Sending GENIE into the neutrino community

Neutrino physicists from around the world met at Fermilab to learn the GENIE code. Photo: Reidar Hahn

When most people hear the word “genie,” they get ready to make a wish. When neutrino physicists hear it, they think of a simulation program the community uses to study the ghostly particles.

Last week more than a dozen physicists visited Fermilab for a meeting of the collaboration behind GENIE. As one of the few places with expertise in the software, Fermilab served as a hub for the user community where students and postdocs came to be trained in the program.

Steering clear of slide shows, scientists at the GENIE collaboration meeting spent the week hunched over various laptops, working on adding new physics models and options to the code.

“With GENIE, we’re attempting to understand and help resolve issues confronting the next generation of experiments at the Intensity Frontier,” said GENIE spokesperson Costas Andreopoulos of the University of Liverpool and STFC’s Rutherford Appleton Laboratory. “We appreciate the effort by Fermilab to host this.”

GENIE is an event generator — a program that spits out different particle event scenarios based on the interaction model that’s fed to it. In particular, GENIE simulates interactions between a neutrino and a target atom. Scientists use event generators to better understand signals in their detectors. By comparing predictions from well-understood physics, they can isolate new phenomena.

GENIE isn’t the only neutrino-event generator out there, but it’s the only one that’s universal: It can handle all neutrino species, all types of interaction targets and all energy ranges. Other neutrino event generators — home-grown project-specific programs focused on a particular neutrino physics model — can’t be used to explore possibilities beyond that model. When Andreopoulos and others developed GENIE — which stands for Generates Events for Neutrino Interaction Experiments — from 2004 to 2006, they designed it to be applicable to any kind of neutrino interaction.

“We aimed to produce a design that allows you to put multiple models into the generator,” Andreopoulos said. “That flexibility wasn’t there from the beginning in other neutrino-event generators.”

And whereas with other comparable software, only scientists on the project in question can provide input, anyone conversant in GENIE can contribute to its development.

“A large number of people can contribute to GENIE,” said Fermilab’s Gabriel Perdue, main organizer of the workshop. “It’s like a crowd-sourcing tool for the neutrino set, so it’s superior for large-scale collaboration compared to other similar programs.”

GENIE serves the entire neutrino community, but only a handful of scientists have strong expertise in it. So representatives from diverse experiments — IceCube, LBNE, MicroBooNE, MINERvA and T2K — convened at the Fermilab meeting to learn the program. Steve Brice, head of Fermilab’s Intensity Frontier Department, hopes that soon its use will become widespread.

“With the workshop, this code can go from being a small-scale project with two or three developers to something that’s prevalent in the user community,” Brice said. “With so many new people on neutrino physics from so many collaborations, we can expect great progress on some difficult problems in neutrino interaction simulations.”

Leah Hesla