ATLAS Soared: Fabiola Gianotti and the Discovery of a Higgs Particle (Women In Science 19)
In a corner of a room, tucked unostentatiously away from the notice of the raving hordes of just barely contained school children using their field trip to Berkeley’s Lawrence Hall of Science to wreak havoc, there lies behind glass a hundred year old circular object no bigger than a water canteen. It’s the world’s first cyclotron, held together by wire and wax, and built by Ernest O Lawrence in 1930 for about $25. It is a charming relic of a time when physics experimentalists could still work profitably alone, and the ancestor of today’s multi-billion dollar Large Hadron Collider, maintained and operated by a staff of thousands of scientists and engineers.
We are going to talk about one of the scientists who worked on one of the experiments performed at the LHC. She is Fabiola Gianotti, famous as the spokesperson and coordinator for the ATLAS project which, working in tandem with its competitive sibling, the Compact Muon Solenoid, announced the discovery of a Higgs particle in 2012. ATLAS alone employed three thousand physicists, with about as many on the CMS, each one of whom deserves as much attention and thanks as we can muster as a civilization, but we begin with Gianotti.
If you’ve been reading this series for a while, parts of her early life will sound familiar. Like Ellen Swallow and Rachel Carson, she had an early love of rambling through nature and stopping to wonder about the unique creatures her father would point out to her along the way, but, like Sofia Kovalevskaya and Margaret Mead, this curiosity was balanced by a strong attraction to artistic expression. For Gianotti, that manifested itself in the study of ancient languages, philosophy and, most importantly, music. Trained in piano performance at the Milan Conservatory, she will often end a day of physics and administrative detail by settling down to her piano at home and getting lost for a while in the elegant puzzles of the early nineteenth composers whose music integrated structure and emotion in a way that physicists and mathematicians seem to find particularly intoxicating.
It was not to piano and philosophy that Gianotti would ultimately turn for a career, however, but to physics, a field that seemed to answer the same basic questions brought up by the humanities, but in ways enticingly nuanced and fundamental. Gianotti puts the conversion down to a lecture about Einstein’s explanation of the photoelectric effect. It doesn’t take much imagination to guess why. In late nineteenth century experiments, it had been shown that, by shining light at a metal, you could cause the ejection of electrons but, mysteriously, and against everything people thought they knew, the intensity of the light didn’t seem to matter, but the color did. Super-intense but low frequency light couldn’t budge a single electron, but the faintest glimmer from a high frequency source would lead to ejection. It’s a puzzle that spoke to a fundamental problem with how light was understood, and Einstein’s solution, that light came in packets with energies tied to their frequency, was bold, creative, and genre-defining. How could that not be interesting to an intelligent person with big questions about the universe?
Gianotti earned her PhD in particle physics from the University of Milan, and at the age of 25 began her association with CERN, which at the time was coming off of its massive success in discovering the W and Z bosons. Those particles had been theorized as having a role in the weak interactions whereby protons and neutrons transform into each other, and in the transfer of momentum during particle collisions, and their discovery filled in a massive section of the Standard Model. Gianotti worked at the Large Electron Positron collider during its last years of service before it was removed from its home in 2000 to make way for the Large Hadron Collider. During those years, she conducted research into the possible existence of Supersymmetry.
That’s important to talk about, because the LHC isn’t just a Higgs-finding device. It also has the potential of discovering some of the high-mass supersymmetric particles that various theorists believe explain several of the remaining dilemmas in our picture of the universe. By this model, every fermion (particles that can’t occupy the same place at the same time, like electrons) has an associated supersymmetric boson (particles that can occupy the same place at the same time, like photons), and vice versa. Advocates of the theory point out how some of the proposed superparticles have behavior that fits what we have been measuring about dark matter, and that, if we can probe high enough energies, we could gain insights into the realm of dark matter and therefore spark an exciting new expansion of the Standard Model.
Couple the theoretical existence of high-mass superpartners with the role of the Higgs boson as a possible mediator between standard and dark matter, and it was clear that all of Gianotti’s questions about Life, the Universe, and Everything, pointed to experiments that could at last be done by the proposed Large Hadron Collider. It would be able to crash hadron streams together with enough energy to produce, if only for a moment, rare high mass particles. By the time it was shut down in 2013 for a scheduled upgrade, the LHC was colliding two 4 TeV beams, for a total output of 8 TeV, enough energy concentrated at one point to form massive particles like the Higgs (remember, mass and energy are equivalent, so if you want a big particle, you need to concentrate a lot of energy at a single location – crashing together hadron beams traveling at nearly the speed of light does just that!)
Gianotti worked initially as the physics coordinator at the ATLAS project of the LHC, a five-story tall wonder of engineering that boggles the imagination in just about every respect. One of its purposes was the discovery of Higgs particles which, even if you make them, decay in 1.56 x 10^-22 seconds. So, there is no way you are possibly going to see one directly. All you can see are its products, but catching those possible products amidst the billions upon billions of other particles being shot out by all the other collisions happening requires sensory equipment of untold precision, and data mining algorithms of ruthless speed and efficiency (if you kept ALL the data produced by ATLAS, it would take mere seconds to fill up the most massive data storage centers on Earth).
It was up to the team of three thousand physicists, data experts, and engineers to solve these problems, while at the same time dealing with demands from funding governments, the public at large, and particular alarmists who wanted to shut the entire project down. And it was up to Gianotti upon becoming spokesperson and overall coordinator to balance all of those tensions while keeping the world informed about what was happening. She fielded the endless questions about whether the LHC would create black holes that would destroy the Earth, traveled to explain the work of the device to the press and government, all while still wearing the hat of an experimental physicist.
And that’s precisely why I wanted her to be first in our look at the scientists of CERN, because that balance of administrative, collaborative, public relations, and scientific work is something that everybody engaged in modern physics has to confront as they move from lab drudge to full scientist. Her visible career as ATLAS spokesperson is the career of all scientists, writ large. We have a romantic notion of science as consisting of exciting moments lingering over experimental apparatuses, but the truth is actually more heroic than that. The self-sacrifice of a great mind chained to a mound of paperwork and an endless gamut of departmental meetings, when all it wants to do is find a quiet place and THINK, is palpable, and a little tragic, and should be kept in mind when we talk about the “cushiness” of research positions as against the “hard and tumble” real world.
Those three thousand people, with Gianotti their shield and voice, worked and innovated and struggled and on occasion slept, and within four years had collected enough data to announce the discovery of a Higgs-like particle, and therefore of the associated Higgs field which not only gives mass to the particles that interact with it, but also disturbs the symmetries between particles of the Standard Model, making those particles different, and allowing for the chemistry of our universe to exist as it does.
The Higgs is the last particle required of the Standard Model, but thankfully we are nowhere near done. Two giant problems with the energy of empty space remain to be solved, as does the tremendous issue of dark matter, and when the LHC comes back online in 2015, it will be armed with 13 TeV of energy to probe those corners of reality. Gianotti stepped down from her post as spokesperson in 2013, but one thing is certain. As long as there are new layers of the universe to unveil, and as long as there is Schubert to be played at night to unwind the strands of the day, Gianotti will be there, probing the secrets of nature’s fields with the best products of humanity’s ingenuity, and listening for the electric chirp of discovery.
Fabiola Gianotti was a finalist for Time’s Person of the Year, and their article on her can be found here . You can find a 2010 interview she gave on the questions ATLAS was investigating here, and a really cool write-up of her lifestyle and work here. For the issues of particle physics that she is investigating, a great introduction is The Particle at the End of the Universe by Sean Carroll. It presents the importance of the Higgs field, as well as of field theory in general, with some great intuitive examples that bypass the messy math involved. If you LIKE messy math, however, Halzen and Martin’s Quarks and Leptons: An Introductory Course in Modern Particle Physics will give you just about whatever you’re looking for.