Subleading power corrections for event shape variables in e + e - annihilation.

We consider subleading power corrections to event shape variables in e + e - collisions at the first order in the QCD coupling α S . We start from the jettiness variable τ 2 and the y 23 resolution variable for the k T jet clustering algorithm and we analytically compute the corresponding cumulative cross section. We investigate the origin of the different power suppressed contributions in the two-jet limit and trace it back to their different coverage of the phase space. We extend our analysis to the case of thrust and of the C -parameter, and we finally discuss a class of observables that depend on a continuous parameter giving different weight to central and forward emissions and we evaluate the corresponding subleading power corrections.