The Uppsala neutron beam facility for electronics testing Österlund, M.; Blomgren, J.; Pomp, S. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
December 2005, 2005-12-00, Letnik:
241, Številka:
1-4
Journal Article
Recenzirano
A new facility producing intense mono-energetic neutron beams has been developed at The Svedberg Laboratory (TSL), Uppsala, Sweden. The facility utilizes the existing cyclotron and a flexible lithium ...target in a rebuilt beam line. The new facility can operate at unsurpassed mono-energetic neutron intensities and provides flexibility of the neutron beam properties, like energy and geometrical shape.
The reaction pd→He3η at threshold was used to provide a clean source of η mesons for decay studies with the WASA detector at CELSIUS. The branching ratio of the decay η→π+π−e+e− is measured to be ...(4.3±1.3±0.4)×10−4.
New data on quasifree polarized neutron-proton scattering in the region of the recently observed d* resonance structure are obtained by exclusive and kinematically complete high-statistics ...measurements with WASA at COSY. This paper details the determination of the beam polarization, checks of the quasifree character of the scattering process, on all obtained Ay angular distributions and on the new partial-wave analysis, which includes the new data producing a resonance pole in D-3(3)-(3)G(3) coupled partial waves at (2380 +/- 10 - i40 +/- 5) MeV-in accordance with the d* dibaryon resonance hypothesis. The effect of the new partial-wave solution on the description of total and differential cross-section data as well as specific combinations of spin-correlation and spin-transfer observables available from COSY-ANKE measurements at T-d = 2.27 GeV is discussed.
Detector setup for a storage ring with an internal target Calén, H.; Carius, S.; Fransson, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/1996, Letnik:
379, Številka:
1
Journal Article
Recenzirano
A detector setup for the cooler storage ring CELSIUS is described. The setup detects particles produced in interactions between the internal beam and a cluster-jet target. Particles emitted in the ...forward direction are measured by means of arrays of plastic scintillators and proportional counters. Particles, particularly photons, emitted more isotropically are measured by means of two calorimeters containing CsI(Na) crystals. The performance of the setup is given for neutral meson production in proton-proton and proton-deuteron interactions in the energy range 290–1360 MeV.
Dibaryons, forbidden by mass to decay into NN
π channel and by quantum numbers into NN channel, may still have escaped detection. In fact, recently an observation of a narrow dibaryon (D) with the ...mass close to 1920 MeV was reported in the process
pp→
γγ+
X. This dibaryon should also appear in the proton-proton bremsstrahlung data from measurements at 200 and 310 MeV, which have been carried out at the CELSIUS storage ring in Uppsala. From these data upper limits of 10 and 3 nb are obtained for the dibaryon production cross section (at 95% confidence level) for the two energies, respectively.
Exclusive measurements of the pp-->pppi super(0)pi super(0) reaction have been performed at CELSIUS/WASA at energies from threshold up to T sub()p1.3 GeV. Total and differential cross sections have ...been obtained. Here we concentrate on energies T sub()pinline image1 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 super(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.
Differential cross sections of the reactions
pp→
dπ
+ and
pp→
pnπ
+ have been measured at
T
p
=400 MeV by detecting the charged ejectiles in the angular range 4°≤
Θ
Lab≤21°. The deduced total cross ...sections agree well with those published previously for neighbouring energies. The invariant mass spectra are observed to be strongly affected by
Δ production and
NN final-state interaction. The data are well described by Monte Carlo simulations including both these effects. The ratio of
pp→
pnπ
+ and
pp→
dπ
+ cross sections also compares favourably to a recent theoretical prediction which suggests a dominance of
np-production in the relative
3S
1
-state.
Exclusive and kinematically complete high-statistics measurements of quasifree polarized np scattering have been performed in the energy region of the narrow resonancelike structure d* with I(JP) = ...0(3 super(+)), M approximately 2380 MeV, and Gamma approximately 70 MeV observed recently in the double-pionic fusion channels pn arrow right dpi super(0)pi super(0) and pn arrow right dpi super(+)pi super(-). The experiment was carried out with the WASA detector setup at COSY having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process dp arrow right np + p sub(spectator). This allowed the np analyzing power, A sub(y) to be measured over a broad angular range. The obtained A sub(y)angular distributions deviate systematically from the current SAID SP07 NN partial-wave solution. Incorporating the new A sub(y)data into the SAID analysis produces a pole in the super(3)D sub(3) - super(3)G sub(3) waves in support of the d* resonance hypothesis.
An exclusive measurement of the decay eta arrow right pi super(+) pi super(-) gamma has been performed at the WASA facility at COSY. The eta mesons were produced in the fusion reaction inline image X ...at a proton beam momentum of 1.7 GeV/c. Efficiency corrected differential distributions have been extracted based on inline image events after background subtraction. The measured pion angular distribution is consistent with a relative p-wave of the two-pion system, whereas the measured photon energy spectrum was found at variance with the simplest gauge invariant matrix element of eta arrow right pi super(+) pi super(-) gamma . A parameterization of the data can be achieved by the additional inclusion of the empirical pion vector form factor multiplied by a first-order polynomial in the squared invariant mass of the pi super(+) pi super(-) system.
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