Below is a list of DPhil projects for 2021 on experiments in preparation; potential graduate students are encouraged to contact supervisors if they have any questions with regard to these projects.

ATLAS upgrade

High-Luminosity Large Hadron Collider (HL-LHC)

The High-Luminosity Large Hadron Collider (HL-LHC) project will increase the luminosity of proton-proton collisions by a factor of 10 beyond the LHC’s design value. A more powerful LHC enables the observation of rare processes that occur below the current sensitivity level, extends searches for new physics, and allows precision measurements of the Higgs boson and other particles. The HL-LHC is currently expected to begin operations in the second half of 2026, with a nominal levelled instantaneous luminosity of L=7.5×1034cm2s1 corresponding to an average of roughly 140 inelastic pp collisions each beam-crossing. The machine will deliver an integrated luminosity of 3000/fb to the ATLAS experiment over ten years starting in 2025. This is a factor ten greater than the target of 300/fb to be delivered by 2023.

The ATLAS collaboration must replace many subdetectors to take full advantage of this accelerator upgrade. Oxford and the UK are leading the Inner Tracker Upgrade (ITk) in the production of the barrel strip silicon tracker and the forward pixel tracker for the upgraded ATLAS detector.

LZ

Professor Kimberly Palladino and Professor Hans Kraus

The nature of dark matter remains one of the biggest unsolved mysteries in modern science. A leading contender in the hunt for dark matter is the LUX-ZEPLIN experiment, which is the primary focus of the Oxford dark matter group. A 10 tonne liquid xenon time projection chamber will be housed at the Sanford Underground Research Facility in South Dakota, with the aim of directly detecting the interactions of dark matter particles with the xenon target. Due to its size, LZ will reach a sensitivity that will either lead to dark matter discovery or, in the absence of a signal, will eventually be limited by the irreducible neutrino background. For further detail, see http://lz.lbl.gov/ or http://www.sanfordlab.org/.

New students joining in October 2021 will do so at an exciting time with commissioning completing and physics data-taking at an early stage. There will be opportunities to participate in on-site activities as well as offline analysis. LZ is a multi-physics machine, with sensitivity to multiple dark matter paradigms over several orders of mass, and both standard-model and novel neutrino processes. Possible thesis topics could revolve around contributions to these high level analyses, but could also be on the important detailed efforts to understand the detector performance through data quality cuts, simulations and modelling. Lastly, with direct dark matter detection being a growing and increasingly competitive field, there are possibilities to undertake R&D work to inform the design of the next generation detector.

DUNE

Professor Giles Barr, Professor Alfons Weber and Dr Xianguo Lu

Liquid argon detectors will play a major role in the future of neutrino physics. These high quality image detectors will allow studying neutrino interactions in great details. They have been chosen for the biggest neutrino project ever constructed – the Deep Underground Neutrino Experiment (DUNE) – and will provide the sensitivity required to study some of the big questions of neutrino physics such as the neutrino mass hierarchy and CP violation. To inform the final DUNE design, the collaboration is building a prototype that will be located at CERN. ProtoDUNE will acquire test-beam data from 2018 providing crucial data sets to understand the response of LAr detectors to different types of particles.

The DUNE group is currently looking to recruit PhD students. Several thesis topics are available within our group to work on DUNE and protoDUNE. The student would be expected to participate in studies to help understanding the physics reach of the future DUNE experiment as well as simulations to help make design decisions. The study topics within DUNE are vast and would allow the student to gain strong experience in programming, data simulation and analysis. In addition, the student would be expected to analyse data from protoDUNE.

SNO+

SNO+: neutrino physics at the SNOLAB facility in Canada
Professor Steve Biller

Some of the most exciting physics to emerge over the last decade has been in the field of neutrino physics. One of the forefront experiments here has been the Sudbury Neutrino Observatory (SNO), based in Canada, which was a recipient of the 2015 Nobel Prize in physics. The SNO group at Oxford have played a leading role in solving the "Solar Neutrino Problem" and clearly demonstrating, for the first time, that neutrinos exists as mixed states which allow them to apparently "oscillate" from one type to another. On the heels of this tremendously successful project, a follow-on experiment, SNO+, is being pursued with a remarkably diverse and interesting range of physics objectives. The main objective of this project is to sensitively search for a very rare process called "neutrinoless double beta decay." An observation of this would both permit a determination of the absolute neutrino masses and would establish that neutrinos act as their own antiparticles, which could have significant consequences for our understanding of the matter/antimatter asymmetry in the universe. This area of study is considered to be of extremely high importance in particle physics and the Oxford group has played a fundamental role in establishing the technique that will be used for this search. In addition, other physics goals include studies of low energy solar neutrinos, oscillations of reactor antineutrinos, searches for non-standard modes of nucleon decay, study of geo-neutrinos generated from within the earth, and to act as an important detector for neutrinos from galactic supernovae. The detector is currently being filled with liquid scintillator and isotope for neutrinoless double beta decay will be introduced in 2019. The incoming PhD student would participate in development, simulation, calibration, operation, analysis and the production of first results.

For further information, visit: http://snoplus.phy.queensu.ca/

LSST

Dr Jeff Tseng and Dr Farrukh Azfar

The coalescence of a binary neutron star system produces both electromagnetic and gravitational waves (GW). In August 2017, the event designated GW170817 heralded joint observations of both types of radiation from such a coalescence, opening a new window into the physics of neutron stars, neutron-rich nucleosynthesis, and post-merger dynamics. Such multi-messenger detections can also provide the next generation of absolute distance measurements in the universe, leading to independent estimates of the Hubble constant. Over the next 10 years, we expect the LIGO-VIRGO detectors to accumulate several times the current number of GW detections, and therefore efficiently detecting the optical counterpart is essential to maximise science gains. The Large Synoptic Survey Telescope (LSST) will begin observing in 2020, and with its fast, deep and wide survey capabilities will play a critical role in this emerging field quickly to detect optical counterparts to GW events. A student on this experiment would begin by helping to develop an observing strategy for the LSST to accomplish this and other goals concurrently - this project would involve proposing modifications to the existing observing schedule, using sensor characterisation and commissioning data to lay the groundwork for and make the first measurement of the Hubble constant using gravitational wave triggers with the LSST. Potential supervisors: Dr Farrukh Azfar, Professor Ian Shipsey in collaboration with partners in the USA.

In addition, core-collapse supernovae are expected to produce neutrinos and gravitational waves in advance of electromagnetic radiation. As in the case of neutron star mergers, the LSST is positioned to be among the first optical telescopes to take measurements of such rare phenomena early in their lifecycle, and improve their localization for more detailed, spectroscopic, and longer-term follow-up by other telescopes. A student pursuing this project will work with the alert mechanisms of the LSST, gravitational wave detectors (e.g, GraceDB), and neutrino detectors (SNEWS), along with models of supernovae and detector responses in order to improve our ability to peer into the dynamics of these violent and yet highly creative forces in the universe.