The ATLAS collaboration has analyzed a dataset of 30,000 trillion proton-proton collisions, exceeding 300 inverse femtobarns, in a search for the rare decay of a Higgs boson pair. This analysis focuses on a specific decay where one Higgs transforms into two photons and the other into bottom quarks, a channel useful for understanding how the Higgs boson interacts with itself, which is key to understanding the early universe and the origin of mass. Studying this process is difficult, as the predicted rate is only one event for every trillion collisions, requiring physicists to employ advanced machine learning techniques to distinguish the signal from background noise. These advancements have allowed the team to set more stringent limits on the Higgs boson’s self-coupling, furthering the quest to understand fundamental particle interactions and potentially reveal physics beyond the Standard Model.
300 fb⁻¹ Run 2 & 3 Data Enhances Higgs Boson Analysis
The ATLAS collaboration’s recent analysis leveraged a dataset equivalent to 30,000 trillion proton-proton collisions, a substantial increase in scale for investigations into Higgs boson interactions, and represents the first measurement based on over 300 inverse femtobarns of collision data. By combining data from the LHC’s Run 2 (2015-2018) and a partial Run 3 (2022-2024) dataset, the team significantly boosted the statistical power of their analysis. The rarity of Higgs boson pair production, predicted to occur in only one in a trillion proton-proton collisions, presents a formidable challenge, compounded by background noise from other Standard Model processes that mimic the desired decay.
To address this, ATLAS physicists employed advanced machine learning techniques, essential for isolating the faint signal from the overwhelming background. As a result of these advancements and the addition of the partial Run 3 dataset, researchers set more stringent limits than previously possible on the signal strength and two key interaction parameters. Specifically, the magnitude of the Higgs boson’s self-coupling was limited to be between −1.6 and 6.6, while the interaction strength between two Higgs bosons and two vector bosons was limited to be between −0.5 and 2.6. These results demonstrate the growing capabilities of the ATLAS collaboration in studying Higgs boson pair production and establish a foundation for future measurements that could reveal fundamental insights into the Universe’s earliest moments. With the full Run 3 dataset forthcoming and the High-Luminosity LHC on the horizon, ATLAS is prepared to further refine our understanding of the Higgs boson and potentially uncover evidence of physics beyond the Standard Model.
Higgs Self-Coupling Limited to −1.6 to 6.6 via ATLAS Measurements
The ATLAS collaboration has refined constraints on the Higgs boson’s self-interaction, a fundamental property linked to the universe’s earliest moments and the origin of mass, through analysis of an exceptionally large dataset. Researchers examined over 300 inverse femtobarns of proton-proton collision data, a volume equivalent to approximately 30,000 trillion collisions, substantially increasing the precision of previous measurements. The team combined data from the LHC’s Run 2 and a portion of Run 3, bolstering the statistical significance of their findings. To overcome these challenges, ATLAS physicists used advanced data analysis techniques, such as machine learning, to help isolate the decay signal from the background, according to the collaboration. This allowed them to place limits on the strength of the Higgs self-coupling, finding it falls between −1.6 and 6.6 when compared to predictions from the Standard Model.
These results represent a significant step toward understanding the Higgs boson’s behavior and its role in the early universe; the self-coupling is critical for explaining the evolution of the universe after the Big Bang. The results underscore the ATLAS Collaboration’s growing ability to explore Higgs boson pair production in this channel, positioning them to further refine our understanding of this fundamental particle.
Studying this decay channel is particularly challenging due to the extremely rare nature of Higgs boson pair production – predicted to occur once in a trillion proton-proton collisions – and the significant background from Standard Model processes that mimic this decay mode.
