New analysis of subthreshold parameters of $\pi \pi $ scattering

Using recent experimental data and lattice calculations of scattering lengths of 𝜋𝜋 scattering and employing dispersive representation of the amplitude based on Roy equations, we compute the subthreshold parameters of this process. We use Monte Carlo sampling to numerically model the probability distribution of the results based on all uncertainties in the inputs. In the second part of the analysis, employing Bayesian inference, we use the new results for the subthreshold parameters to obtain preliminary constraints on the leading order low energy constant 𝐵0 in the context of three-flavour chiral perturbation theory.