Deep in the boson of the universe

HIGGS HUNT

The discovery of a Higgs-like boson will set in motion a new rush among physicists to go where no human being has gone before, and understand the origin of the universe, writes Kalyan Ray

The hunt has actually begun. Last week’s announcement on the discovery of a Higgs-like boson – popular as God Particle – will not bring down the curtains on particle physics. Rather it will kickstart a fervent race among physicists to explore new frontiers of science in their effort to understand nature’s grand design.

More experiments are being carried out at the Large Hadron Collider – the 27-km-long circular underground atom smasher at France-Switzerland border – to find out clues to other mysteries of the universe including the elusive “dark matter” and “string theory” that envisages fundamental building blocks of the universe not as particles but as multi-dimensional strings.

But before responding to other questions on the mysteries of universe, the first one staring at scientists is whether the new particle is the same as described by Peter Higgs and his five colleagues in a 1964 paper in Physical Review Letters or a slightly different cousin of that particle. For many scientists, it’s “a” Higgs-like particle rather than “the” Higgs particle.

“We have only half of total data required. In another five months, we will double the data and make a stronger statement than what is possible at the moment. We are almost sure but additional data will be required to complete confirmation (on the Higgs),” Pune-born Ashutosh Kotwal, one of the team leaders from ATLAS group and a physicist from Duke University told Deccan Herald.

At the moment, scientists only confirm that they have seen a new particle, a boson, whose properties are fairly consistent with Higgs boson.

The universe and the world around us is made of 12 fundamental particles of matter, six quarks and six leptons, and four forces. Developed in the 1970s, the Standard Model describes the behaviour and nature of all these particles and three out of four forces.

Gravity still remains outside the SM, which continues to be the best description of the subatomic world so far. As the Higgs boson is an essential ingredient of SM, its discovery is a rock solid proof of the theory.

Major milestone

“The discovery signifies a day of completion of the most celebrated theory of particle physics. Had it not been found, it would have become a big mystery,” said Satyaki Bhattacharaya, a professor at Saha Institute of Nuclear Physics in Kolkata and one of the Indian scientists experimenting with CMS detector that independently confirmed existence of the God particle. Two LHC detectors, ATLAS and CMS, independently confirmed existence of the new sub-atomic particle with a mass of 126 GeV.

“We have reached a milestone in our understanding of nature,” said CERN Director General Rolf Heuer. “The discovery of a particle consistent with the Higgs boson opens the way to more detailed studies, requiring larger statistics, which will pin down the new particle’s properties, and is likely to shed light on other mysteries of our universe.”

The hunt for the Higgs particle has long been one of the top priorities for particle physics.

The Higgs is associated with a mechanism proposed in the mid-1960s to explain why one of nature's fundamental forces has a very short range while a similar force has infinite range. The first one is electromagnetic force, which brings light to us from the stars, carries electricity around our homes, and gives structure to the atoms and molecules from which we are all made. The other one is the weak force, which drives the energy generating processes of the stars.

The electromagnetic force is carried by particles called photons, which have no mass, whereas the weak force is carried by particles called W and Z that do have mass. Rather like people passing a ball, interacting particles exchange these force carriers. The heavier the ball, the shorter the distance it can be thrown. The heavier the force carrier, the shorter is its range. W and Z particles were discovered at CERN in the 1980s, but the mechanism that gives rise to their mass remains to be unlocked, and the Higgs boson is the key. 

Boson & its avatars

But a simple observation is not enough, however, because the Higgs boson can take many forms. In its basic incarnation, the mechanism is the simplest theoretical model that accounts for the mass difference between photons and W and Z particles, and for the masses of other fundamental particles. 

But there are other formulations of the mechanism linked to theories such as supersymmetry, which could account for the universe's mysterious dark matter, or to theories predicting extra dimensions of space, which, if verified, would truly revolutionise our understanding of the universe we live in.

So once the discovery is confirmed, the next question is: What kind of Higgs boson do we have? “But there is not enough data to identify what kind of Higgs Boson it is and if there is another kind of Higgs Boson,” Kotwal said.

The next step will be to determine the precise nature of the particle and its significance in understanding the universe. Are its properties as expected for the long-sought Higgs boson or is it something more exotic? 

The Standard Model describes the fundamental particles from which we, and every visible thing in the universe, are made, and the forces acting between them. All the matter that we can see, however, appears to be no more than about 4 per cent of the total. A more exotic version of the Higgs particle could be a bridge to understanding the 96 per cent of the universe that remains obscure.

Let the force be with you

The standard model of particle physics explains what the world is and what holds it together. 

The recipe:

*Six quarks, six leptons and four forces.

*Particles transmit forces among each other by exchanging force-carrying particles called bosons. 

*These force mediators carry discrete amounts of energy, called quanta, from one           particle to another.