Physics
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Item Measurement of inclusive quasielastic scattering of polarized electrons from polarized 3He(1990-08) Woodward, C.E.; Beise, E.J.; Belz, J.E.; Carr, R.W.; Filippone, B.W.; Lorenzon, W.B.; McKeown, R.D.; Mueller, B.; O'Neill, T.G.; Dodson, G.; Dow, K.; Farkhondeh, M.; Kowalski, S.; Lee, K.; Makins, N.; Milner, R.; Thompson, A.; Tieger, D.; van den Brand, J.; Young, A.; Yu, X.; Zumbro, J.We report a measurement of the asymmetry in spin-dependent quasielastic scattering of longitudinally polarized electrons from a polarized 3He gas target. This measurement represents the first demonstration of a new method for studying electromagnetic nuclear structure: the scattering of polarized electrons from a polarized nuclear target. The measured asymmetry is in good agreement with a Faddeev calculation and supports the picture of spin-dependent quasielastic scattering from polarized 3He as predominantly scattering from a polarized neutron.Item Measurement of 16O(γ,n)15O at medium energies(1989-05) Beise, E.J.; Dodson, G.; Garçon, M.; Høibråten, S.; Maher, C.; Pham, L.D.; Redwine, R.P.; Sapp, W.; Wilson, K.E.; Wood, S.A.; Deady, M.Exclusive differential cross sections for the 16O(γ,n)15O process have been measured for Eγ=150, 200, and 250 MeV and θL=49°, 59°, and 88°. This measurement is the first of its type to be reported for the energy region above the pion production threshold. An uncollimated bremsstrahlung beam was incident on an H2O target, and neutrons were measured with a recoil proton spectrometer with resolution sufficient to identify the residual 15O ground state. The results are compared to (γ,p) data and to calculations including effects from meson exchange currents.Item Measurement of the spin-dependent asymmetry in 3→(e→,e′) inelastic scattering at low energy transfer(1995-09) Arrington, J.; Beise, E.J.; Bray, B.; Carr, R.W.; Filippone, B.W.; Gao, H.; Lung, A.; McKeown, R.D.; Mueller, B.; Pitt, M.L.; DeSchepper, D.; Dodson, G.; Dow, K.; Ent, R.; Farkhondeh, M.; Hansen, J.-O.; Korsch, W.; Kramer, L.H.; Lee, K.; Makins, N.C.R.; Milner, R.G.; Teiger, D.R.; Welch, T.P.; Candell, E.; Napolitano, J.; Tripp, C.; Wojtsekhowski, B.B.We present the results of a measurement of the spin-dependent asymmetry in 3→(e→,e′) inelastic scattering at kinematics on the low-energy transfer side of the quasielastic peak, including the region near the breakup threshold. Comparison with existing calculations based upon the plane wave impulse approximation shows significant deviation between the data and the model near the breakup threshold. Good agreement between data and theory is seen at higher energy transfer.Item Measurement of the neutron magnetic form factor from inclusive quasielastic scattering of polarized electrons from polarized 3He(1994-08) Gao, A.; Arrington, J.; Beise, E.J.; Bray, B.; Carr, R.W.; Filippone, B.W.; Lung, A.; McKeown, R.D.; Mueller, B.; Pitt, M.L.; Jones, C.E.; DeSchepper, D.; Dodson, G.; Dow, K.; Ent, R.; Farkhondeh, M.; Hansen, J.-O.; Korsch, W.; Kramer, L.H.; Lee, K.; Makins, N.; Milner, R.G.; Teiger, D.R.; Welch, T.P.; Candell, E.; Napolitano, J.; Wojtsekhowski, B.B.; Tripp, C.; Lorenzon, W.We report a measurement of the asymmetry in spin-dependent quasielastic scattering of longitudinally polarized electrons from a polarized 3He target. The neutron magnetic form factor GMn has been extracted from the measured asymmetry based on recent PWIA calculations using spin-dependent spectral functions. Our determination of GMn at Q2=0.19 (GeV/c)2 agrees with the dipole parametrization. This experiment represents the first measurement of the neutron magnetic form factor using spin-dependent electron scattering.Item Determination of the neutron electric form factor in quasielastic scattering of polarized electrons from polarized 3He(1991-08) Jones-Woodward, C.E.; Beise, E.J.; Belz, J.E.; Carr, R.W.; Filippone, B.W.; Lorenzon, W.; McKeown, R.D.; Mueller, B.A.; O'Neill, T.G.; Dodson, G.; Dow, K.; Farkhondeh, M.; Kowalski, S.; Lee, K.; Makins, N.; Milner, R.; Thompson, A.; Teiger, D.; van den Brand, J.F.L.; Young, A.; Yu, X.; Zumbro, J.D.We report a measurement of the asymmetry in spin-dependent quasielastic scattering of longitudinally polarized electrons from a polarized 3He gas target. The asymmetry is measured at kinematics sensitive to the transverse-longitudinal response function RTL(Q2,ω). The value of the neutron electric form factor GEn(Q2=0.16 (GeV/c2))=+0.070±0.100±0.035 is extracted from the asymmetry using a Faddeev calculation of the 3He wave function.Item The Strange Quark Contribution to the Proton’s Magnetic Moment(2004-03) Spayde, D.T.; Averett, T.; Barkhuff, D.; Beck, D.H.; Beise, E.J.; Breuer, H.; Carr, R.; Covrig, S.; Dodson, G.; Dow, K.; Farkhondeh, M.; Filippone, B.W.; Franklin, W.; Hasty, R.; Ito, T.M.; Korsch, W.; Kowalski, S.; McKeown, R.D.; Mueller, B.; Pitt, M.L.; Ramsey-Musolf, M.J.; Ritter, J.; Tieulent, R.; Tsentalovich, E.; Wells, S.P.; Yang, B.; Zwart, T.We report a new determination of the strange quark contribution to the proton’s magnetic form factor at a four-momentum transfer Q2 = 0.1(GeV/c)2 from parity-violating e-p elastic scattering. The result uses a revised analysis of data from the SAMPLE experiment which was carried out at the MIT-Bates Laboratory. The data are combined with a calculation of the proton’s axial form factor GeA to determine the strange form factor GsM (Q2=0.1)=0.37±0.20±0.26±0.07. The extrapolation of GsM to its Q2 = 0 limit and comparison with calculations is also discussed.Item Parity-violating Electron Deuteron Scattering and the Proton’s Neutral Weak Axial Vector Form Factor(2004-03) Ito, T.M.; Averett, T.; Barkhuff, D.; Batigne, G.; Beck, D.H.; Beise, E.J.; Blake, A.; Breuer, H.; Carr, R.; Clasie, B.; Covrig, S.; Danagoulian, A.; Dodson, G.; Dow, K.; Dutta, D.; Farkhondeh, M.; Filippone, B.W.; Franklin, W.; Furget, C.; Gao, H.; Gao, J.; Gustafsson, K.; Hannelius, L.; Hasty, R.; Hawthorne-Allen, A.M.; Herda, M.C.; Jones, C.E.; King, P.; Korsch, W.; Kowalski, S.; Kox, S.; Kramer, K.; Lee, P.; Liu, J.; Martin, J.W.; McKeown, R.D.; Mueller, B.; Pitt, M.L.; Plaster, B.; Quemener, G.; Real, J. S.; Ritter, J.; Roche, J.; Savu, V.; Schiavilla, R.; Seely, J.; Spayde, D.; Suleiman, R.; Taylor, S.; Tieulent, R.; Tipton, B.; Tsentalovich, E.; Wells, S.P.; Yang, B.; Yuan, J.; Yun, J.; Zwart, T.; SAMPLE CollaborationWe report on a new measurement of the parity-violating asymmetry in quasielastic electron scat- tering from the deuteron at backward angles at Q2 = 0.038 (GeV/c)2. This quantity provides a de- termination of the neutral weak axial vector form factor of the nucleon, which can potentially receive large electroweak corrections. The measured asymmetry A = −3.51 ± 0.57 (stat) ± 0.58 (sys) ppm is consistent with theoretical predictions. We also report on updated results of the previous experiment at Q2 = 0.091 (GeV/c)2, which are also consistent with theoretical predictions.Item Measurement of the vector analyzing power in elastic electron-proton scattering as a probe of double photon exchange amplitudes(2001-05) Wells, S.P.; Averett, T.; Barkhuff, D.; Beck, D.H.; Beise, E.J.; Benson, C.; Breuer, H.; Carr, R.; Covrig, S.; DelCorso, J.; Dodson, G.; Eppstein, C.; Farkhondeh, M.; Filippone, B.W.; Forest, T.; Frasier, P.; Hasty, R.; Ito, T.M.; Jones, C.; Korsch, W.; Kowalski, S.; Lee, P.; Maneva, E.; McCarty, K.; McKeown, R.D.; Mikell, J.; Mueller, B.; Naik, P.; Pitt, M.L; Ritter, J.; Savu, V.; Spayde, D.T.; Sullivan, M.; Tieulent, R.; Tsentalovich, E.; Yang, B.; Zwart, T.; SAMPLE CollaborationWe report the first measurement of the vector analyzing power in inclusive transversely polarized elastic electron-proton scattering at Q2 = 0.1 (GeV/c)2 and large scattering angles. This quantity should vanish in the single virtual photon exchange, plane wave impulse approximation for this reaction, and can therefore provide information on double photon exchange amplitudes for electro- magnetic interactions with hadronic systems. We find a non-zero value of A=-15.4±5.4 ppm. No calculations of this observable for nuclei other than spin 0 have been carried out in these kinematics, and the calculation using the spin orbit interaction from a charged point nucleus of spin 0 cannot describe these data.