
We analyze oriented eventshapes in the context of SoftCollinear Effective Theory (SCET) and in fixedorder perturbation theory. Oriented eventshapes are distributions of eventshape variables which are differential on the angle theta(T) that the thrust axis forms with the electronpositron beam. We show that at any order in perturbation theory and for any event shape, only two angular structures can appear: F0 = 3/8 (1+cos(2) theta(T)) and F1 = (1 ¿ 3 cos(2) theta(T)). When integrating over theta(T) to recover the more familiar eventshape distributions, only F0 survives. The validity of our proof goes beyond perturbation theory, and hence only these two structures are present at the hadron level. The proof also carries over massive particles. Using SCET techniques we show that singular terms can only arise in the F0 term. Since only the hard function is sensitive to the orientation of the thrust axis, this statement applies also for recoilsensitive variables such as Jet Broadening. We show how to carry out resummation of the singular terms at (NLL)L3 for Thrust, HeavyJet Mass, the sum of the Hemisphere Masses and Cparameter by using existing computations in SCET. We also compute the fixedorder distributions for these eventshapes at O(alpha(S)) analytically and at O(alpha(2)(S)) with the program Event2.
