Physics (Internal)

Factorization at the LHC: From PDFs to Initial State Jets

This event is part of the HET Seminar Series.

Abstract: Measurements at the LHC or Tevatron often impose restrictions on the hadronic final state, e.g. requiring a certain number of jets. These restrictions can probe the proton prior to the hard collision and introduce a scale muB that is parametrically smaller than the hard partonic scale of the collision. Above muB the colliding partons are part of initial state jets and are described by “beam functions,” rather than being part of protons.

I will discuss the field theoretic definition of beam functions, their renormalization group evolution, and an OPE that relates them to PDFs. I will also discuss a new type of inclusive measurement “isolated Drell-Yan” pp —> X l^+ l^{-}, where the observable allows forward radiation but restricts the hadronic final state X to contain no central jets. This isolation can be used to control backgrounds and also provides a means of directly probing initial state radiation and testing initial state parton shower Monte Carlo.