The two-pion production in pp-collisions has been investigated at CELSIUS in exclusive measurements from threshold up to Tp=1.36 GeV. Total and differential cross sections have been obtained for the ...channels pnπ+π0, ppπ+π−, ppπ0π0 and also nnπ+π+. For intermediate incident energies Tp>1 GeV, i.e. in the region which is beyond the Roper excitation but at the onset of ΔΔ excitation, the total ppπ0π0 cross section falls behind theoretical predictions by as much as an order of magnitude near 1.2 GeV, whereas the nnπ+π+ cross section is a factor of five larger than predicted. An isospin decomposition of the total cross sections exhibits a s-channel-like energy dependence in the region of the Roper excitation as well as a significant contribution of an isospin 3/2 resonance other than the Δ(1232). As possible candidates the Δ(1600) and the Δ(1700) are discussed.
The antenna array LOPES is set up at the location of the KASCADE-Grande extensive air shower experiment in Karlsruhe, Germany and aims to measure and investigate radio pulses from extensive air ...showers. The coincident measurements allow us to reconstruct the electric field strength at observation level in dependence of general EAS parameters. In the present work, the lateral distribution of the radio signal in air showers is studied in detail. It is found that the lateral distributions of the electric field strengths in individual EAS can be described by an exponential function. For about 20% of the events a flattening towards the shower axis is observed, preferentially for showers with large inclination angle. The estimated scale parameters
R
0
, describing the slope of the lateral profiles range between 100 and 200
m. No evidence for a direct correlation of
R
0
with shower parameters like azimuth angle, geomagnetic angle, or primary energy can be found. This indicates that the lateral profile is an intrinsic property of the radio emission during the shower development which makes the radio detection technique suitable for large scale applications.
Low-energy spectator protons (p
s) from quasi-free proton–neutron interactions on deuterium have been measured for the pd→dπ
0p
s and pd→pnπ
0p
s reactions at the CELSIUS storage ring of the The ...Svedberg Laboratory. The experiment used 320 MeV protons incident on a deuterium cluster-jet target. The spectator protons were detected inside the scattering chamber using a silicon detector system which is compatible with a high vacuum. The low target density allows the spectator proton emerge without undergoing significant secondary scattering. Its measurement is therefore a useful tag upon such reactions, allowing cross-sections for quasi-free reactions to be deduced at well-defined centre-of-mass energies. The comparison with the simulation for the pd→dπ
0p
s reaction shows that the energy dependence of the pn→dπ
0 cross-section can be extracted near the threshold. The method greatly improves the experimental resolution achievable in quasi-free p–n reaction studies.
The KASCADE-Grande experiment, located at Campus North of the Karlsruhe Institute of Technology (Germany) is a multi-component extensive air-shower experiment devoted to the study of cosmic rays and ...their interactions at primary energies 1014 -1018 eV. One of the main goals of the experiment is the measurement of the all particle energy spectrum in the 1016 -1018 eV range, i.e. extending the range accessible by KASCADE alone. The Grande detector samples the charged component (Nch ) of the air shower while the original KASCADE array provides in addition a measurement of the muon component (Nμ ). The combined information of Nch and Nμ is used to estimate the energy on an event-by-event basis and to derive the all-particle energy spectrum. Since the calibration of the observables in terms of the primary energy depends on Monte Carlo simulations, three different methods with partially different sources of uncertainties, have been considered and compared to each other to derive the systematics on the energy spectrum. The different methods employed to derive the spectrum and their uncertainties, as well as the implications of the obtained result, are discussed in detail.
Charge symmetry breaking (CSB) observables are a suitable experimental tool to examine effects induced by quark masses on the nuclear level. Previous high precision data from TRIUMF and IUCF are ...currently used to develop a consistent description of CSB within the framework of chiral perturbation theory. In this work the experimental studies on the reaction dd→He4π0 have been extended towards higher excess energies in order to provide information on the contribution of p-waves in the final state. For this, an exclusive measurement has been carried out at a beam momentum of pd=1.2 GeV/c using the WASA-at-COSY facility. The total cross section amounts to σtot=(118±18stat±13sys±8ext) pb and first data on the differential cross section are consistent with s-wave pion production.
Exclusive measurements of the pp -> pp pi(0)pi(0) reaction have been performed at CELSIUS/WASA at energies from threshold up to T(p) = 1.3 GeV. Total and differential cross sections have been ...obtained. Here we concentrate on energies T(p) >= GeV. where the Delta Delta excitation becomes the leading process. No evidence is found for a significant ABC effect beyond that given by the conventional t-channel Delta Delta excitation. This holds also for the double-pionic fusion to the quasibound (2)He. The data are compared to model predictions, which are based on both pi- and rho-exchange. Total and differential cross sections are at variance with these predictions and call for a profound modification of the rho-exchange. A phenomenological modification allowing only a small rho-exchange contribution leads to a quantitative description of the data.
•We compare LOPES radio lateral distributions of air showers with simulations.•Absolute amplitude is reproduced by REAS 3.11 simulations, but lower for CoREAS.•Slope of measured lateral distributions ...is reproduced by both simulation programs.•Rarely measured rising lateral distributions are likely due to refractive index of air.•The lateral distribution is sensitive to energy and mass of the primary particle.
Cosmic ray air showers emit radio pulses at MHz frequencies, which can be measured with radio antenna arrays – like LOPES at the Karlsruhe Institute of Technology in Germany. To improve the understanding of the radio emission, we test theoretical descriptions with measured data. The observables used for these tests are the absolute amplitude of the radio signal, and the shape of the radio lateral distribution. We compare lateral distributions of more than 500 LOPES events with two recent and public Monte Carlo simulation codes, REAS 3.11 and CoREAS (v 1.0). The absolute radio amplitudes predicted by REAS 3.11 are in good agreement with the LOPES measurements. The amplitudes predicted by CoREAS are lower by a factor of two, and marginally compatible with the LOPES measurements within the systematic scale uncertainties. In contrast to any previous versions of REAS, REAS 3.11 and CoREAS now reproduce the shape of the measured lateral distributions correctly. This reflects a remarkable progress compared to the situation a few years ago, and it seems that the main processes for the radio emission of air showers are now understood: The emission is mainly due to the geomagnetic deflection of the electrons and positrons in the shower. Less important but not negligible is the Askaryan effect (net charge variation). Moreover, we confirm that the refractive index of the air plays an important role, since it changes the coherence conditions for the emission: Only the new simulations including the refractive index can reproduce rising lateral distributions which we observe in a few LOPES events. Finally, we show that the lateral distribution is sensitive to the energy and the mass of the primary cosmic ray particles.
Using data measured by the KASCADE-Grande air shower array, an upper limit to the flux of ultra-high energy gamma-rays in the primary cosmic-ray flux is determined. KASCADE-Grande measures the ...electromagnetic and muonic components for individual air showers in the energy range from 10 PeV up to 1 EeV. The analysis is performed by selecting air showers with low muon contents. A preliminary result on the 90% C.L. upper limit to the relative intensity of gamma-ray with respect to cosmic ray primaries is presented and compared with limits reported by other measurements.
The KASCADE-Grande experiment operated at KIT from January 2004 to November 2012, measuring Extensive Air Showers (EAS) generated by primary cosmic rays in the 1016–1018eV energy range. The ...experiment measured, for each single event, with a high resolution, the total number of charged particles (Nch) and of muons (Nμ).
In this contribution we summarize the results obtained about:
(i) the measurement of the all particle energy spectrum, discussing the influence of the hadronic interaction model used to derive the energy calibration of the experimental data.
(ii) The energy spectra derived separating the events according to the Nμ/Nch ratio. This technique allowed us to unveil a steepening of the spectrum of heavy primaries at E∼1016.92±0.04eV and a hardening of the spectrum of light primaries at E∼1017.08±0.08eV.
(ii) A search for large scale anisotropies.
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