Running experiments

Below is a list of DPhil projects for 2024 on running experiments; potential graduate students are encouraged to contact supervisors if they have any questions with regard to these projects.

The new energy frontier
Alan Barr, Daniela Bortoletto, James Frost, Claire Gwenlan, Chris Hays, Todd Huffman, Richard Nickerson, Ian Shipsey, Georg Viehhauser, and Tony Weidberg.

The LHC is now in its third extended run, delivering proton-proton collisions at a record-breaking energy and instantaneous luminosity.  Higgs bosons are being produced in large numbers, allowing us to enter the "precision era" of Higgs physics. Precision measurements of Higgs properties will be performed to seek evidence for physics beyond the Standard Model. Our sensitivity to the production Dark Matter and other exotic particles is also better than it has ever been before. For us, this is a very exciting time, with great opportunities to discover new particles, to test theories, and to explore nature at the smallest scales with the most powerful accelerator in the world.  The period 2024-2025 will be an exciting one, as the LHC produces its final dataset before undergoing a major upgrade to the High-Luminosity LHC. During this time we explore the energy frontier and prepare hardware, software, and analysis improvements for the major detector upgrades planned for the years ahead.

The Oxford ATLAS group has a world-leading physics program with major responsibilities in the areas of the tracking detector, the online event triggering, the Monte Carlo software, and the reconstruction of heavy-flavor jets, missing transverse energy, and muons.

Our research activities

B physics and CP violation at the LHC at CERN
Malcolm John, Sneha Malde or Guy Wilkinson

LHCb makes precision studies of CP violation in the decays of beauty and charm hadrons ('heavy flavour physics') at the CERN LHC. LHCb searches for physics beyond the Standard Model by investigating departures from the unitarity of the CKM matrix and checking whether or not this provides a consistent picture of observed CP-violation. The experiment also has high sensitivity to new physics effects by looking for enhanced rates of heavy flavour decays that are otherwise very rare in the Standard Model, or in unexpected angular distributions of such decays.

The LHCb detector has already collected a wealth of data, the analysis of which will likely form a significant fraction of the doctorate work. The detector is currently being upgraded, coming online in 2022, and which will greatly increase the data collection rate. Major responsibilities of the Oxford group are on the Ring Imaging Cherenkov (RICH) counters and Vertex locator (VELO); the RICH detectors provide particle identification of pions, kaons and protons over the momentum range from 1 to 100 GeV/c, and the VELO reconstructs B-decay vertices to a precision of around 150μm. The group also leads efforts on the particle identification calibrations that are core to the real-time analysis strategy that LHCb are adapting for the start of data taking.

A new graduate student would be expected to work on a combination of the following areas:

• Undertake a significant data analysis; the Oxford LHCb group has broad physics interests which include CP violation, b-hadron decays involving tau leptons, rare B hadronic decays, charm mixing, electroweak physics including a measurement of the W mass, and central exclusive production. A major topic of the group is the measurement of the CKM angle gamma, with special interest in the family of channels B→ D(*)0 K(*) with the D0 decaying into 2-, 3- and 4-body final states. We are also active in searching for very rare beauty and charm channels, including the B→ Dµµ family of decays. A new student could expect to work in any one of the above areas, or develop an alternative analysis effort which is commensurate with the general interests of the group.
• Participate in the commissioning and operation of the RICH or VELO sub-systems, monitoring the performance of the detectors and their readout systems. Of particular interest is maintaining the calibration of the RICH system’s performance using real data, by selecting background-free samples of K’s and π’s from D*±→ D0 (→K π) π±, and Λ0 → pπ decays.
• Develop hardware or simulation for future LHCb upgrades, and which also have applications for other heavy flavour experiments. This could include studies of the physics performance, characterisation and design of future hybrid pixel detectors for precise measurement of heavy-flavour-decay vertices. Alternatively a student could work on the novel prototype TORCH detector to provide enhanced low-momentum particle identification, measuring time-of-flights to a precision of 15 ps.

A subset of the LHCb group are also involved with the BESIII experiment. BESIII, located in Beijing, uses electron positron collisions to create a charm hadron factory. Despite the radically different environments of LHCb and BESIII, there is a high level of synergy between them, and the combination of results is expected to lead to significant improvements in precision and sensitivity to new physics. There are opportunities for students to be involved in this exciting new venture as a part of their DPhil activities.

Students would usually be expected to spend a year or more at CERN as well as publishing much of their thesis work in peer-reviewed journals. Further information can be obtained from any of the above people, or from the LHCb-Oxford group pages.

Professor Kimberly Palladino

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 2023 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.

Tokai to Kamioka neutrino oscillation experiment
Professor Giles Barr and Professor Dave Wark

The Oxford T2K group is eager for new DPhil students to join. We received our first data in November 2009 and have been taking data in both neutrino and anti-neutrino mode. The intensity of the neutrino beam is still increasing allowing for precision measurements. T2K has found the first hint that CP might not be a conserved symmetry in neutrino physics. For information about the group's activities and potential thesis analysis work, please see our research group pages.

Dr Kirsty Duffy and Professor Giles Barr

MicroBooNE is a 170 ton Liquid Argon Time Projection Chamber (roughly the size of a small bus) located at Fermilab near Chicago, Illinois.  It is a pioneer in the U.S. Liquid Argon detector programme, having collected over 500,000 neutrino interactions since 2015.  The MicroBooNE group in Oxford is particularly interested in using this data set to measure neutrino interactions on argon.  Liquid argon detectors provide exquisite images on neutrino interactions, but it comes at a price:  argon is a large nucleaus and nuclear effects are significant.  That adds an extra layer of complication to predicting neutrino interactions on argon.  MicroBooNE is making- in many cases the first ever -- high statistics measurements of neutrino interactions on argon to measure these processes directly.  The measurements we make will be of great interest to future experiments using liquid argon detectors, such as Fermilab's Short Baseline Neutrino programme and DUNE.

A new PhD student on MicroBooNE has the chance to make the first ever measurements of certain neutrino interaction processes on argon.  There may also be the opportunity to search for new physics in the MicroBooNE detector: many models of beyond-the-standard-model physics have been proposed to explaim anomalous results seen in the MiniBooNE experiment, and MicroBooNE is in a strong position to investigate these hypotheses.  A PhD combining work on MicroBooNE and DUNE could also be a possibility, since both use liquid argon detector technology.

Professor Steve Biller, Professor Armin Reichold, Professor Jeff Tseng

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 recipent of the 2015 Nobel Prize in Physics.  The SNO group at Oxford 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 apparently to "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 search for a very rare nuclear process called "neutrinoless double beta decay", an observation of which would both permit a determination of the absolute neutrino masses and would establish that neutrinos act as their own antiparticles - one of the most important unknowns in the entire field of particle physics, with implications spanning particle physics, nuclear physics, astroparticles, and cosmology.  The Oxford group played a fundmental role in establishing the technique that will be used for this search, and continues to develop new experimental and analytical approaches for SNO+ abd future experiments.  Other physics goals include studies of low energy solar neutrinos, oscillations of reactor neutrinos, and geo-neutrinos generated from with the Earth; and searches for non-standard modes of nuclear decay, astrophysical dark matter, and neutrinos from core-collapse supernovae.  Oxford SNO+ members are also active in the Supernova Early Warning System (SNEWS), a worldwide network of neutrino and dark matter detectors aiming to reap a rich harvest of physics from the intense neutrino burst of a galactic supernova.

The SNO+ detector is currently taking data with liquid scintillator, prior to the introduction of the neutrinoless double beta decay isotope.  Incoming DPhil students would participate in the operation, calibration, and analysis of the detector in topics which contribute both to the experiment's main objective, as well as to topics across the range of physics objectives.  Students generally spend approximately six months or more at SNOLAB, which normally entails regularly descending 2.1km to the detector itself!

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