We employ the simplest possible models of scalar-fermion interactions that are consistent with the gauge symmetries of the Standard Model and permit no proton decay to analyze the connections possible among processes that break baryon number by two units. In this context we show how the observation of n-n oscillations and of a pattern of particular nucleon-antinucleon conversion processes -all accessible through e-d scattering -namely, selecting from e − p → e +p , e − p →nν, e − n →pν, and e − n → e −n would reveal that the decay π − π − → e − e − must occur also. This latter process is the leading contribution to neutrinoless double beta decay in nuclei mediated by new short-distance physics, in contrast to that mediated by light Majorana neutrino exchange. The inferred existence of π − π − → e − e − would also reveal the Majorana nature of the neutrino, though the absence of this inference would not preclude it.
We propose † to measure the photo-production cross section of J/ψ near threshold, in search of the recently observed LHCb hidden-charm resonances P c (4380) and P c (4450) consistent with 'pentaquarks'. The observation of these resonances in photo-production will provide strong evidence of the true resonance nature of the LHCb states, distinguishing them from kinematic enhancements. A bremsstrahlung photon beam produced with an 11 GeV electron beam at CEBAF covers the energy range of J/ψ production from the threshold photo-production energy of 8.2 GeV, to an energy beyond the presumed P c (4450) resonance. The experiment will be carried out in Hall C at Jefferson Lab, using a 50 µA electron beam incident on a 9% copper radiator. The resulting photon beam passes through a 15 cm liquid hydrogen target, producing J/ψ mesons through a diffractive process in the t-channel, or through a resonant process in the s-and u-channel. The decay e + e − pair of the J/ψ will be detected in coincidence using the two highmomentum spectrometers of Hall C. The spectrometer settings have been optimized to distinguish the resonant s-and u-channel production from the diffractive t-channel J/ψ production. The s-and u-channel production of the charmed 5-quark resonance dominates the t-distribution at large t. The momentum and angular resolution of the spectrometers is sufficient to observe a clear resonance enhancement in the total cross section and t-distribution. We request a total of 11 days of beam time with 9 days to carry the main experiment and 2 days to acquire the needed t-channel elastic J/ψ production data for a calibration measurement. This calibration measurement in itself will greatly enhance our knowledge of t-channel elastic J/ψ production near threshold. † This document is an updated version of the original proposal PR12-16-007, which was approved with an 'A' rating and a 'high-impact' label by the Jefferson Lab PAC 44 in July 2016. The experiment was awarded 11 days of beam time.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.