Potential Graduate Student Projects

ATLAS Projects

ATLAS upgrades, and searches for things beyond the Standard Model in ATLAS

Contact: Chris Lester
See also: Cambridge ATLAS homepage

The Higgs Boson discovery, while interesting, was really part of "old", very much expected physics. The ATLAS detector has, so far, found no traces of "new" physics: supersymmetric particles, extra dimensions, and so on, despite many searches. Given this situation, phenomenologists need to be sure that all possible search strategies are covered. In the last three years Cambridge ATLAS has used established search methods to look for supersymmetry and black holes. However, a recent discovery of what appears to be an entirely new way of looking for R-parity violating supersymmetry encourages the Cambridge BSM team to focus the coming year’s efforts on developing that new technique. Cambridge ATLAS is also working on two separate upgrade projects (one in the next ATLAS tracker, one in the calorimeter trigger) that will need increasing support over the next four years. A student pursuing a PhD based on BSM searches could potentially use it as an opportunity to gain some experience of detector design and/or operation, thereby increasing his or her future employability. We therefore welcome applications from students who believe they might be able to inject similar creativity into the field of BSM searches, a field which otherwise is perhaps ripe for being shaken up after a period in which it has seen little innovation, and those who might like to combine that with detector work.

In order to become an ATLAS author, new collaboration members have to complete a technical project during their first year. Students will be able to work in a variety of areas, including software and simulation for the ATLAS Level-1 calorimeter upgrade , work on upgraded data-acquisition software for the next generation tracker. (back to top)

Hunting for Dark Matter in ATLAS

Contact: Tina Potter
See also: Cambridge ATLAS homepage

Dark Matter is one of the most compelling mysteries of modern-day physics. With no suitable candidate in the Standard Model of particles, new physics is needed to explain the 26% dark matter in our universe. Supersymmetry (SUSY) offers a potential solution by introducing many new particles, the lightest of which is an excellent dark matter candidate. Discovering new physics such as SUSY is a major goal of the ATLAS experiment at the LHC, and a focus of the Cambridge HEP group. However, the lack of a discovery to date tells us that SUSY may not be easy to find. If SUSY particles are close in mass, the experimental signature can be very difficult to separate from the Standard Model processes. A student could identify areas of SUSY parameter space where ATLAS does, and more importantly, doesn't have sensitivity, and design searches to address these uncovered areas. The PhD project(s) would use the full 13 TeV dataset recorded by ATLAS to search for signs of new physics, using modern multivariate selection techniques, such as artificial neural nets and boosted decision trees. (back to top)

Studies of ZZ Production in ATLAS

Contact: Richard Batley
See also: Cambridge ATLAS homepage

A key process currently being intensively studied at the LHC is the production of gauge boson pairs (diboson production). By testingthe gauge structure of the Standard Model, measurements of diboson production allow indirect searches for new physics beyond the SM and are also important in understanding backgrounds to other processes such as Higgs boson production.

The Cambridge group has focused on the production of ZZ pairs decaying to final states containing two leptons (electrons or muons) plus missing energy (neutrinos), or containing four leptons. The 4-lepton channel is one of the recent Higgs boson discovery channels, and the SM process Z → 4l serves as a test-bed for the reconstruction of H → 4l decays.

The PhD project(s) would be based on analyses of the full 13 TeV data set recorded by ATLAS throughout 2015-2018. As well as improved measurements due to the higher energy and larger data sample, existing analyses could be extended by, for example, looking for new modes of ZZ production such as vector boson scattering. (back to top)

LHCb Projects

Measurement of matter-antimatter asymmetries in B decays

Contact: Val Gibson
See also: Cambridge LHCb homepage

The fact that we live in a Universe made of matter (and no antimatter) is extremely puzzling since, during the Big Bang, matter and antimatter should have been produced in equal amounts. The phenomenon responsible for matter- antimatter asymmetries is called CP violation, which is a well established observation and can be accommodated in a three generation Standard Model. However, the amount of CP violation observed is many orders of magnitude away from that required to produce the amount of matter in the Universe. Therefore physics beyond the Standard Model is required. The project will include the analysis of all the LHCb experiments data taken at the highest LHC centre-of- mass-energy from the start to the current date. The focus of the project will be to use hadronic B meson decays, such as B → DK or Bc → DD, to make a precision measurement of the CP phase γ which is responsible for CP violation in the Standard Model and against which New Physics phenomena can be severely tested.

The project will suit someone who is keen to analyse LHC data. (back to top)

Search for New Physics beyond the Standard Model in rare B decays

Contact: Val Gibson
See also: Cambridge LHCb homepage

The Standard Model of particle physics is a well established monument. However, New Physics beyond the Standard Model is necessary to describe the mass hierarchy of fundamental particles. The LHCb experiment, running at the Large Hadron Collider at CERN, is particularly well suited to look for indirect evidence of New Physics using quantum loop processes. These include rare decays, such as Bd,s → mumu and Bd → K0*mumu decays, and searches for lepton-flavour violation by combining the information from several decays e.g. Bd → K0*mumu ad Bd → K*ee. The huge volume of data collected by LHCb allows for a precision measurements of the decay rates, effective lifetimes and angular observables, which measure the intimate properties of these decays. In turn, the measurements are used to constrain New Physics models. This indirect model-independent approach is very powerful, and is crucial since New Physics still evades detection. The project will include the analysis of all data taken by LHCb from the start to the current date.

The project will suit someone who is keen to analyse LHC data. (back to top)

Neutrino Physics Projects

MicroBooNE

Contact: Tina Potter
See also: Cambridge MicroBooNE homepage

The MicroBooNE neutrino experiment at Fermilab in the US, started taking data in August 2015. MicroBooNE utilises a large liquid Argon (LAr) time projection chamber (TPC), which allows “photograph quality" images of the particle produced in neutrino interactions. The recorded events contain a wealth of information and Cambridge is playing a leading role in the automated computer reconstruction of these images using advanced pattern recognition software. MicroBooNE will run for a further 2-3 years and will search for sterile neutrinos, testing a number of previous claims for this potentially groundbreaking physics signal.

The PhD project is to work on the development of pattern recognition software for LAr-TPC detectors and then apply this to MicroBooNE data. The full reconstruction chain will developed to go from the raw detector images to the detailed properties of the individual neutrino interactions. This reconstruction will then be used to make precise measurements of neutrino cross sections and to test the claims of the possible existence of sterile neutrinos.

This project represents an exciting opportunity to work on the first large LAr detector in an intense neutrino beam. There will also be the opportunity to apply this experience to the first data from the protoDUNE detector at CERN. ProtoDUNE is a large-scale prototype for the vast far detector modules, currently being planned for the DUNE long-baseline neutrino oscillation experiment, which will observe neutrino oscillations over a distance of 1300km. ProtoDUNE will take first data during the summer of 2018.(back to top)

Detector R&D Projects

Development of sensors and novel technologies for particle detection in HEP and beyond.

Contact: Stephen Wotton or Bart Hommels

Prospective students with a keen interest in hands-on practical work are invited to contact us to discuss possibilities in this area. The HEP group has a strong track record in the development of silicon sensors for tracking and single-photon position-sensitive devices for Ring Imaging Cherenkov (RICH) Detectors. Projects may include the development, refinement or upgrade of existing detectors such as these or may focus on the development of more speculative techniques for use in future experiments. Examples of current projects are the development of a RICH detector prototype using solid state sensors or the application of the ATLAS silicon tracking technology to areas beyond the field of High Energy Physics.

Although focussed on detector research and development, there would also be an opportunity to analyse data from running experiments or data taken at beam test facilities. (back to top)

Theory Projects

Theory Beyond the Standard Model at the Large Hadron Collider

Contact: Ben Gripaios

This project will focus on the development of candidate theories of new physics, going beyond the Standard Model (SM). Such physics is needed to solve consistency problems within the SM itself, as well as to describe various observed phenomena that do not have an explanation in the SM.

These include the Dark Matter and Dark Energy in the cosmos, the hierarchy between the electroweak scale and higher energy scales in physics (for example the scale of quantum gravity), the excess of matter versus antimatter that allows us to be here, the number of families of quarks and leptons and the patterns of their masses and mixings, the masses of neutrinos, the apparent unification of gauge interactions, the absence of CP violation in the strong interactions, and more.

Recent research within the group has addressed all of these questions. The challenge is to come up with a theory that extends the SM and which explains some or all of these phenomena, without being in conflict with the many other observations that are consistent with the SM alone. With such theories in hand, one can look for novel experimental signatures, which can be searched for at the LHC and elsewhere. (back to top)

The Quantum Theory of Fluids

Contact: Ben Gripaios

Recently it has been shown that there is a consistent quantum field theory (QFT) description of an ordinary classical fluid. This theory is very different from the other QFTs tha are now ubiquitous in high energy physics and elsewhere, because of the presence of fluid vortices. The project will focus on studying the quantum analogues of classical fluid mechanics phenomena, such as vortices, shocks, surface waves, and Kelvin waves, and in searching for evidence of this behaviour in real-world systems. (back to top)