The structure function of the quasi-free neutron using spectator-tagging in deep-inelastic D(e,e' p_s)X scattering with the CLAS12 Spectrometer

One of the most intriguing open questions in hadronic physics is the behavior of the nucleon structure functions as x → 1, where nearly all of the nucleon’s momentum is carried by a single quark. Deep-inelastic lepton scattering experiments have provided a wealth of precise data on the proton structure function, but measurements of the neutron counterpart remain limited due to the instability of free neutrons. During the 6 GeV era at Jefferson Lab (JLab), the CLAS collaboration pioneered the spectator-tagging technique to extract the nearly on-shell neutron F₂ structure function in the reaction D(e,e'p_s)X, covering the range 0.1 < x < 0.6. Building upon this approach and using the doubled CEBAF beam-energy, the BONuS12 experiment employs the upgraded CLAS12 spectrometer and a dedicated recoil detector to extend the measurement of the quasi-free neutron F₂ structure function up to x ≈ 0.77 over a wide kinematic range in Q² and W . In this talk, we present the first results from the BONuS12 experiment, compare them with earlier measurements, and discuss their implications for our understanding of the nucleon’s partonic structure at large x.