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Neutron Transformations: Future Free and Bound Experimental Searches

Speaker(s) / Presenter(s):
Josh Barrow, University of Tennessee

It is known from the Sakharov conditions that baryon number violation is required to explain the current observable universe's baryon abundance (BA) and associated matter-antimatter asymmetry; further, it seems that Standard Model (SM) B-L conserving processes (such as the sphaleron) are unable to naturally generate an adequate asymmetry without high-scale, effectively untestable physics being invoked to create a primordial lepton asymmetry. An alternative, testable theoretical framework (post-sphaleron baryogenesis) predicts low-scale (observable) B-L violating neutron-antineutron transformations which can produce a viable BA. Such transformations can be sought in future free neutron beam (European Spallation Source, ESS) and intranuclear bound neutron (DUNE, Hyper-Kamiokande) experiments; I will review past incarnations of these experiments, their future sensitivities, and advocate for their complimentary necessity. Current experimental work at ORNL in neutron disappearance phenomena will also be discussed as a stepping stone to these ultimate goals. These topics will be a focus of an upcoming Amherst Center for Fundamental Interactions workshop, a review (pre-CDR) paper from the ESS NNBar Collaboration, and the 2021 Snowmass Process.

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