T2K neutrino experiment starts its search for the unknown

UK particle physicists working on the T2K (Tokai-to-Kamioka) neutrino experiment in Japan celebrated today (24th Nov) as the experiment detected its first neutrinos - fundamental particles which are amongst the least understood in the Universe.

T2K – an international experiment led by Japan and part funded by the UK’s Science and Technology Facilities Council (STFC) - will probe the strange properties of the enigmatic neutrino to unprecedented precision, by firing the most intense neutrino beam ever designed from the east coast of Japan, all the way under the country, to a detector near Japan’s west coast.

Neutrino oscillations are one of the frontiers of current particle physics and the T2K project will move us one step closer to understanding the role of the neutrino in the early Universe and may even shed light on the mystery of why there is more matter than anti-matter in the universe.

Professor Dave Wark of Imperial College London and the STFC Rutherford Appleton Laboratory, the International Co-Spokesperson of T2K, said “It was extremely satisfying to see the first events in the detector. It has been the result of a lot of hard work by a large number of people, and I think we will have a sake or two to celebrate and then send a bottle along to CERN as I hear they are going to need quite a few bottles pretty soon as well.”

Neutrinos interact only weakly with matter, and thus pass effortlessly through the Earth (and mostly through the detectors!). Neutrinos exist in three types, called electron, muon, and tau; linked by particle interactions to their more familiar charged cousins like the electron.

Measurements over the last few decades have shown that neutrinos possess the strange property of neutrino oscillations, whereby one type of neutrino will turn into another as they propagate through space. Neutrino oscillations, which require neutrinos to have mass and therefore were not allowed in our previous theoretical understanding of particle physics, probe new physical laws and are thus of great interest in the study of the fundamental constituents of matter.

Among the international team of around 400 physicists from 12 countries, UK scientists have made a significant contribution to the experiment. With 9 UK institutions involved, the UK has produced vital hardware for both the accelerator and detectors. The UK is also playing a leading role in the analysis software for the experiment and will be fully involved in the most exciting bit – using the data to explore the properties of neutrinos. This is expected to begin in January 2010, when the experiment is scheduled to begin production running.

“Within a year T2K should have sensitivity to neutrino properties beyond any existing experiment, and the search for the unknown will begin,” said Professor Wark.

Professor Keith Mason, CEO of the Science and Technology Facility Council (STFC), said, “We’re very excited to be a part of the T2K project. Neutrinos are incredibly difficult to detect but with the skilful engineering that has gone into this experiment we will soon be able to learn much more about these elusive particles, further understand their role in the formation on the Universe and improve our model of particle physics.”

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Notes for editors

Images

Images of T2K are available from the STFC press office

T2K

The T2K collaboration (link opens in a new window) consists of 508 physicists from 62 institutes in 12 countries (Japan, South Korea, Canada, the United States, the United Kingdom, France, Spain, Italy, Switzerland, Germany, Poland, and Russia). The experiment consists of a new neutrino beam using the recently constructed 30 GeV synchrotron at the J-PARC laboratory in Tokai, Japan, a set of near detectors constructed 280m from the neutrino production target, and the Super-Kamiokande detector in western Japan.

T2K UK collaboration

The T2K UK (link opens in a new window) collaboration is made up of the following institutions:

• STFC Daresbury Laboratory
• STFC Rutherford Appleton Laboratory
• Imperial College London
• University of Liverpool
• University of Warwick
• Lancaster University
• University of Sheffield
• Queen Mary, University of London
• University of Oxford

UK involvement in T2K

The UK has invested £14.3M in the T2K project.

Producing a neutrino beam produces significant engineering challenges, and STFC engineers from the UK were heavily involved in surmounting those challenges. The first challenge is producing a high-power proton accelerator, which is what the KEK accelerator group have built at J-PARC with 30-GeV Main Ring proton synchrotron. The beam from that accelerator is then handed over to the T2K group to produce their neutrino beam. First the proton beam must be bent through a tight angle, focussed, and then collided with a target to produce pions, which are focussed by a set of horn magnets until a He-filled decay volume about 80 meters long and several meters square, where they decay to produce the neutrino beam. The remains of the beam are then absorbed by a graphite beam dump.

An engineering group at the STFC Rutherford Appleton Laboratory (RAL), lead by Dr. Chris Densham, designed and built the high-power window which separates the vacuum of the proton beam line from the He gas of the target station and a baffle to protect the target assembly from a mis-steered beam. They helped design the target itself (carbon rod about a metre long in a complex titanium enclosure which must remain intact while being hit by a 750 kW proton beam, but must be small and light to avoid attenuating the pions), and they helped design the beam dump. All these UK-supplied components are in place and worked well during the weekend beam run. This project has given the UK group key experience in building components for high-power proton facilities.

The T2K experiment also needs three neutrino detectors – two near detectors which measure the neutrino properties before they leave the laboratory, and the Super Kamiokande detector in western Japan to measure the neutrinos after they oscillate. The two near detectors have slightly different roles – one, called the INGRID, measures the neutrino beam direction and profile, the other (just called the off-axis detector) measures its spectrum, composition, and interaction properties. The INGRID detector is designed to see the most neutrinos, and it was this detector which observed the first candidate neutrinos during beam tests on Sunday. This detector was built by groups from Japan and France, but T2K UK collaborators have made significant contributions, providing much of the electronics and its operating software systems (called DAQ software by particle physicists). The electronics were designed, built, and tested at RAL and at Imperial College in London, while the DAQ software has been written by physicists from RAL and Oxford.

The major UK contribution to the experiment is the design and construction of the electromagnetic calorimeter for the off-axis detector, which was designed and is being built by many of the UK groups (and is partially installed). First data from this detector is expected next month. The UK is also playing a leading role in the analysis software for the experiment.

Contacts

• Prof David Wark
  STFC Rutherford Appleton Laboratory
  Tel: +44 (0)1235 446 733
  Mob: +44 (0)778 8186 085
  (Professor Wark is currently in Japan but can be reached on his mobile or via email)
  
  
• Prof Christos Touramanis
  University of Liverpool
  Tel: +44 (0)7973 247 767
  
  
• Dr Chris Densham
  STFC Rutherford Appleton Laboratory
  Tel: +44 (0)1235 446 273
  
  
• Dr. Alfons Weber
  Oxford University and STFC RAL
  RAL: 01235 44 50 92
  Ox: 01865 27 33 15
  GSM: 07950 20 68 65
  
  
• Dr. Yoshi Uchida
  Imperial College London
  Tel: 02075947821
  
  
• Prof. Peter Ratoff
  Lancaster University
  Tel: 01524 593649
  
  
• Dr. Giles Barr
  Oxford University
  Tel:01865 273446
  
  
• Dr. Gary Barker
  University of Warwick
  Tel: 02476523399
  
  
• Dr. Lee Thompson
  University of Sheffield
  work phone: 0114 2224577
  mobile: 07837 119601
  
  
• Julia Short
  Press Officer
  Science and Technology Facilities Council
  Tel: +44 (0) 1793 44 2012
  
  
• Dr Francesca Di Lodovico
  Queen Mary University of London
  tel: ++44 (0) 20 7882 5035
  

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