ATLAS and CMS narrow in on twin Higgs production

The ATLAS and CMS experiments at the Large Hadron Collider (LHC) are investigating the elusive process of double-Higgs production, where two Higgs bosons interact with each other. Detecting this phenomenon is challenging, as it is extremely rare – researchers expect only one pair of Higgs bosons to be produced for every 1,500 single Higgs bosons.

The ATLAS and CMS collaborations have presented new constraints on the double-Higgs production rate, providing insight into the Higgs boson's self-interactions. The discovery of the Higgs boson in 2012 marked a significant milestone in particle physics, but the self-interaction of the Higgs boson has yet to be observed. Understanding this process would test the limits of the Standard Model and shed light on the stability of the vacuum in our universe.

The main challenge in studying double-Higgs production lies in its rarity, but the ATLAS and CMS collaborations have made progress. By combining data from previous LHC runs with data from the LHC's most recent third run and employing novel machine-learning techniques, the experiments have set new constraints on the double-Higgs production rate.

ATLAS has reported a 2.6 standard deviation excess above what would be expected without double-Higgs production, while CMS has ruled out production rates larger than four times the current prediction from the Standard Model. These results provide a promising sign for future analyses that could potentially observe double-Higgs boson production.

The High-Luminosity LHC, set to increase collision rates, will bring the experiments closer to this elusive discovery.