By Sachin Nayak
“The first thing that would enter the minds of most of you, the ‘IIT Junta’, when you think of the Higgs Boson would be ‘The God Particle’. The more well informed of you would think of it as being the missing link in the description of the universe. Each one of you might have different ideas about the Higgs Boson yet the ideas of each one of you would have some element of mystery in it.” On 5th September 2012, Dr. Rohini Godbole in her lecture on the Higgs Boson cleared most of the common misconceptions about the so-called ‘God Particle’.
She started her talk by stating the question that has been lingering in the minds of the physicists from the days of yore. “What is at the heart of matter?”. With scientific advancement, the answer to this question has undergone a rapid transformation but the question has remained the same. We have moved from the theory of Earth, Fire, Wind and Water being the ‘Elements’ to that of the theory of infinitesimal particles like the leptons and the quarks constituting the entire universe. Yet, we don’t have a conclusive answer to this question.
Then, she gave a brief overview of ‘The Standard Model’, the most widely accepted model of the universe at present. The Standard Model (SM) has two components, the ‘bricks’ and the ‘mortar’. The bricks are the leptons and the quarks which form the bulk of the universe. The mortar is the set of force particles, i.e. the gluons, the W bosons etc., which binds these particles to the form in which we know it. She showed the audience how elaborate and complex the SM theory is by saying that out of the 72 Nobel prizes in Physics that have been awarded from 1936 to 2008, 15 have been awarded for contributions to the SM. We now even have a periodic table of the fundamental particles. In this section of her talk, she also showed that SM is not only relevant to the small group of theoretical physicists but also to the whole scientific community as the laws of particle physics which act at a distance of 10^(-15) meters have a great impact on events which occur at cosmological times and astronomical distances. Thus, Dr. Rohini in a short time managed to give a holistic view of the SM.
In the next section of her talk, she explained how the existence of a law of symmetry in Physics called the ‘Gauge Invariance’ pointed to the existence of Higgs boson. When Gauge Invariance is applied to Maxwell’s equations, we get the result that the mass of a photon is zero. This fact is used in Fermi’s explanation of β-decay. But this explanation invokes the mathematician’s ire as it leads to absurd conclusions like the probability of the event of 2 high energy particles colliding being greater than one. This problem was solved by Schwinger who said that high energy particles follow a different mechanism of collision in which they exchange a W+ boson. Unfortunately, this solution implied that the probability of a neutrino and an anti-neutrino colliding had a probability greater than one. Glashow showed this problem could only be solved by ignoring ‘Gauge Invariance’. So, the theoretical physicists had a tricky problem at hand. Gauge Invariance showed the existence of Z, W+ and W- boson whose mere existence raised doubts about the truth of the Gauge Invariance. The chain of ideas had knotted around itself.
This is when physicists like Higgs and Englert came into the picture. 4-5 of these theoretical physicists independently showed how these massive bosons could exist without violating the Gauge Invariance law. Though each of them independently solved this problem, the solution of each one of them predicted that there existed a particle which gave mass to every other particle in the universe. This might give us ideas the theoretical physicists are so clever that they can read one other’s mind telepathically. Definitely, Higgs didn’t have this ability as his solution was the more accurate than the others and thus the mass giving particle was named after him in his honour. Finally, Abdus Salam showed how the Higgs mechanism could be expanded to photons and other particles.
After telling us why theoretical physicists believed that the Higgs Boson existed, Dr. Rohini proceeded to explain the significance of the experiment which took place on 4th July. First, she showed us how elusive the Higgs Boson is with the help of energy diagrams. In her own words, ‘Only 1 in 1013 experiments can lead to the conclusive proof of the existence of the Higgs Boson’. No wonder it is called the ‘God Particle’. She continued by saying that the experiment which took place on 4th July at the LHC was basically an event of 2 high energy protons colliding and giving out two photons at a large angle to each other. This indicated that a massive particle had been formed and had annihilated. This particle had the same characteristics as that predicted for the Higgs Boson by theory. It even appeared in the same energy range as predicted by theory, i.e. 100GeV – 150 GeV. In her own words, “It was like a dream come true for us, the theoretical physicists.”
Still, she believes that scientists don’t really have enough data to formally conclude the existence of the Higgs Boson. A German exchange student addressed a query to Dr. Rohini on the observation of the p-p collision being an oscillation of a ‘Superstring’. She replied in a lighter vein, “It flies like a plane, looks like a bird, so it might be ‘Superstring’”. In light of the recent observation that the neutrinos travelling faster than light turning out to be nothing more than a computer glitch, a person in the audience asked her how the physicists were convinced of the veracity of the experiment. She replied by saying that though the neutrinos which were thought to travel faster than light were produced at CERN, CERN was not the organisation which conducted the embarrassing experiment. She supported her statement by saying that the reports were read and re-read by at least 2000 people and that the experiments at the LHC had taken place only after meticulous planning of over 30 years.
Even if the experiment on the 4th of July provides conclusive proof of the existence of the Higgs Boson, it will only fill in the missing link in the chain of the SM. It will definitely not render Theoretical Physics redundant (and lead to the unemployment of theoretical physicists like Rohini). The reason for this is that then they would have only understood 4% of the matter in the universe. They would still have to probe into the darkness of Dark Energy and Dark Matter constituting the remaining 96% of the universe. They would also have to probe into the niches of the ‘Beyond Standard Model’ theory, which says that the whole universe is made up of oscillating strings. Referring to the discovery of the Higgs Boson just marking the beginning of a new era in Theoretical Physics Dr. Rohini said, “The king is dead; long live the king.”
Dr. Rohini Godbole is one of India’s prominent theoretical physicists. Dr. Rohini did her MSc. from IIT Bombay in 1974 and won the institute silver medal for her performance. Following a PhD from SUNY, Stony Brook, USA, she worked in TIFR and the university of Bombay before joining IISc as a faculty member where she is a professor in the Centre for High Energy Physics at present. Dr. Rohini has made fundamental contributions in High Energy Physics, especially to the ‘Standard Model’ and the ‘Beyond Standard Model’ and has authored over 200 papers in these areas. Many a times, she has been invited to the LHC to work, deliver lectures and offer theoretical formulations of the universe. She has been elected to numerous academies and won many international and national awards and fellowships. She is also the editor of the journal ‘Pramana’.
