Ellis-Karliner angle

In physics, the Ellis-Karliner angle is kinematical angle between the highest energy jets in a three jet event. [J. Ellis and I. Karliner, Nucl. Phys. B148 141, (1979).] The angle is not measured in the lab frame, but in a frame boosted along the energy of the highest energy jet so that the second and third jets are back-to-back. By measuring the distribution of the Ellis-Karliner angle at linear colliders, physicists determined that the gluon has spin one rather than spin zero or spin two. [R. Brandelik "et al.", TASSO Collaboration, Phys. Lett. B97 453 (1980).] [C. Berger "et al.", PLUTO Collaboration, Phys. Lett. B97 459 (1980).]

There is an analogous angle in four jet events called the Bengtsson-Zerwas angle that was used to measure the self-interaction of gluons.

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