D. G. Middleton - The Crystal Ball at MAMI, TAPS, and A2 Collaborations

D. G. Middleton
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D. G. Middleton
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The Crystal Ball at MAMI, TAPS, and A2 Collaborations
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Nuclear Experiment (44)
 
High Energy Physics - Experiment (14)
 
Nuclear Theory (5)
 
High Energy Physics - Phenomenology (3)
 
Physics - Instrumentation and Detectors (2)
 
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Publications Authored By D. G. Middleton

The reactions $\gamma p\to \eta p$ and $\gamma p\to \eta' p$ have been measured from their thresholds up to the center-of-mass energy $W=1.96$GeV with the tagged-photon facilities at the Mainz Microtron, MAMI. Differential cross sections were obtained with unprecedented accuracy, providing fine energy binning and full production-angle coverage. Read More

We report on a new experimental method based on initial-state radiation (ISR) in e-p scattering, in which the radiative tail of the elastic e-p peak contains information on the proton charge form factor ($G_E^p$) at extremely small $Q^2$. The ISR technique was validated in a dedicated experiment using the spectrometers of the A1-Collaboration at the Mainz Microtron (MAMI). This provided first measurements of $G_E^p$ for $0. Read More

The Dalitz decay pi^0 -> e^+e^-gamma has been measured in the gamma p -> pi^0 p reaction with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The value obtained for the slope parameter of the pi^0 electromagnetic transition form factor, a_pi = 0.030+/-0. Read More

The scalar dipole polarizabilities, $\alpha_{E1}$ and $\beta_{M1}$, are fundamental properties related to the internal dynamics of the nucleon. The currently accepted values of the proton polarizabilities were determined by fitting to unpolarized proton Compton scattering cross section data. The measurement of the beam asymmetry $\Sigma_{3}$ in a certain kinematical range provides an alternative approach to the extraction of the scalar polarizabilities. Read More

The Dalitz decays eta -> e^+e^-g and omega -> pi^0 e^+e^- have been measured in the g p -> eta p and g p -> omega p reactions, respectively, with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The value obtained for the slope parameter of the electromagnetic transition form factor of eta, Lambda^{-2}_eta=(1.97+/-0. Read More

High statistics measurements of the photon asymmetry $\mathrm{\Sigma}$ for the $\overrightarrow{\gamma}$p$\rightarrow\pi^{0}$p reaction have been made in the center of mass energy range W=1214-1450 MeV. The data were measured with the MAMI A2 real photon beam and Crystal Ball/TAPS detector systems in Mainz, Germany. The results significantly improve the existing world data and are shown to be in good agreement with previous measurements, and with the MAID, SAID, and Bonn-Gatchina predictions. Read More

The cross section of the $p(e,e'\pi^+)n$ reaction has been measured for five kinematic settings at an invariant mass of $W = 1094$ MeV and for a four-momentum transfer of $Q^2 = 0.078$ (GeV/$c$)$^2$. The measurement has been performed at MAMI using a new short-orbit spectrometer (SOS) of the A1 collaboration, intended for detection of low-energy pions. Read More

2016Feb
Affiliations: 1School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel, 2School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel, 3Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 4Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 5Jožef Stefan Institute, 1000 Ljubljana, Slovenia, 6Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 7Department of Physics, University of Zagreb, HR-10002 Zagreb, Croatia, 8Jožef Stefan Institute, 1000 Ljubljana, Slovenia, 9Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 10Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 11Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 12Department of Physics, University of Zagreb, HR-10002 Zagreb, Croatia, 13Rutgers, The State University of New Jersey, Piscataway, NJ 08855, USA, 14School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel, 15School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel, 16Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 17Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 18Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 19Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 20School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel, 21Jožef Stefan Institute, 1000 Ljubljana, Slovenia, 22University of South Carolina, Columbia, South Carolina 29208, USA, 23Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 24Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem 91904, Israel, 25Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 26Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 27Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 28Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 29Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 30Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 31Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany, 32Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany

Possible differences between free and bound protons may be observed in the ratio of polarization-transfer components, $P'_x/P'_z$. We report the measurement of $P'_x/P'_z$, in the $^2\textrm{H}(\vec{e},e^{\prime}\vec{p})n$ reaction at low and high missing momenta. Observed increasing deviation of $P'_x/P'_z$ from that of a free proton as a function of the virtuality, similar to that observed in \hefour, indicates that the effect in nuclei is due to the virtuality of the knock-out proton and not due to the average nuclear density. Read More

Total cross sections, angular distributions, and invariant-mass distributions have been measured for the photoproduction of $\pi^0\pi^0$ pairs off free protons and off nucleons bound in the deuteron. The experiments were performed at the MAMI accelerator facility in Mainz using the Glasgow photon tagging spectrometer and the Crystal Ball/TAPS detector. The accelerator delivered electron beams of 1508 and 1557~MeV, which produced bremsstrahlung in thin radiator foils. Read More

Photoproduction of $\pi\eta$-pairs from nucleons has been investigated from threshold up to incident photon energies of $\approx$~1.4~GeV. The quasi-free reactions $\gamma p\rightarrow p\pi^0\eta$, $\gamma n\rightarrow n\pi^0\eta$, $\gamma p\rightarrow n\pi^+\eta$, and $\gamma n\rightarrow p\pi^-\eta$ were for the first time measured from nucleons bound in the deuteron. Read More

Differential cross sections for the gamma p -> pi^0 p reaction have been measured with the A2 tagged-photon facilities at the Mainz Microtron, MAMI C, up to the center-of-mass energy W=1.9 GeV. The new results, obtained with a fine energy and angular binning, increase the existing quantity of pi^0 photoproduction data by ~47%. Read More

The first data on target and beam-target asymmetries for the $\gamma p\to\pi^0\eta p$ reaction at photon energies from 1050 up to 1450 MeV are presented. The measurements were performed using the Crystal Ball and TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. The general assumption that the reaction is dominated by the $\Delta 3/2^-$ amplitude is confirmed. Read More

Differential cross sections for elastic scattering of photons from the deuteron have recently been measured at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. These first new measurements in more than a decade further constrain the isoscalar electromagnetic polarizabilities of the nucleon and provide the first-ever results above 100 MeV, where the sensitivity to the polarizabilities is increased. We add 23 points between 70 and 112 MeV, at angles 60deg, 120deg and 150deg. Read More

A multi-cell He gas-scintillator active target, designed for the measurement of photoreaction cross sections, is described. The target has four main chambers, giving an overall thickness of 0.103 $\mathrm{g/cm^{2}}$ at an operating pressure of 2 MPa. Read More

We report on a measurement of the neutron detection efficiency in NaI crystals in the Crystal Ball detector obtained from a study of single p0 photoproduction on deuterium using the tagged photon beam at the Mainz Microtron. The results were obtained up to a neutron energy of 400 MeV. They are compared to previous measurements made more than 15 years ago at the pion beam at the BNL AGS. Read More

The electromagnetic polarizabilities of the nucleon are fundamental properties that describe its response to external electric and magnetic fields. They can be extracted from Compton-scattering data --- and have been, with good accuracy, in the case of the proton. In contradistinction, information for the neutron requires the use of Compton scattering from nuclear targets. Read More

We present new data for the transverse target asymmetry T and the very first data for the beam-target asymmetry F in the $\vec \gamma \vec p\to\eta p$ reaction up to a center-of-mass energy of W=1.9 GeV. The data were obtained with the Crystal-Ball/TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. Read More

The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to measure the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the $\Delta(1232)$ region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Read More

Differential and total cross sections for the quasifree reactions $\gamma p\rightarrow\eta p$ and $\gamma n\rightarrow\eta n$ have been determined at the MAMI-C electron accelerator using a liquid deuterium target. Photons were produced via bremsstrahlung from the 1.5 GeV incident electron beam and energy-tagged with the Glasgow photon tagger. Read More

An experimental study of $\omega$ photoproduction on the proton was conducted by using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. The $\gamma p\to\omega p$ differential cross sections are measured from threshold to the incident-photon energy $E_\gamma=1.40$ GeV ($W=1. Read More

A massive, but light abelian U(1) gauge boson is a well motivated possible signature of physics beyond the Standard Model of particle physics. In this paper, the search for the signal of such a U(1) gauge boson in electron-positron pair-production at the spectrometer setup of the A1 Collaboration at the Mainz Microtron (MAMI) is described. Exclusion limits in the mass range of 40 MeV up to 300 MeV with a sensitivity in the mixing parameter of down to $\epsilon^2 = 8\times 10^{-7}$ are presented. Read More

Precise angular distributions have been measured for the first time for the photoproduction of $\pi^{0}$-mesons off neutrons bound in the deuteron. The effects from nuclear Fermi motion have been eliminated by a complete kinematic reconstruction of the final state. The influence of final-state-interaction effects has been estimated by a comparison of the reaction cross section for quasi-free protons bound in the deuteron to the results for free protons and then applied as a correction to the quasi-free neutron data. Read More

Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz for the photoproduction of mixed-charge pion pairs in the reactions $\boldsymbol{\gamma}p\rightarrow n\pi^0\pi^+$ off free protons and $\boldsymbol{\gamma}d\rightarrow (p)p\pi^0\pi^-$ and $\boldsymbol{\gamma}d\rightarrow (n)n\pi^0\pi^+$ off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4 GeV. Circularly polarized photons were produced from bremsstrahlung of longitudinally polarized electrons and tagged with the Glasgow-Mainz magnetic spectrometer. Read More

Elastic scattering of photons from 12C has been investigated using quasi-monoenergetic tagged photons with energies in the range 65 - 115 MeV at laboratory angles of 60 deg, 120 deg, and 150 deg at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. A phenomenological model was employed to provide an estimate of the sensitivity of the 12C(g,g)12C cross section to the bound-nucleon polarizabilities. Read More

We report the first large-acceptance measurement of polarization transfer from a polarized photon beam to a recoiling nucleon, pioneering a novel polarimetry technique with wide application to future nuclear and hadronic physics experiments. The commissioning measurement of polarization transfer in the $^{1}H$($\vec{\gamma}$,$\vec{p}$)$\pi^{0}$ reaction in the range $0.4Read More

Measurements of $\gamma p \rightarrow K^{+} \Lambda$ and $\gamma p \rightarrow K^{+} \Sigma^0$ cross-sections have been obtained with the photon tagging facility and the Crystal Ball calorimeter at MAMI-C. The measurement uses a novel $K^+$ meson identification technique in which the weak decay products are characterized using the energy and timing characteristics of the energy deposit in the calorimeter, a method that has the potential to be applied at many other facilities. The fine center-of-mass energy ($W$) resolution and statistical accuracy of the new data results in a significant impact on partial wave analyses aiming to better establish the excitation spectrum of the nucleon. Read More

A measurement of beam helicity asymmetries in the reaction 3He(e,e'n)pp has been performed at the Mainz Microtron in quasielastic kinematics in order to determine the electric to magnetic form factor ratio of the neutron, GEn/GMn, at a four momentum transfer Q2 = 1.58 GeV2. Longitudinally polarized electrons were scattered on a highly polarized 3He gas target. Read More

The paper describes a precise measurement of electron scattering off the proton at momentum transfers of $0.003 \lesssim Q^2 \lesssim 1$\ GeV$^2$. The average point-to-point error of the cross sections in this experiment is $\sim$ 0. Read More

Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz for the photoproduction of neutral pion pairs in the reactions $\vec{\gamma}p\rightarrow p\pi^0\pi^0$ and $\vec{\gamma}d\rightarrow (n)p\pi^0\pi^0$, $\vec{\gamma}d\rightarrow (p)n\pi^0\pi^0$ off free protons and off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4 GeV. Circularly polarized photons were produced from bremsstrahlung of longitudinally polarized electrons and tagged with the Glasgow magnetic spectrometer. Read More

The Proton Radius Puzzle is the inconsistency between the proton radius determined from muonic hydrogen and the proton radius determined from atomic hydrogen level transitions and ep elastic scattering. No generally accepted resolution to the Puzzle has been found. Possible solutions generally fall into one of three categories: the two radii are different due to novel beyond-standard-model physics, the two radii are different due to novel aspects of nucleon structure, and the two radii are the same, but there are underestimated uncertainties or other issues in the ep experiments. Read More

A precision measurement of the differential cross sections $d\sigma/d\Omega$ and the linearly polarized photon asymmetry $\Sigma \equiv (d\sigma_\perp - d\sigma_\parallel) \slash (d\sigma_\perp + d\sigma_\parallel)$ for the $\vec{\gamma} p \rightarrow \pi^0p$ reaction in the near-threshold region has been performed with a tagged photon beam and almost $4\pi$ detector at the Mainz Microtron. The Glasgow-Mainz photon tagging facility along with the Crystal Ball/TAPS multi-photon detector system and a cryogenic liquid hydrogen target were used. These data allowed for a precise determination of the energy dependence of the real parts of the $S$- and all three $P$-wave amplitudes for the first time and provide the most stringent test to date of the predictions of Chiral Perturbation Theory and its energy region of agreement with experiment. Read More

A new exclusion limit for the electromagnetic production of a light U(1) gauge boson {\gamma}' decaying to e^+e^- was determined by the A1 Collaboration at the Mainz Microtron. Such light gauge bosons appear in several extensions of the standard model and are also discussed as candidates for the interaction of dark matter with standard model matter. In electron scattering from a heavy nucleus, the existing limits for a narrow state coupling to e^+e^- were reduced by nearly an order of magnitude in the range of the lepton pair mass of 210 MeV/c^2 < m_e^+e^- < 300 MeV/c^2. Read More

2010Sep
Affiliations: 1The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 2The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 3The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 4The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 5The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 6The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 7The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 8The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 9The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 10The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 11The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 12The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 13The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 14The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 15The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 16The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 17The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 18The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 19The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 20The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 21The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 22The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 23The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 24The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 25The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 26The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 27The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 28The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 29The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 30The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 31The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 32The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 33The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 34The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 35The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 36The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 37The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 38The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 39The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 40The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 41The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 42The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 43The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 44The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 45The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 46The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 47The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 48The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 49The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 50The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 51The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 52The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 53The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 54The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 55The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 56The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 57The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 58The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 59The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 60The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 61The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 62The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 63The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 64The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 65The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 66The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 67The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 68The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 69The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 70The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 71The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 72The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 73The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 74The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 75The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 76The Crystal Ball at MAMI, TAPS, and A2 Collaborations, 77The Crystal Ball at MAMI, TAPS, and A2 Collaborations

The circular photon asymmetry for pi0 eta photoproduction on the proton was measured for the first time at the tagged photon facility of the MAMI C accelerator using the Crystal Ball/TAPS photon spectrometer. The experimental results are interpreted within a phenomenological isobar model that confirms the dominant role of the Delta(1700)D33 resonance. The measured asymmetry allows us to identify small contributions from positive-parity resonances via interference terms with the dominant D33 amplitude. Read More

New precise results of a measurement of the elastic electron-proton scattering cross section performed at the Mainz Microtron MAMI are presented. About 1400 cross sections were measured with negative four-momentum transfers squared up to Q^2=1 (GeV/c)^2 with statistical errors below 0.2%. Read More

2010Jul
Affiliations: 1Crystal Ball Collaboration at MAMI, 2Crystal Ball Collaboration at MAMI, 3Crystal Ball Collaboration at MAMI, 4Crystal Ball Collaboration at MAMI, 5Crystal Ball Collaboration at MAMI, 6Crystal Ball Collaboration at MAMI, 7Crystal Ball Collaboration at MAMI, 8Crystal Ball Collaboration at MAMI, 9Crystal Ball Collaboration at MAMI, 10Crystal Ball Collaboration at MAMI, 11Crystal Ball Collaboration at MAMI, 12Crystal Ball Collaboration at MAMI, 13Crystal Ball Collaboration at MAMI, 14Crystal Ball Collaboration at MAMI, 15Crystal Ball Collaboration at MAMI, 16Crystal Ball Collaboration at MAMI, 17Crystal Ball Collaboration at MAMI, 18Crystal Ball Collaboration at MAMI, 19Crystal Ball Collaboration at MAMI, 20Crystal Ball Collaboration at MAMI, 21Crystal Ball Collaboration at MAMI, 22Crystal Ball Collaboration at MAMI, 23Crystal Ball Collaboration at MAMI, 24Crystal Ball Collaboration at MAMI, 25Crystal Ball Collaboration at MAMI, 26Crystal Ball Collaboration at MAMI, 27Crystal Ball Collaboration at MAMI, 28Crystal Ball Collaboration at MAMI, 29Crystal Ball Collaboration at MAMI, 30Crystal Ball Collaboration at MAMI, 31Crystal Ball Collaboration at MAMI, 32Crystal Ball Collaboration at MAMI, 33Crystal Ball Collaboration at MAMI, 34Crystal Ball Collaboration at MAMI, 35Crystal Ball Collaboration at MAMI, 36Crystal Ball Collaboration at MAMI, 37Crystal Ball Collaboration at MAMI, 38Crystal Ball Collaboration at MAMI, 39Crystal Ball Collaboration at MAMI, 40Crystal Ball Collaboration at MAMI, 41Crystal Ball Collaboration at MAMI, 42Crystal Ball Collaboration at MAMI, 43Crystal Ball Collaboration at MAMI, 44Crystal Ball Collaboration at MAMI, 45Crystal Ball Collaboration at MAMI, 46Crystal Ball Collaboration at MAMI, 47Crystal Ball Collaboration at MAMI, 48Crystal Ball Collaboration at MAMI, 49Crystal Ball Collaboration at MAMI, 50Crystal Ball Collaboration at MAMI, 51Crystal Ball Collaboration at MAMI, 52Crystal Ball Collaboration at MAMI, 53Crystal Ball Collaboration at MAMI, 54Crystal Ball Collaboration at MAMI, 55Crystal Ball Collaboration at MAMI, 56Crystal Ball Collaboration at MAMI, 57Crystal Ball Collaboration at MAMI, 58Crystal Ball Collaboration at MAMI, 59Crystal Ball Collaboration at MAMI, 60Crystal Ball Collaboration at MAMI, 61Crystal Ball Collaboration at MAMI, 62Crystal Ball Collaboration at MAMI, 63Crystal Ball Collaboration at MAMI, 64Crystal Ball Collaboration at MAMI, 65Crystal Ball Collaboration at MAMI, 66Crystal Ball Collaboration at MAMI, 67Crystal Ball Collaboration at MAMI, 68Crystal Ball Collaboration at MAMI, 69Crystal Ball Collaboration at MAMI, 70Crystal Ball Collaboration at MAMI, 71Crystal Ball Collaboration at MAMI, 72Crystal Ball Collaboration at MAMI, 73Crystal Ball Collaboration at MAMI, 74Crystal Ball Collaboration at MAMI, 75Crystal Ball Collaboration at MAMI, 76Crystal Ball Collaboration at MAMI, 77Crystal Ball Collaboration at MAMI, 78Crystal Ball Collaboration at MAMI, 79Crystal Ball Collaboration at MAMI, 80Crystal Ball Collaboration at MAMI, 81Crystal Ball Collaboration at MAMI, 82Crystal Ball Collaboration at MAMI, 83Crystal Ball Collaboration at MAMI, 84Crystal Ball Collaboration at MAMI

The gp-->etap reaction has been measured with the Crystal Ball and TAPS multiphoton spectrometers in the energy range from the production threshold of 707 MeV to 1.4 GeV (1.49 =< W >= 1. Read More

After recent improvements to the Pavia model of two-nucleon knockout from $^{16}$O with electromagnetic probes the calculated cross sections are compared to experimental data from such reactions. Comparison with data from a measurement of the $^{16}$O(e,e$'$pn) reaction show much better agreement between experiment and theory than was previously observed. In a comparison with recent data from a measurement of the $^{16}$O($\gamma$,pn) reaction the model over-predicts the measured cross section at low missing momentum. Read More

Cross sections for the ^{3}He(e,e'pn)p reaction were measured for the first time at energy transfers of 220 and 270 MeV for several momentum transfers ranging from 300 to 450 MeV/c. Cross sections are presented as a function of the momentum of the recoil proton and the momentum transfer. Continuum Faddeev calculations using the Argonne V18 and Bonn-B nucleon-nucleon potentials overestimate the measured cross sections by a factor 5 at low recoil proton momentum with the discrepancy becoming much smaller at higher recoil momentum. Read More

Understanding the earth's climate system and how it might be changing is a preeminent scientific challenge. Global climate models are used to simulate past, present, and future climates, and experiments are executed continuously on an array of distributed supercomputers. The resulting data archive, spread over several sites, currently contains upwards of 100 TB of simulation data and is growing rapidly. Read More

This paper reports on the first measurement of the ^16O(e,e'pn)^14N reaction. Data were measured in kinematics centred on a super-parallel geometry at energy and momentum transfers of 215 MeV and 316 MeV/c. The experimental resolution was sufficient to distinguish groups of states in the residual nucleus but not good enough to separate individual states. Read More