We propose the addition of a new "soft-collinear" mode to soft collinear effective theory (SCET) below the usual soft scale to factorize and resum logarithms of jet radii R in jet cross sections. We consider exclusive 2-jet cross sections in e+e− collisions with an energy veto Λ on additional jets. The key observation is that there are actually two pairs of energy scales whose ratio is R
Nearby in the stack
: the transverse momentum
QR
of the energetic particles inside jets and their total energy
Q
, and the transverse momentum
ΛR
of soft particles that are cut out of the jet cones and their energy
Λ
. The soft-collinear mode is necessary to factorize and resum logarithms of the latter hierarchy. We show how this factorization occurs in the jet thrust cross section for cone and
kT
-type algorithms at
O(αs)
and using the thrust cone algorithm at
O(αs2)
. We identify the presence of hard-collinear, in-jet soft, global (veto) soft, and soft-collinear modes in the jet thrust cross section. We also observe here that the in-jet soft modes measured with thrust are actually the "csoft" modes of the theory SCET
+
. We dub the new theory with both csoft and soft-collinear modes SCET
++
. We go on to explain the relation between the "unmeasured" jet function appearing in total exclusive jet cross sections and the hard-collinear and csoft functions in measured jet thrust cross sections. We do not resum logs that are non-global in origin, arising from the ratio of the scales of soft radiation whose thrust is measured at
Qτ/R
and of the soft-collinear radiation at
2ΛR
. Their resummation would require the introduction of additional operators beyond those we consider here. The steps we outline here are a necessary part of summing logs of
R
that are global in nature and have not been factorized and resummed beyond leading-log level previously.