- Staley, Kent W.
The Evidence for the Top Quark.
Cambridge: Cambridge University Press, 2004.
ISBN 0-521-82710-8.
-
A great deal of nonsense and intellectual nihilism has been committed
in the name of “science studies”. Here, however, is an
exemplary volume which shows not only how the process of
scientific investigation should be studied, but also why.
The work is based on the author's dissertation in philosophy, which
explored the process leading to the September 1994 publication of the
“Evidence for top
quark production in
pp
collisions at
√s = 1.8 TeV”
paper in Physical Review D. This paper is a
quintessential example of Big Science: more than four hundred
authors, sixty pages of intricate argumentation from data produced
by a detector weighing more than two thousand tons, and automated examination of
millions and millions of collisions between protons and antiprotons
accelerated to almost the speed of light by the
Tevatron,
all to search, over a period of months, for an elementary particle
which cannot be observed in isolation, and finally reporting
“evidence” for its existence (but not
“discovery” or “observation”) based on a total
of just twelve events “tagged” by three different
algorithms, when a total of about 5.7 events would have been expected
due to other causes (“background”) purely by chance alone.
Through extensive scrutiny of contemporary documents and interviews
with participants in the collaboration which performed the experiment,
the author provides a superb insight into how science on this scale is
done, and the process by which the various kinds of expertise
distributed throughout a large collaboration come together to arrive at
the consensus they have found something worthy of publication. He
explores the controversies about the paper both within the
collaboration and subsequent to its publication, and evaluates claims
that choices made by the experimenters may have a produced a bias in
the results, and/or that choosing experimental “cuts”
after having seen data from the detector might constitute
“tuning on the signal”: physicist-speak for choosing the
criteria for experimental success after having seen the results from
the experiment, a violation of the “predesignation”
principle usually assumed in statistical tests.
In the final two, more philosophical, chapters, the author introduces
the concept of “Error-Statistical Evidence”, and evaluates
the analysis in the “Evidence” paper in those terms,
concluding that despite all the doubt and controversy, the decision
making process was, in the end, ultimately objective. (And, of course,
subsequent experimentation has shown the information reported in the
Evidence paper to be have been essentially correct.)
Popular accounts of high energy physics sometimes gloss over the
fantastically complicated and messy observations which go into a
reported result to such an extent you might think experimenters are
just waiting around looking at a screen waiting for a little ball to
pop out with a “t” or whatever stencilled on the side.
This book reveals the subtlety of the actual data from these
experiments, and the intricate chain of reasoning from the
multitudinous electronic signals issuing from a particle detector to
the claim of having discovered a new particle. This is not, however,
remotely a work of popularisation. While attempting to make the
physics accessible to philosophers of science and the philosophy
comprehensible to physicists, each will find the portions outside
their own speciality tough going. A reader without a basic
understanding of the standard model of particle physics and the
principles of statistical hypothesis testing will probably end up
bewildered and may not make it to the end, but those who do will be
rewarded with a detailed understanding of high energy particle physics
experiments and the operation of large collaborations of researchers
which is difficult to obtain anywhere else.
August 2006 