels of sophistication. At frequencies of several hundreds of MHz, these maps are believed to mainly consist of Galactic synchrotron radiation, which is the radiation caused by electrons spiralling around magnetic field lines in our galaxy. However, it is difficult to rule out the possibility that these maps contain contaminants from outside our galaxy. In this project, we will determine the level of extragalactic contamination by cross correlating our Galactic synchrotron maps with maps of extragalactic structure. If there are statistically significant cross correlations, this will suggest to us that our synchrotron maps are contaminated. Knowing this will help us build a better understanding of our Galaxy's radio emission mechanisms.

The student will first write software to visualize our Galactic Synchrotron maps in order to gain intuition for the morphology of these maps. Next, the student will learn to interface with online databases for obtaining and reprocessing maps of extragalactic structure. Finally, the two types of maps will be compared using cross-correlation software that the student will create from similar publicly available software.

For more information contact: Adrian Liu (acliu at physics dot mcgill dot ca).

Posted on 2020/01/30

Turbulent fluids are difficult to simulate because of the interaction of physical phenomena on multiple lengthscales. For example, viscous effects can cause energy dissipation on very small scales, heating up the fluid in a way that increases the temperature of the fluid as a whole. One method for simulating turbulent fluids is to opt for the computationally expensive route of performing a direct numerical simulation where the extremely fine scales of the fluid are resolved. An alternative is to coarse-grain the equations (essentially averaging over the very fine scales) and then to find ways to incorporate extra terms in the fluid equations that correct for the errors induced by coarse graining. In this project, we use machine learning to help us discover these extra terms (known as "closure terms"). We generate a large suite of direct numerical simulations, which are then fed into a neural network to learn the extra terms "by example." Ultimately, this will allow us to lower the computational cost associated with performing turbulent fluid simulations.

The student will first master the Dedalus simulations package for solving partial differential equations. They will then use Dedalus to generate a training suite of direct numerical simulations. After this, they will learn how to use TensorFlow to construct a neural network, applying it to the training simulations to learn the closure terms.

For more information contact: Adrian Liu (acliu at physics dot mcgill dot ca).

Posted on 2020/01/30

In this collaborative project between the Reisner and Grutter groups, the USRA student will help develop a new technique for making precisely positioned sub 5 nm nanopores. The successful demonstration of nanopore sequencing via engineered protein pores has created considerable industrial interest in nanopore based technologies. The next research frontier in nanopore physics is the development of solid-state nanopore devices, which admit of more scalable fabrication processes and will potentially have higher resolution, decreasing the high sequencing error-rates that are currently the main drawback in nanopore sequencing. We have developed a new approach for fabrication of sub 5 nm pores via local dielectric breakdown induced by a conductive AFM tip across a ~10nm nitride membrane. In our approach, a conductive AFM tip is brought into contact with a nitride membrane sitting on top of an electrolyte reservoir. Application of a voltage pulse leads within seconds to formation of a nanoscale pore that can be detected by a subsequent AFM scan. This method combines the ease of classic dielectric breakdown with the nanoscale pore positioning capability of high energy particle milling techniques such as TEM and FIB.

The student will learn all aspects of the pore-making and characterization process and enable interfacing of pores with chips containing nanochannels. In particular, the student will learn how to fabricate pores via AFM (Grutter lab, assisted by researcher Dr. Miyahara), characterize these devices using IV measurements performed with a patch-clamp amplifier (Reisner lab, assisted by post-doc Dr. Zhang), and develop a chuck that will enable pores to be aligned and embedded in nanochannels. Note that the Grutter and Reisner labs are next door to each other on the 4th floor of the Rutherford building; pores are fabricated in one lab and then walked over and characterized in the other, so use of facilities in both labs is clearly focused towards one project. Professor Reisner will be the primary supervisor with meetings taking place once a week; monthly meetings will take place between all projects participants, including Prof. Grutter.

For more information contact: Walter Reisner (reisner at physics dot mcgill dot ca).

Posted on 2020/01/31

The EXO (Enriched Xenon Observatory) collaboration is searching for lepton-number violating neutrino-less double beta decays (0νββ) in Xe-136. A positive observation would require the neutrino to be its own anti-particle, i.e. the neutrino has to be a Majorana particle, and shed light on various open questions in neutrino physics. The current limit on the 0νββ half life in Xe-136 measured by the EXO-200 collaboration is T_1/2 > 3.5 × 10²⁵ years. New technologies are being developed to further increase the sensitivity of the next generation detector. One of these technologies are silicon photomultipliers (SiPMs). The collaboration is working on developing these devices sensitive to Xe-scintillation light at 175nm.

In this project, you will assemble and commission a test setup that allows one to cool SiPMs to -100C and measure their characteristic I-V curves. You will develop test protocols to allow quality control on SiPMs with fast turn-around times for a large number of SiPMs. This will be a crucial step in the future assembly process of the nEXO detector.

You will join the local EXO group at McGill and learn about neutrino physics and detection techniques using liquid Xe. You will be working on the development and testing of photon sensors as part of an international team of researchers. Your project will be well defined with achievable goals. You will perform every day lab work, and most studies and experiments within a small team of undergraduate and graduate students in our lab at McGill. Senior scientists at McGill and within the nEXO collaboration are happy to help you get started and will help you conduct your measurements.

For more information contact: Thomas Brunner (brunner at physics dot mcgill dot ca).

Posted on 2020/02/06

The EXO (Enriched Xenon Observatory) collaboration is searching for lepton-number violating neutrino-less double beta decays (0νββ) in Xe-136. A positive observation would require the neutrino to be its own anti-particle, i.e. the neutrino has to be a Majorana particle, and shed light on various open questions in neutrino physics. The current limit on the 0νββ half life in Xe-136 measured by the EXO-200 collaboration is T_1/2 > 3.5 × 10²⁵ years. New technologies are being developed to further increase the sensitivity of the next generation detector. One of those is the so-called Ba-tagging technique. Here, the Xe-decay daughter Ba-136 is located inside the detector volume after the decay, extracted from the volume and identified. This Ba-tagging technique will allow the unambiguous identification of �� decays by clearly distinguishing them from background events. This technique will be particularly important to verify an observation once a positive 0νββ signal has been observed.

A Ba-tagging technique is being developed at McGill with the focus on the extraction and identification of Ba-ions from xenon gas. For systematic studies and to determine the efficiency of the identification process we require a single Ba-ion source. The summer projects focuses on the optimization and characterization of a laser-driven single Ba-ion source. A pulsed laser beam is focused on a surface with a known elemental composition where it ablates atoms and ions. Ions are guided away from the surface by electrostatic lenses and injected into the ion identification setup. These well-known ions are used to calibrate the identification setup and determine transport efficiencies throughout the system.

You will be embedded in the local nEXO group at McGill and learn about neutrino physics and ion manipulation techniques. Ion optics geometry and ion transport will be simulated and optimized using the SimIon software. Based on these simulations, initial ion-ablation tests will be performed and ion production will be optimized.

This project is aimed at undergraduate students at all levels, i.e., no special skills, apart from a general understanding of physics and the possibility to fit data using python, are required. All you need is an interest in learning and improving lab skills, and an interest in particle and nuclear physics. We use SolidWorks, LabView, Mathematica, and Python in every-day-business. Some knowledge in any of these programs/languages will help you get started, but is absolutely not required as we have local experts that are happy to assist you.

For more information contact: Thomas Brunner (brunner at physics dot mcgill dot ca).

Posted on 2020/02/06

The EXO (Enriched Xenon Observatory) collaboration is searching for lepton-number violating neutrino-less double beta decays (0νββ) in Xe-136. A positive observation would require the neutrino to be its own anti-particle, i.e. the neutrino has to be a Majorana particle, and shed light on various open questions in neutrino physics. The current limit on the 0νββ half life in Xe-136 measured by the EXO-200 collaboration is T_1/2 > 3.5 × 10²⁵ years. The collaboration is pursuing the development of the next-generation experiment called nEXO. This advanced detector requires the development of new technologies as well as detailed knowledge of the underlying physical processes to reach a sensitivity goal of 10²⁸ years.

We have been developing the Light-only Liquid Xenon (LoLX) experiment which aims at measuring the emission of Cherenkov light in liquid Xe. These measurements will help constrain our simulation models for nEXO and they may improve the suppression of backgrounds by separating events where one or two electrons are emitted. This summer, we plan to commission LoLX and take the first data.

You will be embedded in the local nEXO group at McGill and learn about neutrino physics and the use of liquid Xe as radiation detector. You will participate in data taking and data analysis campaigns and help improve the LoLX setup.

This project is aimed at undergraduate students at all levels, i.e., no special skills, apart from a general understanding of physics and the possibility to fit data using python, are required. All you need is an interest in learning and improving lab skills, and an interest in particle and nuclear physics. We use SolidWorks, LabView, Mathematica, and Python in every-day-business. Some knowledge in any of these programs/languages will help you get started, but is absolutely not required as we have local experts that are happy to assist you.

For more information contact: Thomas Brunner (brunner at physics dot mcgill dot ca).

Posted on 2020/02/06

Measurements of redshifted 21-cm emission of neutral hydrogen allow us to reconstruct a 3D map of large-scale structure in the universe. The distribution of matter encodes a faint imprint, known as baryon acoustic oscillations (BAOs), that correspond to remnant ripples left behind by sound waves echoing through the plasma of the early universe. Precise measurements of BAOs will allow us to understand the universe's expansion history and probe the nature of dark energy. The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a new radio telescope array that will measure BAOs by mapping the southern sky over a frequency range of 400-800 MHz, and the experiment will be sited in the Karoo desert in South Africa. The project complements the Canadian Hydrogen Intensity Mapping Experiment (CHIME), which is surveying the northern sky. The final HIRAX array will consist of 1024 dishes. The aim of this proposed project is to test HIRAX hardware and calibration techniques using a two-element interferometer test bed that is sited at the Dominion Radio Astronomy Observatory in Penticton.

The student who takes on this project will have the opportunity to work on a variety of HIRAX subsystems using the two-element test bed. Possible areas of work include designing and/or constructing receiver mounts, characterizing active feeds and RF-over-fiber electronics, and data analysis to assess subsystem performance.

For more information contact: Cynthia Chiang (chiang at physics dot mcgill dot ca).

Posted on 2020/02/06

Measurements of the radio sky at ~100 MHz and below have the potential to open a new observational window in the universe's history. At the lowest frequencies (tens of MHz), future observations may allow us to one day probe the cosmic "dark ages," an epoch that is unexplored to date. Measurements at these frequencies are extremely challenging due to radio-frequency interference and ionospheric effects. The state of the art among ground-based measurements dates from the 1960s, when Grote Reber caught brief glimpses of the ~2 MHz sky at low resolution. The Array of Long Baseline Antennas for Taking Radio Observations from the Seventy-ninth parallel (ALBATROS) is a new experiment that aims to map the low-frequency sky using an array of autonomous antenna stations. These antenna stations will observe independently, over long baselines, and will be interferometrically combined offline. One array will be installed at the McGill Arctic Research Station on Axel Heiberg Island, a location that is exceptionally radio-quiet and has reduced ionospheric interference relative to lower-latitude sites.

The student who takes on this project will develop the hardware that is needed for the autonomous antenna stations. Possible areas of work include refining the design of the antenna and front-end electronics, developing a power solution for year-long antenna operation, and field testing the antenna stations.

For more information contact: Cynthia Chiang (chiang at physics dot mcgill dot ca).

Posted on 2020/02/06

Measurements of the radio sky at ~100 MHz and below have the potential to open a new observational window in the universe's history. At the lowest frequencies (tens of MHz), future observations may allow us to one day probe the cosmic "dark ages," an epoch that is unexplored to date. Measurements at these frequencies are extremely challenging due to radio-frequency interference and ionospheric effects. The state of the art among ground-based measurements dates from the 1960s, when Grote Reber caught brief glimpses of the ~2 MHz sky at low resolution. The Array of Long Baseline Antennas for Taking Radio Observations from the Seventy-ninth parallel (ALBATROS) is a new experiment that aims to map the low-frequency sky using an array of autonomous antenna stations. These antenna stations will observe independently, over long baselines, and will be interferometrically combined offline. One array will be installed at the McGill Arctic Research Station on Axel Heiberg Island, a location that is exceptionally radio-quiet and has reduced ionospheric interference relative to lower-latitude sites.

The student who takes on this project will develop and test the readout electronics for the ALBATROS stations. In particular, the student will compare independent readout systems and will verify that the timing is sufficiently precise for offline correlation. The student will also help develop the analysis code that is needed to coherently combine data from multiple stations.

For more information contact: Cynthia Chiang (chiang at physics dot mcgill dot ca).

Posted on 2020/02/06

Fast Radio Bursts are a new and mysterious astrophysical phenomenon in which short (few ms) radio bursts appear randomly in the sky. FRBs are thought to be extragalactic due to their dispersion measures that are far higher than the maximum amount available in our Milky Way. With FRB event rates of ~1000 /sky/day, they raise an interesting puzzle regarding their origin, which lie at cosmological distances. Radio pulsars are rapidly rotating, highly magnetized neutron stars. As compact objects, they embody physical extremes of gravity, density and magnetic field. Thanks to their amazing clock-like properties, radio pulsars can be used as cosmic laboratories for a variety of experiments ranging from tests of relativistic gravity to studies of the interstellar medium.

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a new radio telescope recently built in Penticton, BC. CHIME's great sensitivity and large field-of-view (250 sq deg) enable the detection of many FRBs per day — in contrast to the fewer than 2 dozen discovered since 2007. CHIME is also an excellent pulsar observatory, able to detect hundreds of pulsars every day and enabling novel experiments using these high cadence observations.

Here are proposed several possible research projects involving data from CHIME in association with other world-class radio telescopes (Arecibo and the Green Bank Telescope). Possibilities include studying repeating FRBs, searching for FRBs in targeted surveys, monitoring radio pulsars, and developing software tools to search for pulsars with CHIME.

The student, who should have experience and familiarity with programming in the Linux environment, will be given astrophysical data sets from CHIME or other radio telescopes to first familiarize themselves with source properties. Then, depending on exact interest, will analyze existing data obtained in order to understand FRBs or the radio pulsar population, or help develop and test new algorithms for our new pulsar searching pipeline.

For more information contact: Victoria Kaspi (vkaspi at physics dot mcgill dot ca).

Posted on 2020/02/06

Observing the birth of the first stars, galaxies, and black holes in the Universe is an exciting frontier in modern cosmology. One of the most promising approaches to understand this period is through measurements of the global redshifted 21-cm signal at low radio frequencies (<200 MHz). This signal traces the evolution of neutral hydrogen in the intergalactic medium during the formation of the first sources, and can enable us to characterize the sources themselves. The intensity of this cosmological signal is extremely small compared to other sources of radiation. Teams from around the world are trying to conduct this measurement and detect this signal. At McGill we are developing a new instrument, MIST, that will measure the radio spectrum with very high accuracy with the purpose of detecting the global 21-cm signal. MIST is a low-profile, single-antenna instrument that will be deployed at remote locations of the Earth to observe the sky from an environment free from human-generated radio-frequency interference.

The student who joins this project will be involved in the calibration of MIST instrument in the laboratory using state-of-the-art techniques. The goal is to understand the intrinsic response of the instrument to radio signals captured by the antenna. This is a critical experimental task that is required in order to discriminate between features in the measured spectrum that are instrumental, from those that are from the sky. This laboratory calibration has to be done with an accuracy better than 1 part in 10⁴, which would represent an extremely significant development for the radio cosmology and engineering communities.

Interest and experience in radio frequency applications, analog and digital hardware, and programming, would be advantageous.

For more information contact: Cynthia Chiang (chiang at physics dot mcgill dot ca).

Posted on 2020/02/06

The ATLAS experiment at the CERN's Large Hadron Collider in Geneva records the results of the highest energy particle collisions ever produced in laboratory. In 2012, the ATLAS and CMS collaboration announced the discovery of a new elementary particle of nature, the so-called Higgs boson. In order to more precisely study the properties of this new particle, test the validity of the Standard Model of particle physics and further extend the search for new physics phenomena, the ATLAS detector is currently undergoing a major upgrade. Canada is constructing approximately one third of the specialized detectors required for this upgrade. The ATLAS-McGill research group is responsible for the testing and characterization of these Canadian-made chambers. McGill team members are also leading integration and commissioning work, at CERN, of these chambers into the ATLAS experiment. The goal of this summer research project is to participate in the testing and characterization of Canadian-made "thin gap chambers" for the upgrade of the ATLAS experiment. The student will learn about different particle detection techniques and develop a wide range of experimental and laboratory skills.

The student will be asked to participate in all steps of the characterization and testing of these Canadian-made detectors, including detector services installation, detector operation and monitoring, participation in the setup and data taking of cosmic ray data, maintenance of work flow documentation. The student's tasks will also include some of the following: help in the development/maintenance of the laboratory infrastructure, participation in the analysis of cosmic data and/or simulation studies associated with the optimization of the detector testing, development and documentation of the testing work flow.

For more information contact: Brigitte Vachon (vachon at physics dot mcgill dot ca).

Posted on 2020/02/06

VERITAS is an array of four 12-m reflectors in Arizona, used to detect and study astrophysical sources of very high-energy (VHE; energies from 100 GeV to above 10 Tev) gamma rays. The McGill gamma-ray astrophysics group participated in the construction of VERITAS and continues to participate in its calibration, operation and data analysis (see veritas.sao.arizona.edu). Recent improvements include the ability to detect optical transients at the milli-second time scale.

Fermi is an orbiting gamma-ray observatory (see fermi.gsfc.nasa.gov) whose LAT instrument is sensitive to gamma rays in the MeV-to-GeV regime.

This project will comprise analysis of VERITAS and/or Fermi data. Known sources of VHE gamma-rays include supernova remnants and active galactic nuclei, and potential signals include dark-matter annihilation. An ongoing > program is to use the VERITAS optical monitoring in conjunction with VHE observations of CHIME (see chime-experiment.ca) fast-radio bursts.

The research will be managed through frequent (at least weekly) meetings with the supervisor and daily interactions with other members of the gamma-ray group, and a written report will be prepared at the end of the summer.

For more information contact: Ken Ragan (ragan at physics dot mcgill dot ca).

Posted on 2020/02/06

Particle physics aims to understand matter, space and time, and to unify all observables under a single theory of particles and their interactions. Known matter is made out 2 quarks (called mesons, such as pions or kaons) or 3 quarks (baryons, such as protons or neutrons). But states with higher numbers are not forbidden by the Standard Model of particle physics. Do they exist? Data taken by the ATLAS experiment at the LHC or the research centre CERN might reveal such states. The proposed project would call for the observation of neutral kaons and lambdas and see if two such particles might indeed originate from a possible multi-quark state.

The project would call for familiarization with standard analysis packages, software development for event selection and detailed estimations of the backgrounds, as well as creation of new statistical tools to search for signals. Part of the work will be based on previous expertise in the research group. Knowledge of C++ and basic understanding of particle physics concepts would be assets. The student will be based at McGill and work within the ATLAS experimental group. Close and daily direct supervision will be organised.

For more information contact: François Corriveau (corriveau at physics dot mcgill dot ca).

Posted on 2020/02/06

Fluctuations that look self-similar at different length scales appear in many systems, including thermal fluctuations near critical points of phase transitions and quantum fluctuations in particle physics. The fluctuations have a power-law spectrum characterized by critical exponents which are often challenging to predict theoretically. Progress can be made by exploiting that scale invariance often implies conformal symmetry. This has recently led to a new powerful method, the conformal bootstrap, which allows to solve interesting critical points, including one at the endpoint of the liquid-vapor transition in water.

The goal of this project will be to implement the bootstrap method and compute with precision the critical exponents near this phase transition. The bootstrap method exploits self-consistency of a given theory and the project will improve on purely numerical solutions by incorporating recent analytic findings.

The students' first task will be to familiarize themselves with the special functions (generalization of spherical harmonics) that govern conformal symmetry, and their symbolic evaluation implemented in Mathematica. Students will then develop code to numerically solve bootstrap problems, which involve many unknowns, first without, and then including new analytic results for infinite families of coefficients. They will learn skills for symbolic programming and numerical analysis, and develop both written and oral presentation skills.

In addition to weekly meeting with the supervisor, the students will benefit from daily interactions with other members of Professor Caron-Huot's high-energy physics group. A written report will be submitted at the end of the summer.

For more information contact: Simon Caron-Huot (schuot at physics dot mcgill dot ca).

Posted on 2020/02/06

The detection of the blazar TXS 0505+056 in both high-energy neutrinos (using the IceCube neutrino detector) and electromagnetic emission (using telescopes) has ushered in a new era of multi-messenger neutrino astrophysics. This object is a supermassive black hole that is rapidly growing through the accretion of surrounding gas, and this accretion process is though to launch relativistic jets that produces both neutrinos and electromagnetic emission. The IceCube neutrino detector at the South Pole has continued to detect neutrinos from many new objects, and the Haggard research group at McGill has been obtaining multi-epoch optical spectra of new blazars that are the likely counterparts of these new neutrino sources. In this project, the student will model these optical spectra to calculate critical parameters of the accretion flow, which probes the link between the accretion process and the production of neutrinos in the jet.

The student will apply existing methods of estimating accretion flow properties in blazars to new optical spectra, through modeling their spectral features. They will learn model fitting and error analysis, gain expertise in multi-messenger neutrino astrophysics, and develop oral/written presentation skills. Previous experience with modeling optical spectroscopy (especially in Python) will be an asset.

Weekly meetings with the supervisor and daily interactions with other members of Professor Haggard's astronomy group will keep the research on track. A written report will be submitted at the end of the summer.

For more information contact: Daryl Haggard (dhaggard at physics dot mcgill dot ca).

Posted on 2020/02/06

Calculating the dynamics for a complex many-body quantum system is generally a computationally difficult task. Analytical techniques have been developed to tackle some very specialized models, but other models (relevant to important physical processes) become quickly intractable as the number of particles in the system grows. For this reason, new innovative numerical techniques may be required to understand the dynamics of certain important physical processes.

The goal of this project will be to use a form of machine learning (a restricted Boltzmann machine) to understand the quantum dynamics of a model that describes superconductivity (the BCS Hamiltonian) or, equivalently, a spin interacting with a many-spin environment (the 'central-spin' model or Gaudin magnet).

The student assigned to this project will develop a code that will encode the problem of quantum dynamics into a restricted Boltzmann machine, then train the model with a gradient-descent minimization at each time step. The results will be verified for small systems using an exact-diagonalization code (also to be developed by the student). The successful applicant will learn about many-body quantum systems, machine learning, numerical methods (including gradient-descent optimization, exact diagonalization, etc.). If the work yields publishable results, the student will participate in writing/editing the paper (under close supervision) and preparation of figures.

For more information contact: Bill Coish (coish at physics dot mcgill dot ca).

Posted on 2020/02/06

In some two-components materials, quenching the system below a critical point leads to phase separation, where domains of two phases grow and compete throughout the bulk according to well-defined kinetics, a process known as spinodal decomposition. Recent molecular dynamics simulations suggest that in such systems, there exists a non-equilibrium spinodal phase diagram within the concentration-temperature phase space of the equilibrium phase diagram, and which controls the separation of chemically different domains within the regions of solid-solid grain boundaries. This project will use of phase-field crystal modelling of a two-component metal alloy to explore the possibility of two-dimensional spinodal decomposition in 3D samples of polycrystalline single-phase domains, and predict the region of the non-equilibrium phase diagram that controls this process. The successful candidate should ideally know how to program in some language like C or C++ and be proficient in python or Matlab.

For more information contact: Nikolas Provatas (provatas at physics dot mcgill dot ca).

Posted on 2020/02/09

The cosmic microwave background (CMB) is residual radiation from the big bang, giving us a detailed snapshot of the universe when it was less than 400,000 years old. Because the universe was a much simpler place back then, we can directly map CMB observations to the properties of the universe on its largest scales, including its age, size scale, and composition. Several current and upcoming experiments (such as the Simons Observatory) will continue the CMBs long heritage of unveiling the universe, promising to shed light on areas as diverse as the mass of the neutrino, the properties of inflation, and the existence of stable particles unknown to current physics. These new measurements will require ever more careful control of systematic errors as they look for increasingly subtle imprints on the CMB.

TThe student who takes on this project will model how imperfections in how we handle the data affect our estimates of the CMB and hence what we can learn from it in the future. One likely important effect that has received little attention is the impact of how breaking up our maps of the sky into finite-sized pixels interacts with complicated instrumetnal noise. This may lead to surprising effects, such as limiting how well we can understand inflation. The student will simulate instrumental data with known inputs and typical noise, then run software on supercomputers that makes maps from the simulated data. By comparing these maps to the initihe student who takes on this project will model how imperfections in how we handle the data affect our estimates of the CMB and hence what we can learn from it in the future. One likely important effect that has received little attention is the impact of how breaking up our maps of the sky into finite-sized pixels interacts with complicated instrumetnal noise. This may lead to surprising effects, such as limiting how well we can understand inflation. The student will simulate instrumental data with known inputs and typical noise, then run software on supercomputers that makes maps from the simulated data. By comparing these output maps to the initial inputs, the student will quantify how some of these effects could corrupt cosmology results, and investigate ways to reduce their impacts.

For more information contact: Jonathan Sievers (sievers at physics dot mcgill dot ca).

Posted on 2020/02/14

he Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) will be an array of 6m dishes observing redshifted hydrogen emission from the Karoo desert in South Africa. HIRAX will search for dark energy by watching the expansion rate of the universe evolve, over a period from 2 to 6 billion years after the big bang (redshift 2.5 to 0.8). HIRAX will also help us better understand other properties of the universe, like the conditions in the first tiny fraction of a second after the big bang, and the properties of large scale structure in the universe. Unfortunately, foreground emission from our own Milky Way galaxy is much brighter than the cosmological signal HIRAX is searching for, and so extreme care must be taken when analyzing data to ensure foregrounds don't swamp the cosmological signal.

The student who takes on this project will investigate the impact of various instrumental imperfections and how they couple to the cosmology we can measure. Effects include errors in calibrating the instrument, poor understanding of the dishes themselves, and how to arrange the dishes to make the best tradeoff between foreground rejection and keeping the data volume manageable

For more information contact: Jonathan Sievers (sievers at physics dot mcgill dot ca).

Posted on 2020/02/14

Clusters of galaxies are the most massive virialized objects in the universe. Most of the baryons in galaxy clusters are not actually in galaxies, but rather are in a diffuse, hot cloud of gas called the intracluster medium (ICM). As cosmic microwave background (CMB) photons traverse the ICM, they pick up energy causing a net decrease in brightness at low frequencies and an increase in brightness at high frequencies. This effect, called the thermal Sunyaev-Zeldovich (tSZ) effect, is one of the main tools we have to study clusters of galaxies.

The 90 GHz MUSTANG2 camera on the Green Bank Telescope (GBT) is making some of the most sensitive, detailed measurements of the tSZ ever carried out. One of the challenges in making maps of clusters using MUSTANG2 is complicated noise due to clouds, gradual drifts of the detectors, and spectral lines. The student who takes on this project will work with MUSTANG2 data to better understand the noise properties, particularly how the noise behaves on long timescales. The student will then apply that to making SZ maps of galaxy clusters and help constrain the physics of how clusters form.

For more information contact: Jonathan Sievers (sievers at physics dot mcgill dot ca).

Posted on 2020/02/14

The Experiment to Detect the Global EoR Signal (EDGES) recently reported a dip in the average brightness of the sky at a frequency around 80 MHz. While we expect the first stars in the universe to cause such a dip, the depth of the dip observed by EDGES is twice the limit set by basic physics. If confirmed, the EDGES result would be one of the most radically unexpected results in astrophysics, implying that our model for the physics of the young universe is deeply flawed. Unfortunately, this dip is nearly obscured by emission from our own galaxy that is thousands of times brighter. As a result, even tiny instrumental imperfections can allow Milky Way emission to masquerade as the cosmic signal. One of the most common ways this can happen is by a telescope beam that changes with frequency, which can make spatial fluctuations in Milky Way emission mimic the spectral feature from the first stars.

The student who takes on this project will take models of beams from various telescope searching for this dip, and characterize how spatial variation can lead to spectral structure. The student will then work out which spatial scales are important for this effect and make preliminary investigations into what sort of instrument would be needed to fill in missing information that could be used to correct cosmic dawn experiments.

For more information contact: Jonathan Sievers (sievers at physics dot mcgill dot ca).

Posted on 2020/02/14