Spinning the Top

Understand

We propose to measure the threshold lepton asymmetry, that is the forward-backward asymmetry of the charged lepton in ttbar events near the production threshold.

• At threshold top quark pairs are produced in an s-wave.
• Angular momentum conservation then implies that the top spins equal the spin of the initial state which - in the case of quarks - is uniquely fixed by the chirality of the initial quarks.
• Thus measuring final state top spins determines the chirality of the quarks which produced them.