# On HQET and NRQCD Operators of Dimension 8 and Above

## TL;DR

This paper introduces a systematic method for constructing higher-dimensional operators in HQET and NRQCD, facilitating the inclusion of effects necessary for high-precision experimental analyses.

## Contribution

It provides a general, easy-to-use approach for building operators with two heavy or non-relativistic fields and multiple derivatives, and applies it to list terms in the $1/M^4$ NRQCD Lagrangian.

## Key findings

- List of $1/M^4$ NRQCD operators provided
- Method simplifies higher-dimensional operator construction
- Enhances precision in effective field theory calculations

## Abstract

Effective field theories such as Heavy Quark Effective Theory (HQET) and Non Relativistic Quantum Chromo-(Electro-) dynamics NRQCD (NRQED) are indispensable tools in controlling the effects of the strong interaction. The increasing experimental precision requires the knowledge of higher dimensional operators. We present a general method that allows for an easy construction of HQET or NRQCD (NRQED) operators that contain two heavy quark or non-relativistic fields and any number of covariant derivatives. As an application of our method, we list these terms in the $1/M^4$ NRQCD Lagrangian, where $M$ is the mass of of the spin-half field.