Professor Mark Thomson

Professor of Experimental Particle Physics
Professorial Fellow of Emmanuel College and Director of Studies in the Physical Natural Sciences

Group: High Energy Physics

Address:
Room 951 Rutherford Building,
Cavendish Laboratory,
JJ Thomson Avenue,
Cambridge CB3 0HE.
Tel: +44 (0)1223 765122
Fax: +44 (0)1223 353920
Email: thomson "at" hep.phy.cam.ac.uk

Group Administrator:
Felicity Footer
Tel: +44 (0)1223 337227
Fax: +44 (0)1223 353920
Email: felicity "at" hep.phy.cam.ac.uk

Biographical Information

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 the physics of the electroweak interaction, neutrino physics and physics and detectors at a future electron-positron collider. Currently my research time is divided between the ATLAS experiment; the MINOS experiment; development of particle flow calorimetry; and detector design and optimisation for the proposed International Linear Collider and CLIC.

The ATLAS Experiment

The MINOS Experiment

I am currently the UK spokesperson for the MINOS collaboration. MINOS is the world's first high intensity long-baseline beam based neutrino oscillation experiment. Te main goal of the MINOS experiment is to study the phenomenon of neutrino oscillations in a controlled accelerator experiment, and if confirmed, to measure the oscillation parameters. 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 and first beam results were announced in March 2006. A selection of beam neutrino interactions can be found in the event gallery .

My main research activities have been:

development of pattern recognition and reconstruction software;
the analysis of atmospheric neutrino data;
and the development and application of a powerful approach to the search for sub-dominant muon to electron neutrino oscillations.
in addition, the Cambridge MINOS group is working the analysis of charged-current events for muon neutrino disappearance.

CALICE and the International Linear Collider

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. Closely related to this is my work on particle flow calorimetry (see below). I am also co-convener of the joint ECFA/DESY working group on Detector Performance for a future TeV linear collider.

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).

In addition to working on the MINOS experiment I am heavily involved in the design and optimisation of detectors for the proposed 500 GeV-1 TeV e⁺e^- International Linear Collider (ILC). The performance goals for a detector at the ILC are particularly challenging. One of the main difficulties is designing a detector for which the jet energy resolution is comparable to the width of the gauge bosons. My main work is the overall detector design from the point of view of jet energy resolution and in particular calorimeter reconstruction using particle flow. In am leading the optimisation studies for the ILD detector concept.

During the 6 years I spent at CERN I was (and still am) a member of the OPAL collaboration. The OPAL experiment was one of the 4 large particle physics detectors operating at the Large Electron Positron Collider (LEP). The 26 km circumference LEP collider is the highest energy e⁺e^- built to date. My main research with the OPAL experiment centred on the precision experimental measurements of the properties of the W^± and Z bosons (the particles responsible for weak interaction and electroweak unification). The measurements of the guage boson properties enables the Standard Model of particle physics to be tested to incredibly high precision.

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 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^- -> qqlv_l cross-section. Devoloped the algorithms for identifying e⁺e^- -> W⁺W^- -> qqlv_l 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: