The puzzle: understanding how nearly undetectable particles, called neutrinos, interact with normal matter. The solution? The clever MINERvA experiment, which shares its name with the Roman goddess of wisdom.
MINERvA, the Main INjector ExpeRiment for ν-A (where v is a symbol for neutrinos) is the world’s first neutrino experiment to use a high-intensity beam to study neutrino interactions with multiple nucleus sizes at the same time.
MINERvA scientists are currently looking at how low-energy neutrinos interact with ordinary matter like the protons and neutrons that make up the center of the atom. Specifically, MINERvA’s international collaboration of university and lab scientists is studying what happens when neutrinos interact with different elements from helium all the way to lead, which have different sized atomic parts.
The front face of the MINERvA detector sits in its underground home near the end of construction. This front face is no longer visible because of the helium target that was installed upstream. Photo: Reidar Hahn
Imagine an atomic nucleus as racked up pool balls with little springs attached to each other and the neutrino beam as the cue ball. It’s pretty easy to see what happens if you hit the pool balls with very little energy (almost nothing happens) or a lot of energy (they all break apart). But scientists need to know what happens with neutrinos in that middle energy level.
“Some of the energy goes into breaking springs, some goes into breaking apart pool balls. Some goes into ejecting pool balls with energy,” said MINERvA co-spokesperson Kevin McFarland, a researcher at the University of Rochester. “Because it’s such a complicated system — you’re getting a big nucleus full of lots of neutrons and protons bound together with springs — it’s really hard to look at what comes out and infer precisely what the energy of the neutrino was.”
By better understanding how neutrinos interact with the matter all around us, researchers hope to improve our model of how physics — and the universe — works. The information can be used in simulations of other neutrino experiments to correct for the energy that isn’t seen in these interactions and to improve accuracy.
This information is crucial both for current neutrino experiments such as NOvA and in preparation for upcoming neutrino oscillation experiments such as the Deep Underground Neutrino Experiment, or DUNE. At the energies required for those projects, the components of the nucleus begin to break apart, producing a slew of different particles and complex data.
“We’re making measurements that haven’t been measured ever before,” said Minerba Betancourt, postdoctoral researcher for MINERvA. “For example, there’s a channel called quasielastic, in which a neutrino interacts with the detector and produces a muon and a proton. For that type of neutrino interaction, there are not any measurements of iron or lead to scintillator ratios.”
Making new neutrinos
A lot has to happen to produce MINERvA data. The experiment uses Fermilab’s Main Injector accelerator, which produces protons at energies of over 120 times their rest masses. These protons smash into a carbon target in the NuMI beamline, producing particles called pions that then transform into the desired neutrinos.
Sooner or later, a tiny fraction of these neutrinos interact with nuclei in the detector and produce daughter particles. These particles leave the nucleus, causing interactions that produce light in the scintillator detector that scientists record and analyze.
“Neutrinos are neutral, so they don’t have a charge. We can’t see them until they actually produce something,” said Daniel Ruterbories, a postdoctoral researcher for MINERvA. “All of a sudden, particles spontaneously appear.”
MINERvA has a unique ability to study neutrinos with high precision, primarily because of its detector technology. Those detector components, called scintillator bars, are small. That means physicists can measure neutrino interactions in more detail than a typical neutrino detector, which has to be huge because it has to be located hundreds of miles away from the neutrino source.
Moving forward, MINERvA will analyze higher-energy neutrinos. By taking data at about 6 GeV of energy instead of the previous 3 GeV, scientists will be able to study many more interactions in the detector.
“We’re producing a large bucket of events,” Ruterbories said. “We should be able to really focus down and try to answer the questions of how these interactions occur.”
Calling all nature lovers. How would you like the chance to help diversify one of the oldest prairie restorations in Illinois?
Volunteers at Fermilab’s annual Prairie Seed Harvest.
The U.S. Department of Energy’s Fermi National Accelerator Laboratory is looking for volunteers to help with its annual prairie seed harvest. Two harvest events are planned, on Saturday, Sept. 10 and Saturday, Oct. 15, beginning at 10 a.m. Fermilab’s site hosts 1,000 acres of restored native prairie land, and each year community members pitch in to help collect seeds from those native plants.
Less than one-tenth of one percent of native prairies in Illinois remains intact. Fermilab’s restored grassland, begun 41 years ago, is one of the largest prairies in the state. The deep-rooted natural grasses of the prairie help prevent erosion and preserve the area’s aquifers.
The main collection area spans about 100 acres, and within it, volunteers will gather seeds from about 25 different types of native plants. Some of those seeds will be used to replenish the Fermilab prairies, filling in gaps where some species are more dominant than others.
“Our objective is to collect seeds from dozens of species,” said Ryan Campbell, an ecologist at Fermilab. “We have more than 1,000 acres of restored grassland, and it’s not all of the same quality. We want to spread diversity throughout the whole site.”
Once the seeds have been collected, the Fermilab roads and grounds staff will store them in a greenhouse and process them for springtime planting, once controlled burns of the prairie have been conducted. The laboratory has also donated some of the seeds to area schools for use in their own prairies and as educational tools.
Fermilab has been hosting the Prairie Harvest every year since 1974, and the event typically draws more than 200 volunteers. The event will last from 10 a.m. to 2 p.m., with lunch provided. Volunteers will be trained on different types of plants and how to harvest seeds. If you have them, bring gloves, a pair of hand clippers and paper grocery bags.
In case of inclement weather, call the Fermilab switchboard at 630-840-3000 to check whether the Prairie Harvest has been canceled. More information on Fermilab’s prairie can be found on our website. For more information on the Prairie Harvest, call the Fermilab Roads and Grounds Department at 630-840-3303.
Fermilab is America’s premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance LLC. Visit Fermilab’s website at www.fnal.gov and follow us on Twitter at @Fermilab.
The DOE 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 science.energy.gov.
On May 9 the President signed the National Bison Legacy Act, which declares the bison the national mammal of the United States. It was a recognition of the majesty of the bison, whose population, no longer approaching extinction, has grown through conservation efforts.
The bison herd has long been a fixture at Fermilab, a symbol of the laboratory’s pioneering spirit. Fermilab’s founding director, Robert Wilson, welcomed the first herd to the site. They came with their own playful, fictional first-person introduction, as well as some information about their diet, growth and pasture. Go back in time to meet O-Boy, Short Horns, Buffy, Bev and Mev.
Since the bison’s arrival, visitors have come to Fermilab countless times to see the animals. The birth of the season’s first baby bison at the laboratory always makes the local news.
Fermilab herdsman Cleo Garcia and Roads and Grounds head Dave Shemanske are proud of the herd. In this 2-minute video, they talk about the Fermilab bison herd, its history and other fun bison facts.
Image: Diana Brandonisio
Image: Diana Brandonisio
Fermilab is proud of our bison herd, which reminds us daily of our connection to the Midwest prairie and remains a strong symbol of our steady march toward the frontiers of physics.