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We report new p$(\vec{e},e^\prime p)��^\circ$ measurements in the $��^{+}(1232)$ resonance at the low momentum transfer region utilizing the magnetic spectrometers of the A1 Collaboration at MAMI. The mesonic cloud dynamics are predicted to be dominant and appreciably changing in this region while the momentum transfer is sufficiently low to be able to test chiral effective calculations. The results disagree with predictions of constituent quark models and are in reasonable agreement with dynamical calculations with pion cloud effects, chiral effective field theory and lattice calculations. The reported measurements suggest that improvement is required to the theoretical calculations and provide valuable input that will allow their refinements.

We report new p(e, e′p)π̊ measurements in the Δ+(1232) resonance at the low momentum transfer region utilizing the magnetic spectrometers of the A1 Collaboration at MAMI. The mesonic cloud dynamics are predicted to be dominant and appreciably changing in this region while the momentum transfer is sufficiently low to be able to test chiral effective field theory calculations. The results disagree with predictions of constituent quark models and are in reasonable agreement with dynamical calculations with pion cloud effects, chiral effective field theory and lattice calculations. The reported measurements suggest that improvement is required to the theoretical calculations and provide valuable input that will allow their refinements. © Società Italiana di Fisica / Springer-Verlag 2013.

The determination of nonspherical angular momentum amplitudes in nucleons at long ranges (low Q2) was accomplished through the p(, e'p)0 reaction in the region at Q2=0.060, 0.127, and 0.200 (GeV/c)2 at the Mainz Microtron with an accuracy for the cross sections of 4%. The results for the dominant transition magnetic dipole amplitude and the quadrupole to dipole ratios have been obtained with an estimated model uncertainty that is approximately the same as the experimental uncertainty. Lattice and effective field theory predictions agree with our data within the relatively large estimated theoretical uncertainties. Phenomenological models are in good agreement with experiment when the resonant amplitudes are adjusted to the data. To check reaction model calculations additional data were taken for center-of-mass energies below resonance and for the LT' structure function. These results confirm the dominance, and general Q2 variation, of the pionic contribution at large distances.

We report on new H(e,e′p)γ measurements in the Δ(1232) resonance at Q2=0.06 (GeV/c)2 carried out simultaneously with H(e,e′p)π0. It is the lowest Q2 for which the virtual Compton scattering (VCS) reaction has been studied in the first resonance region. The VCS measured cross sections are well described by dispersion-relation calculations in which the multipole amplitudes derived from H(e,e′p)π0 data are used as input, thus confirming the compatibility of the results. The derived resonant magnetic dipole amplitude M1+3/2=(40.60±0.70stat+sys) (10-3/mπ+) at W=1232 MeV is in excellent agreement with the value extracted from H(e,e′p)π0 measurements. © 2008 The American Physical Society.

The determination of nonspherical angular momentum amplitudes in nucleons at long ranges (low Q2) was accomplished through the p(e→,e'p)π0 reaction in the Δ region at Q2=0.060, 0.127, and 0.200 (GeV/c)2 at the Mainz Microtron with an accuracy for the cross sections of 4%. The results for the dominant transition magnetic dipole amplitude and the quadrupole to dipole ratios have been obtained with an estimated model uncertainty that is approximately the same as the experimental uncertainty. Lattice and effective field theory predictions agree with our data within the relatively large estimated theoretical uncertainties. Phenomenological models are in good agreement with experiment when the resonant amplitudes are adjusted to the data. To check reaction model calculations additional data were taken for center-of-mass energies below resonance and for the σLT' structure function. These results confirm the dominance, and general Q2 variation, of the pionic contribution at large distances. © 2008 The American Physical Society.

We report on new H(e, e p)γ measurements in the (1232) resonance at Q2 = 0.06 (GeV/c)2 carried out simultaneously with H(e, e p)π 0. It is the lowestQ2 for which the virtual Compton scattering (VCS) reaction has been studied in the first resonance region. The VCS measured cross sections are well described by dispersionrelation calculations in which the multipole amplitudes derived from H(e, e p)π 0 data are used as input, thus confirming the compatibility of the results. The derived resonant magnetic dipole amplitude M 3/2 1+ = (40.60 ± ; 0.70stat+sys)(10− 3/mπ +) at W = 1232 MeV is in excellent agreement with the value extracted from H(e, e p)π 0 measurements.

This book contains the proceedings of the third international workshop on “From Parity Violation to Hadronic Structure and more ...” which was held from May 16 to May 20, 2006, at the George Eliopoulos conference center on the Greek island of Milos. It is part of a series that started in Mainz in 2002 and was followed by a second workshop in Grenoble in 2004. While originally initiated by the extraction of the strangeness contribution to the electromagnetic form factors of the nucleon, the workshop series has continuously broadened the focus to the application of Parity Violation using hadronic probes and to Parity Violation experiments in atomic physics. Meanwhile there have been many exciting new proposals for using Parity Violation in other areas like in the search for new physics beyond the standard model or in exploring hadron structure. There are also close connections to the open question on the size of the two photon exchange amplitude. Fifty years after the 1956 proposal of Lee and Yang to test the hypothesis of violation of parity symmetry in the weak interaction, the many applications of parity violation in very different experiments are way beyond the scope of what Lee and Yang could have imagined. For the physics topics discussed during this workshop, the application of parity violation has become a standard work horse that allows to extract many physics topics in different experiments.

We report new precise p$(\vec{e},e^\prime p)\pi^0$ measurements at the peak of the $\Delta^{+}(1232)$ resonance at $Q^2=\unit[0.20](GeV/c)^2$ performed at the Mainz Microtron (MAMI). The new data are sensitive to both the electric quadrupole ($E2$) and the coulomb quadrupole ($C2$) amplitudes of the $\gamma^* N\to\Delta$ transition. They yield precise quadrupole to dipole amplitude ratios CMR $= (-5.09 \pm 0.28_{stat+sys}\pm 0.30_{model})%$ and EMR $= (-1.96 \pm 0.68_{stat+sys} \pm 0.41_{model})%$ for $M^{3/2}_{1+} = (39.57 \pm 0.75_{stat+sys}\pm 0.40_{model})(10^{-3}/m_{\pi^+})$. The new results are in disagreement with Constituent Quark Model predictions and in qualitative agreement with models that account for mesonic contributions, including recent Lattice calculations. They thus give further credence to the conjecture of deformation in hadronic systems favoring the attribution of the origin of deformation to the dominance of mesonic effects., Comment: 2 figures

This book contains the proceedings of the third international workshop on “From Parity Violation to Hadronic Structure and more ...” which was held from May 16 to May 20, 2006, at the George Eliopoulos conference center on the Greek island of Milos. It is part of a series that started in Mainz in 2002 and was followed by a second workshop in Grenoble in 2004. While originally initiated by the extraction of the strangeness contribution to the electromagnetic form factors of the nucleon, the workshop series has continuously broadened the focus to the application of Parity Violation using hadronic probes and to Parity Violation experiments in atomic physics. Meanwhile there have been many exciting new proposals for using Parity Violation in other areas like in the search for new physics beyond the standard model or in exploring hadron structure. There are also close connections to the open question on the size of the two photon exchange amplitude. Fifty years after the 1956 proposal of Lee and Yang to test the hypothesis of violation of parity symmetry in the weak interaction, the many applications of parity violation in very different experiments are way beyond the scope of what Lee and Yang could have imagined. For the physics topics discussed during this workshop, the application of parity violation has become a standard work horse that allows to extract many physics topics in different experiments.

We report new precise p (over(e, →), e′ p) π0 measurements at the peak of the Δ+ (1232) resonance at Q2 = 0.20 (GeV / c)2 performed at the Mainz Microtron (MAMI). The new data are sensitive to both the electric (E2) and the Coulomb (C2) quadrupole amplitudes of the γ* N → Δ transition. They yield precise quadrupole to dipole amplitude ratios: CMR = (- 5.09 ± 0.28stat + sys ± 0.30model) % and EMR = (- 1.96 ± 0.68stat + sys ± 0.41model) % for M1 +3 / 2 = (39.57 ± 0.75stat + sys ± 0.40model) (10-3 / mπ+). The new results are in disagreement with Constituent Quark Model predictions and in qualitative agreement with models that account for mesonic contributions, including recent Lattice calculations. They thus give further credence to the conjecture of deformation in hadronic systems favoring the attribution of the origin of deformation to the dominance of mesonic effects. © 2007.

To determine nonspherical angular-momentum amplitudes in hadrons at long ranges (low Q(2)), data were taken for the p((e) over right arrow e’p)pi(0) reaction in the Delta 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-1+(3/2) = (40.33 +/- 0.63(stat+syst) +/- 0.61(model))(10(-3)/m(pi+)), Re(E-1+(3/2)/M-1+(3/2)) = (-2.28 +/- 0.29(stat+syst) +/- 0.20(model))%, and Re(S-1+(3/2)/M-1+(3/2)) = (-4.81 +/- 0.27(stat+syst) +/- 0.26(model))%. These disagree with predictions of constituent quark models but are in reasonable agreement with lattice calculations with nonlinear (chiral) pion mass extrapolations, with chiral effective field theory, and with dynamical models with pion cloud effects. These results confirm the dominance, and general Q(2) variation, of the pionic contribution at large distances.

In this work, a polymer gel-magnetic resonance (MR) imaging method is employed for the dosimetric characterization of a new 125I low dose rate seed (IsoSeed® model I25.S17). Two vials filled with PABIG gel were prepared in-house and one new seed as well as one commercially available 125I seed of similar dose rate and well-known dosimetric parameters (IsoSeed® model I25.S06) were positioned in each vial. Both seeds in each vial were MR scanned simultaneously on days 11 and 26 after implantation. The data obtained from the known seed in each vial are used to calibrate the gel dose response which, for the prolonged irradiation duration necessitated by the investigated dose rates, depends on the overall irradiation time. Data for this study are presented according to the AAPM TG-43 dosimetric formalism. Polymer gel results concerning the new seed are compared to corresponding, published dosimetric results obtained, for the purpose of the new seed clinical implementation, by our group using the established methods of Monte Carlo (MC) simulation and thermo-luminescence dosimetry (TLD). Polymer gel dosimetry yields an average dose rate constant value of Λ = (0.921 ± 0.031) cGy h-1 U-1 relative to MCΛ = (0.929 ± 0.014) cGy h-1 U-1, TLDΛ = (0.951 ± 0.044) cGy h-1 U-1 and the average value of Λ = (0.940 ± 0.051) cGy h-1 U-1 proposed for the clinical implementation of the new seed. Results for radial dose function, gL(r), and anisotropy function, F(r, θ), also agree with corresponding MC calculations within experimental uncertainties which are smaller for the polymer gel method compared to TLD. It is concluded that the proposed polymer gel-magnetic resonance imaging methodology could be used at least as a supplement to the established techniques for the dosimetric characterization of new low energy and low dose rate interstitial brachytherapy seeds. © 2006 IOP Publishing Ltd.

Accurate measurements of the p(→e, e′p)π0 reaction were performed at Q2 = 0.127 (GeV/c)2 in the A resonance energy region. The experiments at the MIT-Bates Linear Accelerator used an 820 MeV polarized electron beam with the out-of-plane magnetic spectrometer system (OOPS). In this Letter we report the first simultaneous determination of both the TL and TL′ ("fifth" or polarized) cross sections at low Q2 where the pion cloud contribution is predicted to dominate the quadrupole amplitudes (E2 and C2). These are the real and imaginary parts of the transverse-longitudinal interference amplitudes and provide a sensitive determination of the Coulomb quadrupole amplitude and a test of reaction calculations. Comparisons with model calculations are presented. The empirical MAID calculation gives the best overall agreement with this accurate data. The parameters of this model for the values of the resonant multipoles are [M1+(I = 3/2)| = (40.9 ± 0.3) × 10-3/mπ, CMR = C2/M1 = -6.5 ± 0.3%, EMR = E2/M1 = -2.2 ± 0.9%, where the errors are due to the experimental uncertainties. © 2003 Elsevier Science B.V. All rights reserved.

We report on the design and performance of compact detector packages currently installed in the four magnetic out-of-plane spectrometers for electron scattering experiments at the MIT-Bates Linear Accelerator Center. The detector packages have been designed to meet the mechanical requirements arising from out-of-plane particle detection. They offer good trajectory and momentum reconstruction, particle identification and time-of-flight measurements for electrons, pions, protons, and deuterons with large momentum bites and in broad kinematical ranges and high luminosities. The detectors have so far been used with great success in out-of-plane measurements of 12C(e→,e′p), 2H(e→,e′p), virtual Compton scattering below pion threshold and in studies of the N→Δ transition in both exclusive reaction channels 1H(e→,e′p)π0 and 1H(e→,e′π+)n. © 2002 Elsevier Science B.V. All rights reserved.

Accurate measurements of the p(e→,e′p)π0 reaction were performed at Q2=0.127 (GeV/c)2 in the Δ resonance energy region. The experiments at the MIT-Bates Linear Accelerator used an 820 MeV polarized electron beam with the out-of-plane magnetic spectrometer system (OOPS). In this Letter we report the first simultaneous determination of both the TL and TL′ (“fifth” or polarized) cross sections at low Q2 where the pion cloud contribution is predicted to dominate the quadrupole amplitudes (E2 and C2). These are the real and imaginary parts of the transverse–longitudinal interference amplitudes and provide a sensitive determination of the Coulomb quadrupole amplitude and a test of reaction calculations. Comparisons with model calculations are presented. The empirical MAID calculation gives the best overall agreement with this accurate data. The parameters of this model for the values of the resonant multipoles are |M1+(I=3/2)|=(40.9±0.3)×10−3/mπ, CMR=C2/M1=−6.5±0.3%, EMR=E2/M1=−2.2±0.9%, where the errors are due to the experimental uncertainties.