Nonrelativistic effective field theory of unstable top

Understand

We develop a new nonrelativistic effective field theory of $\rho$NRQCD [1] to describe the finite lifetime effects in the threshold production of top quark-antiquark pairs.

• The theory is based on the expansion in a parameter $\rho=1-m_W/m_t$ characterizing the dynamics of the top-quark decay.
• Within this framework we compute the nonresonant contribution to the total cross section of the top quark-antiquark threshold production in electron-positron annihilation up to the next-to-next-to-leading order.
• Our method naturally resolves the problem of spurious divergences in the analysis of the unstable top production.