Dark Matter search enhanced by LHC’s new turbocharged ‘Brain’
Press release issued: 26 May 2016
The hunt for Dark Matter taking place at the Large Hadron Collider in CERN has taken a great leap forward thanks to new detection technology developed by a team from the UK, including physicists from the University of Bristol.
The system, installed on the CMS experiment, is being used for the first time anywhere in the world and the pioneering approach will enhance our understanding of the fundamental physics of the universe.
The five-year development, delivery and installation of the new general purpose detector in the CMS experiment at the LHC is thanks to the efforts of a team of researchers, scientists and engineers from the UK.
The upgraded general purpose CMS detector for the LHC pulls together all the data produced in the microsecond after each particle collision. The detector studies the data needed for understanding a wide range of physics including the properties of the Higgs boson, searching for extra dimensions and for the particles that could make up dark matter.
Dr Jim Brooke, Senior Research Associate in the School of Physics at the University of Bristol, who believes the new system is much more flexible than the previous detector, said: "The system effectively receives a digital image of each collision from the detector. This upgrade is like switching to HD TV, the pictures are much higher resolution. We can also process an entire image in one chip; before we had to split them up and process each piece separately.
"With the old system, we mostly relied on identifying one or two high energy particles as a sign of interesting physics. Seeing the whole picture in high resolution means the electronics can begin to decide whether those particles come from a Higgs boson or new physics like dark matter production. It's a really flexible, powerful system, and we’re only just starting to use its capabilities."
Data from the CMS detector must be analysed in less than a millionth of a second to decide whether something interesting has happened and that the data should be kept for further analysis.
Professor David Newbold, Head of the Fundamental Physics Research Group at the University of Bristol and UK spokesperson for the CMS experiment at CERN, said: "Although the CMS detector is huge, all of the collision data has to be immediately analysed by an electronic 'brain' the size of a microwave oven. The scientific results from the LHC depend crucially on selecting a tiny fraction of collisions for detailed analysis, and throwing away the rest. The new technology we are using in CMS is going to increase our chances of spotting Dark Matter and other new particles in the high energy collisions in 2016 - it's like turbocharging our detector."
Dr Alex Tapper from Imperial College London leads the group that was involved in developing the custom electronics boards for the new trigger, added: "Normal PCs are just not fast enough to perform this analysis of the data so we developed a custom processor ourselves. We used a cutting edge chip which is very good at performing many calculations in parallel and built a system using optical fibres to feed enormous amounts of data into the chip. The new system is much more powerful and we hope it will help us make new discoveries in the future."
UK teams involved:
University of Bristol, Imperial College, and a team from STFC's Rutherford Appleton Laboratory were involved in developing the new detector.
The Bristol Particle Physics group is involved in two experiments based at the Large Hadron Collider (LHC) at CERN: CMS and LHCb
The new CMS detection system:
- analyses data at ten terabits per second, or the equivalent of all the broadband connections in Manchester;
- contains 25 billion transistors and 1,500 optical fibre connections;
- scans images from CMS at 40 million frames (that’s 200 full-length movies) each second.
Particle Physics is all about understanding the fundamental building blocks of matter and how they interact with each other. To do this, modern Particle Physicists build large experiments where particles are made to smash into one another. Detectors are built around where these collisions occur, and the particles resulting from the interaction are studied.
CMS is a general purpose detector designed to investigate a wide range of physics including supersymmetry, extra dimensions and particles that could make up dark matter. The scientific goals for the two experiments are the same, but they use different technical solutions. These similar science goals, but different designs allow the two experiments to cross-check results and confirm exciting discoveries such as a Higgs boson.
The Large Hadron Collider
2016 is the second year the LHC will run at a collision energy of 13 TeV. During the first phase of Run 2 in 2015, operators mastered steering the accelerator at this new higher energy by gradually increasing the intensity of the beams.
Beams are made of "trains" of bunches, each containing around 100 billion protons, moving at almost the speed of light around the 27-kilometre ring of the LHC. These bunch trains circulate in opposite directions and cross each other at the centre of experiments. Last year, operators increased the number of proton bunches up to 2244 per beam, spaced at intervals of 25 nanoseconds. These enabled the ATLAS and CMS collaborations to study data from about 400 million million proton–proton collisions. In 2016, operators will increase the number of particles circulating in the machine and the squeezing of the beams in the collision regions. The LHC will generate up to 1 billion collisions per second in the experiments.
The Higgs boson was the last piece of the puzzle for the Standard Model – a theory that offers us the best description of the known fundamental particles and the forces that govern them. In 2016, the ATLAS and CMS collaborations – who announced the discovery of the Higgs boson in 2012 – will study this boson in depth.
But there are still several questions that remain unanswered by the Standard Model, such as why nature prefers matter to antimatter, and what dark matter consists of, despite it potentially making up one quarter of our universe.
The huge amounts of data from the 2016 LHC run will enable physicists to challenge these and many other questions, to probe the Standard Model further and to possibly find clues about the physics that lies beyond it.
This new physics run with protons will last six months. The machine will then be set up for a four-week run colliding protons with lead ions.
STFC & CERN
The Science and Technology Facilities Council (STFC) co-ordinates and manages the UK’s involvement and subscription with CERN. The UK’s influence on both CERN Council and CERN Finance Committee is coordinated through the UK Committee on CERN (UKCC). UK membership of CERN gives our physicists and engineers access to the experiments and allows UK industry to bid for contracts, UK nationals to compete for jobs and research positions at CERN, and UK schools and teachers to visit. UK scientists hold many key roles at CERN. Firms in the UK win contracts for work at CERN worth millions of pounds each year. The impact of winning contracts is often even greater as it enables companies to win business elsewhere.