Chr. Bargholtz

The WASA Detector Facility at CELSIUS

The WASA 4 pi multidetector system, aimed at investigating light meson production in light ion collisions and eta meson rare decays at the CELSIUS storage ring in Uppsala is presented. A unique fea ...

Measurement of eta meson decays into lepton-antilepton pairs

A search for rare lepton decays of the η meson was performed using the WASA detector at CELSIUS. Two candidates for double Dalitz decay η→e+e-e+e- events are reported with a background of 1.3±0.2 e ...

A small size zero-degree spectrometer with germanium detectors

Abstract A small size spectrometer for detecting heavy reaction products emitted at small angles has been developed. It is installed at the synchrotron storage ring CELSIUS in Uppsala. It uses the focussing and bending magnetic elements of the storage ring itself in combination with a detector telescope, made of high-purity germanium, inserted into the ring vacuum. The spectrometer has been used for studies of pion production reactions close to threshold. The spectrometer is described together with results of ray-trace calculations and experimental tests.

Exclusive measurement of two-pion production in the dd -g He-4 pi pi reaction

The results from the first kinematically complete measurement of the dd -> He-4 pi pi reaction are reported. The aim was to investigate a long standing puzzle regarding the origin of the peculia ...

Model-based pulse shape correction for CdTe detectors

Abstract We present a systematic method to improve energy resolution of CdTe-detector systems with full control of the efficiency. Sampled pulses and multiple amplifier data are fitted by a model of the pulse shape including the deposited energy and the interaction point within the detector as parameters. We show the decisive improvements of spectral resolution and photo-peak efficiency that is obtained without distortion of spectral shape. The information concerning the interaction depth of individual events can be used to discriminate between beta particles and gamma quanta.

Measurement of the eta -g pi(+)pi(-)e(+)e(-) decay branching ratio

The reaction 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 ...

Isospin resolved double pion production in the reaction p+d→3He+2π

Abstract Neutral and charged two-pion production in p+d→ 3 He+2 π reactions has been studied at CELSIUS at a proton beam energy of 477 MeV. The total cross section for double pion production is 0.22±0.03 μ b. The ratio of the cross sections for the production of charged pion pairs with isospin T =1 and T =0 was determined to be σ ( π + π − ; T =1)/ σ ( π + π − ; T =0)=1.4±0.4.

The inclusive reaction d + d → 4He + X 29 MeV above the 2π0 threshold☆

Abstract The momentum spectrum of 4 He particles from d + d reactions at E lab = 569 MeV has been measured at zero degrees in the laboratory. The missing-mass spectrum is consistent with a pure phase space behaviour for the isospin zero channel of two pions, corresponding to a total cross section of 43 ± 5 nb.

Vibrations and polarizations in a cluster model description of states in 12C and 16O

Abstract The α-particle model of Bloch and Brink is used to study the importance of vibrations and of polarization of the clusters in low-lying states of 12 C and 16 O. The two effects are found to be approximately of the same importance for the binding energy.

An efficient method for the analysis of data from perturbed angular correlation and multiple-lifetime experiments

Abstract A method for the analysis of data from perturbed angular correlation, or distribution, experiments is described. The method allows for the presence of a prompt admixture, and is also suited for the analysis of lifetime data involving up to three different decay constants. A computer code utilizing this method of analysis has been developed, and extensively tested.