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. Possibilities include improving FRB characterization, studying repeating FRBs, localizing FRBs, 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 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 2021/01/06

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.

Plan B: Some of the subsystem tests can be conducted in our lab facilities at McGill if travel to Penticton is not possible. We will also have access to data from Penticton, so in the event that local lab access is also restricted, the scope of this project will be reworked to focus mostly on a combination of data analysis and electromagnetic simulations.

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

Posted on 2021/01/06

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 because of 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 and/or electronics that are needed for the autonomous antenna stations. Possible areas of work include refining the designs of the antenna and readout electronics, testing a power solution for year-long antenna operation, and field testing the antenna stations at sites within driving distance (e.g. Uapishka Station).

Plan B: If field work is not possible, subsystem development and testing will be conducted in our lab facilities at McGill. If local lab access is also restricted, the scope of this project will be reworked to focus on development of control software, data acquisition, and the analysis pipeline. The readout electronics systems are sufficiently small and portable that testing from home will be a viable option.

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

Posted on 2021/01/06

MATHUSLA is a proposed experiment for the CERN laboratory to search for the decays of very long lived particles (LLPs) produced the the Large Hadron Collider (LHC). The detector will consist of a number of tracking layers in a 100m x 100m array in a surface building above the CMS interaction region of the LHC. Detailed studies are currently underway to optimize the detector layout and evaluate the physics performance of the experiment. These studies have important implications for ongoing detector research and development activities related to the proposed extruded-scintillator signal readout. The McGill group is actively contributing to the MATHUSLA detector research and design effort, and in particular in studies of the performance of silicon photomultipliers for readout of the scintillator bars via wavelength shifting optical fibres.

The student will participate in ongoing simulation studies of the MATHUSLA detector. The student will analyze simulated physics data to determine the impact of different detector design configurations, as well as contribute to the implementation of these configurations within the MATHUSLA (GEANT4) simulation framework. Electronics design and simulation studies may also be conducted within the context of LTSpice or similar tools, and results could be compared with data from testbench measurements. All work can be performed remotely if necessary, and the focus of the studies can be tailored to the interests of the student (e.g. physics or electronics). The student will participate in regular MATHUSLA group meetings and present their work in that context, as well as providing written documentation at the end of the work term.

For more information contact: Steven Roberston (steven at physics dot mcgill dot ca).

Posted on 2021/01/07

The standard model of particle physics is known to provide an incomplete description of our subatomic universe. Many possible extensions predict the existence of additional scalar fields, leading to predictions of the possible existence of additional, and relatively light, Higgs bosons. Such particles can potentially be produced by the Large Hadron Collider at CERN, and their decays could be recorded by the ATLAS detector. The McGill group actively participates in the ATLAS experiment. We are seeking a student to participate in an ongoing analysis of data collected by ATLAS, with the objective of searching for these exotic particles.

The student will participate in ongoing physics studies related to the search for exotic (pseudo)scalar bosons decaying into pairs of muons in collaboration with members of the McGill ATLAS group. This work will focus on studies of simulated LHC physics events, with the goal of optimization of the search strategy, evaluation of uncertainties and determination of the analysis sensitivity. This work will primarily involve computational data analysis and hence can be performed entirely remotely if necessary. The student will interact closely with members of the analysis team via weekly group meetings, and will regularly present their work within the analysis group. A written report will be prepared at the completion of the project.

For more information contact: Steven Roberston (steven at physics dot mcgill dot ca).

Posted on 2021/01/12

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 2021/01/22

During Cosmic Dawn and the subsequent Epoch of Reionization, first-generation galaxies carved out “bubbles” of ionization around them. Studying the shapes and sizes of these bubbles will enable researchers to understand the nature of these galaxies. Low-frequency radio interferometers like the Hydrogen Epoch of Reionization Array or the Square Kilometre Array are currently being constructed with the partial goal of making images of these bubbles. Unfortunately, real-world instrumental effects complicate this effort, making these ionized regions difficult to identify. Recently, machine learning techniques have shown considerable promise when it comes to solving this problem. However, this promise is based on “by eye” examinations of the results. The goal of this project will be to develop metrics to quantitatively evaluate the accuracy of machine learning-based bubble recovery.

The student will first work through a short online tutorial on machine learning and then learn to run already-written machine learning code for ionized bubble identification. They will then apply some standard quantitative metrics to the data and brainstorm new ones with the rest of the research group. Finally, they will learn about how early galaxies are distributed relative to ionized bubbles and evaluate the possibility of using the ionized bubbles as a marker for these galaxies.

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

Posted on 2021/01/22

Advanced manipulation of the amplitude, frequency and phase of light typically involves interactions with nonlinear media. An alternative method, however, is an interaction with a linear medium that is modulated in space and time, having the advantage of working even at low light intensities. Recently, we have devised an experiment whereby coherently generated and detected THz light can interact with a relativistic (both sub- and super-luminal) moving front of conductivity within a semiconductor-filled waveguide. This method allows sophisticated and simultaneous control over both frequency and wave vector of the light through careful tuning of the characteristics (velocity, dispersion, spatial form) of the moving front. This project will develop a numerical model based on finite-difference time-domain simulations to help predict such interactions and search for interesting effects from pulse time-reversal to photonic event horizons. The results of these simulations will be merged with experiments carried out in the Cooke lab.

The student will modify existing finite difference time domain code to accurately model the photonic dispersion of the conductive regions of the semiconductor. They will work to define the experimental parameters required to observe predicted phenomena, taking feedback from experiments to fine tune their code. The student will produce a robust and well commented numerical code for these simulations, and will meet on a weekly basis with Cooke and graduate student to communicate their findings. They will prepare summary documents outlining the results of simulations on regular intervals and be expected to participate in the writing of a journal article.

For more information contact: David Cooke (cooke at physics dot mcgill dot ca).

Posted on 2021/01/28

At TRIUMF, in Vancouver, beams of exotic isotopes are produced by proton-induced nuclear reactions and sent through a series of ion guides to a beam line where the ion beams are overlapped with a laser beam in collinear geometry. 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.

Spectroscopy can be carried out on ion or atomic beams. For working with atomic beams, the ions in the primary beam are converted into atoms by a charge exchange process in an atomic vapour contained in a cell (charge exchange cell). Optimizing this charge exchange process for a given primary beam of interest is required for increasing the sensitivity of the experiment. Optimization can be achieved by choosing the ideal element for charge exchange, by varying the vapour density in the cell and varying the velocity of the ion beam. A study of this charge exchange process for primary beams with Z ranging from 1 to 89 , has been published recently (Vernon et al., Spectrochimica Acta B 153 (2019), 61-83 - DOI 10.1016/j.sab.2019.02.001).

In this project, a student will try to first reproduce those results by writing his/her own program based on the procedures laid out in the paper. He or she will then apply the program for analyzing experimental charge exchange data obtained at TRIUMF in 2020. The project will build on preliminary work done by a summer student in 2020. He or she will be assisted by an experienced group of TRIUMF staff, PDFs, and other McGill graduate students, as well as by Dr. Matthew Pearson, a TRIUMF staff member and an adjunct McGill professor. Since the TRIUMF site is not accessible for summer students this year due to the Corona virus situation, the project will have to be carried out remotely. Regular virtual meetings will be organized for assuring an appropriate supervision of the student.

For more information contact: Fritz Buchinger (fritz at physics dot mcgill dot ca).

Posted on 2021/01/29

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is the first major new telescope to be built on Canadian soil for decades. The telescope will have the capability of mapping the largest volume of the universe ever observed in a single survey. It may unlock mysteries of Dark Energy as well as strange radio bursts that have been seen on the sky. Importantly, it is a new paradigm of telescope - it has no moving parts and images the sky by digitally processing information from several thousand antennas.

The goal for this summer project will be to participate in cosmology data analysis of the CHIME project. In addition, the student will contribute to the characterization of the telescope performance and day to day monitoring and evaluation of the telescope data.

The student will be involved with analyzing sky signals from the CHIME telescope to characterize and subtract foregrounds, and reveal the cosmology signal that maps structure in the universe. This will involve writing and testing analysis code, typically written in Python and executed on Compute Canada supercomputers. The student will work along side graduate students and postdoctoral researchers within the CHIME team. The will take place in person at McGill University, if travel restrictions allow, or will be accomplished with remote platforms such that the student can work from home if travel and in-person meeting restrictions remain.

For more information contact: Matt Dobbs (matt dot dobbs at mcgill dot ca).

Posted on 2021/01/29

Since D'arcy Thompson's book “on growth and form”, many biophysicists have studied the laws of morphogenesis, developing many (complex) models of pattern and structure formations in biology. In parallel, there has never been more quantitative data on biological shapes in general, which allow for the application of new quantitative approaches such as machine learning. But the question remains on how to connect machine learning analyses to model building in biophysics. The project will focus on the description of such connections . Using models from the literature, we will use machine learning techniques to map the biophysical “morphospace”, and project it on a low dimension parameter space. We will use this analysis to identify relevant directions in parameter space. We will project data of our collaborators on this morphospace and will study if and how evolution is moving in the space of possible models.

The student will study biophysics models for pattern formation, perform numerical simulations and machine learning analysis (typically UMAP projections). The student will participate in all group's activities (group meeting, journal club) and will have daily interactions with the supervisor and a senior post-doc, as well as regular interactions with experimental collaborators.

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

Posted on 2021/02/01

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 2021/02/02

Co-supervisors: Professor D. Haggard (McGill), Dr. K. Dage (McGill)

The question of whether or not stellar-mass black holes are hosted by globular clusters is one of the leading open questions in astronomy. While globular clusters are "black hole factories" through normal stellar evolution, some theories predict that black holes will be ejected via multi-body interactions early in the history of the globular cluster. However, recent observational work and theoretical studies in the last 15 years have suggested that not all black holes will be ejected from the cluster. Studies of ultraluminous X-ray sources in extragalactic globular clusters have provided evidence that some of the most exotic black hole candidates reside in globular clusters.

Many ultraluminous X-ray sources hosted by clusters at the outskirts of galaxies may have gone un-detected, and the student will use existing optical and X-ray catalogs (pan-STARRS and the Chandra Source Catalog) to identify new candidate ultraluminous X-ray sources in globular clusters. Previous experience using python will be an asset. The student researcher will also learn to produce publication-quality visualizations, and lead a manuscript in a peer-reviewed scientific journal. Applicants who can contribute to a diverse and inclusive environment are particularly welcome.

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

Posted on 2021/01/02

Co-supervisors: Professor D. Haggard (McGill), Professor J. Ruan (Bishops)

Mergers of black holes have recently been detected through gravitational waves (leading to the 2017 Nobel Prize in Physics), and using these mergers for cosmology is a key science goal of this new frontier. However, there are currently many uncertainties in our understanding of the astrophysics of black hole mergers that limit our ability to perform gravitational-wave cosmology. In this project, we will use cosmological simulations of galaxy formation with state-of-the-art black hole dynamics to study the relation between the orientation of merging massive black holes and the orientation of their host galaxies in the simulations. This investigation is important because misalignments between these orientations can bias the inference of key cosmological parameters (such as the expansion rate of the Universe) based on detections of black hole mergers through both gravitational waves and light. We will undertake this project in close collaboration with Prof. John Ruan (Bishop's U). Due to the pandemic, this summer project will be done remotely with regular videoconference meetings.

The student researcher will learn to write and use computer programs to analyze outputs from cosmological simulations of galaxy formation, produce publication-quality visualizations, and lead a manuscript in a peer-reviewed scientific journal. Applicants who can contribute to a diverse and inclusive environment are particularly welcome.

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

Posted on 2021/02/01

The nEXO (next 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 nEXO 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 join our local research group and participate in commissioning a cryogenic test setup that allows one to cool SiPMs to -100C and measure their characteristic I-V curves. To this end you will set up optics systems with lasers. 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.

As member of our research group you will 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.

Plan B: Over the summer of 2020 the group developed expertise in photon transportation simulations using GPUs. This approach greatly reduces processing times in simulations. If no lab access is possible, you will continue these innovative photon transport simulations.

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

Posted on 2021/02/04

By definition, gas giants must have assembled early in a gas-rich environment. The standard gas accretion theory posits that the cores of gas giants must be ~10 Mearth or larger. Such massive cores are difficult to have assembled primordially from the accretion of pebbles, especially in the inner disk; instead, these cores may have formed by the secondary merger collisions. The aim of the project is to compute the likelihood of such mergers in a gas-rich environment which tends to circularize the orbits of planetary protocores.

First, the student will familiarize themselves with the physics of eccentricity damping by disk gas dynamical friction through literature review and order of magnitude calculations. Next, the student will run a suite of open-source N-body integrator REBOUND to compute the probability of merger collisions as a function of core-to-core spacing, core masses, the number of cores, and the disk gas surface density over a Myr, the typical disk gas lifetime. All required tasks can be done remotely.

For more information contact: Eve Lee (evelee at physics dot mcgill dot ca).

Posted on 2021/02/04

Kepler planets feature a bimodal radius distribution with a clear distinction between super-Earths and sub-Neptunes. This so-called radius valley has been understood as a signature of envelope mass loss but gas accretion alone could also reproduce this feature (Lee & Connors in press). Currently, the data suggests that the location and the shape of the radius valley changes as a function of stellar mass and metallicity, with these quantities being correlated with each other in the data. The aim of the project is to take a deeper look into the hypothesis of primordial radius valley by investigating what this model would predict in terms of any variation in the radius valley with respect to the properties of the host star.

The location of the primordial radius valley is sensitive to the temperature of the disk in which planets form. First, the student will derive the expected scaling relationship between disk midplane temperature, orbital distance, and host stellar mass for both accretion-heated (using the observed stellar mass - accretion rate relation) and irradation-heated disks (using the theory developed in Chiang & Goldreich 1997). Second, the student will derive a first-order approximation of how disk metallicity may affect the disk midplane temperature as a function of orbital distance using a simple one-dimensional radiative diffusion equation assuming optically thick disks. Finally, the student will apply these models of disk temperatures to the theory of primordial gas accretion outlined in Lee & Connors (in press) to quantify how the radius valley shifts with respect to stellar mass and metallicity. All required tasks can be done remotely.

For more information contact: Eve Lee (evelee at physics dot mcgill dot ca).

Posted on 2021/02/04

There are persistent tensions in cosmological measurements of the Hubble parameter coming from local determinations of the expansion rate (type IA supernova luminosities) versus the cosmic microwave background (CMB); similarly there is tension in the structure formation parameter σ₈. These have motivated studies of various models with time-dependent dark energy. The current project aims to constrain the parameters of a novel modification of cosmological expansion, where the vacuum is unstable to negative energy massless ``ghost'' particles plus massive dark matter particles. This creates a growing matter energy density at late times, whose effects can be probed by the CMB and supernova measurements. Such a mechanism has not been previously studied, and it could possibly reconcile tensions in the current data.

The student will learn how to use the CosmoMC software package, which allows one to constrain cosmological parameters using CMB data from the Planck experiment, and combined results of supernova observations. The student will need to make minor modifications to the code (with help from my Ph.D. student) to incorporate the new effects of vacuum decay. The student will learn how to run the code on the Compute Canada supercomputer network. The goal will be to find preferred regions in the overall parameter space---the standard cosmological parameters, plus the new one, which is the rate of decay of the vacuum, $\Gamma$---and determine whether the new physics allows for a better fit to all of the data, or how $\Gamma$ is constrained if not. In addition, the student will read introductory references about cosmology and the CMB, in order to gain an understanding of the physics and the methodology of the CosmoMC code.

For more information contact: Jim Cline (jcline at physics dot mcgill dot ca).

Posted on 2021/02/04

Theorists have been intensively studying the possibility that neutrinos may have nonstandard interactions, beyond their usual weak interactions. This project follows up on a novel proposal, that neutrinos could interact with a new gauge force that couples to the difference between μ and τ lepton number, and that the associated gauge boson $\overrightarrow{A}$ could be an ultralight dark matter particle that behaves as an oscillating condensate, which can alter the self-energies of the μ and τ neutrinos. This in turn could affect the observed oscillations of neutrinos involving these flavors, for neutrinos produced in the earth's atmosphere by cosmic rays, or in long-baseline experiments on earth. The goal of this project is to explore how such modifications would appear in neutrino oscillation data, and to compare predictions of the model to data. This will allow the parameters of the model to be constrained, and to make predictions for possible deviations from standared oscillation signals, which might become detectable in data from future experiments.

This project is well within the reach of an undergraduate student who has taken quantum mechanics, since it is just a two-state system with a time-dependent Hamiltonian. The student will write a computer program to solve the Schrödinger equation and compute the oscillation probability as a function of time. These results will be compared to published data from experiments to determine what level of nonstandard contributions to the oscillation probability can be compatible with current data, and to make projections of the sensitivity of new experiments to detect such effects. The student will explore the model predictions over the manageably small parameter space of the nonstandard interactions, namely the mass of the ultralight vector boson, and the product of its coupling times |$\overrightarrow{A}$| amplitude. In addition, the student will read introductory references about neutrino oscillations and cosmology in order to appreciate the scientific content of the project.

For more information contact: Jim Cline (jcline at physics dot mcgill dot ca).

Posted on 2021/02/04

Among the thousands of recently-discovered planets orbiting other stars, astronomers has uncovered a handful of lava planets: planets with an Earth-like density, but orbiting so close to their star that their surface is molten. The 2000-3000 K dayside of a lava planet is a huge magma pool overlain by vaporized rock, while its nightside may hot due to advection of heat from the dayside, or might be as cold as 100 K if the atmosphere does not extend to the dark side of the planet. By monitoring one of these planets with infrared telescopes over the course of an orbit (as short as 6 hrs for lava planets), we are able to infer whether the planet has a global atmosphere or merely a local rock vapor atmosphere over the magma ocean. This project entails analyzing Spitzer Space Telescope observations of a lava planet to obtain robust estimates of its dayside and nightside temperatures and comparing those inferred properties with different atmospheric scenarios.

The student will use and modify an existing open-source data extraction pipeline Spitzer Phase Curve Analyses to properly treat public Spitzer observations of a lava planet. This will require detrending the observations for known instrumental effects and testing various detector models. Due to the large data volumes and computationally intensive nature of the data reduction and fitting, the analysis will be performed on the Physics computing resources, accessible remotely. All coding will be done in Python and will make use of GitHub.

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

Posted on 2021/02/04

Among the thousands of recently-discovered planets orbiting other stars, astronomers has uncovered a handful of lava planets: planets with an Earth-like density, but orbiting so close to their star that their surface is molten. The 2000-3000 K dayside of a lava planet is a huge magma pool overlain by vaporized rock, while its nightside may hot due to advection of heat from the dayside, or might be as cold as 100 K if the atmosphere does not extend to the dark side of the planet. By monitoring one of these planets with infrared telescopes over the course of an orbit (as short as 6 hrs for lava planets), we are able to infer whether the planet has a global atmosphere or merely a local rock vapor atmosphere over the magma ocean. This project entails analyzing Spitzer Space Telescope observations of a lava planet to obtain robust estimates of its dayside and nightside temperatures and comparing those inferred properties with different atmospheric scenarios.

The student will use and modify an existing open-source energy balance model to simulate the thermal phase variations of a lava planet. Since the current model was developed for giant planets with hydrogen-dominated atmosphere, the student will have to branch and modify the code in order to accommodate more plausible lava planet atmospheres, including oxygen, water, and silicates. If the observations of the lava planet favour an airless nightside, then the student will apply the chemical components they develop to a 1D hydrodynamic simulation run by a collaborator. All coding will be done in Python and will make use of GitHub.

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

Posted on 2021/02/04

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 the observables in a given model, and the project will improve on purely numerical solutions by incorporating recent analytic results.

The student's 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. They will then develop code to numerically solve bootstrap problems, determining the optimal way to combine analytical and numerical constraints. The student will learn skills for symbolic programming and numerical analysis, and develop both written and oral presentation skills. In addition to frequent meetings with the supervisor, the student will benefit from daily interactions with other members of Professor Caron-Huot's high-energy physics.

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

Posted on 2021/02/04

Characterizing errors that can occur in quantum computers can be difficult. In particular, it is often difficult to distinguish between 'coherent' (deterministic) errors due to the over- or under-rotation of a qubit and 'incoherent' errors that may arise from entanglement with an external uncontrolled environment. A reduction in the system purity is a measure of such an error. The purity can be characterized either through a 'swap test' or, for a two-qubit system, directly by measuring the projection of a two-qubit system onto a totally-antisymmetric (spin-singlet) state.

The goal of this project will be to theoretically characterize the expected performance of purity measuremnts that may be performed on a small spin-based quantum computer in the presence of known error sources.

The student assigned to this project will develop (together with the supervisor) numerical and analytical methods to evaluate the quantum process matrix for a two-qubit system based on electron spins, interacting with known environments. The successful applicant will learn about solid-state implementations of quantum computing, aspects of quantum error correction, and benchmarking. 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 2021/02/04

In the Standard Model of particle physics, the self-couplings of electroweak gauge bosons are completely specified by the structure of the theory. Any deviations from this expectation would indicate the presence of new physics phenomena at unprobed energy scales. The McGill-ATLAS research group currently works on novel investigations of the unique interactions between two W bosons and 2 photons (WWγγ). These investigations will allow us to make the first ever observation of the extremely rare reactions pp→Wγγ and of the vector boson scattering process pp→Wγ. If no hints of new physics are found, constraints on new physics phenomena will be derived in a model independent way in the context of an efffective field theory framework. The goal of this summer research project is to take part in the analysis of high energy proton-proton data, and specifically prepare the necessary analysis infrastructure to make it possible to extract meaningful constraints on the existence of new physics phenomena. The student will learn about particle physics theory, various data analysis techniques and develop programming skills.

The student will be asked to participate in the analysis of proton-proton collision data recorded by the ATLAS detector at the LHC. Specifically, the student will be tasked with the implementation of an analysis framework with the goal of calculating constraints on new physics effects based on the measurements of the reactions described above. The student may also have the opportunity to contribute to a study of the new physics reach of future large particle colliders through investigations of multi-boson interactions.

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

Posted on 2021/02/04

The ATLAS experiment at the CERN's Large Hadron Collider (LHC) in Geneva records the results of the highest energy particle collisions ever produced in laboratory. The LHC is scheduled to undergoe a major upgrade in 2025-26 that will result in an increase of its beam intensity by nearly an order of magnitude. In order to cope with this new extreme environmental conditions, the ATLAS detector will undergoe a major upgrade of several of its subsystem. One of these upgrades consists in replacing the entire readout electronics of the Liquid Argon Calorimeter detector, a sub-system responsible for precisely measuring the energy of electrons/photons produced in proton-proton collisions.

The goal of this summer research project is to participate in the ongoing design and development of the future electronics readout (which includes both an analogue and a digital part). The student will learn about particle detector instrumentation, different concepts of analogue and digital electronics, and possibly develop FPGA programming skills.

The student will be tasked with the integration of different electronics components in the lab, and setup of an infrastructure for the testing of the large complex firmware project being developed.

Plan B: The student will participate in simulation studies for the the optimization of different possible parameters of the readout chain, possibly including the development of Machine Learning techniques for the reconstruction of energy in the calorimeter. The student will also have the opportunity to take part in some FPGA firmware programming.

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

Posted on 2021/02/04

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 finishing the construction of approximately one third of the specialized detectors required for this upgrade. The McGill group has been responsible for the testing and characterization of these Canadian-made chambers using cosmic-rays. Knowledge of the precise position of each detector readout electrode is crucial to allow the precise measurement of the position and momentum of muon produced in proton-proton collisions. Cosmic-ray data has the potential to provide valuable information about the relative electrode positions.

The goal of this summer research project is to contribute to the commissioning of these detectors through the analysis of cosmic-ray data collected at McGill. The student will learn about different particle detection techniques, various data analysis techniques and develop programming skills.

The student will be responsible for the development of a new multi-dimensional analysis correlating information from cosmic-ray data, x-ray data, and construction measurements in order to provide the best possible model for the position of individual strip electrodes in the detectors.

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

Posted on 2021/02/04

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 ndemonstration 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, characterize these devices using IV measurements performed with a patch-clamp amplifier (assisted by post-doc Dr. Yazda), and then use this approach to fabricate nanofluidic devices containing two closely separated nano pores for controlled translocation. 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.

Plan B: If pandemic conditions prevent on-site research, the student instead will perform Comsol simulations of pore formation process and ionic transport through pores.

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

Posted on 2021/02/06

How do multiple interacting polymers behave in confined environments? This is a fundamental problem in confined polymer physics with important implications in a range of biological systems, from chromosomal segregation and plasmid distribution in dividing bacteria to chromatin organization. The Reisner group is developing nanofluidic assays to explore how multiple polymer molecules behave in confined environments. These in vitro confinement models, where all parameters can be directly controlled, will enable testing of whether simple polymer theories can explain DNA organization in biological systems. In detail, nanofluidics will be used to confine multiple chains, using either hydrodynamic flow to compress multiple molecules against slit barriers in nanochannels, or pneumatic actuated lids to trap molecules in nanocavity structures. Differential staining of the chains will be used to independently assess the conformation of each chain, determine the degree of partitioning/mixing and assess coupled diffusion of the chain center-of-mass positions. Measurements will be performed as a function of cavity dimension, salt concentration, polymer topology, chain number and size.

The student will learn how to perform confined polymer experiments using Reisner lab fluorescence microscopy platforms. This training includes chain staining protocols, nanofluidic device and microscope operation. The student will then develop automated analysis routines in either Matlab or python to extract key qualities from the videomicroscopy data. The student will be supervised in the lab by a PhD student and meet with Prof. Reisner on a weekly basis.

Plan B: If pandemic conditions prevent on-site research, the student instead will perform molecular dynamics simulation of the confined polymer models.

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

Posted on 2021/02/06

Understanding the physical processes by which galaxies form and evolve remains a key goal o astrophysics. Over recent years we have revealed several determining factors that dictate a galaxy’s evolutionary history: namely galactic mass and environment. Both of these are taken to an extreme in the so-called Brightest Cluster Galaxy (BCG) population These systems are the most massive galaxies at any epoch, presumably hosting the most massive central black holes, and living at the bottom of the gravitational potential wells of dense galaxy clusters These important galaxies grow with cosmic time through interactions with the galaxy cluster and, in particular, its hot gas halo.

In this project the student researcher will search new and unprecedented deep/wide-field X-ray imaging for the giant gas halos that surround galaxy clusters and BCGs The student will be responsible for coding the tools required to mine the X-ray data archive and analyze the imaging Once the imaging analysis has been completed the student will then be ready to measure physical properties of the gas, such as its total mass. A comparative study with the central BCG - looking for correlations between BCG and gas halo properties - will then be conducted by the student.

The project will introduce or hone several key research skills including data archive mining, image processing, and data visualization and presentation. The student researcher will have the opportunity to be involved in the publishing of the results in a peer-reviewed scientific journal.

This project can be conducted in person or online.

For more information contact: Tracy Webb (webb at physics dot mcgill dot ca).

Posted on 2021/02/10

Brunner lab is focusing on developing technologies as part of the international nEXO collaboration. nEXO 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. nEXO requires the development of advanced technologies as well as detailed knowledge of the underlying physical processes to reach a sensitivity goal of 1028 years. At McGill we are contributing to these technical developments. In the process, we generate moderate amounts of data that we store in a data base. We require software to retrieve, process, analyze, and present this data.>/p>

You will be working with members of the McGill nEXO group and develop code to read data from the lab's data base, and analyze and visualize it. Ideally, you will also implement a webpage that updates plots and graphs based on user input. Time and interest permitting, you will also help develop arduino-based data acquisition systems to record and copy to the data base slow control variables in the lab. You will join the local EXO group at McGill and learn about neutrino physics, data management, and detection techniques using liquid Xe.

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

Posted on 2021/02/13

The nEXO (next 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. nEXO effectively consists of two components: an inner detector that searches for 0νββ decay signatures and an outer detector that shields against background radiation and tags passing muons. The McGill group is heavily involved in the design of this outer detector, which is a 1.5 ktonnes water-Cerenkov detector. In particular, the group is working on optimizing the muon veto to a tagging efficiency of close to 100%.

You will join the local nEXO group at McGill and work on GEANT4 simulations of the outer detector. GEANT4 is a simulation toolkit which has been developed at CERN and is commonly used in particle and nuclear physics experiments. In these simulations, you will optimize the placement of light sensors to optimize the muon tagging efficiency in nEXO. Your simulation will help decide on the final placement of these sensors inside the outer detector.

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

Posted on 2021/02/13

Understanding how quickly planets grow is key to interpreting the diverse properties of the many exoplanets that have now been detected. Hydrodynamic simulations of protoplanets embedded in gas disks show that there is a complex flow of gas from the disk into the growing envelope of the planet and out again. The exchange of gas between planet and disk changes the thermal state of the envelope and hence its growth rate.

The goal of this project is to develop steady-state multidimensional models of recycling atmospheres. Less computationally expensive than full simulations, but more detailed than simplified 1D models, these calculations will allow a survey of parameter space to identify the key parameters and conditions when recycling is important.

The project will involve first learning about the different input physics that goes into calculations of planetary envelopes, and then a numerical code will be developed to solve the steady state equations. This work will be carried out in collaboration with the supervisor, with frequent (at least once weekly) meetings, as well as a chance to interact with other group members at group meetings. The project can be carried out remotely.

For more information contact: Andrew Cumming (andrew dot cumming atmcgill dot ca).

Posted on 2021/02/17

The nEXO (next 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. nEXO requires the development of advanced technologies as well as detailed knowledge of the underlying physical processes to reach a sensitivity goal of 10^28 years. To push the detector sensitivity even further, new technologies are required. 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 ββ 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 in vacuum and in xenon gas. 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 working with members of the McGill nEXO group to measure the ion current in our source at various conditions, and analyze and visualize the recorded data. You will join the local EXO group at McGill and learn about neutrino physics, data management, and detection techniques using liquid Xe.

Plan B: If no access to the lab is possible, the data will be collected by a graduate student and you will be analyzing the recorded data. This work will be complemented by ion-transport simulations.

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

Posted on 2021/02/22

Fast radio bursts (FRBs) are some of the most enigmatic objects in astronomy today. They flash for ~1 millisecond, usually never to be seen again. Our understanding of FRBs has been limited by the inability of the telescopes that find them to localize them to individual galaxies. CHIME, CHORD, and HIRAX will build outrigger telescopes separated by hundreds or thousands of kilometers from the main arrays in order to localize thousands of FRBs to their host galaxies, enabling us to answer questions about where they come from, how energetic they are, and possibly use them as probes of cosmology.

Moden radio telescopes process trillions of bits per second. Digital signal processing is therefor often as important as the actual telescopes. One of the key steps in the signal chain is splitting the incoming radio waves into different frequency channels. Unfortunately, a simple Fourier transform spreads power from human-generated interference to other frequencies, contaminating science data. The usual solution is to use a polyphase filter bank (PFB), which reshuffles and windows the incoming data in a way that supresses the leakage, often by orders of magnitude compared to Fourier transforms.

The PFB works very well for standard observing modes for radio telescopes. Localizing fast radio bursts, however, requires undoing the effects of the PFB, before data from far-flung telescopes can be combined. While the Fourier transform is straightforward to invert, symmetries in the PFB mean that the inversion is close to singular, which will degrade our ability to localize FRBs. Since this dual-purpose mode of standard radio observations plus FRB localization is relatively new, alternate techniques that preserve the benefits of the PFB while also preserving information for localization might exist. The goal of this project is to design new filters that can better serve these dual goals. A successful design would be implemented in upcoming telescopes like HIRAX and CHORD.

The role of the student would be to come up with ideas for new filters, and test their performance both in rejecting interference and in invertibility. The first step is for the student to define a metric that scores filters based on both criteria. The next step is to search for new filters that perform well based on the metric derived by the student, possibly using machine learning. Finally, the student will carry out simulations of FRB localizations and compare the improved filter with current filters.

All work can be done remotely, using python (or the language of the student's choice).

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

Posted on 2021/02/24