[Jlab-seminars] Theory Center Seminar

[Mary Fox]

Theory Center Seminar
Wed., Feb. 15, 2017
2:00 p.m. (coffee at 1:45 p.m.)
CEBAF Center, Room L102

Eric Moffat
ODU/JLab

*What Are the Low-Q and Large-x Boundaries of Collinear QCD 
Factorization Theorems? *

Familiar factorized descriptions of classic QCD processes such as 
deeply-inelastic scattering (DIS) apply in
the limit of very large hard scales, much larger than nonperturbative 
mass scales and other nonperturbative
physical properties like intrinsic transverse momentum. Since many 
interesting DIS studies occur at kinematic
regions where the hard scale, Q ∼ 1 – 2 GeV, is not very much greater 
than the hadron masses involved, and
the Bjorken scaling variable xbj is large, xbj > 0.5, it is important to 
examine the boundaries of the most basic
factorization assumptions and assess whether improved starting points 
are needed. Using an idealized field-
theoretic model that contains most of the essential elements that a 
factorization derivation must confront,
we retrace the steps of factorization approximations and compare with 
calculations that keep all kinematics
exact. We examine the relative importance of such quantities as the 
target mass, light quark masses, and
intrinsic Parton transverse momentum, and argue that a careful 
accounting of Parton virtuality is essential
for treating power corrections to collinear factorization. Our 
observations motivate searches for new or
enhanced factorization theorems specifically designed to deal with 
moderately low-Q and large-xbj physics.

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