Constraining new physics from Higgs measurements with Lilith-2

TL;DR

Lilith-2 is an updated Python library that enhances the analysis of Higgs measurements by incorporating detailed likelihoods, correlations, and uncertainties, enabling more precise constraints on new physics models.

Contribution

The paper introduces Lilith-2 with an extensive database and advanced likelihood treatment, improving the accuracy of Higgs data analysis for new physics constraints.

Findings

Validated the new likelihood implementations against experimental results.

Demonstrated the impact of correlations and uncertainties on global fits.

Enabled constraints on various new physics scenarios like 2HDMs and invisible decays.

Abstract

Lilith is a public Python library for constraining new physics from Higgs signal strength measurements. Version 2.0 of Lilith comes with an extensive XML database which includes the ATLAS and CMS Run 2 Higgs results for 36/fb, in addition the the Run 1 results. Both the code and the database were extended from the ordinary Gaussian approximation employed in Lilith-1.1 to using variable Gaussian and Poisson likelihoods. Moreover, Lilith-2 can make use of correlation matrices of arbitrary dimension. We will report on these novelties and ongoing developments. The importance of how correlations and uncertainties are treated will be demonstrated by means of detailed validations of the implemented experimental results. Moreover, we show the effects for global fits of reduced Higgs couplings, 2HDMs of Type I and Type II, and invisible Higgs decays. The program is publicly available on GitHub and can be used to constrain a wide class of new physics scenarios.