This proposal addresses the question: What is the source of the matter/anti-matter asymmetry in the universe? The technical name for this asymmetry is "CP Violation" and the R&D proposed here will be an important step to determine if neutrinos can be an important part of the answer. Specifically, a next generation neutrino oscillation experiment which sends a neutrino beam from Fermilab to NSF's proposed Deep Underground Science and Engineering Laboratory (DUSEL) can address this question. A new type of detector will be necessary, however. The proposed detector is known as a Liquid Argon Time Projection Chamber (LArTPC). This proposal will investigate the capability and feasibility of this detector at useful energies. This proposal seeks to build and operate a prototype detector. This is an important next step in the R&D path towards building a massive LArTPC. The broader impacts of this proposal will bring junior high school teachers into this program as researchers. Further, the PI proposes to develop a school-year program for 6-8 grade girls which draws from this research program. It is noted that in the 6-8 grade, girls begin to perform more poorly than boys in math and science. The PI hopes that the focus on interesting girls in science at a pivotal time for their success will help to encourage them to pursue science.
This CAREER award funded the design, fabrication, data taking, and data analysis of the ArgoNeuT Experiment, which stands for Argon Neutrino Test. This test experiment was designed to perform Research and Development of a new kind of precision detector to study neutrinos, a small particle in the electron family. The detector, called a liquid argon time projection chamber (LArTPC) uses Liquid Argon as the target with which neutrinos interact. Once the neutrinos interact they produce charged particles including muons, electrons and protons. These charged particles knock electrons off of the Argon atoms. These electrons are then drifted from the main volume of Argon to the edge of the detector where they pass through wires and are readout. The readout electrons then produce a computer, photo-like, image of the neutrino interaction. A candidate neutrino interaction is shown in the attached photo. Unlike conventional neutrino detectors which tend to record the neutrino interaction rather coarsely, these LArTPCs record very precise information on the neutrino interaction. As a result, using these detectors allows for precision experiments with very low backgrounds. Neutrino detectors for next generation searches for CP violation will look for differences between neutrinos and anti-neutrinos. Given how these experiments are performed, the detectors will need to be very large – 10s of kilotons of Liquid Argon. ArgoNeuT was designed to help us begin to learn how to build these very large detectors. As a first step in this process in the US, ArgoNeuT was quite small with an inner detector 50 x 50 x 100cm rectangle. The inner detector, the cryostat, and the readout were funded through this CAREER grant. The attached image shows a schematic of the detector. The detector was designed and fabricated in 2008, commissioned in 2009 at Fermilab National Laboratory, and installed in a neutrino beam at Fermilab in 2010 where it took data for 6 months before being removed from the neutrino beam. From 2011 to the completion of this grant, the ArgoNeuT collaboration including students and post-docs partially funded by this grant, have been working to analyze the data and measure neutrino interactions in the detector volume. A first physics paper in the premier physics journal, Physical Review Letters, has already been published. Five other physics analyses are underway which we anticipate will also lead to publication in peer reviewed journals. The first paper is the first every published physics cross section result using these detectors. The Broader Impacts component of this award funded a Saturday program for 6th-8th grade girls named "Girls Science Investigations". This program, run in the lab rooms at Yale University, was designed to be an hands-on interactive lab program to encourage middle school girls to enjoy and pursue science. Over the last 5 years, the program has hosted approximately 100 girls per Saturday session for four Saturdays a year. Activities include making radios, cloud chambers, robots, and studying concepts across physics. The volunteers who teach the girls include Yale female undergraduates, graduate students, post-docs, faculty and retired science teachers. Many of the participants after they "graduate" from the program, continue on as volunteers for the next set of participants. The program has been a huge success. We use evaluations from the girls to help tailor the curricula for the next set of programs.
