New measurements of the EMC effect in very light nuclei

A high precision measurement of the proton elastic form factor ratio $\mu G_{\mathrm{E}}/G_{\mathrm{M}}$ in the range of $Q^2$=0.3 - 0.7~GeV/$c^2$ has been made using recoil polarimetry method in Jefferson Lab Hall A. In this low $Q^2$ range, previous data (Bates, LEDEX) along with many fits and cal...

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Veröffentlicht in:Physical review letters 2009-11, Vol.103 (20)
Hauptverfasser: Seely, J, Gaskell, D, Arrington, J, Fomin, N, Solvignon, P, Asaturyan, R, Benmokhtar, F, Boeglin, W, Boillat, B, Bosted, P, Bruell, A, Bukhari, M.H.S., Christy, M E, Clasie, B, Connell, S, Dalton, M, Day, D, Dunne, J, Dutta, D, El Fassi, L, Ent, R, Fenker, H, Filippone, B W, Gao, H, Hill, C, Holt, R J, Horn, T, Hungerford, E, Jones, M K, Jourdan, J, Kalantarians, N, Keppel, C E, Kiselev, D, Kotulla, M, Lee, C, Lung, A F, Malace, S, Meekins, D G, Mertens, T, Mkrtchyan, H, Navasardyan, T, Niculescu, G, Niculescu, I, Nomura, H, Okayasu, Y, Opper, A K, Perdrisat, C, Potterveld, D H, Punjabi, V, Qian, X, Reimer, P E, Roche, J, Rodriguez, V M, Rondon, O, Schulte, E, Segbefia, E, Slifer, K, Smith, G R, Tadevosyan, V, Tajima, S, Tang, L, Testa, G, Trojer, R, Tvaskis, V, Villano, A
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Zusammenfassung:A high precision measurement of the proton elastic form factor ratio $\mu G_{\mathrm{E}}/G_{\mathrm{M}}$ in the range of $Q^2$=0.3 - 0.7~GeV/$c^2$ has been made using recoil polarimetry method in Jefferson Lab Hall A. In this low $Q^2$ range, previous data (Bates, LEDEX) along with many fits and calculations indicate substantial deviations of the ratio from unity, and continue to suggest that structures might be present in the individual form factors, and in the ratio. In E08-007, with 80\% polarized electron beam for 24 days, we are able to achieve $\sim 0.5\%$ statistical uncertainty. This high precision result will confirm or reute all existing suggestions of few percent structures in the form factors ratio. Beyond the intrinsic interest in nucleon structure, the improved form factor measurements also have implications for DVCS, determinations of the proton Zemach radius and for parity violation experiments.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.103.202301