0000000000170413

AUTHOR

P. Jennewein

showing 50 related works from this author

Real and Virtual Compton Scattering (experiments)

1999

This paper deals with Real and Virtual Compton Scattering off the proton at threshold and the way to deduce information about the nucleon polarizabilities.

Nuclear physicsScattering cross-sectionPhysicsAnomalous magnetic dipole momentProtonAstrophysics::High Energy Astrophysical PhenomenaNuclear TheoryPhysics::Atomic and Molecular ClustersCompton scatteringNuclear ExperimentNucleon
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Compton scattering from the free and bound proton at backward angles above π-threshold

1999

Differential cross sections for Compton scattering from the free proton at Theta(gamma)(lab) = 130.7 degrees in the energy region from 200 MeV to 410 MeV and far quasi-free Compton scattering from the proton bound in the deuteron at Theta(gamma)(lab) = 148.8 degrees in the energy region from 200 MeV to 290 MeV have been measured. The free proton data are in agreement with dispersion-theory predictions based on standard parameters. The difference of the proton polarizabilities has been extracted from the quasi-free data. Our result, - = [9.1 +/- 1.7(stat + syst) +/- 1.2(mod)] x 10(-4) fm(3), is in reasonable agreement with the world average of the free proton data if the backward spin polari…

PhysicsNuclear and High Energy PhysicsBackscatterProton010308 nuclear & particles physicsAstrophysics::High Energy Astrophysical PhenomenaNuclear TheoryCompton scattering01 natural sciencesNuclear physicsDeuteriumPolarizabilityDispersion relation0103 physical sciencesNeutronAtomic physicsNuclear Experiment010306 general physicsSpin-½
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Compton Scattering by the Proton

2001

Compton scattering by the proton has been measured over a wide range covering photon energies 250 MeV < E_\gamma < 800 MeV and photon scattering angles 30^0 < \theta^{lab}_\gamma < 150^0, using the tagged-photon facility at MAMI (Mainz) and the large-acceptance arrangement LARA. The data are in good agreement with the dispersion theory based on the SAID-SM99K parameterization of photo-meson amplitudes. From the subset of data between 280 and 360 MeV the resonance pion-photoproduction amplitudes were evaluated leading to the multipole E2/M1 ratio EMR(340 MeV) =(-1.6 \pm 0.4(stat+syst) \pm 0.2(model)%. From all data below 455 MeV the proton's backward spin polarizability was determined to be …

PhysicsNuclear and High Energy PhysicsPhotonProton010308 nuclear & particles physicsNuclear TheoryCompton scatteringFOS: Physical sciences7. Clean energy01 natural sciencesResonance (particle physics)Scattering amplitudeNuclear physicsHigh Energy Physics - PhenomenologyHigh Energy Physics - Phenomenology (hep-ph)Polarizability0103 physical sciencesPhysics::Accelerator PhysicsHigh Energy Physics::ExperimentNuclear Experiment (nucl-ex)010306 general physicsMultipole expansionNuclear ExperimentNuclear ExperimentSpin-½
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The first Virtual Compton Scattering experiment at MAMI

1999

Abstract Virtual Compton scattering, i.e. the exclusive reaction γ ∗ p → γ′p′ with γ ∗ denoting a virtual photon, provides new insights on the internal structure of the proton. Below π 0 production threshold, this experiment measures the generalized polarizabilities of the proton as defined by Guichon et al [1], [2] and Drechsel et al [3]. These new electromagnetic observables, functions of Q 2 , enlarge the concept of electric (α0 and magnetic (β) polarizabilities in Real Compton Scattering ( Q 2 =0) [4]. The first VCS experiment [5] of this kind was measured at the three spectrometer facility at the Mainz Microtron MAMI for Q 2 =0.33 GeV 2 and we present in this paper the preliminary resu…

PhysicsNuclear and High Energy Physics[PHYS.HEXP] Physics [physics]/High Energy Physics - Experiment [hep-ex]ProtonSpectrometer010308 nuclear & particles physicsCompton scatteringVirtual particleObservable01 natural sciences7. Clean energyNuclear physics0103 physical sciences[PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex]Nuclear Experiment010306 general physicsMicrotron
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Measurement of the ExclusiveH3e(e,e′p)Reaction Below the Quasielastic Peak

2004

New, high-precision measurements of the 3He(e,ep) reaction using the A1 Collaboration spectrometers at the Mainz microtron MAMI are presented. These were performed in antiparallel kinematics at energy transfers below the quasielastic peak, and at a central momentum transfer of 685 MeV/c. Cross sections and distorted momentum distributions were extracted and compared to theoretical predictions and existing data. The longitudinal and transverse behavior of the cross section was also studied. Sizable differences in the cross-section behavior from theoretical predictions based on the plane wave impulse approximation were observed in both the two- and three-body breakup channels. Full Faddeev-ty…

PhysicsNuclear reactionNuclear TheoryMomentum transferPlane waveGeneral Physics and AstronomyImpulse (physics)Few-body systemsNuclear physicsTransverse planeAtomic physicsNuclear ExperimentMicrotronLeptonPhysical Review Letters
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Measurement of the Recoil Polarization in thep(e→,e′p→)π0Reaction at theΔ(1232)Resonance

2001

The recoil proton polarization has been measured in the $p(\stackrel{\ensuremath{\rightarrow}}{e}{,e}^{\ensuremath{'}}\stackrel{\ensuremath{\rightarrow}}{p}){\ensuremath{\pi}}^{0}$ reaction in parallel kinematics around $W\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1232\phantom{\rule{0ex}{0ex}}\mathrm{MeV}$, ${Q}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.121\phantom{\rule{0ex}{0ex}}(\mathrm{GeV}/c{)}^{2}$, and $\ensuremath{\epsilon}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.718$ using the polarized cw electron beam of the Mainz Microtron. All three proton polarization components, ${P}_{x}/{P}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{-…

PhysicsParallel kinematicsRecoil protonRecoilGeneral Physics and AstronomyAtomic physicsPolarization (waves)Physical Review Letters
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Virtual Compton Scattering and polarizabilities

1999

Abstract Virtual Compton Scattering (VCS) off the proton below pion threshold allows access to generalized polarizabilities of the proton. These observables measure the response of the nucleon to low energy electromagnetic field perturbations. This paper presents a comparison with Real Compton Scattering and also results for the first dedicated VCS experiment performed at the Mainz Microtron MAMI with high resolution spectrometers at Q2 = 0.33 GeV2.

Electromagnetic fieldPhysicsNuclear and High Energy PhysicsParticle physicsProton010308 nuclear & particles physicsNuclear TheoryCompton scatteringMeasure (physics)Observable01 natural sciencesNuclear physicsPion0103 physical sciences[PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex]010306 general physicsNucleonNuclear ExperimentMicrotron
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Precise measurements of the neutron magnetic form factor

1998

Abstract The neutron magnetic form factor Gmn has been determined via a measurement of the ratio of cross sections D(e,e′n) and D(e,e′p). The absolute detection efficiency of the neutron detector was measured with high accuracy using tagged neutrons produced from H(n,p)n elastic scattering by means of a high intensity neutron beam. This approach minimizes the model dependence and improves upon the weakest points of previous experiments. Data in the range q2=0.2–0.8 (GeV/c)2 with uncertainties of

Elastic scatteringPhysicsNuclear physicsNuclear and High Energy PhysicsRange (particle radiation)Astrophysics::High Energy Astrophysical PhenomenaMagnetic form factorNeutron detectionNeutronAtomic physicsNeutron radiationNuclear ExperimentIntensity (heat transfer)Physics Letters B
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A Compact Solid State Detector for Small Angle Particle Tracking

1999

MIDAS (MIcrostrip Detector Array System) is a compact silicon tracking telescope for charged particles emitted at small angles in intermediate energy photonuclear reactions. It was realized to increase the angular acceptance of the DAPHNE detector and used in an experimental program to check the Gerasimov-Drell-Hearn sum rule at the Mainz electron microtron, MAMI. MIDAS provides a trigger for charged hadrons, p/pi identification and particle tracking in the region 7 deg &lt; theta &lt; 16 deg. In this paper we present the main characteristics of MIDAS and its measured performances.

PhysicsNuclear and High Energy Physicsbusiness.industryPhysics::Instrumentation and DetectorsDetectorHadronNuclear TheoryFOS: Physical sciencesElectronTracking (particle physics)nucl-exCharged particlelaw.inventionTelescopeOpticslawHigh Energy Physics::ExperimentSum rule in quantum mechanicsNuclear Experiment (nucl-ex)businessNuclear ExperimentInstrumentationMicrotronNuclear Experiment
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The reaction at Eγ = 60 and 80 MeV

1986

Abstract The tagged photon technique has been used to measure the 12C photoproton cross section over the angular range θp = 30°–135° for Eγ = 60 and 80 MeV. Comparison of the results with quasifree knockout and quasideuteron calculations shows that photon interaction with two-nucleon pairs is dominant at least for high excitation energies in the residual nucleus.

PhysicsNuclear and High Energy PhysicsAngular rangePhotonNuclear TheoryMeasure (physics)ResidualNuclear physicsCross section (physics)medicine.anatomical_structuremedicineAtomic physicsNuclear ExperimentNucleusExcitationPhysics Letters B
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Quasi-free Compton Scattering and the Polarizabilities of the Neutron

2002

Differential cross sections for quasi-free Compton scattering from the proton and neutron bound in the deuteron have been measured using the Glasgow/Mainz tagging spectrometer at the Mainz MAMI accelerator together with the Mainz 48 cm $\oslash$ $\times$ 64 cm NaI(Tl) photon detector and the G\"ottingen SENECA recoil detector. The data cover photon energies ranging from 200 MeV to 400 MeV at $\theta^{LAB}_\gamma=136.2^\circ$. Liquid deuterium and hydrogen targets allowed direct comparison of free and quasi-free scattering from the proton. The neutron detection efficiency of the SENECA detector was measured via the reaction $p(\gamma,\pi^+ n)$. The "free" proton Compton scattering cross sect…

Nuclear and High Energy PhysicsProtonNuclear TheoryFOS: Physical sciences7. Clean energy01 natural sciencesHigh Energy Physics - ExperimentNuclear physicsHigh Energy Physics - Experiment (hep-ex)High Energy Physics - Phenomenology (hep-ph)Polarizability0103 physical sciencesNeutron detectionNeutronNuclear Experiment (nucl-ex)010306 general physicsNuclear ExperimentNuclear ExperimentPhysics010308 nuclear & particles physicsScatteringCompton scatteringHigh Energy Physics - PhenomenologyDeuteriumCover (topology)High Energy Physics::Experiment
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The horizontal drift chambers for the focal plane proton-polarimeter of the 3-spectrometer setup at MAMI

2002

Abstract Large-area horizontal drift chambers have been built for use in a proton polarimeter. A gas mixture of 20% argon and 80% ethane is used. The left–right assignment is achieved by measuring the difference of the signals induced on neighboring potential wires. A spatial resolution of 300 μm is achieved.

PhysicsNuclear and High Energy PhysicsArgonProtonSpectrometerPhysics::Instrumentation and Detectorsbusiness.industrychemistry.chemical_elementPolarimeterCardinal pointOpticschemistrybusinessInstrumentationImage resolutionNuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
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Measurement of GEp/GMp via polarization transfer at Q2 = 0.4 GeV /c2

2001

The polarization transfer from longitudinally polarized electrons to protons in the elastic scattering p( e, e' p) has been measured around Q2 = 0.4 (GeV/c)2 with the three-spectrometer facility at the Mainz microtron MAMI. From this polarization transfer the ratio G Ep/(G Mp/μp) has been determined. The ratio is found to be slightly less than unity in agreement with recent results from other laboratories and from the Rosenbluth separation of cross-sections measured with unpolarized electrons.

Nuclear physicsElastic scatteringPhysicsNuclear and High Energy PhysicsHadronNuclear fusionElectronAtomic physicsPolarization (waves)MicrotronThe European Physical Journal A
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First Measurement of the Gerasimov-Drell-Hearn Sum Rule forH1from 0.7 to 1.8 GeV at ELSA

2003

To verify the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the first time experimentally, we measured the helicity dependent total photoabsorption cross section with circularly polarized real photons and longitudinally polarized nucleons in the photon energy range 0.68-1.82 GeV with the tagged photon facility at ELSA. The experiment was carried out with a 4pi detection system, a circularly polarized tagged photon beam, and a frozen spin polarized proton target. The contribution to the GDH sum rule in this photon energy range is [49.9+/-2.4(stat)+/-2.2(syst)] mub.

PhysicsParticle physicsRange (particle radiation)PhotonProton010308 nuclear & particles physicsNuclear TheoryGeneral Physics and AstronomyPhoton energy01 natural sciencesHelicityNuclear physics0103 physical sciencesHigh Energy Physics::ExperimentSum rule in quantum mechanicsNuclear Experiment010306 general physicsNucleonSpin-½Physical Review Letters
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Intermediate resonance excitation in the γp→pπ0π0 reaction

2005

The helicity dependence of the total cross section for the (gamma) over right arrow(p) over right arrow -> p pi(0)pi(0) reaction has been measured for the first time at incident photon energies from 400 to 800 MeV. The measurement, performed at the tagged photon beam facility of the MAMI accelerator in Mainz, used the large acceptance detector DAPHNE and a longitudinally polarized frozen-spin target. This channel is found to be excited predominantly when the photon and proton have a parallel spin orientation, most likely due to the intermediate production of the D-13(1520) resonance. However, the contribution of the antiparallel spin configuration, arising from other reaction mechanisms, is…

PhysicsNuclear and High Energy PhysicsPhotonProton010308 nuclear & particles physicsResonance01 natural sciencesHelicityCross section (geometry)Nuclear physicsExcited state0103 physical sciencesPhysics::Accelerator PhysicsAtomic physicsNuclear Experiment010306 general physicsNucleonSpin (physics)Physics Letters B
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STATUS OF STRANGENESS ELECTRO-PRODUCTION AT MAMI

2009

At the Institut für Kernphysik in Mainz, Germany, the microtron MAMI has been upgraded to 1.5 GeV electron beam energy and can now be used to study strange hadronic systems. The magnetic spectrometer KAOS from GSI was dismantled and re-installed in the spectrometer facility operated by the A1 collaboration. The spectrometer's primary purpose is to study strangeness electro-production. Its compact design and its capability to detect negative and positive charged particles simultaneously under forward scattering angles complements the existing spectrometers. In 2008, an important milestone has been reached by the successful measurement of kaon production off a liquid hydrogen target. The ide…

magnetic spectrometer; particle detector design; kaon electro-production; hypernuclei electro-productionPhysicsNuclear and High Energy PhysicsParticle physicsSpectrometerPhysics::Instrumentation and DetectorsScatteringNuclear TheoryHadronDetectorGeneral Physics and AstronomyStrangenessCharged particleNuclear physicsPhysics::Accelerator PhysicsVacuum chamberNuclear ExperimentMicrotronStrangeness in Nuclear and Hadronic Systems
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Measurement of Helicity-Dependent Photoabsorption Cross Sections on the Neutron from 815 to 1825 MeV

2005

Helicity-dependent total photoabsorption cross sections on the deuteron have been measured for the first time at ELSA (Bonn) in the photon energy range from 815 to 1825 MeV. Circularly polarized tagged photons impinging on a longitudinally polarized LiD target have been used together with a highly efficient 4pi detector system. The data around 1 GeV are not compatible with predictions from existing multipole analyses. From the measured energy range an experimental contribution to the GDH integral on the neutron of [33.9 +/- 5.5(stat) +/- 4.5(syst)] microb is extracted.

PhysicsRange (particle radiation)Photon010308 nuclear & particles physicsNuclear TheoryGeneral Physics and AstronomyPhoton energy7. Clean energy01 natural sciencesHelicityNuclear physicsDeuterium0103 physical sciencesNeutronAtomic physicsNuclear Experiment010306 general physicsMultipole expansionCircular polarizationPhysical Review Letters
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The three-spectrometer facility at the Mainz microtron MAMI

1998

Abstract A set-up of three high-resolution magnetic spectrometers, for simplicity named A, B and C, has been built as the central facility for the precise determination of double and triple coincidence cross sections of hadron knock-out and meson production through the scattering of electrons at the Mainz microtron MAMI. The spectrometers A and C with point-to-point optics in the dispersive plane and parallel-to-point optics in the non-dispersive plane have a solid angle of 28 msr and a momentum acceptance of 20 and 25%, respectively. They each consist of a quadrupole, a sextupole and two dipole magnets, reaching maximum momenta of 735 and 550 MeV/c, respectively. The spectrometer B has a s…

PhysicsNuclear and High Energy PhysicsSpectrometerCherenkov detectorSolid angleElectronlaw.inventionNuclear physicsDipoleDipole magnetlawQuadrupoleNuclear ExperimentInstrumentationMicrotronNuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
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Neutron polarizabilities investigated by quasi-free Compton scattering from the deuteron

2002

Measuring Compton scattered photons and recoil neutrons in coincidence, quasifree Compton scattering by the neutron has been investigated at MAMI (Mainz) at ${\ensuremath{\theta}}_{\ensuremath{\gamma}}^{\mathrm{lab}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}136\ifmmode^\circ\else\textdegree\fi{}$ in an energy range from 200 to 400 MeV. From the data a polarizability difference of ${\ensuremath{\alpha}}_{n}\ensuremath{-}{\ensuremath{\beta}}_{n}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}9.8\ifmmode\pm\else\textpm\fi{}3.6(\mathrm{stat}{)}_{\ensuremath{-}1.1}^{+2.1}(\mathrm{syst})\ifmmode\pm\else\textpm\fi{}2.2(\mathrm{model})$ in units of ${10}^{\ensuremath{-}4}{\mathrm{fm}}^{…

Physics010308 nuclear & particles physicsAstrophysics::High Energy Astrophysical PhenomenaCompton scatteringGeneral Physics and AstronomyFOS: Physical sciencesAstrophysics::Cosmology and Extragalactic Astrophysics7. Clean energy01 natural sciencesHigh Energy Physics - ExperimentHigh Energy Physics - PhenomenologyHigh Energy Physics - Experiment (hep-ex)High Energy Physics - Phenomenology (hep-ph)Deuterium0103 physical sciencesNeutronHigh Energy Physics::ExperimentAtomic physicsNuclear Experiment (nucl-ex)010306 general physicsNuclear ExperimentNuclear ExperimentEnergy (signal processing)Astrophysics::Galaxy Astrophysics
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Virtual Compton Scattering at MAMI γ*p→ γ1p1

1999

The virtual Compton scattering (VCS) is the electron scattering on a proton which radiates a real photon before being detected. The new observables, called Generalized Polarizabilities (GP), extracted from this VCS at threshold can be understood as the deformation of the charge and current distributions of the proton [1]. These GP are functions of the mass of the virtual photon Q2. In real Compton scattering (Q2 = 0), some polarizabilities of the nucleon are already measured [2]. With the VCS, we will generalize these observables by measuring them at different values of Q2.

Nuclear physicsPhysicsPhotonProtonCompton scatteringVirtual particleCharge (physics)ObservableNucleonElectron scattering
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Low-energy Compton scattering and the polarizabilities of the proton

2001

Differential cross-sections for Compton scattering from the proton have been measured at the MAMI tagged photon facility using the TAPS setup. The data cover an angular range of θlab γ = 59°-155° and photon energies ranging from 55 MeV to 165 MeV. Our results are in good agreement with those from previous experiments, but yield higher precision. Using dispersion relations the proton polarizabilities have been determined to be = [11.9±0.5stat.±1.3syst.±0.3mod.] . 10-4 fm 3 and = [1.2±0.7stat.±0.3syst.±0.4mod.)] . 10-4 fm 3. These results confirm the Baldin sum rule which was re-evaluated to be + = [13.8±0.4] . 10-4 fm 3. We can also conclude that there is no significant additional asymptotic…

PhysicsNuclear and High Energy PhysicsPhotonProton010308 nuclear & particles physicsHadronCompton scattering01 natural sciencesNuclear physicsPolarizabilityDispersion relation0103 physical sciencesSum rule in quantum mechanicsAtomic physics010306 general physicsSpin-½The European Physical Journal A
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Polarization transfer in the 4HeH reaction

2001

Abstract Polarization transfer in the 4He ( e → ,e′ p → ) 3 H reaction at a Q2 of 0.4 (GeV/c)2 was measured at the Mainz Microtron MAMI. The ratio of the transverse to the longitudinal polarization components of the ejected protons was compared with the same ratio for elastic ep scattering. The results are consistent with a recent fully relativistic calculation which includes a predicted medium modification of the proton form factor based on a quark–meson coupling model.

PhysicsNuclear and High Energy PhysicsProtonScatteringNuclear Theorychemistry.chemical_elementPolarization (waves)Nuclear physicsTransverse planechemistryPhysics::Accelerator PhysicsNuclear ExperimentMicrotronHeliumPhysics Letters B
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Final State Interaction Effects in 3He(e ,e'p)

2003

Abstract Asymmetries in quasi-elastic 3 He ( e → , e ′ p ) have been measured at a momentum transfer of 0.67 (GeV/ c ) 2 and are compared to a calculation which takes into account relativistic kinematics in the final state and a relativistic one-body current operator. With an exact solution of the Faddeev equation for the 3 He -ground state and an approximate treatment of final state interactions in the continuum good agreement is found with the experimental data.

PhysicsNuclear and High Energy PhysicsCurrent (mathematics)3He-structure010308 nuclear & particles physicsOperator (physics)Continuum (design consultancy)Momentum transferKinematicsState (functional analysis)01 natural sciencesExact solutions in general relativityQuantum mechanicsQuantum electrodynamics0103 physical sciencesFinal-state interactionPolarized electron scattering010306 general physicsGround statePhysics Letters B
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The 1.5GeV harmonic double-sided microtron at Mainz University

2008

Abstract At the Institut fur Kernphysik of Mainz University a harmonic double-sided microtron (HDSM) has been built to extend the experimental capabilities for nuclear and particle physics experiments to higher excitation energies. This novel microtron variant accelerates the 0.855 GeV continuous wave (cw) electron beam of the established three-staged race track microtron (RTM) cascade MAMI B up to 1.5 GeV. It consists of two normal conducting linear accelerators (linacs) through which the electrons are guided up to 43 times by a pair of 90°-bending magnets at each end. For beam dynamical reasons the linacs operate at the harmonic frequencies of 4.90 and 2.45 GHz. The extended facility is c…

PhysicsNuclear and High Energy PhysicsElectronLinear particle acceleratorNuclear physicsAccelerationCathode rayHarmonicPhysics::Accelerator PhysicsNuclear ExperimentInstrumentationMicrotronBeam (structure)ExcitationNuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
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First measurement of the helicity-dependent γ p↦pη differential cross-section

2003

The helicity dependence of the (γ) over right arrow(p) over right arrow -+ peta reaction has been measured for the first time at a center-of-mass angle theta(eta)*= 70degrees in the photon energy range from 780 MeV to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam. and a longitudinally polarized frozen-spin target. The helicity 3/2 cross-section is found to be small and the results for helicity 1/2 agree with predictions from the MAID analysis.

PhysicsScattering cross-sectionNuclear and High Energy PhysicsParticle physics010308 nuclear & particles physicsHadronPhoton energy01 natural sciencesHelicityNuclear physics0103 physical sciencesPhysics::Accelerator PhysicsNuclear fusionPhoton beamNuclear Experiment010306 general physicsMicrotronThe European Physical Journal A
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Measurement of the Gerasimov-Drell-Hearn Integrand forH2from 200 to 800 MeV

2006

A measurement of the helicity dependence of the total inclusive photoabsorption cross section on the deuteron was carried out at MAMI (Mainz) in the energy range $200l{E}_{\ensuremath{\gamma}}l800\text{ }\text{ }\mathrm{MeV}$. The experiment used a $4\ensuremath{\pi}$ detection system, a circularly polarized tagged photon beam and a frozen-spin target which provided longitudinally polarized deuterons. The contribution to the Gerasimov-Drell-Hearn sum rule for the deuteron determined from the data is $407\ifmmode\pm\else\textpm\fi{}20(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}24(\mathrm{syst})\text{ }\text{ }\ensuremath{\mu}\mathrm{b}$ for $200l{E}_{\ensuremath{\gamma}}l800\text{ }\text{ }\m…

PhysicsParticle physicsMeson production010308 nuclear & particles physicsNuclear TheoryGeneral Physics and AstronomyComputer Science::Computation and Language (Computational Linguistics and Natural Language and Speech Processing)01 natural sciencesHelicityNuclear physics0103 physical sciencesSum rule in quantum mechanicsPhoton beamNuclear Experiment010306 general physicsEnergy (signal processing)Physical Review Letters
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The first dedicated Virtual Compton Scattering experiment at MAMI

1999

We measured the absolute cross sections for photon electro-production off the proton, ep to ep gamma , with the high resolution spectrometers at MAMI at momentum transfer q=600 MeV/c and photon polarization epsilon =0.62. We covered the momentum range for the outgoing real photon q'=33/111 MeV/c. From the extracted virtual Compton scattering amplitude we deduce values for two structure functions related to the generalized polarizabilities of the proton.

PhysicsNuclear and High Energy PhysicsPhotonProtonSpectrometer010308 nuclear & particles physicsMomentum transferCompton scattering01 natural sciencesNuclear physicsMomentumAmplitude0103 physical sciencesPhoton polarization[PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex]Nuclear Experiment010306 general physics
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Neutral Pion Threshold Production atQ2=0.05GeV2/c2and Chiral Perturbation Theory

2001

New data are presented on the $p({e,e}^{\ensuremath{'}}p){\ensuremath{\pi}}^{0}$ reaction at threshold at a four-momentum transfer of ${Q}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.05{\mathrm{GeV}}^{2}{/c}^{2}$. The data were taken with the three-spectrometer setup of the A1 Collaboration at the Mainz Microtron MAMI. The complete center of mass solid angle was covered up to a center of mass energy of 4 MeV above threshold. Combined with measurements at three different values of the virtual photon polarization $\ensuremath{\epsilon}$, the structure functions ${\ensuremath{\sigma}}_{T}$, ${\ensuremath{\sigma}}_{L}$, ${\ensuremath{\sigma}}_{\mathrm{TT}}$, and ${\ensuremath{\sigma…

PhysicsParticle physicsPionChiral perturbation theoryHeavy baryon chiral perturbation theoryPhenomenological modelStructure functionSolid angleGeneral Physics and AstronomySigmaVirtual particleNuclear ExperimentPhysical Review Letters
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Backward spin polarizabilityγπof the proton

2002

Using the Mainz $48\mathrm{cm}\ensuremath{\emptyset}\ifmmode\times\else\texttimes\fi{}64\mathrm{cm}$ NaI(Tl) detector and the segmented G\"ottingen recoil detector SENECA in coincidence, Compton scattering by the proton at ${\ensuremath{\theta}}_{\ensuremath{\gamma}}^{\mathrm{lab}}=136\ifmmode^\circ\else\textdegree\fi{}$ has been measured at MAMI (Mainz) in the energy range from 200 to 470 MeV. The new data confirm the previous observation that there is a systematic discrepancy between MAMI and LEGS (Brookhaven) data leading to different spin polarizabilities ${\ensuremath{\gamma}}_{\ensuremath{\pi}}=\ensuremath{-}38.7\ifmmode\pm\else\textpm\fi{}1.8$ and $\ensuremath{-}27.2\ifmmode\pm\else\…

Elastic scatteringPhysicsNuclear and High Energy PhysicsParticle physicsProton010308 nuclear & particles physicsHadronElementary particle01 natural sciencesOrientation (vector space)Nuclear physicsBaryon0103 physical sciences010306 general physicsNucleonEnergy (signal processing)Physical Review C
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Virtual compton scattering under π0 threshold at Q2=0.33 GeV2. Preliminary results

1999

We have measured the absolute unpolarized cross sections for photon electro-production off the proton ep → epγ with the Three-Spectrometer-Setup at MAMI at a momentum transfer q=600 MeV/c and a virtual photon polarization ɛ=0.62. The momentum q ′ of the outgoing real photon range from 33 to 111 MeV/c. We extracted two combinations of the recently introduced generalized polarizabilities [1,2].

PhysicsMassless particleNuclear reactionElastic scatteringNuclear physicsNuclear and High Energy PhysicsPhotonScatteringMomentum transferCompton scatteringVirtual particleAtomic physicsNuclear ExperimentNuclear Physics A
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Helicity dependence of the γ→p→→nπ+π0 reaction in the second resonance region

2003

The helicity dependence of the total cross section for the (γ) over right arrow(p) over right arrownpi(+) pi(0) reaction has been measured for the first time at incident photon energies from 400 to 800 MeV The measurement was performed with the large acceptance detector DAPHNE at the tagged photon beam facility of the MAMI accelerator in Mainz. This channel is found to be excited predominantly when the photon and proton have a parallel spin orientation, due to the intermediate production of the D-13 resonance. (C) 2002 Elsevier Science B.V. All rights reserved.

PhysicsNuclear and High Energy PhysicsPhotonProton010308 nuclear & particles physicsNuclear TheoryResonance01 natural sciencesHelicityCross section (geometry)Nuclear physicsExcited state0103 physical sciencesPiPhysics::Accelerator PhysicsAtomic physicsNuclear Experiment010306 general physicsSpin (physics)Physics Letters B
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Cross sections for the reactionO16(γ, p0)N15at forward angles forEγ=80MeV

1980

PhysicsNuclear and High Energy PhysicsAtomic physicsPhysical Review C
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Helicity Dependence ofγp→Nπbelow 450 MeV and Contribution to the Gerasimov-Drell-Hearn Sum Rule

2000

The helicity dependence of the single pion photoproduction on the proton has been measured in the energy range from 200 to 450 MeV for the first time. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam, and a frozen-spin target. The data obtained provide new information for multipole analyses of pion photoproduction and determine the main contributions to the Gerasimov-Drell-Hearn sum rule and the forward spin polarizability gamma(0).

PhysicsParticle physicsProtonNuclear TheoryGeneral Physics and AstronomyHelicityNuclear physicsPionPolarizabilityPhysics::Accelerator PhysicsHigh Energy Physics::ExperimentSum rule in quantum mechanicsNuclear ExperimentMultipole expansionMicrotronSpin-½Physical Review Letters
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Measurement of the Beam-Helicity Asymmetry in thep(e→,e′p)π0Reaction at the Energy of theΔ(1232)Resonance

2002

In a p((e) over right arrow, e' p)pi(0) out-of-plane coincidence experiment at the three-spectrometer setup of the Mainz Microtron MAMI, the beam-helicity asymmetry has been precisely measured around the energy of the Delta(1232) resonance and Q(2) = 0.2(GeV/c)(2). The results are in disagreement with three up-to-date model calculations. This is interpreted as a lack of understanding of the nonresonant background, which in dynamical models is related to the pion cloud.

PhysicsParticle physicsmedia_common.quotation_subjectGeneral Physics and AstronomyResonanceHelicityAsymmetryCoincidenceNuclear physicsPionNuclear ExperimentMicrotronBeam (structure)Energy (signal processing)media_commonPhysical Review Letters
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Elastic and inelastic photon scattering from 12C

1994

Abstract The elastic and inelastic photon scattering from 12 C was investigated in the energy range of the Δ-resonance ( E γ = 200–500 MeV) at a scattering angle of 40°. The experiment was performed with the tagged photon facility at the cw electron accelerator MAMI ( E e − = 855 MeV). By using a large NaI(Tl) detector having an energy resolution of 1.5%, the elastic scattering could be separated from the inelastic process to the first excited state ( E x = 4.44 MeV of 12 C. The differential cross section for the coherent scattering is compared with a simple static ansatz, that uses the known charge form factor, and with a recent Δ-hole calculation.

PhysicsElastic scatteringNuclear and High Energy PhysicsQuasielastic scattering010308 nuclear & particles physicsScatteringScattering lengthMott scatteringInelastic scatteringDeep inelastic scattering7. Clean energy01 natural sciencesNuclear physics0103 physical sciencesScattering theoryAtomic physics010306 general physicsPhysics Letters B
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Compton scattering from the free and bound proton above π-threshold

2000

The differential cross sections for Compton scattering from the proton have been measured at MAMI with three different detector setups. There is a good agreement among all the results. The theoretical calculation based on dispersion relations shows that there is no drastic change necessary in the parameters of this approach.

PhysicsNuclear and High Energy PhysicsProton010308 nuclear & particles physicsDetectorCompton scatteringCompton wavelengthInelastic scattering01 natural sciencesNuclear physicsDispersion relation0103 physical sciencesNuclear Experiment010306 general physics
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Compton Scattering by the Proton using a Large-Acceptance Arrangement

2001

Compton scattering by the proton has been measured over a wide range covering photon energies 250 MeV lt or approximately=E/sub gamma / lt or approximately=800 MeV and photon scattering angles 30 degrees lt or approximately= theta /sub gamma //sup lab/ lt or approximately=150 degrees , using the tagged-photon facility at MAMI (Mainz) and the large-acceptance arrangement LARA. The previously existing data base on proton Compton scattering is greatly enlarged by more than 700 new data points. The new data are interpreted in terms of dispersion theory based on the SAID-SM99K parametrization of photo-meson amplitudes. It is found that two-pion exchange in the t-channel is needed for a descripti…

Nuclear and High Energy PhysicsProtonNuclear TheoryFOS: Physical sciencesValue (computer science)01 natural sciencesResonance (particle physics)High Energy Physics - ExperimentNuclear physicsHigh Energy Physics - Experiment (hep-ex)High Energy Physics - Phenomenology (hep-ph)Dispersion relation0103 physical sciencesNuclear Experiment (nucl-ex)010306 general physicsNuclear ExperimentNuclear ExperimentQCSpin-½Physics010308 nuclear & particles physicsCompton scatteringHigh Energy Physics - PhenomenologyAmplitudeHigh Energy Physics::ExperimentMultipole expansion
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Photoemission of spinpolarized electrons from strained GaAsP

1996

Strained layer GaAs.95P.05 photo cathodes are presented, which emit electron beams spinpolarized to a degree of P = 75% typically. Quantum yields around QE = 0.4% are observed routinely. The figure of merit P2 × QE = 2.3 × 10−3 is comparable to that of the best strained layer cathodes reported in literature. The optimum wavelength of irradiating light around 830 nm is in convenient reach of Ti:sapphire lasers or diode lasers respectively. The cathodes are produced using MOCVD-techniques. A GaAs.55P.45-GaAs.85P.15 superlattice structure prevents the migration of dislocations from the substrate and bottom layers to the strained overlayer. The surface is protected by an arsenic layer so that n…

Materials sciencebusiness.industrySuperlatticeGeneral ChemistrySubstrate (electronics)PhotocathodeCathodeOverlayerlaw.inventionOpticslawSapphireOptoelectronicsGeneral Materials ScienceQuantum efficiencybusinessMicrotronApplied Physics A Materials Science &amp; Processing
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Evidence for narrow Δ0(1232) states in the 12 C(e,e'pπ−}11 C Reaction

1999

The reaction 12C(e,e'Δ0)11C →12C(e,e'pπ−)11C was investigated at the Mainz Microtron MAMI in a triple coincidence measurement using the three spectrometer setup of the A1 Collaboration. The good missing mass resolution of σm= 0.27 MeV/c2 allowed to select the events belonging to the ground state of 11C. Cutting on these events the excitation energy spectra of 12CΔ0 show evidence for two peaks of about 4 MeV width (FWHM) at 282 MeV and 296 MeV with a significance of about 4.5 standard deviations. The peaks are interpreted in a simple weak coupling model as bound Δ0 states in 12CΔ0.

Nuclear physicsPhysicsNuclear and High Energy PhysicsFull width at half maximumSpectrometerHadronNuclear fusionGround stateMicrotronExcitationSpectral lineThe European Physical Journal A
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Electroproduction of low energy charged pions on9Be,12C and16O

1979

Measurements of electroproduced pions with an energy of 10MeV are presented. The results of a calculation based on the PWIA are compared with the presented data as well as with data at higher pion energies.

Nuclear physicsPhysicsNuclear and High Energy PhysicsPionLow energyHigh Energy Physics::LatticeNuclear TheoryNuclear fusionHigh Energy Physics::ExperimentNuclear ExperimentEnergy (signal processing)Zeitschrift f�r Physik A Atoms and Nuclei
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Experimental Check of the Gerasimov-Drell-Hearn Sum Rule for H1

2004

For the first time we checked the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the proton experimentally in the photon energy range from 0.2-2.9 GeV with the tagged photon facilities at MAMI (Mainz) and ELSA (Bonn). New data of the doubly polarized total cross section difference are presented in the energy range from 1.6 to 2.9 GeV. The contribution to the GDH integral from 0.2-2.9 GeV yields [254+/-5(stat)+/-12(syst)] microb with negative contributions in the Regge regime at photon energies above 2.1 GeV. This trend supports the validity of the GDH sum rule.

PhysicsRange (particle radiation)PhotonProton010308 nuclear & particles physicsAstrophysics::High Energy Astrophysical PhenomenaNuclear TheoryGeneral Physics and AstronomyPhoton energy01 natural sciencesNuclear physicsRegge theory0103 physical sciencesHigh Energy Physics::ExperimentSum rule in quantum mechanicsNuclear Experiment010306 general physicsAstrophysics::Galaxy AstrophysicsPhysical Review Letters
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"Table 1" of "Virtual Compton scattering under pi0 threshold at Q**2 = 0.33-GeV**2: Preliminary results."

1999

No description provided.

POLPhotoproductionPolarizationExclusiveGAMMA* P --&gt; P GAMMA0.0
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"Table 2" of "Polarization transfer in the He-4(e(pol.),e' p(pol.)H-3 reaction."

2004

No description provided.

Electron productionE- HE --&gt; TRITIUM P E-PolarizationExclusive1.576POL/POLE- P --&gt; P E-
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"Table 3" of "Quasi-free Compton Scattering and the Polarizabilities of the Neutron"

2003

Energy dependence of the triple differential cross section w.r.t. the scattered proton.

PhotoproductionTriple Differential Cross SectionExclusiveGAMMA DEUT --&gt; GAMMA P NNuclear ExperimentD3SIG/DE/DOMEGA/DOMEGA
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"Table 1" of "Polarization transfer in the He-4(e(pol.),e' p(pol.)H-3 reaction."

2004

No description provided.

Electron productionE- HE --&gt; TRITIUM P E-PolarizationExclusive1.576POL/POLE- P --&gt; P E-
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"Table 1" of "Compton scattering from the free and bound proton at backward angles above pi threshold."

2000

No description provided.

Single Differential Cross SectionPhotoproduction1.12-1.284GAMMA P --&gt; P GAMMAExclusiveDSIG/DOMEGA
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"Table 2" of "Quasi-free Compton Scattering and the Polarizabilities of the Neutron"

2003

Energy dependence of the quasi-free proton differential cross section.

Single Differential Cross SectionPhotoproduction1.146-1.266ElasticNuclear TheoryPhysics::Accelerator PhysicsGAMMA P --&gt; GAMMA PNuclear ExperimentDSIG/DOMEGA
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"Table 5" of "Quasi-free Compton Scattering and the Polarizabilities of the Neutron"

2003

Energy dependence of the free neutron differential cross section.

Single Differential Cross SectionPhotoproductionElasticAstrophysics::High Energy Astrophysical PhenomenaGAMMA N --&gt; GAMMA NNuclear Theory1.125-1.255Nuclear ExperimentDSIG/DOMEGA
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"Table 4" of "Quasi-free Compton Scattering and the Polarizabilities of the Neutron"

2003

Energy dependence of the triple differential cross section w.r.t. the scattered neutron.

PhotoproductionAstrophysics::High Energy Astrophysical PhenomenaNuclear TheoryTriple Differential Cross SectionExclusiveGAMMA DEUT --&gt; GAMMA P NNuclear ExperimentD3SIG/DE/DOMEGA/DOMEGA
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"Table 1" of "Quasi-free Compton Scattering and the Polarizabilities of the Neutron"

2003

Energy dependence of the free-proton differential cross section.

Single Differential Cross SectionPhotoproductionElasticNuclear TheoryPhysics::Accelerator PhysicsGAMMA P --&gt; GAMMA P1.13-1.327Nuclear ExperimentDSIG/DOMEGA
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