[Theory-seminars] Tomorrow 1PM, Room L102, Duff Neill

[Carlota Andres]

Dear all,

Here a reminder about tomorrow’s seminar.

Monday, September 24, 1PM, Room L102
Duff Neill (LANL), "The Entropy of the QCD cascade"

Taking the example of e^+e^- ---> hadrons, I will show how to
calculate the entropy associated with probability distribution for the
fragmentation process in a QCD parton shower, as a function of the
ultra-violet starting scale and the infra-red cutoffs necessary in
perturbation theory. In terms of jet substructure, this entropy can be
thought as a measure of the degeneracy of how an energetic fat jet can
be decomposed into a set of subjets of a specified angular scale and
minimum energy. I will also argue that this entropy, at least to
leading logarithmic accuracy, is the von-Neumann entropy associated to
the reduced density matrix resulting from tracing over all soft and
collinear radiation below the specified cutoffs. In the long time
limit, this soft and collinear radiation serves to decohere the hard
momentum regions (the resolved jets), giving a semi-classical
probability distribution that forms the basis of any Monte Carlo
simulation of the parton shower. I will comment on other proposals for
the entropy of the parton shower, hopefully clarifying apparent
discrepancies in the literature, and finally discuss the implications
for applications of machine learning to jet substructure.

BlueJeans connection: https://bluejeans.com/321085255

Raza, Vincent, Carlota