Calibration of the Large Solid Angle Detector

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Measurements of 12C(→γ,pp) photon asymmetries for Eγ= 200–450 MeV

The 12C (→γ ,pp) reaction has been studied in the photon energy range 200-450 MeV at the Mainz microtron MAMI-C, where linearly polarised photons were energy-tagged using the Glasgow-Mainz Tagged Photon Spectrometer and protons were detected in the Crystal Ball detector. The photon asymmetry Σ has been measured over a wider Eγ range than previous measurements. The strongest asymmetries were found at low missing energies where direct emission of nucleon pairs is expected. Cuts on the difference in azimuthal angles of the two ejected protons increased the magnitude of the observed asymmetries. At low missing energies the Σ data exhibit a strong angular dependence, similar to deuteron photodisintegration

Gastroesophageal reflux disease is associated with a more severe interstitial lung disease in systemic sclerosis in the EUSTAR cohort

Objectives Gastroesophageal reflux disease (GERD) is frequent in systemic sclerosis (SSc) and could predict progression of interstitial lung disease (ILD). We aimed to analyse (1) the prevalence of GERD among SSc-ILD patients, (2) its association with disease characteristics and (3) predictive factors for ILD progression in SSc-ILD patients with GERD. Methods SSc patients from the EUSTAR database with ILD were included. GERD was labelled as present if reflux/dysphagia was reported at the baseline visit or before. Disease characteristics of patients with and without GERD were compared at baseline. ILD progression was defined as relative FVC decline ≥10% or relative FVC decline between 5–9% in association with relative DLCO decline of ≥15% over 12 ± 3 months of follow-up. Prognostic factors for ILD progression, overall survival and progression-free survival in SSc-ILD patients with GERD were tested by multivariable Cox regression. Results A total of 5462 SSc-ILD patients were included, 4400 (80.6%) had GERD. Patients with GERD presented more frequently with diffuse cutaneous SSc (OR: 1.44 [1.22–1.69], P < 0.001) and more severe lung involvement with lower FVC (85.8 ± 22.1 vs 90.2 ± 20.1, P < 0.001), lower DLCO (60.8 ± 19.7 vs 65.3 ± 20.6, P < 0.001) and worse performance at the 6-min walking test. Female sex (HR: 1.39 [1.07–1.80], P = 0.012) and older age (HR: 1.02 [1.01–1.03], P < 0.001) independently predicted ILD progression in SSc-ILD patients with GERD. Conclusion SSc-ILD patients with GERD appear to suffer from a more severe SSc disease. In this population, female sex may be considered a risk factor for ILD progression

Neutron propagation in 12C for energies 20 to 45 MeV

Neutron transmission in 12C has been estimated by analyzing 12C(gamma,pn) and 12C(gamma,p) data, that were collected simultaneously using the Mainz Microtron (MAMI-A) tagged-photon system, at photon energies from 80 to 157 MeV. Correction has been made for solid angle and threshold effects by use of a Monte Carlo simulation. The corrected ratio of the (gamma,pn) and (gamma,p) data gives an indication of the proportion of emitted protons that have an accompanying neutron. This ratio, which can be interpreted as a lower limit for the neutron transmission in 12C, has been found to be O.80±O.08 for the 20-45 MeV neutrons examined in this experiment. Since the data sets were collected simultaneously, systematic uncertainties associated with the tagger and proton detector cancel in the ratio

Involving young people in research

Full report 'Involving young researchers' by P. Kirby, is published for the Foundation by YPS, ISBN 1-902163345-8SIGLEAvailable from British Library Document Supply Centre-DSC:3927.734141(Dec 1999, N89) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

PiP - A large solid angle scintillation telescope for detecting protons and pions

A ~1 sr solid angle scintillation detector hodoscope for protons of up to ~280 MeV and positive pions of up to ~180 MeV energy has been developed for use in (gamma,pN), (gamma,p pi±) and (gamma,pi+ N) experiments with tagged photons. This paper reports the detailed design of the hodoscope and its performance for detecting protons and positive pions

(γ,2N) reaction in ¹²C

The 12C(γ,pn) and 12C(γ,pp) reactions have been measured for photon energies between 80 and 157 MeV using a photon tagging spectrometer and plastic scintillator detectors. The overall energy resolution was ∼7 MeV, sufficient to determine the initial shells of the emitted nucleons. Corrections were made for solid angle and threshold effects by means of Monte Carlo simulations. For the (γ,pn) reaction both the missing energy and recoil momentum distributions are largely consistent with a two-nucleon absorption process on p-shell an sp nucleon pairs. For the much smaller 12C(γ,pp) cross section the reaction mechanism is not yet understood but the recoil momentum distributions suggest that final state interactions are not dominant

Near threshold photoproduction of η-mesons from complex nuclei

Total and differential cross sections for photoproduction of eta mesons from 12C, 4OCa, 93Nb, and natPb have been obtained up to 790 MeV incident photon energy at the Mainz Microtron (MAMI) with the TAPS spectrometer. The absorption cross section sigma_etaN = (30 ± 2.5 ± 6)mb of eta mesons in nuclear matter and the absorption length lambda = (2.0 ± 0.2 ± 0.4) fm are extracted. No significant depletion of the Sll(1535) strength in the eta photoproduction on nuclei is observed