The hottest job in physics?

If you’ve passed by the old SciBooNE hall at Fermilab in the last couple of months, you might have heard a bit of commotion. A little experiment with big ambitions just finished moving in this week after a year’s worth of planning and research. The Accelerator Neutrino-Neutron Interaction Experiment, called ANNIE, recently settled down and began taking phase one data on April 15.

“We want to better understand the nature of neutrino interactions by looking at their effects on an atom’s nucleus,” said Matthew Wetstein, a co-spokesperson for the ANNIE project and a Fermilab visiting scientist from Iowa State University. ANNIE will be the first realization of a new kind of detector in a large neutrino experiment. The technology will help look for particle interactions that are hard to distinguish in other detectors, he said.

The ANNIE team aims to study phenomena and techniques relevant to neutrino energy and proton decay measurements through the use of a water Cherenkov detector loaded with a chemical element called gadolinium and surrounded by never before used photosensors called large-area picosecond photodetectors (LAPPDs).

Light travels slower in a medium such as glass, water or other transparent materials than in air or in a vacuum. Sometimes, light travels slow enough in these materials that particles can overtake it. That’s why Cherenkov detectors are common in neutrino experiments. When neutrinos hit atoms in such media, the resulting free-flying electrically charged particles emit their own light, known as Cherenkov radiation, and these detectors record this light, allowing scientists to identify the type of particle and calculate its energy. In ANNIE’s case, neutrinos streaming down the Fermilab Booster Neutrino Beam will strike water molecules in the detector and knock off neutrons. Neutrons are electrically neutral and do not emit Cherenkov radiation, so they need to be detected some other way. After the initial neutrino-nucleus collisions, the gadolinium salts in the water effectively capture the neutrons and subsequently emit photons, which can be detected by photosensors.

“Neutrons have always been a challenging particle to detect,” Wetstein said. “We hope ANNIE can determine how many neutrons are produced when neutrinos interact.”

Observing this neutron release is useful because neutrons carry some energy with them that was transferred from the neutrino collision. Physicists believe higher-energy neutrino-nucleus interactions produce a larger number of knocked-off neutrons. To test this, ANNIE physicists will use accelerator-born neutrinos that have an energy level similar to atmospheric neutrinos, which have some of the highest-energy yields. The ANNIE team aims to understand how tagging free-flying neutrons can help them differentiate between a possible proton-decay signal and background noise from the neutrinos.

One of the best ways for the team to determine the effects of neutron tagging is to use the LAPPDs, a photosensor technology that researchers had been developing for nearly five years prior to the 2015 proposal for ANNIE. These sensors are currently in the commercialization phase.

LAPPDs are based on a technology called microchannel plates, which are tiny arrays with densely packed, tinier tubes that detect light. Conventional photodetectors, for physics research and commercial use, have single-pixel resolutions. In large neutrino experiments, these single-pixel phototubes can detect, for example, only one “blob” of charge coming from three separate photons in a neutrino-nucleus collision. Now with LAPPDs, scientists can read each individual photon, retrace where the photon came from and determine the time the light was emitted roughly 10 times better than previous photodetectors.

Think of it as tracing photons’ movements at the scale of 50 to 60 trillionths of a second.

High-precision timing with LAPPDs and accurate neutron tagging with the gadolinium-loaded water detector takes neutrino and proton-decay research to another level.

Thirty collaborators, including postdoctoral researchers and students, were very active in building and installing the electronics, water systems and photodetection tubes.

“We’ve done an excellent job of working together and making it happen as quickly as possible,” said Mayly Sanchez, a co-spokesperson for the ANNIE project and an Intensity Frontier fellow at Fermilab.

Now that the ANNIE detector is in its home in the Fermilab SciBooNE building and taking data, the collaboration is preparing to analyze their results.

“For phase one, we will be doing some neutrino background measurements for the ultimate physics measurements that we want to do,” Sanchez said. “The physics measurement in phase two will have an impact both in our knowledge of neutrino interactions and as the first application of a new photodetector technology in high-energy physics.”

Phase one, supported by Fermilab, will continue until the Fermilab accelerator shutdown begins in July. The main physics experimentation and R&D studies will take place during phase two, which awaits funding. ANNIE researchers, supported by the U.S. Department of Energy Office of Science and the National Science Foundation, will later compare results from both phases to see what the experiment yields.

“We learned what it takes to get an experiment like ANNIE off the ground at Fermilab,” Wetstein said. “I’m really proud that we got the whole thing from basically a big proposal to a fully designed experiment to turning all of our systems on within a year.”

ANNIE’s collaborating institutions are Argonne National Laboratory, Fermilab, Iowa State University, Ohio State University, Queen Mary University of London, University of California, Berkeley, University of California, Davis, University of California, Irvine, University of Chicago and University of Sheffield.

Near the end of the competitive Space Race in the early 1970s, a Soviet institution joined forces with a young Fermi National Accelerator Laboratory to work toward a greater understanding of the subatomic world. The Joint Institute for Nuclear Research in Dubna, Russia, which celebrated its 60th anniversary on March 26, remains an important, long-running Fermilab collaborator.

This relationship began in 1972 when JINR sent some of the first Soviet scientists to Fermilab. Together, American and Soviet scientists worked at the lab’s first accelerator system, using a Soviet-built jet hydrogen target in the proton beam.

“After this initial collaboration, there were quite a few scientists traveling between the United States and the Soviet Union,” said Dmitri Denisov, co-spokesperson on the DZero experiment and head of Fermilab’s Particle Physics Initiatives Department. “There were many labs in the USSR active in accelerator-based particle physics and using high-energy accelerators that resembled the science at Fermilab.”

Soviet scientists from multiple institutions soon noticed the similarities between the USSR and U.S. experiments as well as interesting, mutual scientific goals. In spite of the tension between the two nations, Fermilab became one of the few places in the U.S. for Soviet scientists testing their prototypes, conducting R&D projects and performing sophisticated, long-term experiments, Denisov said. This collaboration became a symbol of two competing countries overcoming their differences and working together to move the field of particle physics forward.

By the late 1980s and into the 1990s, CDF and DZero became a major focus at Fermilab for Russian particle physicists. At that time, Denisov was a young graduate student and worked with the Institute for High Energy Physics in Protvino, a small city near Moscow. He, along with a few other colleagues, joined the DZero experiment.

“We were all eager to come here, and about one or two years later, we planned to go back and construct a similar, even larger experiment in the USSR,” he said. “But the situation became difficult as the USSR disintegrated in 1991.”

Russian particle physics experimentation slowed down, and many projects ended. One option was to come to Fermilab and keep up with the ongoing experiments here. Although there were very few of them at the time, Russian scientists at Fermilab contributed to the discovery of the top quark. Soon after the discovery, more scientists came to the lab to work with other collaborators, upgrading the DZero detector or joining the CDF experiment.

Experiments at the Tevatron, which was the world’s highest-energy collider in the early 2000s, was the peak of Russian collaboration at Fermilab and provided a great opportunity to plan for future projects with Russia. By about 2005, a total of almost 300 scientists and engineers from Russian laboratories and universities joined Fermilab in several experiments. At the end of the Tevatron run, a couple of years later, many Russian scientists and engineers joined projects such as NOvA and Mu2e.

In early 2014, as the crisis in Ukraine unfolded, U.S. and Russian relations grew fragile, and additional approvals were necessary for Russian users and visiting scientists visiting Fermilab.

Aleksandr Simonenko, a contributing scientist from JINR, used to visit Fermilab for six months out of the year in 2007 for the CDF experiment. Simonenko now visits Fermilab for almost three months out of the year for the Mu2e experiment. Russian institutions continue to send their scientists to Fermilab to work on experiments such as CDF, DZero, Muon g-2, Mu2e and NOvA.

Last year, 75 scientists from 10 collaborating Russian institutions and laboratories worked at Fermilab.

“I think all scientists should participate in collaborations like this one, because each time you come, you get some additional experience and learn about the work of other places,” Simonenko said.

With the proposed international DUNE experiment, Fermilab may be able to further boost Russian participation.

“We must think of our work as science without borders,” Denisov said. “Science doesn’t depend on politics that much, but it’s beneficial to exchange our cultures and views. Science brings us together, and it is the same here just as it is in Russia. That’s why we work well together.”

As organizations and institutions around the United States push for higher standards in science and mathematics education, some communities have to get creative in finding sufficient resources to meet these expectations. One teacher in South Bend, Indiana, reached out for better opportunities for its students.

On March 18, Riley High School juniors and seniors attended a QuarkNet masterclass to discuss some of the research and analysis they conducted during this spring semester. According to a 2015 Indiana Department of Education review, Riley is one of the more diverse schools in the state: Nearly 30 percent of its student population is black, and 20 percent are Hispanic.

During the QuarkNet program, the students received first-hand experience working with data from the CMS experiment at CERN.

“The masterclass helps students understand how we reconstruct data in our detectors and identify the mass of each particle event in the data collected,” said Daniel Karmgard, a Fermilab visiting scientist, QuarkNet mentor and a physics professor at the University of Notre Dame. “Part of what we’re showing them is how to apply concepts they have already learned in the classroom to particle physics.”

The one-day masterclass is meant to provide an engaging way for students to do physics – one that closely resembles how particle physicists do their own research.

“The usual classroom science course can be quite bland because of all the worksheets and normal labs done in high school,” said Ben Dowd, an 18-year-old senior participating in QuarkNet masterclass program. “I really enjoyed listening to our masterclass mentor; he was very educated, and I felt like I learned a lot from him. He explained some of his work on CMS, then during the videoconference, the moderators explained what they did at Fermilab with their research, and it was extremely fascinating.”

In the few weeks leading up to the masterclass, the students were introduced to particle physics, learned how to analyze the data coming from the LHC and then got started on research and analysis. On the day of the masterclass, students from teacher Susan Sakimoto’s class at Riley went to Notre Dame University and attended a videoconference moderated by Fermilab physicists. Students from Zurich, Switzerland, and Catania, Italy, also pooled their results from their CMS data analysis and joined the conversation.

Depending on the results the students obtained, the QuarkNet mentor and moderators can show the students evidence of a Z boson, J/Psi and Upsilon mesons or the Higgs boson.

“My students always enjoy this experience,” Sakimoto said. “They like learning something real and having their own data. It’s also a great link to the Higgs boson news events, since the students find some Higgs boson candidates.”

Erik Bidwell, an 18-year-old senior who attended the masterclass, said he is doing an independent study on Einstein’s theory of relativity this semester.

“I never understood how much the LHC incorporated relativity in their particle physics research,” Bidwell said. “I was already interested in pursuing a job in science, but the masterclass allowed me to expand my knowledge of a future in physics, and the topic interests me more than ever before.”

The QuarkNet masterclass program proved to be an effective way to teach students applicable and collaborative physics. Interested teachers submit requests to a QuarkNet program for their physics students to participate in masterclasses.

Prior to teaching at Riley, Sakimoto was a geophysics assistant professor at Notre Dame and a research scientist at NASA’s Goddard Space Flight Center in Maryland. This is the third year she introduced her Riley students to QuarkNet, and she is delighted by their enthusiasm.

“QuarkNet masterclasses help all of my students stay interested in physics and willing to participate,” she said. “It is particularly welcome in sparking interest in women and minorities, who are traditionally not well-represented in physics.”