The discovery that neutrinos have non-zero mass has brought with it new complexity in the neutrino sector as well as a host of possible new phenomena in particle physics, astrophysics, and cosmology. As we explore this new complexity, many questions arise. Why does neutrino mixing look so different than quark mixing? Are maximal mixings present, and if so, what underlying symmetries cause this? What mechanism drives the smallness of the neutrino masses, and what does it imply about physics at ultra-high energy scales? Do neutrinos violate the combined charge/parity (CP) symmetry, and is this violation large enough to produce the universe we observe today – a universe full of matter but not antimatter?

My research focuses on the neutrino sector of particle physics, addressing questions of weak mixing, neutrino masses, CP violation, and physics beyond the Standard Model. One piece of this is the currently operating NOvA experiment, a long-baseline neutrino oscillation experiment situated along Fermilab's NuMI neutrino beam. The broad physics program we are carrying out with NOvA includes: determining the ordering of the neutrino masses; constraining the phase δ of the PMNS matrix in search of leptonic CP violation; elucidating the flavor structure of neutrinos, in particular providing a leap in precision on whether the ν₃ state is maximally mixed and, if it is not, determining whether the μ or τ flavor dominates; and providing new precision on the dominant "atmospheric" oscillation parameters |Δm²₃₂| and θ₂₃. This program is supplemented by a range of both bread-and-butter and exotic measurements: neutrino-nucleus scattering, sterile neutrino searches, supernova neutrinos, monopole searches, and more.

Nature can choose to make leptonic CP violation or non-maximal ν₃ mixing arbitrarily hard to discover through careful parameter tuning, and some degeneracies can remain after NOvA if the CP phase lies in an unfavorable range. Even in more favorable cases, definitive CPv observation and precision measurements of PMNS mixing parameters still require a new experiment. My group is actively involved in the development of the next-generation DUNE experiment through which we are pursuing an ambitious physics program including an improved neutrino mass hierarchy measurement regardless of other parameter values; observation of leptonic CP violation at >5σ for 50% of parameter space; world-leading supernova neutrino observation capabilities particularly (and uniquely) in the ν_e channel; and a wide range of searches for physics beyond the Standard Model, including baryon number violation.

I was previously involved in the the MINOS long-baseline experiment, which completed data taking in 2012. In MINOS, I focused on θ₁₃-driven ν_e appearance and on searches for new physics through comparisons of neutrino and antineutrino oscillations. Further back in time I was involved in the MiniBooNE program, with the primary goal of testing the unexpected LSND evidence for ν_μ→ν_e transitions at high apparent Δm².

Members of the group

Select articles and presentations
For a complete publications list or for arXiv links to items below, see here.

• R. B. Patterson, a summary talk on our recent joint NOvA and T2K data analysis, plus updated NOvA-only results using the latest neutrino-mode data (2024).
• "Expanding neutrino oscillation parameter measurements in NOvA using a Bayesian approach", NOvA, Phys. Rev. D 110, 012005 (2024).
• "Performance of a modular ton-scale pixel-readout liquid argon time projection chamber", DUNE, arXiv:2403.03212 (2024).
• A review article aimed at those entering the field of long-baseline experiments: F. Lodovico, R. B. Patterson, M. Shiozawa, and E. Worcester, "Experimental Considerations in Long-Baseline Neutrino Oscillation Measurements", Ann. Rev. Nucl. Part. Sci. 73, 69 (2023).
• "Measurement of ν_μ charged-current inclusive π⁰ production in the NOvA near detector", NOvA, Phys. Rev. D 107, 112008 (2023).
• "Low exposure long-baseline neutrino oscillation sensitivity of the DUNE experiment", DUNE, Phys. Rev. D 105, 072006 (2022).
• "Improved measurement of neutrino oscillation parameters by the NOvA experiment", NOvA, Phys. Rev. D 106, 032004 (2022).
• "Design, construction and operation of the ProtoDUNE-SP Liquid Argon TPC", DUNE, JINST 17, P01005 (2022).
• "Deep Underground Neutrino Experiment (DUNE) Near Detector Conceptual Design Report", DUNE, arXiv:2103.13910 (2021).
• "Prospects for beyond the Standard Model physics searches at the Deep Underground Neutrino Experiment", DUNE, Eur. Phys. J. C 81, 322 (2021).
• "Supernova neutrino burst detection with the Deep Underground Neutrino Experiment", DUNE, Eur. Phys. J. C 81, 423 (2021).
• "First results on ProtoDUNE-SP liquid argon time projection chamber performance from a beam test at the CERN Neutrino Platform", DUNE, JINST 15, P12004 (2020).
• "Neutrino interaction classification with a convolutional neural network in the DUNE far detector", DUNE, Phys. Rev. D 102, 092003 (2020).
• "Long-baseline neutrino oscillation physics potential of the DUNE experiment", DUNE, Eur. Phys. J. C 80, 978 (2020).
• First ever evidence (4.4σ) of electron antineutrino appearance. "First measurement of neutrino oscillation parameters using neutrinos and antineutrinos by NOvA", NOvA, Phys. Rev. Lett. 123, 151803 (2019).
• "The DUNE Far Detector Technical Design Report", DUNE, Volume 1: Introduction to DUNE, Volume II: DUNE Physics, Volume IV: Far Detector Single-phase Technology. And from more recently: "The DUNE Far Detector Vertical Drift Technology. Technical Design Report", DUNE, JINST 19, T08004 (2024).
• "New constraints on oscillation parameters from ν_e appearance and ν_μ disappearance in the NOvA experiment", NOvA, Phys. Rev. D 98, 032012 (2018).
• "The Single-Phase ProtoDUNE Technical Design Report", DUNE, arXiv:1706.07081 (2017).
• "Search for active-sterile neutrino mixing using neutral-current interactions in NOvA", NOvA, Phys. Rev. D 96, 072006 (2017).
• "Constraints on oscillation parameters from ν_e appearance and ν_μ disappearance in NOvA", NOvA, Phys. Rev. Lett. 118, 231801 (2017).
• R. B. Patterson, "Perspectives on neutrino physics", a review talk at Pheno 2016.
• "First measurement of electron neutrino appearance in NOvA", NOvA, Phys. Rev. Lett. 116, 151806 (2016); "First measurement of muon neutrino disappearance in NOvA", NOvA, Phys. Rev. D 93, 051104(R) (2016).
• R. B. Patterson, "First oscillation results from NOvA", JETP Seminar at Fermilab in conjunction with APS DPF meeting, Aug 2015. Slides and video here.
• R. B. Patterson, "Prospects for measurement of the neutrino mass hierarchy", Annual Rev. Nucl. Part. Sci. 65, 177 (2015).
• C. Backhouse and R. B. Patterson, "Library Event Matching event classification algorithm for electron neutrino interactions in the NOvA detectors", Nucl. Instrum. Meth. A 778, 31 (2015). Describes a novel, quite generalizable, and optimal (at least in principle) classification algorithm. Developed originally for MINOS. Evolved considerably for use in NOvA.
• R. B. Patterson, "The current experimental situation in neutrino physics", a review talk at Frontiers in Particle Physics: From Dark Matter to the LHC and Beyond, Aspen Winter Conference (2014).
• "Combined analysis of ν_μ disappearance and ν_μ→ν_e appearance in MINOS using accelerator and atmospheric neutrinos", MINOS, Phys. Rev. Lett. 112, 191801 (2014).
• R. B. Patterson, "The NOvA experiment: status and outlook", Nucl. Phys. Proc. Suppl. 235, 151 (2013). The "status" part is very dated but the article still serves as an introduction to NOvA.
• "Electron neutrino and antineutrino appearance in the full MINOS data sample", MINOS, Phys. Rev. Lett. 110, 171801 (2013).
• "Improved measurement of muon antineutrino disappearance in MINOS", MINOS, Phys. Rev. Lett. 108, 191801 (2012).
• "Improved search for muon-neutrino to electron-neutrino oscillations in MINOS", MINOS, Phys. Rev. Lett. 107, 181802 (2011).
• The first MiniBooNE result (RBP thesis): Phys. Rev. Lett. 98, 231801 (2007). The anomalous event count below 475 MeV is discussed in a follow-up paper: Phys. Rev. Lett. 102, 101802 (2009).
• "First observation of coherent π⁰ production in neutrino-nucleus interactions with E_ν<2 GeV", MiniBooNE, Phys. Lett. B 664, 41 (2008).
• A few neutrino-nucleus cross section results in MiniBooNE: doubly-differential CC quasi-elastic scattering XS: Phys. Rev. D 81, 092005 (2010), NC π⁰ production: Phys. Rev. D 81, 013005 (2010), CC π⁰ production: Phys. Rev. D 83, 052009 (2011).
• R. B. Patterson et al., "The extended-track event reconstruction for MiniBooNE", Nucl. Instrum. Meth. A 608, 206 (2009). Describes a technique for event reconstruction in Cherenkov and Cherenkov+scintillation detectors that allows for full but computationally efficient treatment of a detector's optical properties during event likelihood calculations. The approach has been taken up by many experiments since then the original MiniBooNE application (e.g. T2K).

Recent work is supported by the Department of Energy, the Alfred P. Sloan Foundation, the Beatrice and Sai-Wai Fu Graduate Fellowship, and Caltech.