In scientific terminology, a hypothesis transmutes into theory only after it has been verified. In the next year or so, the “God Particle Hypothesis” will either become a theory, or be discarded along with curiosities like ether and geo-centrism.
Whatever happens will lead to a deeper understanding of the so-called Standard Model (SM), which attempts to explain ways in which electromagnetic and nuclear forces interact at sub-atomic levels. Our understanding of how stars are formed and generate energy, and of cosmology – the origin and possible end of the universe – depends on the SM. (The SM ignores gravity).
Since 1964, the SM has revolved around the search for an elusive particle that could explain various puzzling details. Variously known as the God Particle or the Higgs Boson, this hypothetical particle is thought to have imparted mass to elementary particles, just after the Big Bang.
Its existence was postulated simultaneously in three separate papers, by six different physicists, including Peter Higgs (working alone), Francois Englert & Robert Brout (in collaboration), Gerald Gulanik, Carl Hagen & Tom Kibble (in collaboration). If it exists, it would be the simplest explanation for mass.
It’s common to infer the existence of particles and quantum theory largely developed through searches for particles that “should” exist. Apart from the Higgs, every particle hypothesised in the SM has been found.
Elementary particles are very small. They appear and vanish through decay in complicated interactions that last just fractions of a second. The general method of discovery consists of accelerating particles and smashing them together at very high speeds in controlled environments.
The break ups lead to the appearance of elementary particles that can be detected by fluctuations in energy patterns even as they decay. Mass and energy are equivalent at sub-atomic level and the mass of elementary particles is often indicated in energy units.
When it came to the possible mass of the Higgs Boson, there were huge differences in predictions. Further modifications arose in the 1970s after work done by, among others, Steven Weinberg and Abdus Salam. Some hypotheses suggest entire families of Higgs may exist. There are over 100,000 possible ranges where the Higgs may be found. There are also versions of the SM, including one championed by Stephen Hawking, which assume the Higgs doesn’t exist.
The biggest atom-smasher is the Large Hadron Collider (LHC) located inside 27 kms of circular tunnels under the mountains of the Swiss-French border. Beams of particles are fired at each other inside these tunnels, which are tightly insulated from external influences. Detectors collect data from those high-energy collisions, seeking new particles and other information.
The LHC collects huge amounts of data. But it takes months or even years to process and make sense of it. There are two teams, Atlas and CMS, tasked to specifically search for the possible presence of the Higgs Boson.
In July, there was much excitement when scientists announced the LHC had discovered “excess events” at one of the ranges where the Higgs Boson was predicted to possibly exist. The excess could have meant the Higgs had been nailed down. But since then the data gathered at that range, has more than doubled and the excess has diminished. So that’s a damp squib.
According to Sergio Bertolucci, director, research and computing, European Organisation for Nuclear Research (CERN), the search is proceeding on the following lines: “Rather than dropping a hook in a pond, we are fishing with a new technique. We remove all the water from the pond. If there is no fish, we will conclude that the Higgs doesn’t exist.”
The LHC data will gradually exclude various mass-ranges where the Higgs cannot exist. However, with over 100,000 possible ranges, this will take lots of data. The experimental data presented at the XXVth Lepton-Photon Symposium in August at the TIFR in Mumbai, now rules out the existence of the Higgs Boson inside the 145 GeV (giga-eletron-volt) to 466 GeV range with 95 per cent certainty. There are a couple of “islands” in this 145-466 zone that could still harbour the Higgs. But chances are, the Higgs, if it exists, is either a light particle (less than 145 Gev) or heavy (above 466 Gev).
Based on the current rate of data acquisition, LHC researchers predict they will either have found the Higgs by end-2012. Or, they will have confirmed that it does not exist. Either way, that will mean modifications to the SM and confirmation or rejections of various subsidiary hypotheses.
If the Higgs doesn’t exist, the range of the unknown expands. The Higgs would be the simplest possible explanation for mass, which is a fundamental quality. So if it doesn’t exist, another explanation for mass has to be found. That may involve the holy grail of physics — a unification of electromagnetic and nuclear forces with the effect of gravity.
