Physicists in successful search for the elusive Higgs particle

Posted on 04/07/2012

Researchers from the Large Hadron Collider at CERN, including a number of  physicists from Royal Holloway, have today (4 July) confirmed that they have found a new particle consistent with the long-sought Higgs boson.

These results mark a significant breakthrough in our understanding of the fundamental laws that govern the universe

The Centre for Particle Physics at Royal Holloway has been a member of the ATLAS experiment, which today consists of more than 3000 physicists from 174 universities in 38 countries, since its inception 20 years ago.  The College's ATLAS group, numbering about twenty scientists (including academics, postdoctoral researchers, engineers and PhD students) plays an important role in the exciting search for the so-called Higgs boson.

The Royal Holloway’s ATLAS group has been involved in many different aspects of the ATLAS project. From the early stages the College’s physicists have played a vital role in the electronics and software used to extract the data from the detector, particularly the so-called trigger system, which figures out which of the many particle collisions are of potential interest and should be retained for further study.

The group also plays a major role in physics analysis, including studies of the top quark, searches for signs of physics that go outside the Standard Model and also, of course, the search for the Higgs boson. In the area of the Higgs search, Royal Holloway’s ATLAS group have made important contributions to the development of the statistical methods used to analyse the data, to the study of the important case where the Higgs boson decays into two photons, and also to the more difficult case where it decays into a pair of so-called b-quarks.

The latest results in the search for the elusive Higgs particle were revealed to the world this morning at CERN (the European Laboratory for Particle Physics, in Geneva, Switzerland).  The spokespersons of the world's two largest physics collaborations – the ATLAS and CMS experiments at the Large Hadron Collider (LHC) – presented the very latest results that include a large amount of new data collected since April 2012.

The LHC is a 27 km long underground particle accelerator that collides very high-intensity and high-energy beams of protons. The huge ATLAS and CMS particle detectors are used to record and analyse the results of these collisions.  In the 1960s the Higgs particle was predicted to exist to explain why other elementary particles have mass, but for many years no direct sign of it could be found in experiments. The search for the Higgs has been the subject of especially intense focus since the LHC started collecting data three years ago.

The data collected at the LHC in 2011 showed some tantalising indications of the possible existence of the Higgs particle.  This evidence, however, fell short of the strict standards required to claim discovery of a new particle.  In order to verify or disprove these hints, more data was required.  Since April 2012, the LHC has been in data-taking mode again, and the number of particle collisions recorded has since doubled.  

The results presented by the ATLAS and CMS experiments today at CERN show a clear excess of collisions with properties consistent with containing a Higgs particle. These results are by far the strongest to date to back up the hypothesis that the Higgs particle is an experimental reality, and not just a theoretical construct.

CERN Director General Dr Rolf Heuer summarised the presentations by saying: "We have a discovery. We have observed a particle consistent with the Higgs. It is an historic milestone but only the beginning."

Dr Pedro Teixeira-Dias, from the Department of Physics at Royal Holloway, said: “In twenty years of searching for the Higgs boson, today has definitely been the most exciting day!  This is the day we will open a bottle of Champagne I have been keeping in my office for a while…”

Royal Holloway PhD student Rob Cantrill added:  "I feel extremely privileged to be involved and to work with some amazing people on this very historical analysis."

Professor Glen Cowan, who is part of Royal Holloway’s ATLAS Group, said: "My confidence that we've found the Higgs is extremely high. If it doesn't exist, then the probability of seeing something that looks so much like the Higgs coming from a random fluctuation is roughly the same as being dealt a royal flush."

Prof Grahame Blair, Director of the Centre for Particle Physics at Royal Holloway added: "This is a fantastic achievement for the LHC and in particular for the researchers, including those at Royal Holloway, who have been searching for the Higgs.  Our physicists are also looking for many other particles and phenomena, so we can expect lots of exciting times ahead."


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