Massive stars end their lives in explosions called core-collapse supernovae. These explosions produce very large numbers of weakly interacting particles called neutrinos. Scientists working on the Deep Underground Neutrino Experiment, hosted by Fermilab, are seeking to perform a detailed measurement of supernova neutrinos. This effort could lead to groundbreaking discoveries in particle physics and astrophysics, including the first observation of the transition of a supernova into a neutron star or black hole.
To detect supernova neutrinos, DUNE will primarily search for reactions in which a neutrino collides with an argon nucleus and transforms into an electron. Precise 3-D images of these “charged-current” reactions will be recorded by advanced particle detectors. The images will then be compared with the results of simulations. A new computer program called MARLEY, described in this manuscript, generates the first complete simulations of charged-current reactions between supernova neutrinos and argon nuclei.
The MARLEY program allows researchers to study a variety of scientific questions. Theoretical physicists can use it to better understand what future measurements from DUNE might be able to tell us about the nature of neutrinos, stars and the wider universe. Experimental physicists can use MARLEY to practice analyzing “fake data” from a simulated supernova in preparation for the real thing. Building on pioneering reconstruction techniques first developed for the ArgoNeuT experiment and published in Physical Review D, the MicroBooNE collaboration carried out such simulations recently. All of these physics analysis tasks can be accomplished without requiring MARLEY users to be experts in nuclear physics. Several scientific papers have been published that include results calculated with MARLEY, and more are expected in the future.
A simulated supernova neutrino interaction in the MicroBooNE detector, produced using MARLEY. This work lays a strong foundation for future supernova neutrino measurements with DUNE. Credit: MicroBooNE collaboration
One of the most useful pieces of information that DUNE scientists plan to measure is the energy of each supernova neutrino that scatters within the detector. This data will provide insight into the way a supernova unfolds and test our current understanding of supernovae. Because neutrinos are weakly interacting, this cannot be done directly. Instead, scientists must carefully measure and add up the energies of all particles that are produced by a neutrino-argon reaction: not only the outgoing electron, but also any particles that are ejected from the nucleus itself. These may include gamma-rays, protons, neutrons, and sometimes clusters of neutrons and protons bound together. A full description of each neutrino collision includes the energy and direction of the electron, as well as similar details about the ejected nuclear particles. A new paper in Physical Review C explains how MARLEY provides the first theoretical model that can predict all of this information for charged-current collisions of supernova electron neutrinos with argon.
This research is funded by DOE Office of Science, DOE NNSA through the Nuclear Science and Security Consortium and a John Jungerman-Charles Soderquist graduate fellowship at the University of California, Davis.
The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit science.energy.gov.
Neutrinos have fascinated physicists like Gina Rameika for decades. Inspired by Ray Davis’ discovery that the number of electron neutrinos created by the sun did not match theoretical predictions – known as the solar neutrino deficit – she has been studying neutrinos for more than 25 years.
On April 1, Rameika assumed the role of co-spokesperson for the international Deep Underground Neutrino Experiment, elected by a collaboration of more than 1,000 physicists and engineers. DUNE, hosted by Fermilab, comprises people from more than 200 institutions in 33 countries.
Rameika was a member of the international team of scientists who discovered the tau neutrino by making the first observation of its interactions with matter using the Direct Observation of the Nu Tau, or DONuT experiment at Fermilab. She served as project manager for building the Main Injector Neutrino Oscillation Search, or MINOS, experiment at Fermilab and headed the Fermilab Neutrino Division from 2014 to 2016.
She has worked on advancing plans for DUNE since the 2000s, many years before the experiment obtained its official name. Since then, she has served in a variety of positions within the DUNE collaboration, and, as the construction coordinator, was instrumental in the success of the single-phase ProtoDUNE detector at CERN. For the past two years, she held the position of resource coordinator within the DUNE collaboration, overseeing finances and staffing, among other duties.
“Gina has enormous experience building and delivering projects, which is extremely important,” said Stefan Soldner-Rembold, who was elected DUNE co-spokesperson in 2018. “You need to have both an understanding of the science, of the physics, and how a project works and how the detectors work and how to manage, and Gina has all these great abilities and has done this before. I’m really excited about having the opportunity to work with Gina.”
DUNE requires the construction of neutrino detectors in two locations: a detector the size of a three-story house to be located at Fermilab in Batavia, Illinois and a gigantic detector, about 60 meters long and more than 20 times larger than existing detectors of its kind, in new caverns a mile underground at the Sanford Underground Research Facility in Lead, South Dakota.
The construction of detector modules has begun. As co-spokesperson, Rameika will coordinate the construction and delivery of the huge number of components being built around the world by 10 consortia formed among the 200-plus DUNE institutions. She might be thought of as the keeper of the big picture for all the puzzle pieces that have to fit together to form the DUNE jigsaw.
The DUNE collaboration published the blueprint for its huge detector in February 2020. One of Rameika’s top priorities is to document — in the form of memoranda of understanding — exactly what each of the consortia will deliver.
“My priority is to work with our international partners to plan and build this detector, which is truly a global effort,” said Rameika, who succeeds outgoing DUNE co-spokesperson Ed Blucher.
DUNE will feature detector modules filled with a total of 70,000 tons of liquid argon. This summer construction crews will start the excavation of the large caverns that will house the detector modules and related infrastructure. Cavern excavation is expected to be completed in 2024.
“A project like this requires a decade from planning to construction,” Soldner-Rembold commented. “We have a lot of shovels in the ground now and people building things. It will take a good part of this decade to reach a point where we can take data.”
Rameika wrote a paper about the solar neutrino puzzle when she was a freshman in college. Now she has the opportunity to build the best neutrino experiment in the world and tackle other questions involving the neutrino, such as the role neutrinos have played in the evolution of the universe.
“This is science and measurements that have never been done,” she said. “We’re building an experiment to uncover the deepest mysteries of the neutrino.”
The international Deep Underground Neutrino Experiment is supported by the Department of Energy Office of Science.
Fermilab is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science.