Search results for "Sst"
showing 10 items of 538 documents
The decay of 8.7 min237Pa
1974
The beta and gamma radiations of237Pa have been investigated employing semiconductor and scintillation spectrometers and coincidence techniques. Sources of237Pa were obtained after bombardments of238U with bremsstrahlung and 14-MeV neutrons and subsequent chemical separation. From the total of 18γ-rays following the decay of 8.7±0.2 min237Pa 17 transitions, representing 99.9% of theγ-ray intensity, could be placed in a level scheme of237U. AQ β- value of 2.25±0.1 MeV has been determined.
Bremsstrahlung and the underlying event structure
1990
Abstract In this talk we address the problem of the structure of the underlying event and its dependence upon a specific trigger. Generally speaking, events selected without any special trigger, like the minimum bias events, need not have the same characteristics as those selected by the jet trigger or through the W and Z-boson selection criteria. We use perturbative QCD in order to unfold part of the structure. In particular we concentrate on the contribution to the underlying event structure which comes from initial state bremsstrahlung. In the present paper we discuss the relationship between transverse momentum and transverse energy for W and Z-boson production both in the low as well a…
Spectroscopy of excited state positronium
1994
Electric dipole transitions in the microwave range have been induced between the fine-structure levels of positronium in the excited staten=2. As an indication of the transitions, we used the increase in Lyman-α radiation when the metastable 23S1-level is depopulated. The results for the transitions 23S1→23P0,1,2 areΝ 0=18499.65±1.20±4.00 MHz,Ν 1=13012.42 ±0.65±1.54 MHz andΝ 2=8624.38±0.54±1.40 MHz. The first error is statistical and the second systematic. The precision of the present measurement has improved by a factor of 3, compared to previous data. Recent bound state QED-calculations have been extended to the orderR t8 α 4lnα −1. The not yet completely calculated orderR t8 α 4 is estim…
Photonuclear reactions induced by a clinical linac
2015
1st NUBA International Conference on Nuclear Physics and Astrophysics -- SEP 14-21, 2014 -- Akdeniz Univ, Antalya, TURKEY
First measurement of target and beam-target asymmetries in theγp→π0ηpreaction
2015
The first data on target and beam-target asymmetries for the gamma p -> 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. The data are in particular sensitive to small contributions from other partial waves.
Physics at MAMI
2008
The Mainz Microtron MAMI has delivered a high quality electron beam with maximum energy of 880MeV for many years. Recently the MAMI C stage with its maximum energy of 1.5GeV was put into operation successfully and is delivering beam routinely now. The A1 collaboration is doing electron scattering experiments with a “Three Spectrometer Setup”. A first experiment using the MAMI C beam to measure the “Recoil polarisation and beam-recoil double polarisation of eta electroproduction on the proton in the region of the S11(1535) resonance” has been finished. A new, very compact magnetic spectrometer (KaoS) suitable especially for the detection of kaons is being installed now. The A2 collaboration …
Results from the Real Photon Programme at MAMI
1995
The accelerator MAMI (Mainzer Mikrotron) with its excellent beam properties and its duty factor of 100% allows to apply coincidence techniques in intermediate energy nuclear physics, which has led to a variety of results with high precision. The real photon collaboration (A2) uses energy tagged bremsstrahlung photons with energies up to 800 MeV. We have results on total photon absorption (proton, deuteron, 3He and U), on Compton scattering (proton, 4He and 12C) and on meson production, especially on π°- and η-photoproduction. Double pion production on the proton and the deuteron was measured. The two and three body breakup of 3He was investigated as well as the reactions (γ,NN) and (γ, π ± …
N14(γ,π+)14Cgsat photon energies of 230, 260, and 320 MeV
1990
The pion angular distribution for {sup 14}N({gamma},{pi}{sup +}){sup 14}C{sub g.s.} has been measured at photon energies of 230 and 260 MeV. These data are consistent with the trend of our earlier data at 200 and 320 MeV. Additional forward angle data were obtained at 320 MeV. The results are compared to several calculations based on the distorted-wave impulse approximation and on the delta-hole model. The data are best fit by the calculations of Tiator {ital et} {ital al}. which use the delta-hole model in the resonance channel. These calculations fit the 230 MeV data well and underestimate the 260 and 320 MeV data by about 25%.
Generalized polarizabilities of the nucleon in baryon chiral perturbation theory
2017
The nucleon generalized polarizabilities (GPs), probed in virtual Compton scattering (VCS), describe the spatial distribution of the polarization density in a nucleon. They are accessed experimentally via the process of electron-proton bremsstrahlung ($ep\to ep\gamma$) at electron-beam facilities, such as MIT-Bates, CEBAF (Jefferson Lab), and MAMI (Mainz). We present the calculation of the nucleon GPs and VCS observables at next-to-leading order in baryon chiral perturbation theory (B$\chi$PT), and confront the results with the empirical information. At this order our results are predictions, in the sense that all the parameters are well-known from elsewhere. Within the relatively large unc…
Break-up and Coherent Photoproduction ofηMesons on the Deuteron
1997
We present new break-up and coherent data for $\ensuremath{\eta}$ meson photoproduction on the deuteron, using a deuterium target and tagged bremsstrahlung photons up to 1 GeV. The differential cross sections for the coherent process were measured from threshold to 800 MeV. They are much smaller than those previously reported. The break-up channel provides a direct measurement of the neutron to proton differential cross section ratios. At the ${S}_{11}(1535)$ resonance peak, ${\ensuremath{\sigma}}_{n}/{\ensuremath{\sigma}}_{p}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.68\ifmmode\pm\else\textpm\fi{}0.06$ leading to an isoscalar to isovector amplitude ratio of ${A}_{s}{/A}_{\ensurem…