In high energy physics, event shapes observables are quantities used to characterize the geometry of the outcome of a collision between high energy particles in a collider. Specifically, event shapes observables quantify the general pattern traced by the trajectories of the particles resulting from the collision.^[1][2]

The most common event shape observables include:

• The sphericity;

• The aplanarity;

• The thrust.

• The C-parameter;

• The jet broadening.