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H2020Individual fellowship2016–2018

hh · Search for Higgs boson pair production

Horizon 2020 — Marie Skłodowska-Curie Actions

Duration
2016-03-21 → 2018-03-20
EU contribution
€183,455
Participants
1
Scheme
MSCA-IF-EF-ST

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Results in brief

Search for Higgs boson pair production

The Standard Model (SM) of particle physics has been a tremendous success, particularly with the discovery of the Higgs boson in 2012 by the ATLAS and CMS collaborations. Since then, research has focused on measurement of the properties of the newly discovered particle. A deviation of a measurement from the SM prediction would be a sign of new physics “beyond” the SM (BSM). The BSM physics is required to answer many remaining open questions in the SM. Our project “hh” aims to observe new physics in the Higgs boson sector through the search for a Higgs boson pair, considering both resonant and non-resonant production. Many BSM theories predict the existence of heavy particles that can decay to a pair of Higgs bosons, such as minimal supersymmetric extension of the SM, twin Higgs and composite Higgs models. These heavy particles are identified as a resonance in the Higgs boson pair invariant mass spectrum. The enhancement of the non-resonant Higgs boson pair cross-section might occur through loop corrections involving new particles or through non-SM couplings. This project is based on the data collected in 2015 and 2016 by the ATLAS experiment in the Large Hadron Collider at CERN. The results of this project indicate non-significant deviations from the SM predictions. Tight upper limits are set in both the non-resonant and resonant modes in the mass range 260 GeV to 1 TeV, improving the sensitivity by a factor up to 10 compared to the previous ATLAS results. The Higgs boson self coupling, a fundamental parameter, cannot be directly probed with the currently available data but was significantly constrained in this project. The prospects of measuring the Higgs boson self-coupling in the high luminosity LHC (HL-LHC) were also studied within this project.

Data: CORDIS, © European Union

Project objective

Within two years of the discovery of a Higgs boson with a mass near 125 GeV, a set of properties measurements have confirmed, within current experimental/theory uncertainties, its Standard Model (SM) nature. Nevertheless, beyond the SM theories offer a rich phenomenology and exciting prospects for the discovery of New Physics in the Higgs sector. This project aims to observe physics beyond the SM in the Higgs boson sector through the search for Higgs boson, h pairs in the hh->γγb bbar channel, which benefits from the large h-> b bbar branching ratio, efficient diphoton trigger, low backgrounds and excellent diphoton invariant mass resolution. Both the resonant and non-resonant production are considered. To this end, the proton-proton collision data collected by the ATLAS experiment at a centre-of-mass energy of 13 TeV at the Large Hadron Collider over the next two years, will be used and are expected to amount to 70/fb. The proposal to search for anomalous Higgs boson production and for heavy resonant states decaying to hh is original, and innovative methods in all aspects of the project will be employed. The results of the project, which will provide new information on the h self-couplings and the production of new resonances decaying to hh, will be interpreted within various theoretical frameworks, with emphasis in two Higgs-doublet models.

Original text from CORDIS.

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Data: CORDIS, © European Union