Rediscovery helps point way to Higgs boson

UCD scientists use software developed in Ireland to ‘rediscover’ sub-atomic particles first seen 25 years ago

A team of Irish physicists is in Paris today to present their research findings to an international audience of 1,000. Had the same achievement revealed today been delivered 25 years earlier, they could have expected a Nobel Prize for their efforts.

Dr Ronan McNulty heads the group from University College Dublin and will be presenting the Irish team’s latest findings at the 35th International Conference on High Energy Physics.

It is the largest and most important annual meeting of the international particle physics community, says Dr McNulty and being invited to present data is a particular honour.

The meeting takes on even greater significance given that it will hear the first of the results coming from the world’s biggest atom smasher the Large Hadron Collider (LHC) at Cern, the European nuclear research centre.

The LHC has been smashing protons together for the past six months at energies 100,000 times hotter than the centre of the sun.

Four main experiments placed around the 27km-long LHC ring have been collecting data and the interpretation of some of this early data will feature at the Paris meeting, McNulty says.

The Irish group is involved in an experiment called LHCb and has played a central role in the findings to be presented this afternoon.

The team has spent five years working on the software needed to interpret the raw data coming from the LHCb experiment. And it was team member James Keaveney who actually dug out the data that McNulty will present in Paris. Keaveney was searching through the data and spotted the signatures of two important particles, the Z boson and the W boson. He “rediscovered” the two particles originally found by physicists Carlo Rubbia and Simon van der Meer in the mid-1980s.

Finding the Z and W was the physical evidence needed to unify the connection between electricity, magnetism and radioactivity, McNulty says. “That was why it was such an important discovery.” Rubbia and van der Meer’s work took the Nobel Prize for physics in 1984. McNulty joked about the Irish find, saying: “We are 25 years too late to claim the Nobel Prize for discovering them. Nonetheless, it doesn’t diminish the thrill of finding these exotic particles in our first data.”

The re-discovery of known particles is still important because it shows that the LHCb and other experiments attached to the LHC are working properly and delivering valuable data.

It will also help the scientists as they increase energy levels in the LHC and intensify their hunt for another particle, the all important Higgs boson. The LHC was built in part to help find the Higgs boson, the only remaining sub-atomic particle yet to be found by high energy physicists.

It represents the missing puzzle piece that if discovered will complete the “Standard Model” which describes all the sub-atomic particles and their interactions with one another.

That is why the rediscovery of the Z and W is significant, McNulty says. “It is important because when you start to look for the Higgs it is a similar process, but a much rarer event.”

The analysis software developed at UCD will be central to the discovery of the Higgs as the scientists at Cern including the UCD research group contribute to this international effort.