Q&A: Tommaso Dorigo on the dynamics of physics collaborations

For nearly a quarter century, the top quark was the most sought-after particle in physics. First predicted in 1973, the most massive of the six theorized quarks eluded detection for decades, causing consternation in the particle-physics community. Finally, in 1995, two collaborations working with data from Fermilab’s Tevatron collider jointly published the top quark’s detection.

Particle physicist and science blogger Tommaso Dorigo had a front-row seat to the top quark discovery. Dorigo first visited Fermilab as an undergraduate and later became a member of the Collider Detector at Fermilab (CDF) collaboration. Dorigo’s new book, Anomaly! Collider Physics and the Quest for New Phenomena at Fermilab, chronicles his experiences there and seeks to give readers an insider’s view of how particle physicists work and think. In the November issue of Physics Today, reviewer Kent Staley says that Dorigo “provides an engaging and insightful perspective on the pursuit of physics discoveries at CDF.”

Physics Today recently caught up with Dorigo to talk about Fermilab, life in a large collaboration, and the post-Higgs era for particle physics.

PT: Tell us a bit about your career. How did you begin working at Fermilab? Which projects and investigations were you most involved with?

DORIGO: I first visited Fermilab for three months in 1992 as a summer student. My project, which later became my undergraduate thesis at the University of Padova, was the search for pairs of top quarks in a final state with no leptons. Such an effort was then thought hopeless, ridden as it was with large backgrounds. It was a challenge worth taking, as we eventually published a first observation of that decay in 1997. After 1992 I continued to visit Fermilab many times a year, first as a PhD student, then as a Harvard postdoctoral student, and later as a researcher with my current institution, the Italian National Institute for Nuclear Physics.

After the discovery of the top quark, I split my time between the upgrade of the muon system of the CDF detector and many analysis activities—most notably, the study of hadronic jet reconstruction with the goal of improving the chances of finding the Higgs boson, another “hopeless” challenge. You know how that story ended. The Higgs was discovered by the CMS [Compact Muon Solenoid] and ATLAS [A Toroidal LHC Apparatus] experiments [at CERN] in 2012, at a time when their Tevatron competitors were just squeezing out evidence of the same particle in their data. But by then I had been also serving as a member of the CMS experiment for many years, so the discovery of the Higgs did not escape me. It was a two-horse race where I was sitting in both saddles.

PT: What was the most surprising or challenging thing about working in a large collaboration like CDF?

DORIGO: Back in those years, CDF looked like a large collaboration, yet now CMS and ATLAS have an order of magnitude more collaborators. This makes a tremendous difference, as there is no chance that decisions can be made by sitting in the same room and arguing until exhaustion. In CDF that was still possible, and it was challenging, surprising, and exciting. You could feel that your opinion counted—if it had scientific merit—and was considered with care by your colleagues, regardless of your academic title. It was an amazingly open environment where an undergraduate could take a seat around a table and sit elbow to elbow with the biggest shots in the field and still feel at ease. I learned things at the speed of light there. I am especially grateful to some of the old masters in CDF for the knowledge I absorbed there, most of all Giorgio Bellettini, who at more than 80 years of age is still the spokesperson for that glorious experiment.

PT: What inspired you to write a book about your experiences at Fermilab?

DORIGO: I have always thought that the sociological aspects of the way the CDF experiment operated were unique and worth recounting to those outside the collaboration. I also believe that the story of the way cutting-edge science was performed at Fermilab needed to be told. As a particle-physics blogger, I understood long ago that there is a demand for information about how particle physics is really done―and I also saw that my colleagues can get quite annoyed if you let outsiders peek inside those decision processes. But those processes are of paramount interest.

For example, large collaborations support the invaluable merits of peer review in the production of scientific results. Yet the peer review that large physics collaborations get when they submit a result for publication is irrelevant—a pair of external reviewers will never be able to scrutinize those analyses as deeply as needed. Instead, collaborations employ an internal review process to verify the quality of the work. That process is correctly unforgiving but unfortunately also sometimes brutal. In exceptional cases, it gets to the point of hampering the open sharing of information among scientists.

The fact that this internal scrutiny is never explained to the public, and its proceedings are not made accessible in any way after an article is published, should be a concern for the field. Some articles from CDF were published despite criticism from a minority of the collaborators. Those criticisms were never made public, but if they had been, the conclusions of the article would have been taken with more skepticism.

So I wrote my book. I took care to follow the old adage “If you’re going to tell people the truth, be funny or they’ll kill you.” That was easy, as CDF history is full of funny anecdotes to tell.

PT: Now that the Higgs boson has been detected, what do you think will come next for particle physics?

DORIGO: I am by nature an informed pessimist. Eleven years ago I wagered $1000 that the LHC [CERN’s Large Hadron Collider] would discover the Higgs boson but find no new physics. This was at a time when 90% of my colleagues thought otherwise. Now most of them have grown wiser. I do not say this to be self-congratulatory, however. Mine was a sort of insurance bet, one that I would have been deliriously happy to lose. Yet I did win it. And I would wager that $1000 again. While there are reasons to believe that our understanding of fundamental physics is incomplete, we have really no clue what the missing pieces might be, nor where and how they could show up.

So particle physics today is in a difficult situation. With the LHC reaching maturity, this would be the right time to plan for the next big machine, which could enable us to investigate more deeply into the structure of matter. But we have little in terms of hints that we might find something worth the effort. So as a pessimist I think that we are not headed to a new big discovery anytime soon. With multimessenger astrophysics now proving to be such an exciting new way to study fundamental physics and the origin and composition of the universe, maybe one could argue that society should invest more in that direction.

PT: What’s next for Fermilab, given that the Tevatron collider has been inactive since 2011?

DORIGO: Particle physics in the US is also in a difficult situation. The 1993 decision to cancel the Superconducting Super Collider—a collider larger and more powerful than the LHC—is still making itself felt today.

Since the demise of the Tevatron, Fermilab has wisely turned to the thriving field of neutrino physics, as well as to a number of other projects that do excellent science. Yet let’s not forget that a large number of Fermilab scientists are heavily involved in the LHC experiments and will be main players in whatever new project comes about at the next big machine.

PT: What are you reading right now?

DORIGO: Nothing! That is, there’s a pile of books resting on my bedside table, but they have languished there for a while now. Since I am always enthralled by explaining physics with easy-to-grasp, descriptive analogies, I am trying to finish the book L’Analogie: Coeur de la Pensée by Douglas Hofstadter and Emmanuel Sander. It is an amazingly interesting work, but I’m processing it quite slowly, partly because it’s in French, a language I have not mastered.