Abstract
We point out that the LDMX (Light Dark Matter eXperiment) detector design, conceived to search for sub-GeV dark matter, will also have very advantageous characteristics to pursue electron-nucleus scattering measurements of direct relevance to the neutrino program at DUNE and elsewhere. These characteristics include a 4-GeV electron beam, a precision tracker, electromagnetic and hadronic calorimeters with near 2$\pi$ azimuthal acceptance from the forward beam axis out to $\sim$40$^\circ$ angle, and low reconstruction energy threshold. LDMX thus could provide (semi)exclusive cross section measurements, with detailed information about final-state electrons, pions, protons, and neutrons. We compare the predictions of two widely used neutrino generators (GENIE, GiBUU) in the LDMX region of acceptance to illustrate the large modeling discrepancies in electron-nucleus interactions at DUNE-like kinematics. We argue that discriminating between these predictions is well within the capabilities of the LDMX detector.
Highlights
The discovery of neutrino masses and flavor mixing represents a breakthrough in the search for physics beyond the Standard Model
Performing this reconstruction accurately and consistently for both neutrinos and antineutrinos requires a detailed understanding of howneutrinos interact with nuclei—a subtlety that has already impacted past oscillation fits [1,2,3], despite the availability of near detectors, which can help tune cross section models and constrain other systematic effects
Initial states of the interacting nucleons are affected, by nuclear binding and motions inside a nucleus. Multinucleon effects, such as mesonexchange currents (MEC), which arise from scattering on interacting nucleon pairs, likewise have to be considered. To model this rich physics, experiments rely on event generator codes, among them GENIE [5,6] and GiBUU [7,8,9,10,11], which are used as benchmarks in this paper
Summary
Multinucleon effects, such as mesonexchange currents (MEC), which arise from scattering on interacting nucleon pairs, likewise have to be considered To model this rich physics, experiments rely on event generator codes, among them GENIE [5,6] and GiBUU [7,8,9,10,11], which are used as benchmarks in this paper. What electron scattering offers is precisely controlled kinematics (initial and final energies and scattering angles), large statistics, in situ calibration of the detector response using exclusive reactions, and a prospect of swapping different nuclear targets This allows one to zero in on specific scattering processes and to diagnose problems that are currently obscured by the quality of the neutrino scattering data. We quantify how future LDMX data can be used to test and improve physics models in lepton-nucleus event generator codes
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