Taking advantage of both the high mass resolution of the COSY-11 detector and the high energy resolution of the low-emittance proton beam of the cooler synchrotron COSY, we determine the excitation ...function for the pp→ppη(') reaction close to threshold. Combining these data with previous results, we extract the scattering length for the η(')-proton potential in free space to be Re(a(pη(')))=0±0.43 fm and Im(a(pη(')))=0.37(-0.16)(+0.40) fm.
The proton–proton elastic differential cross section at very small four momentum transfer squared has been measured at three different incident proton momenta in the range of 2.5 to 3.2 GeV/c by ...detecting the recoil proton at polar angles close to 90∘. The measurement was performed at COSY with the KOALA detector covering the Coulomb–nuclear interference region. The total cross section σtot, which has been determined precisely, is consistent with previous measurements. The values of the slope parameter B and the relative real amplitude ratio ρ determined in this experiment alleviate the lack of data in the relevant energy region. These precise data on ρ might be an important check for a new dispersion analysis.
We present the first determination of the energy-dependent amplitudes of N⁎ resonances extracted from their decay in KΛ pairs in p+p→pK+Λ reactions. A combined Partial Wave Analysis of seven data ...samples with exclusively reconstructed p+p→pK+Λ events measured by the COSY-TOF, DISTO, FOPI and HADES Collaborations in fixed target experiments at kinetic energies between 2.14 to 3.5 GeV is used to determine the amplitude of the resonant and non-resonant contributions into the associated strangeness final state. The contribution of seven N⁎ resonances with masses between 1650 MeV/c2 and 1900 MeV/c2 for an excess energy between 0 and 600 MeV has been considered. The Σ–p cusp and final state interactions for the p–Λ channel are also included as coherent contributions in the PWA. The N⁎ contribution is found to be dominant with respect to the phase space emission of the pKΛ+ final state at all energies demonstrating the important role played by both N⁎ and interference effects in hadron–hadron collisions.
Mapping the density distribution and monitoring density changes under volcanoes and geological reservoirs is a major challenge in geology and volcanology. Muon radiography has a high potential to ...advance this field, but often there are no inexpensive high-end detectors available that are suitable for field installations. A DIRC-type Cherenkov detector as a muon camera has a small dimension and is suited for such field applications (MagmaDIRC idea). In measuring directions and energies of the incoming muons one can turn the mass density integrals along the lines of flight into a radiography image, and by discarting low-energy muons with their blurred angular information one obtains sharper images. In particular one may detect the time variation of the mass density distributions situated above the horizon line in a volcanic edifice that occurs when magma is filling its plumbing system or when the level of a lava lake changes. Using numerical simulations, we discuss design aspects and the requirements of such a DIRC system. Two sites are identified for proof-of-principle field measurements. The required measurement times are estimated for the given site conditions and morphology based on the specifications of an operational DIRC system. The merits of DIRC sensors are contrasted to other muon radiography techniques.
Abstract
A high-density and low-power (<300 mW/channel) data acquisition (DAQ) system integrating 2240 readout channels inside a single OpenVPX crate is presented. It is intended to be used in ...various applications, e.g. gaseous or scintillator-based particle detectors. 14 payload slots, controller and data concentrator communicate via a multi-gigabit backplane. Each payload slot consists of a front module for digital and a rear transition module for analog processing. A pair of modules implements 160 full readout chains including amplification/shaping, sampling, and feature extraction. The sampling rate and ADC resolution are configurable for 100–1000 MS/s and 14–8 bit, respectively. To extract the pulse arrival time we used a proper shaping of signals and a timing algorithm based on a non-linear rise approximation, which strongly reduces the sampling phase error, thus providing a good performance at moderate (100–250 MS/s) sampling rates. This allows raw data acquisition, arrival time extraction, energy calculation, and pile-up reconstruction for all 160 channels to be implemented in a single FPGA. It occupies less than 30% of its processing resources. The system was tested using the proton beam at COSY (Cooler Synchrotron) at Juelich Research Center (Germany). An off-detector DAQ with a 12-m long cabling was investigated. It introduces considerable additional thermal noise and crosstalk affecting the timing performance. For a sampling rate of 150 MS/s, the time resolution was found to be about 270 ps.
We report on the experimental search for the bound state of an η meson and He3 nucleus performed using the WASA-at-COSY detector setup. In order to search for the η-mesic nucleus decay, the pd→3He2γ ...and pd→3He6γ channels have been analysed. These reactions manifest the direct decay of the η meson bound in a He3 nucleus. This non-mesonic decay channel has been considered for the first time. When taking into account only statistical errors, the obtained excitation functions reveal a slight indication for a possible bound state signal corresponding to a 3He-η nucleus width Γ above 20 MeV and binding energy Bs between 0 and 15 MeV. However, the determined cross sections are consistent with zero in the range of the systematic uncertainty. Therefore, as final result we estimate only the upper limit for the cross section of the η-mesic He3 nucleus formation followed by the η meson decay which varies between 2 nb and 15 nb depending on possible bound state parameters.
Stopped antiproton annihilation can initiate an effcient chain of reactions to produce Ξ hyperons in recoil free kinematics, suitable for further investigations of Ξ
N
interactions. Four delayed ...decays and presence of eight charged particles in the final state provide a clean reaction signature and allow for usage of a non-magnetic detection system. With the low energy phase space cooled antiproton beam from ELENA at the CERN AD or future FLAIR facility the realisation of this experiment would become possible. In this article the foreseen detector setup and the experimental program will be presented.
To classify clusters of hits in the electromagnetic calorimeter (EMC) of ANDA (antiProton ANnihilation at DArmstadt), one has to match these EMC clusters with tracks of charged particles ...reconstructed from hits in the tracking system. Therefore the tracks are propagated to the surface of the EMC and associated with EMC clusters which are nearby and below a cut parameter. In this work, we propose a helix propagator to extrapolate the track from the Straw Tube Tracker (STT) to the inner surface of the EMC instead of the GEANE propagator which is already embedded within the PandaRoot computational framework. The results for both propagation methods show a similar quality, with a 30% gain in CPU time when using the helix propagator. We use Monte-Carlo truth information to compare the particle ID of the EMC clusters with the ID of the extrapolated points, thus deciding upon the correctness of the matches. By varying the cut parameter as a function of transverse momentum and particle type, our simulations show that the purity can be increased by 3–5% compared to the default value which is a constant cut in the ANDA simulation framework PandaRoot.
The design of straw tube detector modules developed for the PANDA Forward Tracker is presented. One module consists of 32 straws with 10 mm diameter, arranged in two staggered layers, and has a very ...low material budget of only 8.8ċ10−4X0. The overpressure of the working gas mixture of 1 bar makes the module self-supporting and enables the use of lightweight and compact support frames. Detection planes in the Forward Tracker consist of modules mounted closely, without gaps, next to each other on a support frame. A module can be mounted and dismounted from the frame without the need to remove the neighboring modules, enabling fast repairs. Technical details of the detector design and the assembly procedure of the straw tubes and the straw modules as well as results of performed tests of the modules are given.
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