Search results for "HRES"
showing 10 items of 695 documents
Performance of the photon spectrometer TAPS for deep subthreshold pion detection
2005
Abstract We present in this paper the characteristics of the BaF 2 spectrometer, TAPS, which allow to detect rare electromagnetic events in a high hadronic background. The case of deep subthreshold pions produced in 36 Ar+ 197 Au collisions at 25A and 35A MeV, in which the pion signal is much weaker than the hadronic background and comparable to the cosmic ray background, is studied.
Multi-nucleon mechanism for subthreshold antiproton production in proton-nucleus reactions
1995
We study a many-body (multipion) mechanism for ¯p subthreshold production in proton-nucleus collisions. The incoming proton and the interacting nucleons in the target act as sources of pions that merge to produce a nucleon-antiproton pair. The calculation takes fully into account the initial state interaction and antiproton absorption in the final state. The cooperation of several nucleons in the initial state reduces the threshold for the reaction allowing for production rates that may account for 15–50% of the total ¯p production. We point out that this contribution should be added to the primary ¯p production mechanism due toΔ formation and rescattering, as found by other groups, and sho…
Front-End Electronics for the KAOS Spectrometer at MAMI
2009
A new front-end electronics system has been developed for the electron arm tracking detectors in the Kaos spectrometer at the Mainz microtron MAMI. The signals of multi-anode photomultipliers are collected by 96-channel front-end boards, digitized by double-threshold discriminators and the signal time is picked up by F1 TDC chips. The system was designed to process more than 4,000 channels and to cope with the high electron flux in the spectrometer and the high count rate requirement of the detectors. A subset of 288 channels was installed and successfully used in the 2008 data taking period of the Kaos spectrometer.
Photoproduction of $\eta$ $\pi$ pairs off nucleons and deuterons
2016
Quasi-free photoproduction of $\pi\eta$-pairs has been investigated from threshold up to incident photon energies of 1.4 GeV, respectively up to photon-nucleon invariant masses up to 1.9 GeV. Total cross sections, angular distributions, invariant-mass distributions of the $\pi\eta$ and meson-nucleon pairs, and beam-helicity asymmetries have been measured for the reactions $\gamma p\rightarrow p\pi^0\eta$, $\gamma n\rightarrow n\pi^0\eta$, $\gamma p\rightarrow n\pi^+\eta$, and $\gamma n\rightarrow p\pi^-\eta$ from nucleons bound inside the deuteron. For the $\gamma p$ initial state data for free protons have also been analyzed. Finally, the total cross sections for quasi-free production of $…
The binding energy of 184 476 X in the droplet model
1985
The positron spectrum emitted in the U-U-reaction at subthreshold energy could be interpreted in terms of the formation of a giant nucleus if the binding of the latter is 100 MeV stronger than predicted by the usual droplet model parametrisation. We analyse the extrapolation to giant nuclei by accounting properly for the error propagation when the parameters are fitted to measured binding energies and radii. The influence of higher order terms is discussed.
Cross section ratio and angular distributions of the reaction p + d -> 3He + eta at 48.8 MeV and 59.8 MeV excess energy
2014
We present new data for angular distributions and on the cross section ratio of the p + d -> 3He + eta reaction at excess energies of Q = 48.8 MeV and Q = 59.8 MeV. The data have been obtained at the WASA-at-COSY experiment (Forschungszentrum J\"ulich) using a proton beam and a deuterium pellet target. While the shape of obtained angular distributions show only a slow variation with the energy, the new results indicate a distinct and unexpected total cross section fluctuation between Q = 20 MeV and Q = 60 MeV, which might indicate the variation of the production mechanism within this energy interval.
Deuteron electrodisintegration near threshold with the Bonn potential
1987
Deuteron electrodisintegration near threshold is calculated for the Bonn potential including consistent meson exchange currents. Experimental data can fairly well be described over the whole q-range if GE is used as electromagnetic form factor for the exchange current, whereas F1 leads to a large overestimation at high q.
Near threshold photoproduction of eta mesons off the proton.
1995
We have measured precise total and differential cross sections for the reaction $\ensuremath{\gamma}p\ensuremath{\rightarrow}p\ensuremath{\eta}$ from threshold to 790 MeV at the MAMI accelerator in Mainz with the neutral meson spectrometer TAPS. Resonance parameters of the ${S}_{11}$(1535) resonance and the electromagnetic coupling $\ensuremath{\gamma}p\ensuremath{\rightarrow}{S}_{11}$ have been extracted from the data. Contributions from the ${D}_{13}$(1520) resonance to $\ensuremath{\eta}$ photoproduction in the threshold region have been identified for the first time via interference terms in the angular distributions.
Mass and low-lying levels ofIn106,108from theCd106,108(p,nγ)reactions
1984
106In has been studied via the reaction 106Cd(p,nγ)106In in the energy range Ep=7-9 MeV. Inbeam γ-ray excitation functions, γ-γ coincidence measurements, and β+-delayed γ-ray excitation functions have been used to identify thirteen levels in 106In. From this new level scheme the energy separation of the high-spin ground state and the low-spin isomer has been determined to be 28.6±0.5 keV. The threshold energy of the strongest low-lying γ-ray transition yields a mass excess for 106In of -80601±15 keV. Spins for some states are suggested by comparing the excitation functions to Hauser-Feshbach calculations. In-beam γ-ray excitation functions for the 108Cd(p,nγ)108In reaction give a mass exces…
Photoproduction of π 0 mesons off protons and neutrons in the second and third nucleon resonance regions
2018
Photoproduction of mesons off quasi-free nucleons bound in the deuteron allows to study the electromagnetic excitation spectrum of the neutron and the isospin structure of the excitation of nucleon resonances. The database for such reactions is much more sparse than for free proton targets. Single $\pi^0$ photoproduction off quasi-free nucleons from the deuteron was experimentally studied. Nuclear effects were investigated by a comparison of the results for free protons and quasi-free protons and used as a correction for the quasi-free neutron data. The experiment was performed at the tagged photon beam of the Mainz MAMI accelerator for photon energies between 0.45~GeV and 1.4~GeV, using an…