This search for exotic long-lived particles considers the possibility of “dark particles.” photonThis occurs when the Higgs boson decays into muons and travels through the detector.
The CMS experiment announced the first exploration of new physics using data from Experiment 3 of the Large Hadron Collider. A new study considers the possibility of “dark photon” production in the decay of the Higgs boson within the detector. Dark photons are exotic long-lived particles. They are “long-lived” because their average lifetime is over one billionth of a second, which is an extremely long life for a particle produced at the LHC. It is also “exotic” because: They are not part of the standard model of particle physics.
Although the Standard Model is a powerful theory about the fundamental building blocks of the universe, many physics questions remain unanswered, and the search for phenomena beyond the Standard Model continues. The new CMS results define more constrained limits on the parameters of the Higgs boson’s decay into dark photons, further narrowing the area in which physicists can search for the Higgs boson.
Dark photon theory and particle detection
In theory, a dark photon would travel a measurable distance within a CMS detector before decaying into a “displaced muon.” If scientists traced the trajectories of these muons, they would find that they never reached the point of impact. This is because the trajectory comes from a particle that has already traveled some distance without any trace.
LHC Experiment 3 begins in July 2022 and has a higher instantaneous luminosity than previous LHC experiments. This means that there are always more conflicts that researchers can analyze. The LHC generates tens of millions of collisions every second, but only a few thousand of them can be stored because recording every collision would quickly consume all available data storage. For this reason, CMS includes real-time data selection algorithms called triggers that determine whether a particular collision is interesting. So it’s not just large amounts of data that could help uncover evidence of dark photons, but also ways to fine-tune trigger systems to look for specific phenomena.
Advances in trigger systems and data collection
“We’ve really improved our ability to trigger displaced muons,” says Juliet Alimena of the CMS experiment. “This allows us to collect far more events than before for muons that are only hundreds of micrometers to meters away from the point of impact. Thanks to these improvements, we can now collect far more events than before for muons that are only a few hundred micrometers to a few meters away from the point of impact. If you do, CMS is now much more likely to find it.”
The CMS trigger system is essential to this search and was specifically improved between runs 2 and 3 to search for exotic long-lived particles. As a result, the collaboration allowed him to use the LHC more efficiently, yielding strong results using just one-third the amount of data compared to previous searches. To do this, the CMS team improved the trigger system by adding a new algorithm called the Undirected Muon Algorithm. This improvement means that even with just four to five months of data from Run 3 in 2022, more displacement muon events were recorded than in the much larger Run 2 dataset from 2016-18. It means that. The new coverage of the trigger significantly expands the momentum range of detected muons, allowing the team to explore new regions where long-lived particles may be hidden.
Future plans and continued exploration
The CMS team will continue to analyze all data acquired during the remaining years of Run 3 operations using the most powerful techniques, with the aim of further exploring physics beyond the Standard Model.