Eur. Phys. J. A 57, 80 (2021) $\gamma p \rightarrow K^+ \Lambda$ differential cross sections and recoil
polarisation data from threshold for extremely forward angles are presented.
The measurements ...were performed at the BGOOD experiment at ELSA, utilising the
high angular and momentum resolution forward spectrometer for charged particle
identification. The data discriminates between conflicting results in the world
data set and enable extraction of the cross section as the minimum momentum
transfer to the recoiling hyperon is approached.
The $\gamma p \rightarrow K^+\Sigma^0$ differential cross section at
extremely forward angles was measured at the BGOOD experiment. A three-quarter
drop in strength over a narrow range in energy and ...a strong dependence on the
polar angle of the $K^+$ in the centre-of-mass of the reaction is observed at a
centre-of-mass energy of 1900\,MeV. Residing close to multiple open and hidden
strangeness thresholds, the structure appears consistent with meson-baryon
threshold effects which may contribute to the reaction mechanism.
Measurements of target asymmetries and double-polarization observables for the reaction \(\gamma p\to p\pi^0\pi^0\) are reported. The data were taken with the CBELSA/TAPS experiment at the ELSA ...facility (Bonn University) using the Bonn frozen-spin butanol (C\(_4\)H\(_9\)OH) target, which provided transversely polarized protons. Linearly polarized photons were produced via bremsstrahlung off a diamond crystal. The data cover the photon energy range from \(E_{\gamma}\)=650 MeV to \(E_{\gamma}\)=2600 MeV and nearly the complete angular range. The results have been included in the BnGa partial wave analysis. Experimental results and the fit agree very well. Observed systematic differences in the branching ratios for decays of \(N^*\) and \(\Delta^*\) resonances are attributed to the internal structure of these excited nucleon states. Resonances which can be assigned to SU(6)\(\times\)O(3) two-oscillator configurations show larger branching ratios to intermediate states with non-zero intrinsic orbital angular momenta than resonances assigned to one-oscillator configurations.
The reaction $\gamma p \rightarrow p \pi^0 \eta$ has been studied with the
CBELSA/TAPS detector at the electron stretcher accelerator ELSA in Bonn for
incident photon energies from threshold up to ...3.1 GeV. This paper has been
motivated by the recently claimed observation of a narrow structure in the
M$_{N\eta}$ invariant mass distribution at a mass of 1678 MeV/$c^2$. The
existence of this structure cannot be confirmed in the present work. Instead,
for E$_{\gamma}$ = 1400 - 1500 MeV and the cut M$_{p\pi^0} \le 1190 $ MeV/$c^2$
a statistically significant structure in the M$_{p\eta}$ invariant mass
distribution near 1700 MeV/$c^2$ is observed with a width of $\Gamma\approx 35$
MeV/$c^2$ while the mass resolution is $\sigma_{res}$ = 5 MeV/$c^2$. Increasing
the incident photon energy from 1420 to 1540 MeV this structure shifts in mass
from $\approx$ 1700MeV/c$^2$ to $\approx$ 1725 MeV/$c^2$; the width increases
to about 50 MeV/$c^2$ and decreases thereafter. The cross section associated
with this structure reaches a maximum of $\approx$ 100 nb around E$_{\gamma}
\approx$ 1490 MeV (W $\approx $ 1920 MeV), which coincides with the $p a_0$
threshold. Three scenarios are discussed which might be the origin of this
structure in the M$_{p\eta}$ invariant mass distribution. The most likely
interpretation is that it is due to a triangular singularity in the $\gamma p
\rightarrow p a_0 \rightarrow p \pi^0 \eta$ reaction
The BGOOD experiment at the ELSA facility in Bonn has been commissioned within the framework of an international collaboration. The experiment pursues a systematic investigation of non-strange and ...strange meson photoproduction, in particular \(t\)-channel processes at low momentum transfer. The setup uniquely combines a central almost \(4\pi\) acceptance BGO crystal calorimeter with a large aperture forward magnetic spectrometer providing excellent detection of both neutral and charged particles, complementary to other setups such as Crystal Barrel, Crystal Ball, LEPS and CLAS.
In the framework of the ATTRACT-uRANIA project, funded by the European Community, we are developing an innovative neutron imaging detector based on micro-Resistive WELL (\(\mu\) -RWELL) technology. ...The \(\mu\) -RWELL, based on the resistive detector concept, ensuring an efficient spark quenching mechanism, is a highly reliable device. It is composed by two main elements: a readout-PCB and a cathode. The amplification stage for this device is embedded in the readout board through a resistive layer realized by means of an industrial process with DLC (Diamond-Like Carbon). A thin layer of B\(_4\)C on the copper surface of the cathode allows the thermal neutrons detection through the release of \(^7\)Li and \(\alpha\) particles in the active volume. This technology has been developed to be an efficient and convenient alternative to the \(^3\)He shortage. The goal of the project is to prove the feasibility of such a novel neutron detector by developing and testing small planar prototypes with readout boards suitably segmented with strip or pad read out, equipped with existing electronics or readout in current mode. Preliminary results from the test with different prototypes, showing a good agreement with the simulation, will be presented together with construction details of the prototypes and the future steps of the project.
The Multi-Blade is a Boron-10-based neutron detector designed for neutron reflectometers and developed for the two instruments (Estia and FREIA) planned for the European Spallation Source in Sweden. ...A reflectometry demonstrator has been installed at the AMOR reflectometer at the Paul Scherrer Institut (PSI - Switzerland). The setup exploits the Selene guide concept and it can be considered a scaled-down demonstrator of Estia. The results of these tests are discussed. It will be shown how the characteristics of the Multi-Blade detector are features that allow the focusing reflectometry operation mode. Additionally the performance of the Multi-Blade, in terms of rate capability, exceeds current state-of-the-art technology. The improvements with respect to the previous prototypes are also highlighted; from background considerations to the linear and angular uniformity response of the detector.
The European Spallation Source (ESS), presently under construction in Lund, Sweden, is designed to be the world's brightest neutron source. When it will be in operation, ESS will deliver an ...instantaneous neutron flux on detectors that will be without precedent. A down side of the high brightness will be the increase of background, especially from gamma-rays and fast-neutrons.Considering that scattering cross-sections of many samples tend to be relatively low and that the gamma- and fast-neutronbackgrounds tend to be considerable high at spallation facilities Che +14, the signal-to-noise ratio of a measurement needs to be maximised. The sensitivity of a thermal-neutron detector to gamma-rays and to fast-neutrons is a very important characteristic, as it defines the best achievable signal-to-noise ratio for the measurement. It is therefore crucial to measure the gamma- and fast-neutron- sensitivities of all detectors that will be installed on the instruments at ESS.
European Spallation Source (ESS) will deliver neutrons at high flux for use in diverse neutron scattering techniques. The neutron source facility and the scientific instruments will be located in ...Lund, and the Data Management and Software Centre (DMSC), in Copenhagen. A number of detector prototypes are being developed at ESS together with its European in-kind partners, for example: SoNDe, Multi-Grid, Multi-Blade and Gd-GEM. These are all position sensitive detectors but use different techniques for the detection of neutrons. Except for digitization of electronics readout, all neutron data is anticipated to be processed in software. This provides maximum flexibility and adaptability and allows deep inspection of the raw data for commissioning which will reduce the risk of starting up new detector technologies. But it also requires development of high performance software processing pipelines and optimized and scalable processing algorithms. This report provides a description of the ESS system architecture for the neutron data path. Special focus is on the interface between the detectors and DMSC which is based on UDP over Ethernet links. The report also describes the software architecture for detector data processing and the tools we have developed, which have proven very useful for efficient early experimentation, and can be run on a single laptop. Processing requirements for the SoNDe, Multi-Grid, Multi-Blade and Ge-GEM detectors are presented and compared to event processing rates archived so far.
The Multi-Blade is a Boron-10-based gaseous detector developed for neutron reflectometry instruments at the European Spallation Source (ESS) in Sweden. The main challenges for neutron reflectometry ...detectors are the instantaneous counting rate and spatial resolution. The Multi-Blade has been tested on the CRISP reflectometer at the ISIS neutron and muon source in UK. A campaign of scientific measurements has been performed to study the Multi-Blade response in real instrumental conditions. The results of these tests are discussed in this manuscript.
