First measurement of the Ar(e,e′)X cross section at Jefferson Laboratory

Abstract

The success of the ambitious programs of both long-and short-baseline neutrino-oscillation experiments employing liquid-argon time-projection chambers will greatly rely on the precision with which the weak response of the argon nucleus can be estimated. In the E12-14-012 experiment at Jefferson Lab Hall A, we studied the properties of the argon nucleus by scattering a high-quality electron beam off a high-pressure gaseous argon target. Here, we present the measured 40 Ar(e, e ) double differential cross section at incident electron energy E = 2.222 GeV and scattering angle θ = 15.54 • . The data cover a broad range of energy transfers, where quasielastic scattering and delta production are the dominant reaction mechanisms. The result for argon is compared to our previously reported cross sections for titanium and carbon, obtained in the same kinematical setup.Precise determination of charge-parity (CP) symmetry violation in the lepton sector-necessary to shed light on the matter-antimatter asymmetry in the universeis among the highest priorities of particle physics. Over the next two decades, this issue will be a primary science goal of the Deep Underground Neutrino Experiment (DUNE) [1], together with a search for proton decay, measurement of the electron-neutrino flux from a corecollapse supernova-should one occur in our galaxy during the lifetime of DUNE-and search for physics beyond the standard model.In the next few years, the Short-Baseline Neutrino (SBN) program [2] at Fermilab will provide a definitive answer to the question of the existence of sterile neutrinos, which could be the source of electron-like events recently reported with statistical significance 4.8σ by the MiniBooNE Collaboration [3].Both DUNE and the SBN program (will) employ liquid-argon time-projection chambers as their detectors, the advantages of which are low threshold momenta for particle detection and high spatial resolution, allowing (among others) for precise neutrino-energy reconstruction and distinguishing photons from electrons. As a consequence, the success of both programs in studying neutrino oscillations with unprecedented precision will greatly rely on the precision with which we understand

Threshold cusps and triangle singularities in hadronic reactions

“…The study carried out in Ref. [103] suggests a possible emergence of the a 1 (1420) peak in the π − f 0 (980) distribution of the decay τ − → ν τ π − f 0 (980), and the branching fraction was predicted. Similarly, in Ref.…”

“…[102], the TS effect of the K * K K loops in the decay of B →D * πf 0 (980) was studied. In these works [102,103], the production of the πa 0 (980) mode was also calculated. The predictions in these works can be confronted with future experimental data to clarify the nature of the a 1 (1420) peak.…”

Constraints in modeling the quasielastic response in inclusive lepton-nucleus scattering

“…In Fig. 6 the (e, e ′ ) JLab data for carbon, argon and titanium [48,49] are compared with the results from RPWIA, RMF, and ED-RMF models. Although the focus of this work is on the QE response (corresponding to the peak at E ′ ≈ 2 GeV in Figs.…”

“…RPWIA, RMF and ED-RMF predictions compare with the JLab data from[48,49] (εi = 2222 MeV, θe = 15.541 deg). Panels (a), (b) and (c) correspond to scattering on the target nuclei 12 C,48 Ti and 40 Ar, respectively. Thinner lines represent the QE, MEC and SPP contributions, thicker lines show the sum.…”

Lepton-nucleus cross section measurements for DUNE with the LDMX detector

“…However, by systematically analyzing electron data on mirror nuclei, in which neutrons in one nucleus have the same shell structure as protons in another, one can learn about both proton and neutron wave functions [25][26][27].…”