February 21, 2013
Deep Science For Everyone: Higgs Boson
On a cold February night, about 100 people braved the weather and the icy mountain roads to attend a lecture in Lead, SD. “Deep Science for Everyone: In Search of the Higgs boson” was an hour of heavy science, good food, and laughter in the Historic Homestake Opera House.
The lecture was part of the Deep Science for Everyone lecture series presented by the Sanford Underground Research Facility. Sanford is a National Laboratory located deep inside the Homestake gold mine. The purpose of the series is to bring cutting-edge, highly theoretical science out into the light and make it accessible to the general public.
With a cash bar, two tables of hors d’oeuvres and a table of desserts, the mood was light and engaging inside the Opera House, despite the 12-degree weather outside and the thick layers of ice on the side streets. The location was intriguing by itself. Built in 1914 by the Homestake Gold Mine as a resource for the mineworkers and their families, the Opera House has been a center of life in the Deadwood / Lead area for nearly a century. At one time, 20,000 people a month attended performances of touring opera singers, vaudeville acts, ballets, stage plays and boxing matches. But that’s not all the Opera House had to offer. The “Jewel of the Black Hills” had a heated swimming pool, a six-lane bowling alley, a billiard hall, a library, and was a movie house in the 30’s and 40’s. There was a fire in 1984 that caused extensive damage that is still under repair today. The stage behind Dr. Heinemann had elaborate trim work that was soot scarred, and the walls around the stage were bare brick with obvious scorch marks. It added a layer of ambience to the lecture that would not have been afforded in a more modern space.
The lecture on February 12 was a celebration of the fact that scientists at the Large Hadron Collider (LHC) at CERN, located on the Franco-Swiss border, just might have discovered the Higgs boson, perhaps the most elusive particle theorized to date. Physicist Beate Heinemann of the University of California, Berkeley is a member of the ATLAS collaboration at the LHC, searching for proof of the Higgs boson, extra-spatial dimensions, and the particles of dark matter. Heinemann’s lecture explained the basic workings of the LHC, the construction of the ATLAS detector, the theories of the Higgs field and boson, and the discovery of what she calls the “Higgs-like” boson last year.
Particle physics got its start around 300 B.C. when Democritus developed a theory that the universe consists of empty space and invisible particles, called atoms. These particles differed from each other in form, position, and arrangement. Democritus and his colleagues thought the atom was indivisible, but we know differently now. In 1874, George Stoney put the theory of the electron forth, and Joseph Thompson measured the electron in 1898. The electron is a smaller particle making up part of the atom. Quantum physics gets its start with Max Planck and Albert Einstein in the early 1900’s, and the race to identify the different particles was on.
Heinemann demonstrated that currently, there are 12 fundamental particles that have been discovered. There are six “flavors” of quarks: up, down, strange, charm, bottom and top; along with six “flavors” of leptons; electrons, muons, tau, electron neutrinos, muon neutrinos, and tau neutrinos. According to Heinemann, almost all of life is made up of the up and down quarks and the electron.
The LHC is a 17-mile circumference particle accelerator that straddles the border of Switzerland and France. Basically, think of it as a giant superconducting magnetized tube, buried 100 meters underground, with six experiment stations along the way; ALICE, ATLAS, CMS, LHCb, TOTEM, and LHCf. Each station has a collaboration of scientists. According to Heinemann, for example, there are 3000 scientists from 38 countries working on ATLAS alone. Heinemann joked that 1,000 of those scientists are students, who “do most of the work.” The collider works on Einstein’s iconic equation, E=mc2, where E is the energy released by the collision which equals the mass (m) of the particles colliding at twice the speed of light (c).
Approximately 1 billion protons a second fly at nearly the speed of light in both directions along the tube, and their collisions and interactions are studied at each of the different experiment stations.
Of those billion collisions a second, only about 400 are “interesting” and worth studying. Out of those 400, 1 in 50 results in a “Higgs” boson. Now, the scientists aren’t saying conclusively that they have discovered the boson, because they still have more tests to run. But the likelihood that the detection is simply due to random fluctuations currently stands at about 1 in 100 billion – a clear indication that the signal found at the LHC is most likely due to the Higgs.
So, what is the Higgs boson? In order to understand this mysterious particle, we first must examine what is known as the Higgs field. We know that there are fields that permeate the Universe that interact with particles in nature in various ways. In fact, we explain the propagation of light and the effect of gravity as interactions with specific fields. Just about the only aspect of particles we haven’t been able to explain at all, is mass. This is where the Higgs field comes in. In 1964, Peter Higgs theorized a field that permeates all matter, and imparts mass. Depending on how a particle interacts as it moves through the field, that’s how much mass the particle has. Heinemann explained this with what she called the “celebrity effect.”
Imagine a large, boring cocktail party, full of equally boring people. It would be easy for most people to move through this room without attracting much attention, because everyone is equally boring. Now, if this was a cocktail party full of boring music enthusiasts and Lady Gaga walked into the room, she would quickly gather a following. This gathering of boring cocktail goers would grow to the point that Lady Gaga would find it extremely difficult to move through the room. She has gained “mass.” Massless particles, such as photons and gravitrons – a theoretical particle thought to impart the gravitational force – have no interaction at all with the Higgs field and can therefore move at the speed of light. Other particles slow down as they interact, like the top quark, which has the mass of a gold atom.
Each field has a quantum, or measurable amount of physical interaction. For the electromagnetic field, this quantum is a photon. For the Higgs field, the quantum is the boson. The Higgs boson isn’t quite a particle, and it isn’t quite a force like gravity. It is, to try to put it simply, the physical manifestation of the interaction of particles with the invisible Higgs field. A boson is a force carrier “particle.”
Heinemann explained the Standard Model, which is the model we use to explain these forces and fields. First, she apologized for the “very imaginative” name of the model. (I did mention the laughter at this lecture, yes?) According to the model, there are four fundamental forces in the universe, with different ranges and strengths. Gravity has the biggest range, and yet the weakest strength. Electromagnetic force is many times stronger than gravity, and has just as great a range. The strong and weak forces have very short ranges, affecting things only on a subatomic level. Even so, the weak force is much stronger than gravity, and the strong force is the strongest of the four. Each force has its own quanta or carrier particle. Now, the limitation of the Standard Model is that it only incorporates three of the four forces, leaving out gravity.
In 1948, Nobel Prize winning physicist Richard Feynman invented a series of diagrams to represent the mathematical expressions that describe the behavior of the subatomic particles. Heinemann showed many of these diagrams as she explained the forces and particles. When Higgs theorized the boson in 1964, he did so using Feynman’s diagrams and the Standard Model. The truly exciting news from ATLAS and CMS last year is that the “Higgs-like” particles they are observing fit these diagrams almost as if designed that way. When Heinemann displayed the original diagrams and the plot of the datum ATLAS and CMS had accumulated, the deviations were imperceptible.
The question and answer session after the organized lecture was probably the best part of the whole night. The audience was made up of everything from particle and string physicists to chemists, to schoolteachers and folks who just “lived up the street.” Heinemann entertained questions from them all. One chemist asked Heinemann to explain the collisions of protons in the LHC in terms of car collisions, a concept she could understand. Heinemann told us that the 400 or so “interesting” collisions were like head on, full force collisions, generating a great deal of energy. The other nearly billion collisions were some variation of a side swipe, creating some energy but not enough to cause interesting and study-worthy interactions. The best question of the night, however, was one that stumped Heinemann, Dr. Kevin Lesko and a couple of other physicists. One audience member asked Heinemann to explain the correlation between the Higgs field, thought to permeate everything and the older physics theory of “the ether.” Her final explanation was very well delivered and informative, but the part I enjoyed was watching three physicists put their heads together to “group think” what the ether theory had been. It was so far behind where they thought on a daily basis, and so far out of favor, that it took three of them to remember all the bits and pieces to be able to answer the question.
Heinemann explained some of the upcoming research expected to happen at the LHC. They have shut down operations until 2015 to have time to do maintenance and upgrades of several key components. The collider currently operates at an energy level of 8 TeV (teraelectron volts), but when it restarts, the output will be nearly 14 TeV – the upper limit of the current design, allowing for many different observations to be made. A few things that she mentioned as possible avenues of research were dark matter, super symmetry, and extra-spatial dimensions. Heinemann admitted, to a great deal of laughter, that the idea of extra-spatial dimensions was “far out string theory” and not something she could easily wrap her head around. I have to admit, I was picturing Sheldon Cooper from The Big Bang Theory trying to explain the string theory concept of tiny little dimensions coinciding with ours.
In the past year, ATLAS alone has published over 123 papers, 65 of which were on new physics being discovered or theorized as a result of their data collection.
Image Credit: Photos.com