Evolution of parton showers and parton distribution functions

Understand

Initial state evolution in parton shower event generators involves parton distribution functions.

• We examine the probability for the system to evolve from a higher scale to a lower scale without an initial state splitting.
• A simple argument suggests that this probability, when multiplied by the ratio of the parton distributions at the two scales, should be independent of the parton distribution functions.
• We call this the PDF property.