Flavour physics describes the different types of matter particles (quarks and leptons) and flavour-changing interactions. We are striving to answer fundamental questions such as why particles have different masses and why the Universe is made of matter (or where is the anti-matter)? Lancaster investigates these questions through research involving both quarks and leptons. We also use particles containing heavy quark flavours to examine the nature of the strong interaction that binds quarks and antiquarks together to form hadrons and holds together protons and neutrons to form atomic nuclei.

We study the fundamental properties of neutrinos at the Tokai to Kamioka (T2K) experiment in Japan, the MicroBooNE and SBDN experiments at Fermilab, USA. By studying neutrinos from a wide range of sources, both natural and man-made, the transformation of one neutrino into another (oscillations) can be investigated. Such oscillations can be used to search for CP violation in the lepton sector, which may explain the observed dominance of matter in our universe. They also permit a search for physics that is not defined by the Standard Model. The T2K experiment has shown the first hints that this CP violation is non-zero through precise measurements of the appearance of electron neutrinos in a muon-neutrino beam.

We are also studying the matter anti-matter asymmetry using the ATLAS experiment via decays of particles containing bottom (b)-quarks. The primary process examined is the decay of the Bs or its antiparticle to a J/ψ and a φ particle. In our Standard Model of particle physics, this decay can behave differently for the particle and antiparticle. Our studies attempt to measure the difference and are an indirect way of searching for new particles 'beyond the Standard Model', which can enhance or reduce the difference through quantum mechanical effects. We also study the decays of other particles containing beauty quarks, looking both for expected and unexpected states.

Lancaster is also making precision measurements of the decay of the top quark to tau leptons.

Team

• Dr Andrew Blake
• Professor Guennadi Borissov
• Professor Roger Jones
• Professor Vakhtang Kartvelishvili
• Dr Laura Kormos
• Professor Jaroslaw Nowak
• Professor Helen O'Keeffe

The Standard Model of particle physics cannot wholly explain the observed Universe. For example, it cannot explain the existence of dark matter and dark energy. Lancaster is carrying out an extensive programme searching for phenomena that are not included in the Standard Model.

The NA62 experiment will search for new physics at energy scales up to 100 TeV by observing and studying the ultra-rare decay of a charged kaon (K±) to a charged pion (π±), a neutrino and an anti-neutrino (which only occurs in one in 1010 decays). NA62 is also searching for dark matter candidates such as heavy neutral leptons, dark photons and axion-like particles as well as looking for differences between matter and anti-matter.

The study of neutrino oscillations also enables searches for new physics. For example, the MicroBooNE experiment is searching for oscillations mediated by hypothesised 'sterile' neutrinos, which cannot be detected directly. Both T2K and MINOS+ (which has now completed its data-taking phase) are also conducting searches for sterile neutrinos.

On the ATLAS experiment, we are searching for new massive particles that decay to a pair of particles, for example, two quark jets, two Higgs or two J/ψ particles. In all of these analyses, we are searching for a resonance (peak) in a mass spectrum.

We are searching for:

• excited quarks
• quantum black holes and additional bosons that can decay to two jets
• gravitons that can decay to two Higgs particles
• hidden supersymmetric particles that can decay to two J/ψ particles (or other onia)

Team

• Dr James Ferrando
• Dr Andrew Blake
• Professor John Dainton
• Dr Harald Fox
• Professor Roger Jones
• Professor Vakhtang Kartvelishvili
• Professor Jaroslaw Nowak
• Professor Helen O'Keeffe
• Dr Karim Massri

We are investigating the properties of the recently-discovered Higgs boson. In particular, we measure the CP properties of the Higgs boson and the fraction of Higgs particles that decay to taus. When the LHC is running at High Luminosity, the measurement of the cross-section of two-Higgs events will be used to determine the shape of the Higgs potential. We are also working on the International Linear Collider, a Higgs factory that is planned to be built in Japan. The Higgs boson properties will be measured with high precision when this e+ e- collider is made.

We are searching for unusual or exotic combinations of quarks which can shed light on the strong interaction. During the few first years of LHC running, we were pleased to discover the first new particle seen at the LHC, the χb(3P). To study the strong interaction, we focus on particles called ‘onia’ that are made up of quark-antiquark pairs. Their production and various ways of decaying act as a very precise test of theories of the strong interaction. We also study the creation of pairs of onia and onia in association with other objects such as W and Z bosons. These can test essential processes such as double parton scattering, which is a necessary background to understand when searching for new particles and when studying the decays of the Higgs boson. Such studies can also reveal the unexpected; in the D0 experiment, we have observed a state, the X(5568), which we interpret as a combination of two quarks and two anti-quarks.

An understanding of how neutrinos interact with matter is essential for current and future neutrino oscillation experiments as well as for testing the Standard Model of particle physics. Because neutrinos only interact via the weak force, they are challenging to study, resulting in limitations to current neutrino interaction cross-section data and models. Using data and measurements from existing experiments such as MicroBooNE and T2K, neutrino interaction models can be investigated and improved. These experiments will lead to a better understanding of neutrinos and improved precision for future investigations. We measure neutrino interaction cross-sections as well as develop the Monte Carlo models that allow us to test our understanding.

Team

• Dr James Ferrando
• Dr Harald Fox
• Professor Roger Jones
• Professor Vakhtang Kartvelishvili
• Professor Jaroslaw Nowak
• Dr Laura Kormos
• Professor Helen O'Keeffe

Lancaster plays critical roles in the research and development for upcoming neutrino experiments DUNE and SBND in the USA, and Hyper-Kamiokande in Japan, as well as on upgrades for the ATLAS detector at the LHC at CERN. Using our extensive experience of and understanding from existing experiments, we are helping to shape the future of particle physics, keeping Lancaster at the forefront of the field for years to come. This work includes not only hands-on hardware development and construction, but also data simulations and sensitivity studies, detector design optimisation, quality assurance, data acquisition and triggering methods, and particle reconstruction algorithms.

Upgrades to the LHC accelerator are planned to increase the luminosity, which will enable the experiments to collect up to 3000 fb-1 of data. This will lead to severely increased occupancy and radiation damage of the tracking detectors.

The ATLAS experiment plans to introduce an all-silicon inner tracker to cope with the elevated luminosity. Lancaster is involved in several aspects of the construction of the new sub-detector. We will test all UK pixel endcap sensors before they are assembled and are developing expertise with FPGA-based readout systems to be able to test individual pixel modules and the detector during assembly – with up to 5 Gbit/s. We are also leading experts for bending the CO2 cooling pipes made from Titanium with only 100 µm wall thickness into the required shapes and will pressure-test them to make sure they are safe at up to 100 atmospheres.

One recurring challenge for future particle physics investigations is that the experiments are getting larger and larger. Instrumenting of larger and larger volumes with existing technology is very costly – therefore, new ideas for cost-efficient particle detectors have to be pursued, and we believe that the key to realising significant savings is to use industrially available technologies for our purposes. One example of industrially available technology is HV-CMOS processes that are typically used to produce ASICs (application-specific integrated circuits) for the automotive industry. We found that they can also be used to create outstanding particle detectors. Lancaster is focusing on understanding the radiation damage to the silicon bulk of these sensors.

Another example is to assess whether thin-film technology – capable of producing square-meter-size panels for TFT-screens and solar cells at a little cost – could be used to create particle detectors. To this end, Lancaster has teamed up with collaborators in Mexico, the USA and Germany; our expertise is in exploring sensors based on GaAs and c-Si (single-crystalline silicon) thin films. We are also looking into the option to create cost-efficient scintillation detectors from a cheap, everyday plastic: PEN (Polyethylene naphtalate). In this project, we are collaborating with colleagues in Dortmund, Munich, Prague and at Oak Ridge National Laboratory.

Team

• Dr Andrew Blake
• Dr Harald Fox
• Dr Laura Kormos
• Dr Daniel Muenstermann
• Professor Jaroslaw Nowak
• Professor Helen O'Keeffe

To do all of this exciting physics, advanced software and a global computing system are required. At Lancaster, we are developing tracking tools for the high luminosity future running of ATLAS, as well as the software frameworks to exploit new computing techniques and architectures. We also develop the job management software required to simulate, process and analyse LHC data in a comprehensive computing system. We provide one of the most extensive computing and data storage facilities for particle physics and participate in the management and operation of the distributed computing for particle physics and other physical sciences in the UK.

Team

• Professor Roger Jones

Supervisor

Dr Harald Fox

Description

The discovery of the Higgs Boson in 2012 showed us the principle way how the breaking of the electroweak symmetry is realised in nature. However, several aspects of that mechanism are still being investigated. Two examples are the matter – anti-matter symmetry (CP) of the new Higgs boson, and the existence of further bosons in addition to the Higgs. At Lancaster we are analysing ATLAS data collected at the LHC in the hadronic di-tau final state.

The di-tau final state is the most accessible final state where the Higgs boson couples to fermions directly. This signal allows us to measure the CP properties of the Higgs boson. The Standard Model predicts a CP-even scalar Higgs with no CP violation in the production or decay. On the other hand, we know that there is not enough CP violation in the quark sector of the Standard Model to explain the existence of the universe. Observation of a new source of CP violation is hence necessary. Measuring the Higgs couplings and its CP properties is hence an important test for the Standard Model.

While the existence of the Higgs boson confirms the electroweak phase transition via a symmetry breaking potential, the shape of the potential and the exact nature of the mechanism is not constrained by theory or measurements so far. We use the di-tau final state to search for additional scalars to test models of the phase transition.

Supervisor

Dr James Ferrando

Description

"Exclusive hadronic decays of the W-boson are predicted by the Standard Model but have never been observed. Depending on the decay mode, the expected branching fractions could be as high as 1 per million. This project aims to exploit the large sample of > 100 million top-quark-pair production events available from Run 2 of the LHC to search for such decays, as well as new similarly sized datasets from Run 3. Each top quark decays to a bottom quark and W-boson. Exclusive W decay events can then be searched for by requiring that one W Boson decays to a charged lepton and neutrino and then studying the decay of the other W boson.

For this project it is envisaged to study exclusive W-decays into a vector-meson and lepton pair (e.g. W-> e + nu + J/Psi). The branching ratio for such decays has been recently calcualted and found to lie in the 10-^-6 -> 10^-7 range, making them accessible with the full LHC Run2 and Run 3 data.

In addition to analysis of ttbar datasets, it is planned to study and develop dedicated triggers for exclusive decays in direct W production as part of this Ph.D. project. If succesfully deployed these could potentially enhance the searchable sample of W bosons by two orders of magnitude compared to the top-quark pair production dataset.

Students interested in this PhD project should apply via the Lancaster University admission system. Applicants are normally expected to have the equivalent of a first (1) or upper second (2.1) degree class in Physics or Astrophysics. The Lancaster Physics Department holds an Athena SWAN silver award and JUNO Champion status and is strongly committed to fostering inclusion and diversity within its community."

Funding is available on a competitive basis. To be considered for a funded studentship, please submit your application by 31^st January 2025

Supervisors

Dr Harald Fox

Description

Future particle experiments will impose extreme requirements on their tracking detectors, taking today's silicon sensor technology to the very limit. To extend the physics reach of the LHC for example, upgrades to the accelerator are planned that will increase the peak luminosity by a factor 5 to 10. This will lead to much-increased occupancy and radiation damage of the sub-detectors, requiring the exchange of the current inner trackers with all-silicon ones.

Lancaster has a long-standing tradition of silicon detector R&D in CERN's RD50 collaboration and is now focusing on R&D for future pixel detectors – the innermost sub-detector of particle physics experiments and thus exposed to the harshest conditions.

Possible PhD projects would include irradiation and characterisation of planar pixel sensors, which are being produced for LHC detector upgrades like ATLAS.

Beyond those, the PhD project may also involve the characterisation of novel HV-CMOS pixel sensors which promise very good radiation tolerance while being extremely lightweight and cost-efficient. These are considered the baseline choice for the upgrades of LHCb and other experiments like EIC, as well as future collider experiments. The first large-area prototype chip has been received from the foundry. Initial tests of this chip have begun. Results and in-depths characterisations are eagerly awaited by the community and could be part of the PhD project.

Students interested in this PhD project should apply via the Lancaster University admission system. Applicants are normally expected to have the equivalent of a first (1) or upper second (2.1) degree class in Physics or Astrophysics. The Lancaster Physics Department holds an Athena SWAN silver award and JUNO Champion status and is strongly committed to fostering inclusion and diversity within its community.