Nuclear Theory/RIKEN Seminar

"Universal Transverse Momentum Dependent Fragmentation"

Presented by Duff Neill, LANL

Friday, March 17, 2017, 2:00 pm — Small Seminar Room, Bldg. 510

Fragmentation is the earliest and perhaps most interesting QCD jet
observable, since it directly deals with the parton-hadron duality at
the end of the QCD cascade. The most basic fragmentation observables
all enjoy the property of being universal, in the sense that a
sufficiently energetic parton that initiates the cascade factorizes
from the rest of the event, so that the underlying soft structure of
the event to a good approximation does not change the fragmentation
spectrum. With the luminosities and resolution of modern detectors, we
can begin to study the fragmentation process in three dimensions: both
the energy spectrum and the transverse fluctuations to the collinear
direction of initiating hard parton. However, when one wants to study
the transverse fluctuations, one becomes very sensitive to the
underlying jet definition, in particular, how the collinear direction
is defined. Intuitive definitions of the jet direction, like the total
momentum of the jet constituents, are inherently sensitive to soft
processes, and can spoil the universality of the spectrum. I will
discuss how a simple change in the jet definition removes this soft
sensitivity, and allows one to study the intrinsic three dimensional
structure of collinear splittings, which should be process
independent.

Hosted by: Heikki Mantysaari

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