Speaker
Description
I will discuss a new class of non-global observables defined by a veto on transverse-energy ($E_T$) flow inside an azimuthal interval $\Delta\phi$ about a chosen reference axis. Such vetoes are widely used in LHC measurements involving missing transverse momentum, yet they probe a kinematic regime whose logarithmic structure has not been explored before. We show that these observables exhibit logarithms more singular than any previously reported: both non-global logarithms (NGLs) and coherence-violating logarithms (CVLs) acquire an extra power of the large logarithm relative to standard non-global observables. I will focus on the CVL sector---computing the leading coherence-violating contribution and showing that it is enhanced from NDL to NNDL accuracy---which makes this observable an unusually sensitive probe of collinear-factorization breaking at hadron colliders. Capturing these enhanced CVLs requires resummation techniques beyond the standard non-global toolkit, which I will discuss. I will also summarize the all-orders analysis for $pp$ collisions, including analytical resummation at next-to-double-logarithmic accuracy and numerical leading-logarithmic resummation in the Veneziano limit.