HiggsSignals: Confronting arbitrary Higgs sectors with measurements at the Tevatron and the LHC

Abstract: HiggsSignals is a Fortran90 computer code that allows to test the compatibility of Higgs sector predictions against Higgs rates and masses measured at the LHC or the Tevatron. Arbitrary models with any number of Higgs bosons can be investigated using a model-independent input scheme based on HiggsBounds. The test is based on the calculation of a chi-squared measure from the predictions and the measured Higgs rates and masses, with the ability of fully taking into account systematics and correlations for the signal rate predictions, luminosity and Higgs mass predictions. It features two complementary methods for the test. First, the peak-centered method, in which each observable is defined by a Higgs signal rate measured at a specific hypothetical Higgs mass, corresponding to a tentative Higgs signal. Second, the mass-centered method, where the test is evaluated by comparing the signal rate measurement to the theory prediction at the Higgs mass predicted by the model. The program allows for the simultaneous use of both methods, which is useful in testing models with multiple Higgs bosons. The code automatically combines the signal rates of multiple Higgs bosons if their signals cannot be resolved by the experimental analysis. We compare results obtained with HiggsSignals to official ATLAS and CMS results for various examples of Higgs property determinations and find very good agreement. A few examples of HiggsSignals applications are provided, going beyond the scenarios investigated by the LHC collaborations. For models with more than one Higgs boson we recommend to use HiggsSignals and HiggsBounds in parallel to exploit the full constraining power of Higgs search exclusion limits and the measurements of the signal seen at around 125.5 GeV.

• The paper introduces HiggsSignals, a tool that uses chi-square statistical methods to compare model predictions with experimental data.
• It employs both peak-centered and mass-centered approaches to evaluate overlapping signals and account for theoretical mass uncertainties.
• The tool’s validation against ATLAS and CMS results underscores its potential for probing non-Standard Model Higgs sectors.

Overview of "Confronting Arbitrary Higgs Sectors with Measurements at the Tevatron and the LHC"

The paper "Confronting arbitrary Higgs sectors with measurements at the Tevatron and the LHC" introduces a computational tool, HiggsSignals, designed to evaluate the compatibility of theoretical predictions from various Higgs sector models against experimental data obtained from the Tevatron and the Large Hadron Collider (LHC). The tool is model-independent regarding the Higgs sector and facilitates comprehensive comparisons using available Higgs boson data.

Key Features and Methodology

HiggsSignals is implemented in Fortran90/2003 and employs a $\chi^2$ statistical framework to quantitatively compare model predictions with experimental observations of Higgs boson signal rates and masses. Two primary methodologies are included in the software:

1. Peak-Centered $\chi^2$ Method: This approach evaluates the compatibility of model-predicted Higgs signal rates with measured signals at specific experimentally hinted Higgs masses. It considers the possibility of multiple Higgs bosons contributing to an observed signal, ensuring that unresolved experimental signals are accurately assessed.
2. Mass-Centered $\chi^2$ Method: This approach compares predicted signal strengths at the model's Higgs mass predictions directly with experimental trend lines (e.g., $$plots) across different mass ranges. This method allows for evaluating models without assuming a specific signal mass, attributing variations due to theoretical mass uncertainties.</li> </ol> <h3 class='paper-heading' id='statistical-approach-and-input-requirements'>Statistical Approach and Input Requirements</h3> <p>The$$\chi^2$ evaluation incorporates a combination of systematic uncertainties such as those in signal rates, luminosity, and, importantly, addresses theoretical uncertainties in predicted Higgs masses. The input needed from users includes Higgs masses, production cross-sections, decay rates, and coupled uncertainties, configurable via SLHA format in the case of supersymmetric models. The application provides results as both screen output and selectable structured SLHA block formats.

   Validation and Application

   The paper demonstrates the application and validity of HiggsSignals through comparison with official results from ATLAS and CMS, offering insights into its reliability for conducting Higgs coupling modifier fits under various assumptions. When applied to published data, the tool's predictions of signal strengths and extracted coupling constants show substantial congruence with official results. The application is powerful for testing potential new physics models, where Higgs sector predictions vary significantly from the Standard Model (SM).

   Conclusion and Future Implications

   HiggsSignals stands as a pivotal tool for theoretical physicists focusing on Higgs physics, providing a robust statistical methodology to confront model predictions with rich experimental datasets. It opens up avenues for probing beyond the SM Higgs models even as more precise data becomes available. Future developments would profit significantly from enhanced access to detailed experimental uncertainties and correlations, promoting more intricate testing of Higgs sector theories as the LHC continues to deliver high-precision data.

   In conclusion, HiggsSignals empowers the particle physics community to rigorously validate myriad Higgs sector hypotheses against empirical data, reinforcing the interplay between theory and experiment in high-energy physics. Its development highlights the ongoing evolution in methodologies facilitating such investigations, with implications cascading across numerous theoretical models awaiting confrontation with the enigmatic Higgs landscape.