Exclusive measurements of the quasi-free pn→ppπ− and pp→ppπ0 reactions have been performed by means of pd collisions at Tp=1.2 GeV using the WASA detector setup at COSY. Total and differential cross ...sections have been obtained covering the energy region Tp=0.95–1.3 GeV (s=2.3–2.46 GeV), which includes the regions of Δ(1232), N⁎(1440) and d⁎(2380) resonance excitations. From these measurements the isoscalar single-pion production has been extracted, for which data existed so far only below Tp=1 GeV. We observe a substantial increase of this cross section around 1 GeV, which can be related to the Roper resonance N⁎(1440), the strength of which shows up isolated from the Δ resonance in the isoscalar (Nπ)I=0 invariant-mass spectrum. No evidence for a decay of the dibaryon resonance d⁎(2380) into the isoscalar (NNπ)I=0 channel is found. An upper limit of 180 μb (90% C.L.) corresponding to a branching ratio of 9% has been deduced.
The spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungszentrum Jülich in spring 1998. An initial scientific goal is to study K
+-production in pA collisions at ...subthreshold energies far below the free NN-threshold at
T
p=1.58
GeV. This requires the identification of K
+-mesons in a background of pions and protons, about 10
6 times more intense. In this paper the sophisticated detection system and the software procedures for kaon identification are described. With the help of TOF, energy-loss and range measurements as well as the track information from wire chambers, it is possible to measure
d
2σ/
dΩ
dp
for deep subthreshold K
+ production at beam energies down to
T
p=1.0
GeV.
The Proton-Induced SpAllation (PISA) experiment performed at the internal beam facility of the COSY storage ring in Jülich, Germany, which is aimed at the precise measurement of double differential ...cross-sections over a broad range of energies and angles for spallation reactions induced by protons of 200–
2500
MeV
energy in various targets, is presented. In this paper the emphasis is put on the design, principles of operation and performance of a Bragg Curve Detector (BCD) optimized for internal beam experiments at storage rings. Very clean and distinct product identification (with
Z up to ∼14) from reactions, in which a Ni target was bombarded with a
1.9
GeV
circulating proton beam, is obtained. The individual elements are resolved for emission energies higher than
0.5
MeV/
nucleon
. Moreover, due to the detector read-out achieved by coupling a specially designed current sensitive preamplifier directly to a sampling ADC, the shape analysis of the signals from the BCD allows the isotope identification of light particles with
A up to ∼11. It is also found that the BCD can be used efficiently as a thin Δ
E detector for the telescope consisting of the BCD and a series of silicon detectors.
Differential cross sections have been extracted from exclusive and kinematically complete high-statistics measurements of quasifree polarized $\vec n$p scattering performed in the energy region of ...the d* (2380) dibaryon resonance covering the range of beam energies Tn = 0.98 - 1.29 GeV (√ s = 2.32 - 2.44 GeV). The experiment was carried out with the WASA-at-COSY setup having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process dp → np + pspectator. In this way the np differential cross section σ (Θ) was measured over a large angular range. The obtained angular distributions complement the corresponding analyzing power Ay (Θ) measurements published previously. A SAID partial-wave analysis incorporating the new data strengthens the finding of a resonance pole in the coupled 3D3 - 3G3 waves.
New data on both total and differential cross sections of the production of η mesons in proton–deuteron fusion to He3η in the excess energy region 13.6MeV≤Qη≤80.9MeV are presented. These data have ...been obtained with the WASA-at-COSY detector setup located at the Forschungszentrum Jülich, using a proton beam at 15 different beam momenta between pp=1.60GeV/c and pp=1.74GeV/c. While significant structure of the total cross section is observed in the energy region 20MeV≲Qη≲60MeV, a previously reported sharp variation around Qη≈50MeV cannot be confirmed. Angular distributions show the typical forward-peaking that was noted earlier. For the first time, it is possible to study the development of these angular distributions with rising excess energy over a wide interval.
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