# The pi+ pi+ scattering length from maximally twisted mass lattice QCD

## TL;DR

This study computes the pion-pion scattering length in the I=2 channel using lattice QCD with twisted mass fermions, extrapolating to physical pion mass and analyzing lattice artifacts.

## Contribution

First lattice QCD calculation of the I=2 pion-pion scattering length using maximally twisted mass fermions with systematic error analysis.

## Key findings

- Scattering length at physical pion mass: m_pi a_pipi(I=2)=-0.04385(28)(38)
- Results consistent with chiral perturbation theory
- Lattice artifacts checked at different lattice spacings

## Abstract

We calculate the s-wave pion-pion scattering length in the isospin I=2 channel in lattice QCD for pion masses ranging from 270 Mev to 485 Mev using two flavors of maximally twisted mass fermions at a lattice spacing of 0.086 fm. Additionally, we check for lattice artifacts with one calculation at a finer lattice spacing of 0.067 fm. We use chiral perturbation theory at next-to-leading order to extrapolate our results. At the physical pion mass, we find m_pi a_pipi(I=2)=-0.04385(28)(38) for the scattering length, where the first error is statistical and the second is our estimate of several systematic effects.