The CMS experiment at the Large Hadron Collider (LHC) has recently conducted a groundbreaking study in its quest to uncover new physics. This innovative research focuses on the possibility of “dark photon” production in the decay of Higgs bosons within the detector. Dark photons are enigmatic long-lived particles that deviate from the Standard Model of particle physics, the leading theory that describes the fundamental constituents of the Universe. By shedding light on the properties of dark photons, the CMS experiment takes us one step closer to unraveling the mysteries that lie beyond the realm of the known.
Unveiling the Elusiveness of Dark Photons
Dark photons possess two distinctive features that make them fascinating for physicists: their longevity and their departure from the Standard Model. With an average lifetime exceeding a tenth of a billionth of a second, these particles persist for an extensive duration compared to many others produced at the LHC. In addition, their classification as “exotic” signifies their divergence from the established frameworks of particle physics. With numerous unanswered questions lingering within the scientific community, the search for phenomena beyond the Standard Model remains a top priority.
The latest findings from the CMS experiment present refined limitations concerning the decay parameters of Higgs bosons into dark photons. This narrowing down of the search space empowers physicists to target their investigations more effectively. Theoretically, dark photons should travel a measurable distance within the CMS detector before disintegrating into “displaced muons.” Remarkably, the tracks left by these muons do not extend all the way to the collision point. Instead, they originate from a particle that has already traveled a significant distance without leaving any observable trace. Unraveling these tracks and their origins holds the key to unlocking the existence of dark photons.
The commencement of Run 3 at the LHC in July 2022 marked a significant milestone in particle physics. With a higher instantaneous luminosity compared to previous runs, this phase introduces a greater number of collisions, generating substantial volumes of data for analysis. The LHC produces tens of millions of collisions per second; however, storing every collision would quickly deplete available data storage. Consequently, the CMS experiment is equipped with a real-time data selection algorithm called the trigger, responsible for determining the significance of each collision. The trigger system not only assists in managing the increased volume of data but also enhances the search for specific phenomena.
Juliette Alimena, a member of the CMS experiment, emphasizes the team’s improved ability to trigger on displaced muons. This enhancement enables the researchers to capture a significantly higher number of events featuring muons that have deviated from the collision point by distances ranging from a few hundred micrometers to several meters. Consequently, CMS is now more equipped than ever to potentially detect the existence of dark photons and explore their properties.
The CMS trigger system plays a pivotal role in the hunt for dark photons. It underwent substantial refinements between Runs 2 and 3 to accommodate the search for exotic long-lived particles. As a result of these enhancements, the collaboration achieved impressive results using only one-third of the data utilized in previous searches. The addition of a new algorithm, known as a non-pointing muon algorithm, significantly improved the trigger system’s efficiency. Even with just four to five months of data from Run 3 in 2022, the CMS team managed to record more events featuring displaced muons than the much larger Run 2 dataset covering the period between 2016 and 2018. The continuous deployment of cutting-edge techniques and the analysis of all data collected during the remaining years of Run 3 operations will continue to drive the exploration of physics beyond the Standard Model.
The ongoing efforts of the CMS experiment symbolize humanity’s unyielding quest to unravel the mysteries of the cosmos. By venturing into uncharted territories beyond the confines of the Standard Model, physicists push the boundaries of knowledge and understanding. The search for dark photons represents a significant step forward in this journey. Through meticulous data analysis, innovative trigger systems, and refined search capabilities, the CMS experiment is poised to make groundbreaking discoveries in the years to come. This exciting research holds the potential to transform our understanding of the fundamental nature of the Universe and pave the way for new discoveries that challenge our existing theories.