Speaker
Description
In this talk, I will discuss a class of non-global observables in which transverse-energy flow is vetoed inside an azimuthal interval $\Delta\phi$ defined with respect to a suitable reference axis. Such vetoes are widely used in measurements involving missing transverse momentum at the LHC and probe a kinematic regime that has not previously been explored. We show that these observables exhibit novel logarithmic structures: both non-global logarithms (NGLs) and coherence-violating logarithms (CVLs) acquire an additional power of the large logarithm $L$, making them more singular than in standard non-global observables. This enhancement can be traced to the large rapidity range spanned by the veto region, connecting the azimuthal-veto observable to a broader class of observables involving large rapidity gaps. For $pp$ collisions, I will discuss the all-orders logarithmic structure, including analytical resummation at next-to-double-logarithmic accuracy (NDL) and numerical leading-logarithmic (LL) resummation in the large-$N_c$ limit. I will also discuss the enhanced CVLs, their connection to large rapidity gaps, and the implications for their resummation and for probing collinear-factorization breaking at hadron colliders.