Flavour Physics and CP Violation  

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 investigate 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 MINOS+ experiments at Fermilab, USA and the SNO+ experiment in SNOLab, Canada.   By studying neutrinos from a wide range of sources, both natural and man-made, the transformation of one neutrino into another (oscillations) can be studied.  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 explained 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. The SNO+ experiment in Canada studies oscillations of neutrinos emitted by our Sun.  

We are also studying the matter anti-matter asymmetry using the ATLAS experiment via decays of particles containing bottom (b)-quarks. The main 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.  

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

Beyond the Standard Model  

The Standard Model of particle physics cannot completely 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 hypothesized “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. 

The SNO+ experiment will be used to search for neutrinoless double-beta decay and invisible modes of nucleon decay. An observation of neutrinoless double beta decay would indicate that neutrinos are their own antiparticles, with wide-ranging implications for both particle physics and cosmology. 

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. Specifically 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, and hidden supersymmetric particles that can decay to two J/ψ particles (or other onia).

  • Prof. Iain Bertram
  • Dr Andrew Blake
  • Prof. John Dainton
  • Dr Harald Fox
  • Prof. Roger Jones
  • Prof. Vakhtang Kartvelishvili
  • Dr Jaroslaw Nowak
  • Dr Helen O'Keeffe  
  • Dr Giuseppe Ruggiero

Electroweak and Standard Model  

We are investigating the properties of the recently-discovered Higgs boson.  In particular, we are measuring 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 builtin Japan. The Higgs boson properties will be measured with high precision when this e+ e- collider is built. 

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).   In order 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 production of pairs of onia and onia in association with other objects such as W and Z bosons. These can test important processes such as double parton scattering, which is an important background to understand when searching for new particles and when studying the decays of the Higgs boson. Such studies can also reveal the unexpected; on the D0 experiment we have observed a state, the X(5568), which can be interpreted 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 difficult 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, leading to a better understanding of neutrinos and to improved precision for future experiments.  We measure neutrino interaction cross sections as well as develop the Monte Carlo models that allow us to test our understanding. 

  • Prof. Iain Bertram  
  • Dr Harald Fox  
  • Prof. Roger Jones 
  • Prof. Vakhtang Kartvelishvili 
  • Dr Laura Kormos  
  • Dr Helen O'Keeffe  

Detector Development and Future Experiments 

Lancaster plays key 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 optimization, quality assurance,  data acquisition and triggering methods, and particle reconstruction algorithms.  

    To extend the physics reach of the LHC experiments, upgrades to the 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 will be 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 experiments 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 realizing significant savings is to use industrially available technologies for our purposes. One example of an industrially available technology are HV-CMOS processes that are normally 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 very low cost – could be used to produce particle detectors. To this end, Lancaster has teamed up with collaborators in Mexico, the USA and Germany; our expertise is in exploring detectors 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.

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

    Computation for Experimental Particle Physics 

    In order to do all of this exciting physics, advanced software and a world-wide computing system is 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 worldwide computing system. We provide one of the largest 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. 

    • Prof. Roger Jones 

    Experiments  

    ATLAS  

    • Prof. Iain Bertram  
    • Prof. Guennadi Borissov 
    • Dr Harald Fox  
    • Prof. Roger Jones 
    • Prof. Vakhtang Kartvelishvili 
    • Dr Daniel Muenstermann 
    • Dr Giuseppe Ruggiero

    DUNE 

    • Dr Andrew Blake 
    • Dr Jaroslaw Nowak  

    GridPP 

    • Prof. Roger Jones 

    Hyper-K 

    • Dr Laura Kormos  
    • Dr Helen O'Keeffe  

    ILC Detector 

    • Dr Harald Fox 
    • Dr Daniel Muenstermann 

    MicroBooNe 

    • Dr Andrew Blake 
    • Dr Jaroslaw Nowak  

    NA62 

    • Prof. John Dainton  
    • Prof. Roger Jones 
    • Dr Giuseppe Ruggiero  

    SNO+ 

    • Dr Laura Kormos  
    • Dr Helen O'Keeffe  

    SBND 

    • Dr Andrew Blake 
    • Dr Jaroslaw Nowak   

    T2K 

    • Dr Andrew Blake 
    • Dr Laura Kormos  
    • Dr Jaroslaw Nowak  
    • Dr Helen O'Keeffe  
    • Prof. Peter Ratoff