Giovanna Cottin, an academic at the Universidad Adolfo Ibáñez and young researcher at the Saphir Millennium Institute, will head, together with two other researchers in theoretical physics, a group dedicated to building bridges between the Large Hadron Collider experiments and long-lived particles, which are elementary particles that have been theorized but not yet discovered. This work is part of the research of Cottin, who has specialized in the development and implementation of strategies to detect these particles predicted by solid theoretical models. If discovered, these new particles would open the doors to a new physics.
By Jorge Román
Since it became operational in 2009, the Large Hadron Collider (LHC) has revolutionized physics. In addition to confirming the existence of the Higgs boson in July 2012, the LHC has found nearly 60 hadrons (non-elementary particles), among many other findings. However, it has not yet found clear signs of the existence of new elementary particles or of physics that goes beyond the standard model (the current theory that explains subatomic phenomena).
One of the possible reasons why new particles have not been detected may be that the right signals are not being searched for. This is what Giovanna Cottin argues in her recently awarded Fondecyt project "Searching for New Physics at the Lifetime Frontier". ("Searching for New Physics at the Lifetime Frontier"). There are theories that go beyond the standard model and predict the existence of long half-life particles that have not yet been detected. Cottin's work consists precisely in characterizing the possible exotic signals that would generate these particles and, with this, give clues to the experimental physics community about what to look for. It is the stage prior to data analysis: it would be like telling a detective whether to look for fingerprints, hairs, skin remnants or specific stains at a "crime scene" and how to collect these signals in order to analyze them correctly.
Francisca Garay, an academic at the Institute of Physics of the Pontificia Universidad Católica de Chile and Alternate Director of our institute, explains that "in the experiments, for example, in Atlas, [...] we look for particles that decay immediately, so there is a lot of physics that we could be losing because we are looking "wrong", that is, not thinking that there could be particles that travel a lot".
The 11th workshop of the long-lived particle community was held today. Giovanna Cottin presented on long-lived neutral lepton signals and moderated a session on the long-lived particle working group at the LHC.
The 11th workshop of the long-lived particle community was held today. Giovanna Cottin presented on long-lived neutral lepton signals and moderated a session on the long-lived particle working group at the LHC.
"I've always liked to have a good understanding of where the area [of particle physics] is going," Cottin explains. For her, working as one of the people coordinating the theoretical group "aligns super well" with her research and that is one of the reasons she decided to accept the role. She says she feels a lot of "responsibility to the scientific community" in taking on this task, which she recognizes as an opportunity to "squeeze" the questions she has been asking in her research.
An initiative open to the global physics community
The LLP Working Group - the Long-Lived Particle Working Group at the LHC, which is part of CERN's LPCC center - brings together experimental and theoretical physicists to generate discussion and discoveries in the area of long-lived particles at the LHC. This center was created in 2020 because these are of great importance in theoretical predictions.
"This initiative is not closed to CERN," Cottin explains. "The idea that this exists at CERN is to open up these studies to the world community." Because, in fact, there is a large informal worldwide community called the Long-Lived Particle Community made up of long-lived particle researchers from all over the world. Creating this theoretical working group at CERN is a way to synthesize the work that community does and to channel its research through support and coordination from CERN.
Cottin's leadership is shared with Nishita Desai (an academic at the Tata Institute for Fundamental Research, who works with dark matter models) and José Francisco Zurita (an academic at the Institute of Corpuscular Physics of the University of Valencia and CSIC, who specializes in models predicting new Higgs bosons), together with nine other researchers representing the LHC experiments. "They needed someone else and that's why they called me," says Cottin, whose role as coordinator was approved by all. She considers it not only a recognition of her work, but also a sign of how the search for long-lived particles has grown in the world physics community.
"Giovanna's appointment [...] is not only important for her as a scientist -because of the recognition of her contribution and expertise in this area-, but it is also very important for our theoretical group within Saphir", says Juan Carlos Helo, academic at the Universidad de La Serena and associate researcher at the Saphir Millennium Institute. According to Helo, Cottin's new position will give greater visibility to the activities of Saphir's theoretical physics group within the long-lived particle community.
"If it is possible, thanks to the input from the LLP theoretical group, for the experiments to change their search types, assuming that there could be particles that live longer, there is the potential to discover new physics," says Garay. And that Giovanna Cottin is on the team leading the theoretical area of this search "is super important. [...] She has a lot of passion, especially for this topic, [...] so she is going to leave everything on the track".
Giovanna Cottin, an academic at the Universidad Adolfo Ibáñez and young researcher at the Saphir Millennium Institute, talks in this video about the importance of particle physics and how enriching diversity is in the scientific community.
Giovanna Cottin, an academic at the Universidad Adolfo Ibáñez and young researcher at the Saphir Millennium Institute, talks in this video about the importance of particle physics and how enriching diversity is in the scientific community.
New opportunities
Cottin sees this opportunity as a way to harvest projects for the future: determine what is needed, define interesting research topics, and solicit support from the theoretical and experimental community internationally. "We want to get the juice out of the LHC results," says Cottin, "we need to know what those results look like when you choose a different model [than the usual ones]."
As Cottin explains, determining which theoretical model to apply in experimental physics research is complex "because there are many, many more theoretical models than experimental results". That means that there are human limitations to this work, since the experimental analysis is very complex and does not necessarily fit two or more models. There are models that predict the presence of dark matter, others that predict the presence of neutral heavy leptons and others that explain some anomalies, but there are many, many more. Therefore, the model to choose depends very much on the direction the theoretical group wants to take, on the questions it considers essential. This is also a risk, because the model chosen may not produce any results.
However, Cottin is clear that if the course taken does not bear fruit, there is a great openness to amend the path: "Science is always dynamic. And when things warrant a change of course, it will be changed, but always with the objectives of a mandate imposed by CERN [...] that has to do with helping these CERN experiments and with the potential that these experiments have in [discovering] new physics," says Cottin.
Cottin's work with the long-lived particle theory group also opens up several opportunities: new topics to explore and a deepening of the ties of the Saphir Millennium Institute's theory group with CERN and the international long-lived particle community. "New projects with scientists from this international scientific community could also be articulated," says Juan Carlos Helo.
"I feel it's going to be super fruitful and positive for Saphir," says Cottin. She believes this is an opportunity to "strengthen the connections with CERN in the theoretical area". Her dream is that "with some recommendation from this group, a new fundamental particle will be discovered," says the researcher. "That would be the ultimate: to help in this search in an assertive and accurate way".