Particle physics aims to understand matter, space and time, and to unify all observables under a single theory of particles and their interactions. Complementary to the discovery goals of the Large Hadron Collider (LHC) experiments, the International Linear Collider will be able to examine in details the properties of the Higgs, the mechanisms of electroweak symmetry breaking, the generation of masses and search for dark matter. The McGill group is participating in R&D detector design and construction in the framework of the international CALICE collaboration. We work on a novel type of Digital Hadron Calorimeter to achieve particle reconstruction to unprecedented accuracy.

This summer job would require detailed analysis of the latest calorimeter test beam data taken at CERN to determine the detector response calibration and realize performance studies such as linearity in the response to different types of particles, as well as energy, angle and position resolutions. Strong motivation and commitment are expected. The candidate should be familiar with C programming and preferably already computer fluent under Linux. The work would take place at McGill under daily supervision. Basic understanding of particle physics concepts would be an asset.

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

Posted on 2014/12/18

The year 2012 marked the discovery of a Higgs boson by the ATLAS and CMS particle physics experiments at the Large Hadron Collider (LHC) of CERN in Geneva. We now have to investigate in detail the properties of the Higgs. The LHC and its experiments have upgrade plans to deal with the increase of event rates, the need for even greater precision and search for new physics phenomena. The ATLAS group at McGill is involved in the construction and validation of a new muon detector, called the New Small Wheel, that will address all these issues. Canada is building 40% of the new detector with the thin gap chamber technology. The components will be tested and characterized at McGill in a new facility using cosmic muons before being shipped to CERN.

The project involves all aspects of the measurements: manutention, high voltage, gas flow, electronics, triggering, data acquisition, online monitoring and offline analysis. New algorithms have to be developed to map the new chambers with maximum efficiency and precision. The work would take place under very close daily supervision. For students who also want to do hardware and be at the leading edge of the field!

These professors are looking for two students for this project

For more information contact: François Corriveau (corriveau at physics dot mcgill dot ca), Brigitte Vachon (vachon at physics dot mcgill dot ca) or Andreas Warburton (awarburt at physics dot mcgill dot ca).

Posted on 2015/01/03

The discovery of a Higgs boson by the ATLAS and CMS particle physics experiments at the Large Hadron Collider (LHC) of CERN in Geneva was but the beginning. We now have to investigate in detail the properties of this Higgs and its couplings. One possibility is to investigate its production with that of the top quark, Since the top has a mass closest to the one of the Higgs, it should give extra sensitivity to the measurements.

The project would call for familiarization with the standard analysis packages, development of tools for event selection and detailed estimations of the backgrounds. Knowledge of C++ and understanding of basic particle concepts would be assets. The applicant is also strongly encouraged to participate to the summer undergraduate research program of the Institute of Particle Physics of Canada which could support a trip to CERN, where the large part of the research could be carried out. This a challenging project for very motivated students. Close and daily supervision would be organised.

For more information contact: François Corriveau (corriveau at physics dot mcgill dot ca), Brigitte Vachon (vachon at physics dot mcgill dot ca) or Andreas Warburton (awarburt at physics dot mcgill dot ca).

Posted on 2015/01/03

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 laser beams. 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, and to measure nuclear magnetic dipole and electric quadrupole moments. Such measurements give us information about the variation of nuclear size and shape over a series of isotopes. We have recently made many modifications to improve the sensitivity of these measurements for nuclear beams of low intensity and very short lifetimes. More details of these developments have been acknowledged in an article on TRIUMF Research Highlights.

Our technique requires stabilization of the laser frequency to very high precision over lengthy experimental runs. One component of the feedback system that locks this frequency is a scanning Fabry-Perot interferometer, a device that produces sharp fringes at specific optical wavelengths. A student participating in the project will construct and test a new interferometer for use in the visible wavelength region. 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. When I (Crawford) am at McGill, I will supervise the student by a weekly TRIUMF-McGill video link.

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

Posted on 2015/01/06

We are developing a device that can determine the direction to a source of MeV gamma rays to within a degree in under a minute. Such a detector is useful in safety and security applications where radioactive sources are involved. It makes use of ideas borrowed from gamma-ray astronomy where space-borne telescopes are used to find the coordinates of gamma-ray bursts (GRBs).

Various iterations of the detector have been produced and involve slabs of scintillator material read out by photomultipliers. The latest version is equipped with silicon photomultipliers, recently developed solid-state photon detectors which are more compact than conventional vacuum-tube devices.

The student will characterize the instrument and participate in design studies leading to a field-deployable version which will emphasize efficiency and ease of use. S/he will develop analysis code and calibration protocols as well as the related documentation.

Weekly meetings with the supervisor and daily interactions with other members of the gamma-ray group will keep the research on track. A written report will be submitted at the end of the summer.

Experience with electronics and knowledge of Python is an asset but not a requirement.

For more information contact: David Hanna (hanna at physics dot mcgill dot ca).

Posted on 2015/01/09

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is the first major new telescope to be built on Canadian soil for decades. Now in its commissioning phase, 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 pathfinder for 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 the commissioning and first observations of the CHIME pathfinder instrument, which is 1/5 the size of the full CHIME telescope, by evaluating the early sky signals, and participating on the construction, assembly and characterization of the electronic system for the full CHIME telescope. The student will perform hands-on lab work, write computer code and test scripts to characterize and calibrate circuit boards, as well as computer-based analysis of the data.

For more information contact: Matt Dobbs (mdobbs at physics dot mcgill dot ca).

Posted on 2015/01/14

We recently acquired a new set of tails for our ³He Mössbauer cryostat so that it can be operated vertically with both the sample and Mössbauer source cooled to liquid helium emperatures. Most of the hardware has been built in the Physics workshop, so the project will involve working with the technicians in the condensed matter group to assemble the system, followed by testing at room temperature. Once the required performance standards are demonstrated, we will cool down to 300mK to establish full operation.

The spectrometer is intended to support research on molecular magnets and halcogenide-based spinel spin-ice systems, so depending on the rate of progress over he summer, a “real” data-taking campaign should be possible, with results to be published in a research journal.

The student's role will involve:

• Working with technicians on the assembly of the new vertical insert for the cryostat
• Testing of the insert using standard Mössbauer samples
• Installing and commissioning the vacuum system in collaboration with our technicians
• Staged testing of the cryostat and the Mössbauer spectrometer at 80K, 5K, 1.5K and 0.3K using standard samples
• ¹⁶⁶Er or ¹⁷⁰Yb Mössbauer spectroscopy measurements on some chalcogenide-based spinel spin-ices

For more information contact: Dominic Ryan (dominic at physics dot mcgill dot ca).

Posted on 2015/01/16

The rare earth ions in several pyrochlore systems (e.g. RTi₂O₇ and RSn₂O₇) form a network of corner-sharing tetrahedra, and if the first-neighbour exchange interactions are antiferromagnetic, then the magnetic system is geometrically frustrated. If certain other conditions are met, the magnetic ground state has a large residual entropy and by analogy with the solid form of water, they are often call “spin ices”.

We have recently started a project to use Mössbauer spectroscopy to study magnetic ordering in a new group of compounds that include the same magnetic network of corner-sharing tetrahedra, but adopt a spinel structure rather than the pyrochlore structure of the better-known titanates and stannates. The local environments of the rare earth ions are quite different in the two structures allowing us to compare the impacts of these differences on the magnetic ground states.

The project will involve a mix of sample preparation, basic characterisation for quality assurance followed by more detailed magnetic studies of the ordering behaviour.

The student's role will involve:

• Working with our sample preparation technician to prepare and characterise several of these new chalcogenide spinel materials (RCd₂S₄ and RCd₂Se₄)
• Using x-ray diffraction to confirm sample quality
• Using our Quantum Design Physical Properties Measurement System (PPMS) to study the bulk magnetic behaviour of the samples
• Using ¹⁶⁶Er, ¹⁷⁰Yb and possibly ¹⁶¹Dy Mössbauer spectroscopy to study magnetic ordering in the new materials down to 1.56K.

For more information contact: Dominic Ryan (dominic at physics dot mcgill dot ca).

Posted on 2015/01/16

The elementary building block of quantum information is called a quantum bit (qubit). Like its classical counterpart, a qubit is a two-level system, but governed by the laws of quantum mechanics. Physical implementations of qubits are typically realized in “effective” two-level systems. This means that out of an n-level system, two levels have been chosen to encode information and form a logical subspsace.

Here, we are interested in studying qubits formed in a subspace when these qubits are controlled using Landau-Zener physics. This control method involves sweeping a time-dependent control parameter to move an initially prepared quantum state through an energy-level anti-crossing. Recent technological developments allow to use this kind of quantum evolution to coherently manipulate a variety of systems that are of interest for quantum information. However, recent experimental results are often understood in terms of two-level state crossings, while in reality there are many levels crossing.

The successful applicant will learn and develop analytical methods to understand the time-evolution of an interacting multi-level system. Understanding the time-evolution would further allow to design control sequences that minimize leakage out of the logical subspace (the qubit subspace). This work is to be done at McGill University under daily supervision.

Prof. Coish is looking for two students for this project

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

Posted on 2015/01/19

Fiber-based microcavities hold promise for integrating solid state systems into ultra-high finesse optical resonators. Formed by mirrors deposited on the tips of laser-ablated optical fibers, these microcavities can combine ultra-small mode volumes with state-of-the-art mirror coatings. A primary challenge is to design a cavity platform compatible with cryogenic temperatures, flexible enough to position the cavity mode around a desired location, and stable enough to permit high-bandwidth locking. This research project centers around developing and testing a design for tunable, piezo-actuated fiber cavities for operation at cryogenic temperatures. First, the unknown thermal contraction of commercial piezo stacks will be calibrated by measuring the change in length with temperature of a Fabry-Perot cavity with a fiber mirror mounted on the piezo. These results will make it possible to design a more complex multi-axis system incorporating thermal contraction compensation. Finally, a characterization of the cryogenic performance of this device will determine its suitability for mode matching to a point emitter and high-bandwidth locking.

The student will initally build and then test the stability and thermal misalignment of a simple single-axis shear piezo design. These results will provide data necessary for the next step: design and construction of a multi-axis device. The student will take primary responsibility for design and construction of this device, and collaborate with a graduate student to test it inside an existing optically-accessible cryostat. As time allows, the student may also be involved in developing a locking scheme to stabilize the cavity length at cryogenic temperatures.

For more information contact: Lily Childress (childress at physics dot mcgill dot ca).

Posted on 2015/01/21

As evidenced by this year's chemistry Nobel Prize for advancements in single-molecule fluorescence imaging, the development of nanoscopy techniques is of central importance to biology. Convex Lens-induced Confinement (CLiC), a new technique pioneered by Prof. Leslie, constitutes a step forward in this breakthrough technology development as it allows for the precise manipulation and observation of biological macromolecules from the nano to microscale. This conceptually simple, high-throughput technique has already proven to be capable of imaging complete bacterial DNA molecules (Berard et al., PNAS 2014), opening the door to new mechanistic discoveries at the single-molecule scale.

For this project, the student will develop tools that extend CLiC for the visualization of protein-DNA interactions and complexes. The candidate will design, build and characterize a nanofluidic device that enables simultaneous reagent exchange and direct visualization of protein-DNA interactions in-situ. The candidate will develop image analysis software specific to the experimental platform which extracts biophysical information from the reacting and diffusing systems, such as binding affinities and rates, as well as diffusivities. The PI, a senior grad student, and an extensive collaborative team will provide mentorship, resources and regular meetings to support the student's training in molecular biology, physics, engineering, and quantitative data analysis.

Prof. Leslie is looking for two students for this project

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

Posted on 2015/01/23

Immune cells have to constantly process external noisy information about their environment before taking actions. This problem can be formulated using statistical decision theory, as recently illustrated in (Lalanne & PF, PNAS, 2015). The goal of the project will be to study another aspect of immune detection: information transmission. After detection of ligands, T cells release a flurry of cytokines in their surroundings to attract other immune cells. The student will use information theory combined to a computational evolution approach to study the optimum strategies of T cells aiming at transmitting information to other cells.

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

Posted on 2015/02/06

The ATLAS detector at the CERN's Large Hadron Collider will undergoe significant upgrades during the 2018 LHC shutdown. These upgrades are necessary in order for the detector to continue to efficiently identify secondary particles produced in proton-proton collisions at the highest foreseen beam intensity and center-of-mass energy. As part of one of these upgrades, Canada will build one third of all required particle chambers for the upgrade of its muon small wheel. Each "thin gap chambers" built in Canada will be sent to McGill University in order to be fully tested and characterized using cosmic-ray muons.

The goal of the proposed research project is to help develop the final data analysis to be used for the cosmic-ray testing at McGill of the Canadian-built thin gap chambers. First, simulated cosmic-ray muon events will be compared with preliminary data recorded using a prototype thin gap chamber at McGill. The student will have the opportunity to get involved in the data taking as well as the analysis of the real and simulated data. The student will be tasked with quantifying the degree to which cosmic-ray muons undergoe multiple scattering and its effect on the measurement of the efficiency and spatial resolution of the thin gap chamber under test. If time permits, the student will also participate in the development and testing of a method to measuring the relative alignments of the four different planes of a prototype thin gap chamber.

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

Posted on 2015/02/06

DNA PAINT is a new technique in the field of super-resolution imaging, which relies on the spontaneous association and dissociation of small DNA ‘imager strands’. Being able to characterize and precisely control the kinetics of the binding and unbinding of these strands could lead to substantial improvements in this technology, specifically the resolution and imaging time. Convex Lens-induced Confinement (CLiC) is a novel microscopy technique that confines a sample to a finely-tunable chamber, which could offer the degree of control necessary to investigate and improve DNA PAINT.

For this project, the student will regularly conduct experiments on a variety of samples using the DNA PAINT technique. The student will be in charge of assembling the DNA PAINT images using a custom software package, as well as performing analysis of the kinetics of this data. If necessary, the student will also design an improved method of control for the CLiC device. The student will also be in charge of identifying and exploring potential new systems of interest made accessible to DNA PAINT thanks to the improvements offered by the usage of CLiC. The project will involve close collaboration with both the PI and multiple graduate students in the lab, as well as collaborators both at McGill and at other institutions. The student will receive training in microscopy (optics, experiment design, device control), quantitative data analysis (Matlab), sample handling and fluorescent staining (DNA nanostructures, microtubules). This research is expected to lead toward publication in an international peer-reviewed journal and presentations at conferences and workshops, providing the student with training in writing and oral communication.

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

Posted on 2015/02/06

This project will use a new phase field crystal model derived from classical density unctional theory to study the growth of single-crystal and polycrystalline graphene rom comprise two components. The first will use analytical techniques to determine the model's used structures computing using the McGill HPC Centre and other Compute Canada supercomputing acilities.

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

Posted on 2015/02/09

Radio pulsars are rapidly rotating, highly magnetized neutron stars. We know of only a tiny fraction of the Milky Way's radio pulsar population, as previous surveys for these objects have been limited by sensitivity. We are currently conducting radio pulsar surveys of the Plane of the Milky Way using the 305-m Arecibo telescope in Puerto Rico, the largest radio telescope in the world, and also of the full Northern sky using the 100-m Green Bank Telescope in West Virginia, the largest fully steerable telescope in the world. The proposed research project is to assist in the analysis of data from Arecibo, in particular evaluating pulsar candidates produced by our software pipeline, and following up on newly discovered sources to determine their properties.

The student's role will be to investigate output from our pulsar search software pipeline using a web-based viewing tool, and to identify promising pulsar candidates for further investigation. The student may assist in remote observations of these candidates. For sources that are confirmed to be real pulsars, the student will assist in studying them by verifying their periods are not integer harmonics of that identified by our code, by looking for evidence of binarity, and by searching for counterparts at other wavelengths using online archives.

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

Posted on 2015/02/09

VERITAS is an array of four 12-m reflectors in Arizona that are 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/).

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.

The discovery of thousands of exoplanets has opened up a new field of astronomy, the study of planets orbiting other stars. Particularly interesting are the new class of ?super Earths? that are abundant throughout the Galaxy (although not in our own solar system!). These objects, with masses a few to ten times the Earth?s mass, are observed to have a wide range of radii. The radius of a super-Earth tells us the mean density of the planet and offers clues to the conditions under which it formed. In particular, the radius of a super-Earth is very sensitive to how much gas it is able to hang onto from the gas disk in which it forms.

This project will involve modelling super-Earths embedded in a gas disk in order to understand the range of radii that would be expected. The student will numerically-integrate the equations that describe the structure of the planets atmosphere, including effects such as convection and the heating from infalling solid material. The results will be compared with observations of planet masses and radii. Some prior programming experience would be helpful, but it does not have to be extensive. The student will meet with the supervisor at least once a week and will also take part in weekly group meetings.

For more information contact: Andrew Cumming (cumming at physics dot mcgill dot ca).

Posted on 2015/02/16

Topological insulators have been discovered a few years a go and have changed the way we classify states of matter. This means that on top of the usual symmetry classification, one can classify systems according to their topology.

The topology of a system is determined through the evaluation of a non-local operator. This is a straight forward procedure in the case of non-interacting, periodic systems but turns out to be a challenging task in disordered or interacting system. In this project we explore the possibility of determining the topology of the system through its entanglement entropy as an alternative to the non-local operator method. The entanglement entropy is well defined even for disordered systems and therefore this method may be useful.

For more information contact: Tami Pereg-Barnea (tamipb at physics dot mcgill dot ca).

Posted on 2015/02/20

The project will make use of recent observations with the Chandra X-ray observatory, to search for and characterize X-ray pulsars in globular clusters, exploiting CalculQuebec High Performance Computing to perform exhaustive searches for pulsations. The candidate for this position should be willing to learn programming languages (C, C++) and all aspects of parallelization of code in the CalculQuebec HPC environment; the physics and astrophysics of millisecond pulsars; and how to perform research activities in support of these.

For more information contact: Robert Rutledge (rutledge at physics dot mcgill dot ca).

Posted on 2015/02/27