We report new precise H(e,e(')p)pi(0) measurements at the Delta(1232) resonance at Q(2)=0.127 (GeV/c)(2) obtained at the MIT-Bates out-of-plane scattering facility which are particularly sensitive to the transverse electric amplitude (E2) of the gamma(*)N-->Delta transition. The new data have been analyzed together with those of earlier measurements to yield precise quadrupole to dipole amplitude ratios: Re(E(3/2)(1+)/M(3/2)(1+))=(-2.3+/-0.3(stat+syst)+/-0.6(model))% and Re(S(3/2)(1+)/M(3/2)(1+))=(-6.1+/-0.2(stat+syst)+/-0.5(model))% for M(3/2)(1+)=(41.4+/-0.3(stat+syst)+/-0.4(model))(10(-3)/m(pi(+))). The derived amplitudes give credence to the conjecture of deformation in hadrons favoring, at low Q2, the dominance of mesonic effects.

We report on a measurement of the tensor analyzing power T20 in elastic electron-deuteron scattering in the range of fourmomentum transfer from 1.8 to 3.2 fm −1 . Electrons of 704 MeV were scattered from a polarized deuterium internal target. The tensor polarization of the deuterium nuclei was determined with an ion-extraction system, allowing an absolute measurement of T20. The data are described well by a non-relativistic calculation that includes the effects of mesonexchange currents.PACS numbers: 13.40. Gp, 21.45.+v, 25.30.Bf, 29.25.Pj The deuteron, as the simplest nucleus, serves as a sensitive testing ground for a variety of nuclear models (nonrelativistic [1,2], fully covariant [3,4]). The charge and current distributions inside the nucleus can be probed with elastic electron scattering at intermediate energies.Elastic electron scattering off the spin-1 deuteron is completely described in terms of three electro-magnetic form factors: the charge monopole G C , the magnetic dipole G M and the charge quadrupole G Q . Measurement of the unpolarized cross section yields the structure functions A(G C ,G M ,G Q ) and B(G M ). When the tensor analyzing power T 20 is also determined, all three form factors can be separated [5]. A large body of data is available for A and B for values of the four-momentum transfer Q of up to 12 fm −1 , while T 20 has been measured up to 4 fm −1 , albeit with limited accuracy. The observable T 20 contains an interference between G C and G Q and is thus sensitive to the effects of short-range and tensor correlations in the ground-state wave function of the deuteron. In this paper absolute measurements are presented on the analyzing powers in the ↔ 2 H(e,e ′ d)-reaction for Q-values between 1.8 and 3.2 fm −1 with a high accuracy.The cross section for elastic electron-deuteron scattering with unpolarized electrons and tensor-polarized deuterium nuclei can be expressed as [5] with σ 0 the unpolarized cross section, T 2i the tensor analyzing powers and P zz the degree of tensor polarization. The polarization axis of the deuteron is defined by the angles θ * and φ * in the frame where the z-axis is along the direction of the three-momentum transfer q and the x-axis is perpendicular to z in the scattering plane. The experiment was performed using a 704 MeV electron beam in the AmPS storage ring [6] and a tensorpolarized deuterium internal target [7] at NIKHEF. By stacking several pulses of electrons, produced by the medium-energy accelerator, circulating currents of up to 150 mA were stored in the ring. A beam life time in excess of 2000 s was obtained by compensating synchrotron radiation losses with a 476 MHz cavity.Nuclear-polarized deuterium gas was provided by an atomic beam source. Deuterium atoms are produced by means of an RF dissociator. Atoms with their electron spin up are focused into the target-cell feed tube by two sextupole magnets, whereas those with spin down are defocused. A medium-and a strong-field RF-unit induce transitions between the hyperfine states, resulting in...

Abstract. To determine nonspherical angular-momentum amplitudes in hadrons at long ranges (low Q 2 ), data were taken for the p( e, e p)π 0 reaction in the ∆ region at Q 2 = 0.060 (GeV/c) 2 utilizing the magnetic spectrometers of the A1 Collaboration at MAMI. The results for the dominant transition magnetic dipole amplitude and the quadrupole to dipole ratios at W = 1232 MeV are M Experimental confirmation of the presence of nonspherical hadron amplitudes (i.e. d states in quark models or p-wave π-N states) is fundamental and has been the subject of intense experimental and theoretical interest (for reviews see [1][2][3]). This effort has focused on the measurement of the electric and Coulomb quadrupole amplitudes (E2, C2) in the predominantly M 1 (maga Current address:

We report new measurements of the neutron charge form factor at low momentum transfer using quasielastic electrodisintegration of the deuteron. Longitudinally polarized electrons at an energy of 850 MeV were scattered from an isotopically pure, highly polarized deuterium gas target. The scattered electrons and coincident neutrons were measured by the Bates Large Acceptance Spectrometer Toroid (BLAST) detector. The neutron form factor ratio GEn/GMn was extracted from the beam-target vector asymmetry AedV at four-momentum transfers Q2=0.14, 0.20, 0.29, and 0.42 (GeV/c)2.

We report the first precision measurement of the proton electric to magnetic form factor ratio from spin-dependent elastic scattering of longitudinally polarized electrons from a polarized hydrogen internal gas target. The measurement was performed at the MIT-Bates South Hall Ring over a range of four-momentum transfer squared Q2 from 0.15 to 0.65 (GeV/c)(2). Significantly improved results on the proton electric and magnetic form factors are obtained in combination with existing cross-section data on elastic electron-proton scattering in the same Q2 region.