Fermilab scientist Laura Fields receives $2.5 million DOE award to study beams of shape-shifting ghost particles

(From Fermi News)

August 5, 2020 | Zack Savitsky

Laura Fields
Laura Fields

The answer to one of the most fundamental questions in physics may lie in the universe’s most abundant matter particle: the neutrino. But interpreting and verifying data from neutrino experiments require reducing uncertainties in some very complicated particle interactions.

To advance this pivotal work, Fermilab scientist Laura Fields received a U.S. Department of Energy Early Career Research Award, an annual recognition of rising scientists in universities and national laboratories. The five-year $2.5 million grant will support Fields in identifying and reducing uncertainties in the composition of neutrino beams — improving measurements and boosting confidence in physics experiments with important implications.

According to the working theories, the Big Bang should have generated roughly equal amounts of matter and antimatter, which annihilate one another upon contact. However, from what we can tell, the universe seems to be composed almost entirely of matter (otherwise our universe would be empty or perhaps full of the mysterious dark matter).

To pin down the root of this mystery, scientists are looking to neutrinos — ghostly particles that sail through the universe and pass undetected through your body by the trillion every second — for clues. Aside from being frustratingly difficult to detect, neutrinos have another strange quality: They shape-shift. There are three different types, or “flavors,” of neutrinos (electron, muon and tau types), and the particles oscillate between these states as they travel.

In the search for the root of the matter-antimatter asymmetry, scientists are studying whether neutrinos and antineutrinos oscillate in the same way. To test this hypothesis, the international Deep Underground Neutrino Experiment, or DUNE, hosted by Fermilab, will use magnetic instruments called focusing horns to produce beams of neutrinos and antineutrinos and measure their oscillation rates with two different detectors — a near detector on the lab site and a far detector underground in South Dakota. A difference between the shape-shifting tendencies of matter and antimatter particles would violate the supposed symmetry and could help scientists understand why everything exists.

Precise measurements of neutrino oscillations require precise simulations. Toolkits such as Geant4, widely used in high-energy physics, simulate the passage of particles through matter, predicting what happens when particles interact with nuclei to form new particles. But the models are not completely accurate.

“The problem is that we don’t really know very well how many neutrinos are in our beam or what their flavor and energy composition is,” Fields said. “Because of all of these uncertainties, what Geant4 predicts will happen in the beamline may not be exactly what happens.”

Fields is working to reduce the uncertainty in the number, energy and flavor — known collectively as the “flux” — of the neutrinos below the current estimate of 10%.

Scientists make up for flux uncertainties by taking more data on similar particle interactions in different contexts. The extra data on neutrinos and the particles that produce them allow for more accurate simulations and more confident inferences.

“In addition to oscillations, DUNE will also make a lot of measurements at the near detector looking for beyond-the-Standard Model physics,” Fields said. “And the better we know our beam, the more certain we can be that any unexpected data is due to some exciting new physics rather than not understanding our equipment.”

A focusing horn focuses beams of charged particles, some of which eventually decay into neutrinos. Part of Fields’s work is to measure the charged particles after they’ve been focused. To date, nobody has precisely studied these particles downstream of a focusing horn. Photo: Reidar Hahn, Fermilab

Fermilab accelerators produce the DUNE neutrino beams by shooting protons at a solid target. The proton-target interaction gives off charged particles that are focused into beams and then decay into neutrinos. Because the parent particles are charged and focused, the chargeless neutrinos continue on in the same direction.

Fields’s proposal aims to cut the beam flux uncertainty in half by studying and modeling the interactions that produce neutrinos in two different ways.

First, other experiments, including the NA61 at CERN where Fields is a collaborator, already study target-based nuclear interactions. Fields plans to bring a DUNE target core to the NA61 experiment and analyze the data to learn more about the particles that decay into neutrinos.

Second, the proposal calls for measuring the neutrino-producing particles after they’re focused by a magnetic horn. To date, nobody has  precisely studied these particles downstream of a focusing horn. To pull it off, Fields and her colleagues will use another Fermilab experiment, called EMPHATIC, and build a precision-motion table to move the detectors and scan the whole horn.

Aside from funding the construction of the precision-motion table and the transport and powering of a focusing horn, the Early Career Research Award grant will fund 50% of Fields’s time and cover two postdoctoral research associates who will help with data collection and analysis.

The data for uncertainty reduction will be made public and eventually used to tune Geant4 simulations and improve nuclear physics models. At the very least, Fields’s work will boost the accuracy and reliability of DUNE’s findings.

“Laura is doing the foundational work that is critical for an experiment like DUNE to succeed,” said James Amundson, Scientific Computing Division head at Fermilab. “Her effort should make the whole process more efficient so we can get more physics out of the experiment.”

Fermilab neutrino research is supported by the DOE 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, visit science.energy.gov.

Amit Bashyal (far right) at the Neutrino summer school in Illinois.
Amit Bashyal (far right) at the Neutrino summer school in Illinois.

5th year grad student Amit Bashyal’s team won a group presentation prize at the International Neutrino Summer School for their study of magnetization of DUNE experiment far detectors. Students were divided into groups given a short time to do an original study and then present it! Congratulations Amit and team!

3 other Schellman group members and alumni are pictured. Laura Fields (Fermilab, 6th from left) and Cheryl Patrick (UCL, 7th from left) were lecturers at the summer school and 2nd year student Sean Gilligan (3rd from right) also attended.

Jennifer Hobbs – Data Scientist

Jen Hobbs worked in the Schellman group as an undergraduate and beginning grad student at Northwestern.  She and Howard Budd (Rochester) built the testing system for all 32,000 scintillating fibers for the MINERvA experiment using LabView.  I knew she was good when she got frustrated with the slow device drivers and rewrote them during her first summer at Fermilab. When MINERvA was complete she switched to neuroscience so she could continue doing hands-on stuff in the lab.

Her dissertation was on the relation between physical motion and neural signals from rat whiskers and won the Journal of Experimental Biology Outstanding Paper Award in 2015.


She then became a data scientist applying her expertise in quantitative studies of motion to – SPORTS!

She’s featured in the most recent issue of Symmetry Magazine


Differential QE-like cross section dσ(E_QEν)/dQ^2_QE, in bins of E_QEν. Inner error bars show statistical uncertainties; outer error bars show total (statistical and systematic) uncertainty. The red histogram shows the MINERvA-tuned GENIE model used to estimate smearing and acceptance.

The much anticipated paper version of Cheryl Patrick’s thesis has been accepted by Physical Review D.   Check it out at:


The data release is available at


Update:  It is published in Phys. Rev. D which is now open access:


Cheryl Patrick successfully defended her thesis:

Measurement of the Antineutrino Double-Differential Charged-Current Quasi-Elastic Scattering Cross Section at MINERvA in March and is now a postdoc on SuperNEMO at University College London.

Heidi Schellman, Cheryl Patrick PhD and Laura Fields
Heidi Schellman, Cheryl Patrick PhD and Laura Fields. Cheryl is wearing the official PhD hat.

She came back to the US to give a fantastic Fermilab Wine and Cheese talk in June 2016 which has been written up in Fermi NewsWatch the video!

Leah Welty-Rieger got her PhD from the University of Indiana on the D0 experiment. After a year as a web designer she joined the Schellman group as a postdoc.  While at Northwestern she independently applied for and received a URA Fellowship to join the g-2 magnetic moment experiment.  She now works part-time as a GEANT consultant for the g-2 experiment at Fermilab.

Who says postdocs can't have kid (and Cub's tickets).
Who says postdocs can’t have kids (and Cubs tickets).
Chris Pratt analyzed Z boson decays on the D0 experiment while getting degrees in Integrated Science and Mathematics (with a certificate in Finance from Kellogg) at Northwestern.  He uses the data analysis skills he learned in the Schellman group as an Associate Analyst at NERA Economic Consulting in Chicago.

Chris and Miranda at the Great Wall.  A long way from the Quad Cities!
Chris and Miranda at the Great Wall. A long way from the Quad Cities!
Tracy Taylor Thomas received her doctorate in the Schellman group on the D0 experiment at Fermilab. Her 1997 doctoral thesis was on “Strongly interacting color singlet exchange in proton – anti-proton collisions at 1800-GeV”. Instead of staying in Illinois as a postdoc, she moved to Portland Oregon and used her computing skills as a software engineer at U.S. Software, she is now the Director for Professional Services Operations at Jive Software and a popular Portland beer critic.

Jive Software looks like a fun place to work.
Jive Software looks like a fun place to work.