## Friday, December 23, 2016

### Sidney Drell: 1926-2016

Stanford News and The New York Times brought us sad news yesterday. Sidney Drell died at home in Palo Alto (the town around Stanford) on Wednesday, December 21st, at age of 90.3.

The information was confirmed by his daughter Persis Drell, also a particle physicist and recently the director of SLAC (Sidney Drell has only been a deputy director of SLAC in his life). One more daughter and one son survived him, along with three grandkids.

I am old enough to remember his name primarily for the Bjorken-Drell textbook of quantum field theory. They wrote Relativistic Quantum Mechanics and Relativistic Quantum Fields. The QFT textbook played the same role that was probably played by Peskin-Schroeder in the following decades. Its influence was huge. Among other things, the mostly minus convention for the metric has also been known as the Bjorken-Drell convention. That's a way to say that they basically defined the mainstream in particle physics.

Note that the first edition of Peskin-Schroeder appeared in October 1995, more than five years after I started to study QFT, so it's clear that I had to be led to an older text like Bjorken-Drell.

I remember that I was intrigued by the idea that the Bjorken-Drell textbook really explained everything I needed to fully describe both wave-like and particle-like properties of the electromagnetic field. But it took me some time to see through all the equations that looked complicated – to figure out that the quantum field with the "same" Hamiltonian that we know as the total energy of the field in classical electrodynamics is rewritten as a higher-dimensional harmonic oscillator which may be quantized into photons. This point is really so simple and the book made it look so hard (when I was about 16) so I tend to think that books have gotten more pedagogically edible.

Although it was my first QFT textbook I studied, I switched to other books, like Ramond's, rather early so I don't even remember whether Bjorken-Drell included a systematic treatment of the Feynman diagrams (my guess would be No). But I am sure that the strong and weak interactions are covered in a way that is hopelessly outdated today.

But the books with Bjorken (a key guy behind our understanding of the deep inelastic scattering) are very far from Drell's only achievements, of course. His name is often used in the Drell-Yan process, the annihilation of a quark-antiquark pair from two hadrons to a lepton-antilepton pair through a neutral intermediate boson (Z or photon).

Sidney Drell was born in 1926 in Atlantic City, New Jersey, to Russia Jewish emigrants (dad was a pharmacist and mother was a teacher). He got his degrees from Princeton (where he was admitted at age of 16) and University of Illinois and quickly began to work for the U.S. government. He defended nuclear deterrence. These days, Donald Trump and Vladimir Putin announced that they want to revive nuclear arms races which must be a lot of fun and that's what Drell was defending during the cold war, too. A superpower must be able to show its muscles. He was an important policymaker under Johnson and Nixon (so he was bipartisan, as you can see) and a shadow adviser to Kissinger.

(Fred Singer is telling me that he, Fred, taught Drell as the instructor of a lab course when Drell was a senior at Princeton. Drell sometimes joked that it was this lab course that decided that Drell had to become a theorist. C.S.Wu supervised those courses but she wasn't a professor due to her being she. She was lucky to be allowed in – women were somewhat reasonably considered distractions by Princeton up to the 1950s and couldn't easily enter the physics building.)

However, later, Drell would denounce Reagan's Star Wars and he also led the efforts to reduce the nuclear weapons, as agreed by Reagan and Gorbachev (I guess that you must have heard some of the politicians' names that surrounded Drell all the time), and even more recently, he reasonably argued (like others) that Islamic terrorists don't care about their destruction so deterrence no longer works and the nuclear weapons are useless in that context.

Google Scholar offers 1450 papers with the name "Sidney Drell", starting from the books cited 5,000 and 3,000 times, and some five papers usually with Yan with 500-1,000 citations. Basically all his papers may be considered applications of quantum electrodynamics (QED) or aspects of QCD and lattice QCD where he focused on the electromagnetic part of the interactions, too.

Sidney Drell has been a member of NAS, AAAS, won the Fermi award in 2000, the National Medal of Science from Obama in 2013 (picture at the top).

R.I.P., Prof Drell.