How wide is the Higgs boson? Addressing limitations to the measurement of total Higgs boson decay rates

• Applicant: Dr. Martina Laura Ojeda
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 566263241

During the first decade of Large Hadron Collider (LHC) running, various theoretical frameworks were developed to enable impressive progress during the exploratory phase of operating a new machine and characterising a new particle, the Higgs boson. The assumptions built into these frameworks proved very effective for the initial phase of LHC measurements. With excellent input from the theory community, it has been possible to achieve measurements expected to be out of reach of the LHC, in particular in the context of Higgs boson physics. A noteworthy example is the Higgs boson width, which allows an inclusive characterisation of Higgs boson decays and provides a probe for Higgs boson interactions with new, unobserved particles. Now, with the accumulation of new data, the advancement of analysis methodologies and a deeper understanding of the detector, many of the assumptions that were so useful before have become unnecessary and have the potential to become detrimental. For this reason, I propose a research project that, instead of focusing on enhancing the precision of existing measurements, will concentrate on scrutinizing some of the foundational assumptions underlying one of these measurements and identifying areas where these assumptions can be reevaluated or relaxed. This proposal centres on the implementation of updated frameworks for the determination of the total Higgs boson decay width (ΓH). Specifically, two complementary methods will be implemented to lift the main assumptions in the current determination of ΓH. The overarching objective of the project is to contribute to the transition to more robust frameworks for measurements performed during the upcoming phases of the LHC and to provide the high energy physics community with additional information regarding the nature of new non-Standard Model physics processes. This will be a critical input to future colliders.

• DFG Programme: Emmy Noether Independent Research Groups