The SLAC Summer Institute
Fred Gilman
Leith Symposium: Physics and Friendships
December 12, 2014
The SLAC Summer Institute
• We owe David Leith for the creation and
success of the SLAC Summer Institute.
• The talks at the 40th Anniversary session at the
2012 SSI provide an excellent view of the
whole history of the SSI, its beginnings,
directors, staff, pictures, all coupled to the
progress of science over those 40 years and
new generations of lecturers and participants.
• I was a lecturer 1973-1975; became a coDirector in 1976 (and occasional speaker); and
in recent years I have been a student.
A Personal View
• I will give a personal view, concentrating on
the SSI’s early years within a broad scientific
context on the one hand, and its special role
for SLAC in that period on the other.
• I will “benefit” from hindsight over many
decades, which can be a big advantage
(or not).
• There is always the pitfall of recalling only
how smart we all (well, almost all) were.
• Nevertheless, I will set the stage from my own
experiences.
A Wonderful “Coincidence”
• The early years of the SSI overlap with the
revolutionary period from the late 1960s to the
late 1970s that took us from the rapid and often
unanticipated discoveries of the 50s and 60s –
with conflicting paradigms contending to
understand a wealth of phenomena – to a
spectacularly simple theory that successfully
represents nature in the domain of energies that
we have been able to probe so far.
My Perspective Pre-Revolution
• As a Princeton grad student “dispersion theory”
was in vogue, and the word “quarks” went
unspoken by the faculty. (1962-1965)
• Arthur Wightman: Can relativistic quantum
field theory be formulated as a mathematically
fully understood theory and represent nature?
• As a Caltech postdoc, the algebra of currents,
abstracted from currents involving quarks, was
at its peak. But one carefully threw away the
quarks, kept the resulting physical currents,
and disavowed real quarks. “Do you mean
concrete quarks made of concrete?”
My Perspective Pre-Revolution II
• At SLAC (1967- ) a more open minded flow of
ideas was in the air as the Linac began
operations. The idea of a “quasi-elastic” peak
in electron-proton inelastic scattering due to
electrons striking the quarks inside the proton
made a prominent appearance in Bjorken’s
1967 Lepton-Photon Symposium talk at SLAC.
I remember this well as Bj’s scientific secretary.
• In 2 years at the Lepton-Photon Symposium
Liverpool, scaling – the consequence of pointlike quarks in the proton, was the centerpiece
and SLAC jumped to the center of HEP.
It Was the Best of Times
• Into this era, the SSI was born in 1973.
• From data on electron, muon, and neutrino
scattering experiments over a large kinematic
range, the picture of quark constituents of the
nucleon quarks had become conclusive.
• The theorists had caught up, with gauge
theories of the electroweak and strong
interactions, plus the understanding of how to
compute their consequences systematically.
• In November 1974, the J/Ψ was discovered,
and …
Other Evidence for Quarks:
A Parallel Piece of the History
• The algebra of currents leads to relations
between amplitudes for π N → N* → π Δ
• David’s group took data for these processes
and analyzed them to provide the amplitudes
for many different N* resonances in the 1970s.
• The relative sign is predicted correctly by the
algebra of currents (or quark models) of ~25
pion and photon amplitudes. The likelihood this
is an accident is extremely small, and gives
strong evidence for quarks. Feynman loved it,
but everyone believed by then anyway.
The SSI in the Best of Times
• As many of the great discoveries occurred at
SLAC, it wasn’t hard to get excellent speakers
for the SSI lectures or topical conference.
• First, concentrate on the 1975 SSI (just before
the Lepton-Photon Symposium), in the middle
of a dizzying pace of discoveries: charmonium
spectroscopy; R is a constant (twice); jets; and
possible evidence of a heavy lepton ( π – μ,
déjà vu), undisguised even with the name U for
“unknown.”
SSI 1975 – The Peak
SSI 1975: Harari
SSI 1975: Jets
Gail Hanson – Quarks Again
SSI 1976 – The Triumph of Charm
• Charmed particles were discovered at SPEAR
during the summer of 1976, in time for the SSI
in mid-August.
• We were treated to excellent lectures on the
“new particles” by Gary Feldman, Dave
Jackson, and David Hitlin, plus the triumphant
talks by Shelly Glashow and Alvaro de Rujula
in the Topical Conference.
SSI 1976: Dave Jackson
SSI 1976: Dave Jackson II
SSI 1976: Alvaro de Rujula
SSI 1977 Preface and Purpose
The Role of the SSI
• The SSI fulfilled the role envisioned for it.
• It went beyond that role by building links in the
world-wide fabric of particle physics.
• Even more important in my view, the SSI
provided a recurring venue for the whole
SLAC science community to interact
informally, to understand the breakthrough
science being produced, and to feel a part of
a great laboratory changing the course of
particle physics. In a way, it continued and
expanded the tradition of talks in Pief’s living
room and feelings of inclusion.
The Role of the SSI (continued)
• Important as well were the social events,
from the opening reception to the informal
buffet dinners, which brought spouses and
families into the tradition.
• Thanks to Doreen and Barbara and our
families and to many other SLAC families.
Conclusion
The SLAC Summer Institute was much more
than an educational effort; it helped make SLAC
a very special place at a magical time, the
coming together of one of the great intellectual
achievements of the 20th century.
Congratulations David, and thanks for the many
years of friendship and our work together.