Measurement of the Neutron F_{2} Structure Function via Spectator Tagging with CLAS

Baillie, N.; Tkachenko, S.; Zhang, J.; Bosted, P.; Bültmann, S.; Christy, M.; Fenker, H.; Griffioen, K.; Keppel, C.; Kuhn, S.; Melnitchouk, W.; Tvaskis, V.; Adhikari, K.; Adikaram, D.; Aghasyan, M.; Amaryan, M.; Anghinolfi, M.; Arrington, J.; Avakian, H.; Baghdasaryan, H.; Battaglieri, M.; Biselli, A.; Branford, D.; Briscoe, W.; Brooks, W.; Burkert, V.; Carman, D.; Celentano, A.; Chandavar, S.; Charles, G.; Cole, P.; Contalbrigo, M.; Crede, V.; D’Angelo, A.; Daniel, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Dey, B.; Djalali, C.; Dodge, G.; Domingo, J.; Doughty, D.; Dupre, R.; Dutta, D.; Ent, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Fradi, A.; Gabrielyan, M.; Gevorgyan, N.; Gilfoyle, G.; Giovanetti, K.; Girod, F.; Gohn, W.; Golovatch, E.; Gothe, R.; Graham, L.; Guegan, B.; Guidal, M.; Guler, N.; Guo, L.; Hafidi, K.; Heddle, D.; Hicks, K.; Holtrop, M.; Hungerford, E.; Hyde, C.; Ilieva, Y.; Ireland, D.; Ispiryan, M.; Isupov, E.; Jawalkar, S.; Jo, H.; Kalantarians, N.; Khandaker, M.; Khetarpal, P.; Kim, A.; Kim, W.; King, P.; Klein, A.; Klein, F.; Klimenko, A.; Kubarovsky, V.; Kuleshov, S.; Kvaltine, N.; Livingston, K.; Lu, H.; Macgregor, I.; Mao, Y.; Markov, N.; Mckinnon, B.; Mineeva, T.; Morrison, B.; Moutarde, H.; Munevar, E.; Nadel Turonski, P.; Ni, A.; Niccolai, S.; Niculescu, I.; Niculescu, G.; Osipenko, M.; Ostrovidov, A.; Pappalardo, L.; Park, K.; Park, S.; Pasyuk, E.; Anefalos Pereira, S.; Pisano, S.; Pozdniakov, S.; Price, J.; Procureur, S.; Prok, Y.; Protopopescu, D.; Raue, B.; Ricco, Giovanni; Rimal, D.; Ripani, M.; Rosner, G.; Rossi, P.; Sabatié, F.; Saini, M.; Salgado, C.; Schott, D.; Schumacher, R.; Seder, E.; Sharabian, Y.; Sober, D.; Sokhan, D.; Stepanyan, S.; Stepanyan, S.; Stoler, P.; Strauch, S.; Taiuti, MAURO GINO; Tang, W.; Ungaro, M.; Vineyard, M.; Voutier, E.; Watts, D.; Weinstein, L.; Weygand, D.; Wood, M.; Zana, L.; Zhao, B.

doi:10.1103/PhysRevLett.108.142001

We report on the first measurement of the F2 structure function of the neutron from the semi-inclusive scattering of electrons from deuterium, with low-momentum protons detected in the backward hemisphere. Restricting the momentum of the spectator protons to ≲100 MeV/c and their angles to ≳100° relative to the momentum transfer allows an interpretation of the process in terms of scattering from nearly on-shell neutrons. The F2n data collected cover the nucleon-resonance and deep-inelastic regions over a wide range of Bjorken x for 0.65<Q2<4.52 GeV2, with uncertainties from nuclear corrections estimated to be less than a few percent. These measurements provide the first determination of the neutron to proton structure function ratio F2n/F2p at 0.2≲x≲0.8 with little uncertainty due to nuclear effects.