Speaker
Description
Every measurement in particle physics is shaped as much by what
escapes detection as by what is recorded. Soft gluons and photons can
go unseen, but they leave a universal imprint on the theoretical
predictions for almost all observables at the Large Hadron Collider
(LHC), for example. I will discuss how far this universality extends,
from the classic "soft theorems" to regions where the radiation begins
to resolve the structure of the underlying hard process, and what this
means for precision predictions at the LHC. Color, never observed
directly, decides how heavy quarks bind into quarkonia. And particles
that leave no trace at all may reveal the nature of dark matter
through the energy they carry away. Along the way I reflect on what we
learn from both seeing and not seeing, a question that has run through
Michael Krämer's work for three decades.