For a week spanning the months of July and August, scientists from around the world virtually gathered to attend the prestigious biennial ICHEP conference. At ICHEP, some of the most exciting physics results of the year are unveiled. CMS scientists from Fermilab and the LHC Physics Center, known as LPC, were well-represented at the conference.
Plenary talks present an overview of a particular field of research and are generally given by experienced researchers with an acknowledged grasp of the subject matter. Chris Palmer, associate research scholar at Princeton University and distinguished researcher at the Fermilab LHC Physics Center, gave a plenary talk about the entire LHC Higgs research program, presenting results from both ATLAS and CMS.
His talk covered all facets of investigations of the Higgs boson, ranging from precise refinements of physics processes that researchers have studied since it was discovered in 2012 to highly energetic processes such as the simultaneous production of a Higgs boson and a top quark-antiquark pair. Palmer also presented studies of Higgs boson production that explored such things as the possibility of anomalous couplings in the decay of Higgs bosons into four leptons and CP violation in the decay of Higgs bosons to tau leptons. These studies could shed light on whether the Higgs boson experiences unexpected interactions, leading to discoveries of new physics.
One of the most exciting measurements was the announcement by the CMS experiment of evidence of the decay of Higgs bosons into a pair of muons and the ATLAS announcement of a similar result, though with lower statistical significance. Since Higgs bosons preferentially decay into heavier particles and muons are extremely light, this process is very rare (occurring in about one decay out of 5,000). This measurement will lead to an important validation to the claim that the mass of quarks and charged leptons arises solely from interactions with the Higgs field.
Fermilab research associate Nick Smith gave a parallel talk about the decay of Higgs bosons into hadrons using the CMS detector. Parallel talks are more focused, taking the viewer into a deep dive into the details of analyses. Smith’s talk presented new neural net techniques for differentiating the decay of Higgs bosons into charm versus bottom quarks and improvements for reducing unwanted backgrounds.
Fermilab research associate Cristián H. Peña presented a parallel talk on CMS’ searches for long-lived particles. Long-lived particles can travel a considerable distance in the detector before decaying. In the talk, Peña outlined searches for particles that decay as far as 50 millimeters from where they were created. He also described interesting techniques that will improve experimental capabilities in the upcoming run.
Fermilab research associate Karri Di Petrillo presented a description of the development of the MIP timing detector, or MTD, for CMS. The MIP timing detector is expected to be a crucial upgrade for future high-luminosity running. As the luminosity increases, this will lead to more simultaneous collisions in the detector. Simultaneous collisions mean simultaneous tracks, and it is very important to be able to assign the various tracks to their respective collisions. Di Petrillo presented the overall plan, as well as reviewed the R&D and test beam studies that will guide the development of this important upgrade to CMS.
Fermilab scientist Bo Jayatilaka gave an important parallel talk describing the CMS collaboration’s diversity and inclusion efforts, aimed at broadening the number of people who participate in the experiment. He covered efforts aimed at many underrepresented groups and reported how the collaboration is mindfully and proactively attempting to ensure that no individual is overlooked when decisions are made about who should lead groups within the experiment or when high-visibility talks are assigned. These efforts are mainly carried out by the CMS Diversity Office, whose goal is to develop methods to support all collaboration members and then share these methods with the wider particle physics world.
Two other LPC-related researchers gave presentations. Philip Chang, a postdoc at the University of California, San Diego, described measurements by CMS of events in which three weak bosons were simultaneously produced. And Julie Hogan, an assistant professor of physics at Bethel University and an affiliate of Brown University, presented CMS data on vector-like quarks.
The ICHEP conference is a fascinating one. It is one of the bigger conferences in the field, drawing significant participation throughout the community. The first conference in this series began in 1950, and this year was the first time it was held in a video-only format. The next one will be held in 2022 in Bologna, where we all hope will be able to gather in person to hear about even more exciting advances.
Don Lincoln is a Fermilab scientist on the CMS experiment.
CMS Department communications are coordinated by Fermilab scientist Pushpa Bhat.