A Subleading Power Operator Basis for the Scalar Quark Current

Understand

Factorization theorems play a crucial role in our understanding of the strong interaction.

• For collider processes they are typically formulated at leading power and much less is known about power corrections in the $\lambda\ll 1$ expansion.
• Here we present a complete basis of power suppressed operators for a scalar quark current at $\mathcal{O}(\lambda^2)$ in the amplitude level power expansion in the Soft Collinear Effective Theory, demonstrating that helicity selection rules significantly simplify the construction.
• This basis applies for the production of any color singlet scalar in $q\bar{q}$ annihilation (such as $b \bar b \to H$).