Note: The following telephone interview was broadcast by the BBC on the occasion of CERN’s announcement on December 13. The CERN announced that it had fairly conclusive data that confirmed the glimpsing of a Higgs boson in experiments conducted at the Large Hadron Collider. The interviewee, Dr. G. Baskaran, is a distinguished physicist currently engaged with research at the Perimeter Institute, Canada.
My comments appear in square brackets, [ ], and explain concepts that are required to understand Dr. Baskaran's answers. Statements spoken by the interviewer are marked with bold letters.
The audio of the interview is linked herewith: http://www.bbc.co.uk/emp/worldwide/player.swf
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Interviewer: Before we begin a discussion on the Higgs boson, it is important to understand the background of this experiment. Physicists began the search for this particle with the belief that everything in this universe is composed of atoms, and atoms of nuclei. It was due to the contribution of technology that they were then able to break open the nuclei and enter it to find many new particles.
The consequential research has been going on for many years, and led to the formation of a cogent theory that could explain the behavior of all those particles. Physicists called this theory the Standard Model. As they began to work with it, they came across an important glitch: using just those particles that constituted the Standard Model, they couldn’t explain gravitation. Subsequently, physicists directed themselves to find a suitable solution, which took the form of the Higgs boson.
Just like mathematicians, when faced with a problem, use a variable ‘X’ in their equations so they can proceed with their calculations, particle physicists used the Higgs boson as their ‘X’ and proceeded with their unknotting of the universe’s riddles. Since this substitution, which happened in the 1960s, calculations have been going on relatively smoothly but the lack of knowledge of the Higgs’s properties remained elusive.
In this context: on December 13, scientists working at the CERN’s Large Hadron Collider announced that they may have glimpsed the Higgs boson during one of their experiments. When Dr. G. Baskaran, distinguished research chair at the Perimeter Institute in Canada and a Ramanna Fellow with the Institute of Mathematical Science, Chennai, was asked about this announcement, he had this to say: “The things we see in nature, the rocks and sand—as we delve deeper and deeper into them, we come across molecules and atoms. Inside these atoms, we have electrons—orbiting the nucleus—and protons and neutrons inside the nucleus.”
“These elementary particles cannot be seen by the naked eye but only by sophisticated instruments. These particles have been the foundation for a new theory. At such nanoscopic levels of observation, Newton’s laws fail and, instead, quantum theory comes to life. The physics for this theory dates back to almost a century, since the discovery of the electron by Thompson and Einstein’s baptism of photons as the carriers of electromagnetic waves.”
“It was observed that all these particles had mass, and with even more experiments, the values of those masses were found: the particles are very, very light, yes, but they did have a definite mass. So when you consider the mass of the photon, it is zero. The energy for the photon comes from its momentum: it travels at a very high speed. It is impossible to trap or localize a photon, and this has been verified by particle physicists.”
“Avvayyar [a Tamil poet] once spoke about breaking open a sea of particles only to flood seven oceans, and something similar has been happening in the quest for understanding these particles. For example, once physicists broke open the proton, they found quarks and gluons, and when quarks and gluons ‘reacted’, they found neutrinos. The field of physics that concerns itself with the smashing-discovering process is called high-energy physics.”
“Researchers soon realized that they couldn’t experiment with these smaller and smaller particles directly. Instead, they accelerated beams of such particles to high velocities and forced them to collide head-on. At that moment, like how two cars crash into each other and are shot to smithereens, the particles in the beam lose their consistency, break apart, and whatever particles are inside are liberated. Soon, high-energy physics branched out to yield accelerator physics, which deals only with the acceleration of particles to extreme speeds and energies.”
“When particles have an electric charge, placing them close to an electric field will either make the particles move toward or away from the field, in the process accelerating them. According to Albert Einstein, nothing can move faster than light (or photons) and so these particles are accelerated to close to 90-95 per cent the speed of light. When they collided at such speeds, the resulting spew of particles is sieved through to find the building blocks of matter.”
Where and how does the Higgs boson appear in this mesh of theories and particles?
“In the 20th century, great physicists like Dirac put together the theory of quantum electrodynamics (QED) to understand how particles and forces work together. QED assumes that particles like electrons have mass and that photons don’t. Subsequently, the question QED asks is why electrons have mass and photons don’t, and why so much mass and not some more or some less.”
“In the zoo of elementary particles—about 50 of them were assumed to exist by the time QED was formulated—a pattern was beginning to emerge when physicists attempted to answer the question. The pattern would eventually become the Standard Model, and in the meantime, physicists Abdus Salam, Steven Weinberg and Sheldon Glashow were awarded the Nobel Prize for their efforts in working the Model out. I knew Prof. Salam personally; now he is no more.”
“The trio’s principle contribution was a framework within which theories could be analyzed to determine how mass is generated. This framework worked with what are now called the Higgs field, the Higgs mechanism and the gauge bosons. The significance of their theory was that all those particles that were hypothesized by them were eventually observed in experimental setups. Everything but the Higgs boson.”
In all mathematical calculations up to this point, most predictions have been hinged on the possible existence of the Higgs boson. Therefore, it became important to look for this particularly.
“While the theory was successful, the significance of ‘sighting’ the particle kept growing. The boson—a moniker named for Satyendra Nath Bose—worked its magic in unseen ways, and that was frustrating. Now, the elementary particles are classified as bosons and fermions. Electrons, protons and neutrons are all fermions, and photons are bosons. The Higgs boson is what is called a scalar boson.”
[All particles have a property called spin that is one of the definers of their state in quantum physics. Fermions have fractional spin, like ½. Bosons, on the other hand, have integer spin, like 1 or 0. Any boson termed scalar will have a spin of 0.]
“Research in physics has revealed that the Higgs boson exists in a ‘rain of energy’, i.e. its energy is in the range of a hundred giga-electron volt (GeV). Once they set about combing for appearances of the Higgs boson in reactions that happened at such an energy level, however, they couldn’t find anything of relevance. In furtherance of this search, the Large Hadron Collider (LHC) was set up at the CERN in Europe. In an experiment conducted in this ultra-precise high-energy accelerator, scientists have claimed today that they have glimpsed the Higgs boson.”
“There is a fascinating correlation between the search for the Higgs boson and the question of why particles have mass, which was brought out by a physicist named Yoichiro Nambu who won the Nobel Prize in physics for it [in 2008]. Nambu’s theory explained the origin of mass using the phenomenon of BCS-superconductivity.”
[Named for John Bardeen, Leon Anderson Cooper and John Robert Schrieffer, the BCS theory explains that superconductivity is the result of electrons, in extremely cold temperatures, condensing into boson-like pairs, called Cooper pairs that cannot be “kicked” by the ambient temperature to resist the flow of electric current.]
“Nambu was inspired by Cooper’s idea of pairing to suggest that the two mechanisms—pair-generation and mass-generation—were similar. This is the beautiful thing about physics: two seemingly unrelated phenomena observed in fields conceptually far-apart will find kinship simply because physics is unbiased and unifying. Anyway, this similarity between the two mechanisms provides an alternate name for the Higgs boson: the Anderson-Higgs boson. Dr. [Phil] Anderson is a renowned man in physics, who currently works at Princeton university, and I have been collaborating with him since 1984.”
What will physics look like if the truth of the Higgs boson is cemented?
“In my opinion, it will only complete a chapter in the history of elementary particle physics and reopen the next chapter for study. Elementary particle physics requires many other theories to become fully explicable like, for instance, supersymmetry. According to supersymmetry—which Abdus Salam was also involved in—every fermion ought to have a boson counterpart. This means that the electron should have a corresponding electronic boson. However, such bosons are yet to be spotted. Their significance arises out of the possibility that such counterpart-bosons could be responsible for determining which particle has how much mass.”
“At the cutting edge of physics research, at which the LHC lies, one of the goals is to find these supersymmetric partners. Another is to find dimensions other than the four we engage with [length, breadth, depth and time]. Some physicists argue that there multi-dimensional systems of the order of 22 dimensions, whose signatures might pop up during experiments at the LHC.”
At the same time, the CERN announcement only claims a possibility of the Higgs boson’s existence, not a certainty. They also haven’t announced what conditions or phenomena will establish such a certainty. Why do you think this is so?
“The Higgs boson is extremely short-lived, i.e. the particle decays before instruments in the detectors can focus on it and record its properties. For example, an electron might escape detection by speeding away, sometimes it might decay under higher energies to smaller particles, but the electron will have remained an electron until the moment it ‘dies’, either by decaying or annihilating in the presence of a positron to yield a gamma ray.”
“An electron’s lifetime is very, very long. The lifetime of a Higgs boson, on the other hand, is very, very low. Therefore, the way to detect a Higgs boson is to look for the presence of its decay signature. A lot of errors can creep into the process of looking for this signature. This is why physicists, who are reluctant to commit that they’ve eliminated all errors, are also reluctant to claim that they’ve found the Higgs boson for sure.”
Interviewer: Dr. G. Baskaran, senior professor, Institute of Mathematical Science, Chennai
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