Professor Mark Thomson

Professor of Experimental Particle Physics
Professorial Fellow of Emmanuel College
Co-spokesperson of the DUNE collaboration

Group: High Energy Physics

Room 951 Rutherford Building,
Cavendish Laboratory,
JJ Thomson Avenue,
Cambridge CB3 0HE.
Tel: +44 (0)1223 765122
Email: thomson "at"

Group Administrator:
Charlotte King
Tel: +44 (0)1223 337227
Email: felicity "at"

Modern Particle Physics

Published September/October 2013) :

Modern Particle Physics is a new up to date textbook aimed at final year undergraduate students and first year graduate students. It covers all topics ain contemporary particle physics and is accessible to students with a grounding in quantum mechanics and special relativity.

Modern Particle Physics is published by Cambridge University Press. Further details can be found on the CUP web pages.

Biographical Information

2015-2018              Co-spokesperson of the DUNE collaboration
2008-              Professor of Experimental Particle Physics at the Cavendish Laboratory and Professorial Fellow of Emmanuel College, Cambridge
2004-2008 Reader in Experimental Particle Physics at the Cavendish Laboratory and Fellow of Emmanuel College, Cambridge
2000-2004 University Lecturer in Physics at the Cavendish Laboratory and Fellow of Emmanuel College, Cambridge
1996-2000 Staff Research Physicist, CERN, Geneva, Switzerland
1994-1996 CERN Fellow, CERN, Geneva, Switzerland
1992-1994 Research Fellow in the High Energy Physics group, University College London, London.
1988-1991 D.Phil. in Experimental Particle Astrophysics in the Department of Nuclear Physics, Oxford
1985-1988 BA Physics at the University of Oxford

Research Summary

My main research interests are neutrino physics, the physics of the electroweak interactions, and the design of detectors at a future colliders. I am co-spokesperson of the DUNE collaboration and my research time is shared between DUNE and the MicroBooNE experiment, where the Cambridge neutrino group is adapting particle flow calorimetry techniques for large liquid argon TPC detectors for neutrino physics.


LBNF/DUNE will be the largest particle physics project ever undertaken in the US. It involves firing an intense neutrino beam from Fermilab, near Chicago, to the DUNE far detector in the Sanford Underground Research Facility (SURF) in South Dakota; a distance of 1300 km. The DUNE far detector is conceived as four vast liquid argon time projection chambers (LAr-TPCs), each consisting of an active volume of 10,000 tons of liquid argon. The LAr-TPC technology provides 3D images of the particles produced in neutrino interactions. The experiment aims to discover CP violation in neutrino oscillations, which could explain the observed excess of matter over antimatter in the Universe. It also enables a powerful search for proton decay, which is predicted in Grand Unified theories, and is sensitive to neutrinos from core collapse super-novae. DUNE is a major international collaboration of almost 700 scientists (and rapidly growing). The installation of the far detector is planned for 2021. Cambridge has been a member of the predecesor LBNE collaboration since the very early days of the experiment concept. In 2014, the collaboration was reformulated into the Long Baseline Neutrino Facility (LBNF) and the Deep Underground Neutrino Experiment (DUNE), with increased international involvement. I was elected as co-spokesperson of the collaboration in 2015. We are currently working on the reconstruction of the neutrino interactions in the LBNF LAr TPC. The Cambridge DUNE group uses state-of-the-art PandoraPFA reconstruction tools, initially developed for particle flow reconstruction at a future linear collider. The reconstruction of LBNF events is particularly challenging due to the higher energy neutrino beam spectrum that results on complex final states.

The MicroBooNE Experiment

Cambridge joined MicroBooNE in 2013. The MicroBooNE detector is a large 170 ton Liquid Argon (LAr) Time Projection Chamber (TPC) located along the Booster Neutrino Beam (BNB) line The experiment will measure low energy neutrino cross sections and investigate the low energy excess events observed by the MiniBooNE experiment. The detector serves as the necessary next step in a phased program towards the construction of massive kiloton scale LArTPC detectors for the LBNE experiment. The experiment is due to take first data in 2014. The Cambridge MicroBooNE group is working on state-of-the art reconstruction software for extracting physics observables from the "photograph-like" images of neutrino interactions in the LAr TPC. This work is based on the PandoraPFA SDK, initially developed for particle flow reconstruction at a future linear collider. PandoraPFA provides a powerful and flexible environment for developing fast reconstruction algorithms. The current goal is to provide a first fully-automated event reconstruction for a LAr detector in time for the first beam data.

The MINOS Experiment

The MINOS experiment is a second-generation Long Baseline (LBL) neutrino oscillation experiment. A beam of muon neutrinos is produced from protons extracted from the Main Injector at Fermilab (just outside Chicago). These are then detected 735 km away in the main 5400 ton MINOS Far Detector half a mile underground in the Soudan mine. A web-based live event display for the MINOS far detector (developed in Cambidge) shows what is currently happening in the MINOS far detector. In addition a much smaller (1000 ton) Near Detector, is located 290 m from the decay pipe. If neutrinos have mass then some of the muon neutrinos will oscillate to become tau neutrinos during the journey to the Soudan mine. Neutrino oscillations are investigated by studying and comparing the rates and energy spectra of Charged Current interactions in the MINOS near and far detectors. Beam data taking commenced in March 2005. A selection of beam neutrino interactions can be found in the event gallery .

The Cambridge MINOS group have played a major role in the MINOS research activities including:

  • development of pattern recognition and reconstruction software;
  • the analysis of atmospheric neutrino data;
  • the development and application of a powerful approach to the search for sub-dominant muon to electron neutrino oscillations. The results, along with those from T2K, provided the first evidence for a non-zero value of theta_13;
  • the of charged-current events for muon neutrino disappearance.

Particle Flow Calorimetry

I am currently working on the development of Particle Flow Calorimetry which is a new technique for large scale particle physics detectors. It has the potential to provide improvements of more than a factor of two on current calorimetric methods for reconstructing jet energies. This work was initially developed in the context of the ILC, where the main conceptual designs are optimised for Particle Flow Calorimetry. In order to study its potential, I developed the PandoraPFA particle flow reconstruction code which is currently being used to evaluate the performances of different ILC detector options. Through this work I have demonstrated the feasibility of Particle Flow Calorimetry and the my research is currently leading the field.

The ILC and CLIC

The proposed ILC is likely to be the next large global accelerator project after the LHC. It is currently being designed to operate at electron-positron centre-of-mass energies between 200 GeV and 1 TeV. My main research activity in this area is the in the overall design of an ILC detector. I am a convenor of the ILD detector concept working group on the design and optimisation of the ILD conceptual design, based on the advanced particle flow reconstruction software developed in Cambridge.

An alternative accelerating technology is offered by CLIC . It would enable the scientists to explore an energy region at the multi TeV scale (3Tev CLIC). It would, thanks to it's unique combination of high energy and experimental precision, provide significant fundamental physics information in a complementary fashion to future discoveries at the LHC and the ILC. Since CLIC operates in the high beamstrahlung regime, the background of e+e- pairs and hadronic interactions is large. This imposes strong requirements on the detector design. A reduction in background events at the interaction point would be beneficial. This could be achieved using the particle flow algorithm Pandora.

The CALICE project aims to perform research and development work for calorimetry at a future linear collider. The current baseline design for the calorimetry uses a highly segmented Silicon-Tungsten (SiW) electromagnetic calorimeter. The performance of a prototype SiW detector will be evaluated in a test beam environment. The CALICE project will also investigate possible HCAL options (digital/analogue).

The ATLAS Experiment

The ATLAS experiment at the Large Hadron Collider (LHC) at CERN is one of the two large experiments at the forefront of the energy frontier of particle physics. My effort on ATLAS is focussed on the design and physics motivation for the upgrade to the first level hardware calorimeter trigger, where the UK is developing a new system for the Phase-1 luminosity upgrade of the LHC, due to be installed at CERN in 2018.

The OPAL Experiment at LEP

The OPAL experiment ran from 1989-2000. It was designed to test the Standard Model of the electroweak interaction with unprecedented precision. My main research with the OPAL experiment at CERN, centred on the precision experimental measurements of the properties of the W± and Z bosons responsible for mediating the neutral and charged current weak interactions. I have performed a number of important measurments at both LEP 1 (e+e- -> Z0) and LEP 2 (e+e- -> W+W-). These are summarised below:
Quartic Gauge Boson Couplings: Obtained the first experimental limits on possible anomalous quartic gauge boson couplings by studying hard photon radiation in WW events.
Measurments of the WW cross-section: Responsible for the OPAL measurements of the e+e- -> W+W- -> qqlvl cross-section. Devoloped the algorithms for identifying e+e- -> W+W- -> qqlvl events with high efficiency.
W Boson mass: Contributed to OPALs measurements of the W boson mass at and above threshold.
Measurements of the tau-polarization at LEP 1: Applied the method of Maximum Entropy to the reconstruction of ECAL clusters in the OPAL detector.
Studies of the ee->Z->tau+tau- at LEP 1:
Measurements of the LEP 1 luminosity: