| 1. |
- Aguar-Bartolome, P., et al.
(författare)
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New determination of the eta transition form factor in the Dalitz decay eta -> e(+) e(-) gamma with the Crystal Ball/TAPS detectors at the Mainz Microtron
- 2014
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 89:4
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Tidskriftsartikel (refereegranskat)abstract
- The Dalitz decay eta -> e(+) e(-) gamma has been measured in the gamma p -> eta p reaction with the Crystal Ball and TAPS multiphoton spectrometers, together with the photon-tagging facility at the Mainz Microtron MAMI. The experimental statistic used in this work is one order of magnitude greater than in any previous measurement of eta -> e(+) e(-) gamma. The value obtained for the slope parameter Lambda(-2) of the eta transition form factor, Lambda(-2) = (1.95 +/- 0.15(stat) +/- 0.10(syst)) GeV-2, is in good agreement with recent measurements conducted in eta -> e(+) e(-) gamma and eta -> mu(+) mu(-) gamma decays, as well as with recent form-factor calculations. The uncertainty obtained in the value of Lambda(-2) is lower compared to results from previous measurements of the eta -> e(+) e(-) gamma decay.
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| 2. |
- Aguar-Bartolome, P., et al.
(författare)
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Measurement of the gamma p -> K-0 Sigma(+) reaction with the Crystal Ball/TAPS detectors at the Mainz Microtron
- 2013
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 88:4
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Tidskriftsartikel (refereegranskat)abstract
- The gamma p -> K-0 Sigma(+) reaction has been measured from threshold to E-gamma = 1.45 GeV (W-CM = 1.9 GeV) using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. In the present experiment, this reaction was searched for in the 3 pi(0)p final state, by assuming K-S(0) -> pi(0)pi(0) and Sigma(+) -> pi(0)p. The experimental results include total and differential cross sections as well as the polarization of the recoil hyperon. The new data significantly improve empirical knowledge about the gamma p -> K-0 Sigma(+) reaction in the measured energy range. The results are compared to previous measurements and model predictions. It is demonstrated that adding the present gamma p -> K-0 Sigma(+) results to existing data allowed a better description of this reaction with various models.
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| 3. |
- Kashevarov, V. L., et al.
(författare)
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Experimental study of the gamma p -> pi (0)pi(0) p reaction with the Crystal Ball/TAPS detector system at the Mainz Microtron
- 2012
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 85:6
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Tidskriftsartikel (refereegranskat)abstract
- The gamma p -> pi(0)pi(0) p reaction has been measured from threshold to 1.4 GeV using the Crystal Ball and TAPS photon spectrometers together with the photon tagging facility at the Mainz Microtron. The experimental results include total and differential cross sections as well as specific angular distributions, which were used to extract partial-wave amplitudes. In particular, the energy region below the D-13(1520) resonance was studied.
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| 4. |
- Feldman, G., et al.
(författare)
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New results for Compton scattering on deuterium : A better determination of the neutron electromagnetic polarizabilities
- 2015
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Ingår i: Proceedings of Science. - 1824-8039.
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Tidskriftsartikel (refereegranskat)abstract
- The electric and magnetic polarizabilities of the proton are now well known, owing to Compton scattering measurements on hydrogen targets; however, the neutron polarizabilities are still relatively uncertain, compared to the proton values. To address this problem, a multiinstitutional collaboration has conducted a program of elastic Compton scattering experiments on deuterium at the MAX IV Laboratory in Lund, Sweden using tagged photons in the energy range Eγ= 65-115 MeV. We assembled at one laboratory, for the first time, three of the world's largest NaI detectors, each having better than ΔE/E ∼ 2% photon energy resolution. We have measured elastic Compton scattering cross sections at lab angles of θγ= 60°, 120° and 150° over this energy range in 8 MeV steps. This effectively doubles the world's set of elastic Compton scattering data from deuterium and provides valuable input for chiral effective field theory (χEFT) calculations. These new deuterium data overlap previous measurements and extend them by 20 MeV to higher energies. Based on χEFT fits to the expanded world data set, new values for the neutron electric and magnetic polarizabilities have been obtained with greater accuracy than previously achieved, decreasing the statistical error by more than 30%.
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| 5. |
- Myers, L S, et al.
(författare)
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Measurement of compton scattering from the deuteron and an improved extraction of the neutron electromagnetic polarizabilities.
- 2014
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Ingår i: Physical Review Letters. - 1079-7114. ; 113:26
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Tidskriftsartikel (refereegranskat)abstract
- 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. Here, we report a new measurement of elastic photon scattering from deuterium using quasimonoenergetic tagged photons at the MAX IV Laboratory in Lund, Sweden. These first new data in more than a decade effectively double the world data set. Their energy range overlaps with previous experiments and extends it by 20 MeV to higher energies. An analysis using chiral effective field theory with dynamical Δ(1232) degrees of freedom shows the data are consistent with and within the world data set. After demonstrating that the fit is consistent with the Baldin sum rule, extracting values for the isoscalar nucleon polarizabilities, and combining them with a recent result for the proton, we obtain the neutron polarizabilities as α_{n}=[11.55±1.25(stat)±0.2(BSR)±0.8(th)]×10^{-4} fm^{3} and β_{n}=[3.65∓1.25(stat)±0.2(BSR)∓0.8(th)]×10^{-4} fm^{3}, with χ^{2}=45.2 for 44 degrees of freedom.
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| 6. |
- Feldman, G., et al.
(författare)
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Compton scattering from deuterium and the polarizabilities of the neutron
- 2008
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Ingår i: Few-Body Systems. - : Springer Science and Business Media LLC. - 0177-7963 .- 1432-5411. ; 44:1-4, s. 325-328
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Konferensbidrag (refereegranskat)abstract
- A new program of Compton scattering on deuterium is under way at the tagged-photon facility at MAX-Lab in Lund, Sweden. We will measure differential cross sections between 60A degrees and 150A degrees over the photon energy range 60-115 MeV in 5 MeV steps, with the ultimate goal of obtaining new precision information on the electric and magnetic polarizabilities of the neutron.
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| 7. |
- Myers, L. S., et al.
(författare)
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Compton scattering from C-12 using tagged photons in the energy range 65-115 MeV
- 2014
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 89:3
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Tidskriftsartikel (refereegranskat)abstract
- Elastic scattering of photons from C-12 has been investigated using quasimonoenergetic tagged photons with energies in the range 65-115 MeV at laboratory angles of 60 degrees, 120 degrees, and 150 degrees. 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 C-12(gamma,gamma)C-12 cross section to the bound- nucleon polarizabilities.
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| 8. |
- Myers, L. S., et al.
(författare)
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Compton scattering from the deuteron below pion-production threshold
- 2015
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 92:2
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Tidskriftsartikel (refereegranskat)abstract
- 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 60 degrees, 120 degrees, and 150 degrees. Analysis of these data using a chiral effective field theory indicates that the cross sections are both self-consistent and consistent with previous measurements. Extracted values of alpha(s) = [12.1 +/- 0.8(stat) +/- 0.2(BSR) +/- 0.8(th)] x 10(-4) fm(3) and beta(s) = [2.4 +/- 0.8(stat) +/- 0.2(BSR) +/- 0.8(th)] x 10(-4) fm(3) are obtained from a fit to these 23 new data points. This paper presents in detail the experimental conditions and the data analysis used to extract the cross sections.
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| 9. |
- Reiter, A., et al.
(författare)
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Measurement and simulation of the neutron response of the Nordball liquid scintillator array
- 2006
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 565:2, s. 753-762
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Tidskriftsartikel (refereegranskat)abstract
- The response of the liquid scintillator array Nordball to neutrons in the energy range 1.5 < T-n < 10 MeV has been measured by time of flight using a Cf-252 fission source. Fission fragments were detected by means of a thin-film plastic scintillator. The measured differential and integral neutron detection efficiencies agree well with predictions of a Monte Carlo simulation of the detector which models geometry accurately and incorporates the measured, non-linear proton light output as a function of energy. The ability of the model to provide systematic corrections to photoneutron cross-sections, measured by Nordball at low energy, is tested in a measurement of the two-body deuteron photodisintegration cross-section in the range E-gamma = 14-18 MeV. After correction the present H-2 (gamma, n)p measurements agree well with a published evaluation of the large body of H-2(gamma, p)n data. (c) 2006 Elsevier B.V. All rights reserved.
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| 10. |
- Sims, D. A., et al.
(författare)
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(γ,n) study of the isovector quadrupole resonance in 40Ca
- 1997
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Ingår i: Physical Review C: covering nuclear physics. - 2469-9985. ; 55:3, s. 1288-1294
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Tidskriftsartikel (refereegranskat)abstract
- The forward-to-backward asymmetry of neutrons emitted in the 40Ca(γ,n0) reaction was measured at photon energies in the range of 27–50 MeV. An energy-dependent asymmetry was observed that is interpreted as evidence of interference between the isovector quadrupole resonance and the giant dipole resonance. Data analysis in terms of semiclassical and direct-semidirect models estimate the isovector quadrupole resonance to be at an excitation energy of 31.0±1.5 MeV, with a width of 16.0±1.5 MeV, and exhausting most of the energy-weighted sum rule for the isovector quadrupole resonance.
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