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SUMMARY:Glauber Gluons and Multiple Parton Interactions - Jonathan Gaunt (
 DESY Hamburg)
DTSTART:20140926T150000Z
DTEND:20140926T160000Z
UID:TALK54474@talks.cam.ac.uk
CONTACT:Damien George
DESCRIPTION:I show that for hadronic transverse energy E_T in hadron-hadro
 n collisions\, the classic Collins-Soper-Sterman (CSS) argument for the ca
 ncellation of Glauber gluons breaks down at the level of two Glauber gluon
 s exchanged between the spectators. Through an argument that relates the d
 iagrams with these Glauber gluons to events containing additional soft sca
 tterings\, I suggest that this failure of the CSS cancellation actually co
 rresponds to a failure of the `standard' factorisation formula with hard\,
  soft and collinear functions to describe E_T at leading power. This is be
 cause the observable receives a leading power contribution from multiple p
 arton interaction (or spectator-spectator Glauber) processes. I also sugge
 st that the same argument can be used to show that a whole class of observ
 ables\, which we refer to as MPI sensitive observables\, do not obey the s
 tandard factorisation at leading power. MPI sensitive observables are obse
 rvables whose distributions in hadron-hadron collisions are disrupted stro
 ngly by the presence of multiple parton interactions (MPI) in the event. E
 xamples of further MPI sensitive observables include the beam thrust and t
 ransverse thrust.
LOCATION:Seminar Room B\, Rutherford Building\, Cavendish Laboratory
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