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Detail of a collision event in the Large Hadron Collider as part of the ATLAS Higgs Search (Photo courtesy of CERN)

Recreation of a collision event in the Large Hadron Collider (Photo courtesy of CERN)

The ATLAS team, from left: Stewart Martin-Haugh, Valeria Bartsch, Anthony Rose, Antonella De Santo, Fabrizio Salvatore and Tina Potter. LHC image courtesy of Maximilien Brice

University of Sussex physicists were celebrating today (Wednesday 4 July) following news of a giant step for science with the discovery of a tiny sub-atomic particle.

Dr Antonella De Santo was in London with other leading physicists to break the news that scientists at the Large Hadron Collider at CERN (the European Organisation for Nuclear Research) in Switzerland had discovered an elusive particle smaller than an atom which is highly likely to be the Higgs boson, which scientists say proves theories of how the Universe works.

A boson is a sub-atomic particle described as “the most sought-after particle in modern physics” and its apparent discovery follows on from the landmark discovery of electrons more than 100 years ago. The boson is named after British scientist Peter Higgs, who predicted its existence 50 years ago.

The results mark a significant breakthrough in our understanding of the fundamental laws that govern the Universe.

Dr De Santo and her Sussex team are part of ATLAS, one of two LHC experiments (the other is called CMS) that presented data today at a seminar at CERN, confirming the existence of the particle that to date existed only in theory. The seminar announcement was relayed to British scientists in London by satellite.

Dr De Santo’s team was responsible for collecting and analysing data created by the LHC, in which high-energy beams are smashed together deep below the earth’s surface at CERN to recreate conditions in the Universe as they were after the Big Bang.

Dr De Santo says: “Today is a great day to be involved in experimental particle physics. The Large Hadron Collider is a 'once-in-a-lifetime' opportunity to do great science and we are now beginning to harvest the fruits of many years of hard work and perseverance. This is a truly collaborative effort and I, with all my colleagues and the young people that work with us, feel very proud and privileged to be part of it.”

UK Funders Science and Technology Facilities Council's Chief Executive, Professor John Womersley, who announced the discovery to scientists and journalists at a packed Westminster Hall, said: “I’m delighted that we have indeed discovered a particle consistent with the Higgs boson. Obviously having found a new particle, there is still much, much more to do at the LHC – we need to confirm that this new particle is the reason some particles have tangible mass while others are insubstantial, as proposed by Peter Higgs and other scientists, who predicted that a particle like this one must exist for our current understanding of the Universe to work.”

Speaking of the findings the Minister for Universities and Science David Willetts said: “This news from CERN is a breakthrough in world science. The UK has made an enormous contribution over the last 20 years supporting the search for the Higgs Boson. Our researchers, universities and industry partners have been instrumental in making the Large Hadron Collider such a success. They deserve recognition for their contribution to this scientific milestone that will change the way we look at the universe from now on.”

The UK is a world leader in particle physics and has played a central role in this research, from the theorists who formulated the model known as the Higgs mechanism, to the engineers and scientists who have designed, built and exploited the LHC – one of the most complex scientific instruments ever built.

The next step will be to determine the precise nature of the particle and its significance for our understanding of the universe.

Positive identification of the new particle’s characteristics will take considerable time and data. But whatever form the Higgs particle takes, our knowledge of the fundamental structure of matter is about to be enriched.

WHAT’S IT ALL ABOUT? HIGGS BOSON QUESTIONS AND ANSWERS

What is the Higgs boson?

The Higgs boson is a type of elementary, sub-atomic particle. Its existence hasn’t been proven yet but it’s widely believed to play a key role in shaping the way the Universe functions. Finding out whether or not the Higgs boson exists is one of the main objectives of the Large Hadron Collider (LHC), which is located at CERN (the European Organisation for Nuclear Research) in Switzerland.

Why is the Higgs boson important?

Physicists have developed a theory called ‘the Standard Model’ to explain how the various types of elementary particle that make up the visible Universe interact.  With the exception of neutrino physics, results from other particle physics experiments match the Standard Model extremely well - but only if one missing piece, the Higgs boson, is assumed to exist. Based on the particles discovered to date, the Standard Model could not otherwise explain why some particles have mass (e.g. electrons), while others don’t (e.g. photons which make up light).  Theoretical physicists believe that the Higgs boson is the key.

So most physicists conclude that another, so far undiscovered, elementary particle must exist – the Higgs boson – and that this gives other particles their mass.  In terms of our understanding of matter and the basic forces shaping the Universe, this is a critical issue: without mass, there would be no matter.

How does the discovery of the Higgs boson compare to earlier scientific discoveries?

The search for the Higgs boson mirrors the discovery of the electron.  The concept of the electron was first proposed in 1838 to explain the chemical properties of the atom but its presence was not confirmed by British physicist and Nobel prize winner JJ Thompson until 1897. 

A century on, the electron’s existence underpins modern science.  Manipulating or harnessing phenomena such as electricity, magnetism and thermal conductivity rely on our understanding of the electron – applications include cathode ray tubes (television), radiotherapy treatments for cancer patients, lasers (CDs, energy, manufacturing etc), microscopes, and, of course, particle accelerators like the LHC.  Spintronics, the technique of manipulating electron ‘spin’, has the potential to bring us faster computers, increased data storage and more efficient photovoltaic cells.

Our search for knowledge about our Universe continues and it is impossible to determine where it will lead in terms of fundamental knowledge or applications.  For example, we do not know why photons, the particles that make up light, have no mass.

JJ Thompson could not have predicted where his discovery of the electron would lead, and similarly we do not know where the discovery of the Higgs boson could lead. Each advance opens up a new frontier of science.

What does the Higgs boson actually do?

It’s believed that Higgs bosons are responsible for determining how much mass other types of elementary particle have. The theory goes as follows: countless numbers of Higgs bosons make up an energy field (‘the Higgs Field’) that extends throughout the Universe. When other types of elementary particle move through the Higgs Field, some do so very easily (like an arrow flying through the air); this results in them having little mass and, in some cases, no mass at all. But other, less ‘streamlined’ types of elementary particle don’t move through the Higgs Field so easily and this results in them having a relatively high mass.

 Where does the name ‘Higgs boson’ come from?

Sub-atomic particles are divided into two categories: bosons and fermions. Generally speaking, bosons are force-carrying particles while fermions are associated with matter. The Higgs boson is named after Professor Peter Higgs, a theoretical physicist at the University of Edinburgh. Professor Higgs was one of a number of physicists who predicted the existence of what’s now known as the Higgs boson, which has been dubbed ‘the most sought-after particle in modern physics’.  A number of other researchers, including Thomas Kibble of Imperial independently or jointly proposed a similar mechanism, but it has become generally known as the Higgs Mechanism.

How could you ‘see’ a Higgs boson?

You can not directly see a Higgs boson. It’s believed that, with the right experiment in place, a decaying Higgs boson would leave behind a detectable ‘footprint’ in the form of a unique configuration of other particles. Higgs bosons should (according to current theories) be created a few times in every trillion high energy particle collisions at the LHC.

Just how close is the LHC to success?

The LHC is the most powerful particle accelerator ever built. Beams of protons or ions are accelerated close to the speed of light and smashed into each other, recreating conditions that existed just after the Big Bang kick-started the Universe over 14 billion years ago.  This was when all sub-atomic particles were created.

Funded by STFC, UK scientists have contributed key equipment and expertise to the LHC. Four major detectors are being deployed there – with two focused on finding the Higgs boson. 

These two huge detectors (ATLAS and CMS) have now both generated data indicating the possible presence of a Higgs boson. Scientists are poring through the data to ensure that the early indications of the Higgs have not been produced by random fluctuations. Depending on the actual properties of the Higgs boson, more data could be needed to provide a sufficient basis for firm conclusions to be drawn – hopefully within the next 12 months.

What happens next?

Confirming the existence of the Higgs boson will provide vital evidence that the Standard Model accurately accounts for how and why energy and matter behave as they do. It will act as a springboard to further research and an improved understanding of the Universe. Ultimately, it may have spin-off benefits in fields as diverse as medicine, computing, electronics and manufacturing.   

Discovering the Higgs marks the start of a new phase in particle physics – for example, dark matter, which forms 23 per cent of the Universe, is not explained in the Standard Model, but the properties of the Higgs boson could point to which extensions of the theory are likely to be correct, setting the direction for particle physics research. Conversely, the properties of the Higgs boson could close off some theoretical options, so particle physics is set for a period of dramatic change if the Higgs is discovered.

Can we switch off the LHC now?

Definitely not – finding the Higgs will be just the start of understanding its properties and implications for particle physics. Also, the LHC has much wider science goals than simply finding the Higgs boson (see below).

Why is the Higgs boson sometimes called the ‘God Particle’?

The media often use this phrase – taken from a 1990s popular science best-seller – as a layman’s term for the Higgs boson. However, it gives a misleading idea of the particle’s nature and function.

How much money the UK has invested in the LHC?

The Science and Technology Facilities Council (STFC) pays the UK contribution to the CERN budget, which is determined on a formula basis related to net national income. The current UK share of the CERN budget is 14.77%, £104.5M a year. STFC also supports UK participation in the four LHC experimental detector projects.

The UK has invested more than £500 million on the LHC in funding direct to CERN and to the University groups in this country that have contributed to the construction and preparation of the accelerator and the experimental detectors.

Was any of the LHC built in the UK?

The UK has played a major role in the LHC’s design, development and operation, with 15 University groups and the STFC Rutherford Appleton Laboratory involved in the design and construction of the four detectors. At CERN, many key roles are held by UK personnel. UK scientists and engineers have been central to all the major LHC developments, from Professor Higgs’ theoretical work that underpins the research, the initial LHC proposals, detector design and build, day-to-day operation of the LHC, and now data analysis.

During the construction phase of the LHC, CERN spent a significant proportion of its budget with industry. UK industry played its part in the construction of the accelerator.

How many UK scientists are involved?

There are more than 200 UK nationals employed by CERN of whom more than half are in the scientific grades. In addition, more than 560 UK scientists regularly work at CERN.