The Σ+ hyperon production was measured at the COSY-11 spectrometer via the pp→nK+Σ+ reaction at excess energies of Q=13 MeV and Q=60 MeV. These measurements continue systematic hyperon production ...studies via the pp→pK+Λ/Σ0 reactions where a strong decrease of the cross section ratio close-to-threshold was observed. In order to verify models developed for the description of the Λ and Σ0 production we have performed the measurement on the Σ+ hyperon and found unexpectedly that the total cross section is by more than one order of magnitude larger than predicted by all anticipated models. After the reconstruction of the kaon and neutron four momenta, the Σ+ is identified via the missing mass technique. Details of the method and the measurement will be given and discussed in view of theoretical models.
The total cross section of the reaction pp→ppK+K− has been measured at excess energies Q=10 MeV and 28 MeV with the magnetic spectrometer COSY-11. The new data show a significant enhancement of the ...total cross section compared to pure phase space expectations or calculations within a one boson exchange model. In addition, we present invariant mass spectra of two particle subsystems. While the K+K− system is rather constant for different invariant masses, there is an enhancement in the pK− system towards lower masses which could at least be partially connected to the influence of the Λ(1405) resonance.
A large area efficient trigger scintillator with SiPM read out Grzonka, D.; Bergmann, P.; Hahnraths von der Gracht, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2022, Letnik:
1041
Journal Article
The strong nuclear interaction is probed at short-distance and high-momenta using new measurements of the $^{12}$C$(e,e'p)$ and $^{12}$C$(e,e'pn)$ reactions, at high-$Q^2$ and $x_B>1$. The data span ...a missing-momentum range of 300-850 MeV/c and is predominantly sensitive to the dominant proton-neutron short-range correlated (SRC) pairs and complements previous $^{12}$C$(e,e'pp)$ measurements. The data are well reproduced by theoretical calculations using the Generalized Contact Formalism with both chiral and phenomenological nucleon-nucleon ($NN$) interaction models. This agreement, observed here for the first time, suggests that the measured high missing-momentum protons up to $850$ MeV/c belonged to SRC pairs. The measured $^{12}$C$(e,e'pn)$ / $^{12}$C$(e,e'p)$ ratio is consistent with a decrease in the fraction of proton-neutron SRC pairs with increasing missing-momentum. This confirms the transition from an isospin-dependent tensor $NN$ interaction at $\sim 400$ MeV/c to an isospin-independent scalar interaction at high-momentum around $\sim 800$ MeV/c.
The straw tube tracker of the ANDA experiment Costanza, S.; Benussi, L.; Braghieri, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2010, Letnik:
617, Številka:
1-3
Journal Article
Recenzirano
MathML equationANDA is a new experiment that will be installed at HESR, the new antiproton storage ring under construction as a part of the FAIR facility at Darmstadt, Germany. This experiment, that ...will investigate QCD in the charmonium mass regime and other aspects of particle and nuclear physics, will be a fixed target detector with a central spectrometer and a forward one. The central tracker will provide information about decay vertices, momenta and types of charged particles emitted after MathML equation annihilations. The design of the Straw Tube Tracker (STT) together with experimental results of the R&D phase are presented here.
Cryogenic target with very thin “gold finger” heat pipe Abdel-Samad, S.; Abdel-Bary, M.; Kilian, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2006, 2006-1-00, Letnik:
556, Številka:
1
Journal Article
Recenzirano
An extremely light stainless steel heat pipe of 0.1
mm wall thickness and 5
mm diameter has been developed to transport heat from the liquid hydrogen/deuterium target to the cooling machine. As a ...further improvement an important reduction of the heat load to the cold parts of the system is achieved by coating the heat pipe and the target finger with a thin polished gold layer. This brings the radiation heat load from 1400
mW on the non-isolated stainless steel surface system down to 70
mW on the gold-coated system. A further reduction to 0.05
mW is achieved by using an aluminum heat shield at 50
K around the cold parts at 15
K. Finally, the heat load was further reduced by a factor 11, without changing the geometry, by coating both sides of the aluminum shield with a thin gold mirror layer. This new, very slim “gold finger” target system shows safe and stable performance even with a low power-cooling machine.
PDF
