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  • 1.
    Bargholtz, Chr
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Chernyshev, B.A
    Gerén, L
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Grebenev, V.N
    Gurov, Yu.B
    Karpuhkin, V.S
    Laukhin, I.V
    Martemyanov, B.V
    Matveev, V.A
    Lindberg, Karl
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Shafigullin, R.R
    Sopov, V.S
    Tegnér, Per-Erik
    Zartova, Irina
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Tagging of η mesons using the pd3Heη reaction near threshold2006Inngår i: Instruments and experimental techniques (New York), ISSN 0020-4412, E-ISSN 1608-3180, Vol. 49, nr 4, s. 461-467Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A zero-degree spectrometer for tagging η mesons on the CELSIUS/WASA facility is described, and its characteristics are presented. Tagging of η mesons is performed by detecting 3He ions produced by reaction pd3Heη close to the production threshold. The low background level (<2%) is in good agreement with the data obtained earlier on the SATURNE accelerator.

  • 2.
    Bargholtz, Christoph
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. kärnfysik.
    Gerén, Linda
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. kärnfysik.
    Lindberg, Karl
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. kärnfysik.
    Tegnér, Per-Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. kärnfysik.
    Zartova, Irina
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. kärnfysik.
    Calén,, H.
    The Svedberg Laboratory, Uppsala, Sweden.
    Ekström,, C.
    The Svedberg Laboratory, Uppsala, Sweden.
    Fransson,, K.
    The Svedberg Laboratory, Uppsala, Sweden.
    Kupsc, À.
    The Svedberg Laboratory, Uppsala, Sweden.
    Marciniewski,, P.
    The Svedberg Laboratory, Uppsala, Sweden.
    Ruber,, R. J. M.Y.
    The Svedberg Laboratory, Uppsala, Sweden.
    Measurement of h meson decays into lepton-antilepton pairs2008Inngår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 77, nr 3, s. 32004-32008Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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 events. This allows to set an upper limit to the branching ratio of 9.7×10-5 (90% CL). The branching ratio for the decay η→e+e-γ is determined to (7.8±0.5stat±0.8syst)×10-3 in agreement with world average value. An upper limit (90% CL) for the branching ratio for the η→e+e- decay is 2.7×10-5 and a limit for the sum of the η→μ+μ-μ+μ- and η→π+π-μ+μ- decays is 3.6×10-4.

  • 3.
    Bargholtz, Christoph
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. kärnfysik.
    Gerén, Linda
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. kärnfysik.
    Lindberg, Karl
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. kärnfysik.
    Tegnér, Per-Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. kärnfysik.
    Zartova, Irina
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. kärnfysik.
    Kupść, A.
    Department of Nuclear and Particle Physics, Uppsala University.
    Shafigullinc, R.R:
    Moscow Engineering Physics Institute (State University), .
    Properties of the WASA pellet target and a stored intermediate-energy beam2008Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 587, nr 2-3, s. 178-187Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Experimental data from the reaction close to threshold have been used to investigate time-dependent properties of the WASA pellet target and the stored beam of 892.8 MeV protons in the CELSIUS accelerator. The detection of 3He ions in solid-state detectors provides an excellent almost background free trigger for η production. Pellet interactions with the surrounding material and with the beam lead to evaporation of deuterium gas into the beam pipe. Approximately 30% of the registered η decay events are due to interactions in deuterium gas outside the pellets. Due to beam–target interaction the beam is transversely heated and appears to acquire a component of a slightly lower energy.

  • 4.
    Bargholtz, Christoph
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Tegner, Per-Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Zartova, Irina
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Jacewicz, M.
    Uppsala University, Uppsala, Sweden.
    Johansson, T
    Uppsala University, Uppsala, Sweden.
    Lindberg, Karl
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Keleta, S.
    Uppsala University, Uppsala, Sweden.
    Koch, I.
    Uppsala University, Uppsala, Sweden.
    Kullander, S.
    Uppsala University, Uppsala, Sweden.
    Schönning, K.
    Uppsala University, Uppsala, Sweden.
    Thörngren Engblom, P.
    Uppsala University, Uppsala, Sweden.
    Wolke, M.
    Uppsala University, Uppsala, Sweden.
    Calén, H.
    The Svedberg Laboratory, Uppsala, Sweden.
    Ekström, C.
    The Svedberg Laboratory, Uppsala, Sweden.
    Fransson, K.
    The Svedberg Laboratory, Uppsala, Sweden.
    Marciniewski, P.
    The Svedberg Laboratory, Uppsala, Sweden.
    Ruber, R.J.M.Y.
    The Svedberg Laboratory, Uppsala, Sweden.
    Gustafsson, L.
    Uppsala University, Uppsala, Sweden.
    Höistad, B.
    Uppsala University, Uppsala, Sweden.
    Kupść, A.
    The Svedberg Laboratory, Uppsala, Sweden.
    Measurement of the η -> π+π-e+e- branching ratio2007Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 644, nr 5-6, s. 299-303Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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 ηπ+πe+e is measured to be (4.3±1.3±0.4)×10−4.

  • 5.
    Kastlander, Johan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Bargholtz, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Efficient in situ method to determine radionuclide concentration in soil2005Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 547, nr 2-3, s. 400-410Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A simple realisation of the so-called peak-to-valley method is described combining simulations of photon transport in soil with measured detector properties. Comparisons regarding the total activity of Cs-137 determined from gamma spectra recorded in situ to results from soil sampling show excellent agreement for six different sites in Sweden with different surface properties and activities ranging from 15 to 1000 kBq/m(2). These results are quite insensitive to assumptions regarding soil composition. Our results for the burial depth are more sensitive to assumptions regarding soil composition, however, still in general agreement with the results from the soil samples.

  • 6.
    Kastlander, Johan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Bargholtz, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    In-situ method to determine depth distribution of buried activity2011Inngår i: Applied Radiation and Isotopes, ISSN 0969-8043, E-ISSN 1872-9800, Vol. 69, nr 5, s. 773-779Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method is described to determine the depth distribution of buried activity offering an alternative to conventional soil sampling and laboratory analysis by in-situ measurements with small detectors inserted into the ground. As ad demonstration of the method small-scale variations in the distribution of Cs-137 in a riparian marsh in central-eastern Sweden are determined using lanthanum bromide detectors (LaBr3). The results show variations of the activity ranging between 400 and 2200 kBq/m^2 over an area not exceeding 350 m^2. The decrease of the average activity since 2003 coincides with the physical decay indicating that no net redistribution of activity into this part of the marsh has occurred during the inter weening years.

  • 7.
    Kastlander, Johan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Bargholtz, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Investigation into the properties of CdTe detectors for in-situ measurements2008Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 596, nr 3, s. 409-416Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As part of a program investigating means to improve gamma-ray spectra obtained with CdTe detectors, we report results obtained with two 10×10×5 mm^3 CdTe detectors, one planar the other of quasi-hemispheric geometry. Applying a combination of cooling and pulse rise-time discrimination with the quasi-hemispheric detector, we obtain a resolution of 4 percent at 662 keV and a peak-to-valley ratio of 92 at a loss of approximately 25 percent of the counts in the full-energy region.

  • 8.
    Kastlander, Johan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Bargholtz, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Batres-Estrada, G
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Behrooz, K
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Development of methods to use CdTe detectors in field measurements2006Inngår i: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 41, s. 523-526Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We are currently investigating the possibility to use CdTe detectors for in situ determinations of radionuclide concentration in soil. Buried activity can be reliably determined by a comparison of the count rate in the photo peak and the region between the photo peak and Compton edge. However, the pulse-height spectrum from CdTe detectors is severely deteriorated, due to poor charge collection, in particular for high gamma-ray energies. Our efforts have, therefore, been concentrated on improving the peak to valley ratio for such detectors. A simple, non-discriminating, algorithm for the analysis of output from two amplifiers with different shaping times is described. By means of this algorithm the peak-tovalley ratio for a small planar CdTe detector is improved by more than a factor of six compared to the uncorrected ratio without loss of efficiency.

  • 9. Petren, H.
    et al.
    Bargholtz, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Bashkanov, M.
    Bogoslavsky, D.
    Calen, H.
    Clement, H.
    Demiroers, L.
    Ekstrom, C.
    Fransson, K.
    Faldt, G.
    Gerén, Linda
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hoistad, B.
    Ivanov, G.
    Jacewicz, M.
    Jiganov, E.
    Johansson, T.
    Keleta, S.
    Khakimova, O.
    Koch, I.
    Kren, F.
    Kullander, S.
    Kupsc, A.
    Lindberg, Karl
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Marciniewski, P.
    Morosov, B.
    Pauly, C.
    Petukhov, Y.
    Povtorejko, A.
    Schonning, K.
    Scobel, W.
    Skorodko, T.
    Stepaniak, J.
    Tegnér, Per-Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Engblom, Pia Thörngren
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Tikhomirov, V.
    Wilkin, C.
    Wolke, M.
    Zabierowski, J.
    Zartova, Irina
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Zlomanczuk, J.
    eta-meson production in proton-proton collisions at excess energies of 40 and 72 MeV2010Inngår i: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 82, nr 5, s. 55206-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The production of eta mesons in proton-proton collisions has been studied using the WASA detector at the CELSIUS storage ring at excess energies of Q = 40 MeV and Q = 72 MeV. The eta was detected through its 2 gamma decay in a near-4 pi electromagnetic calorimeter, whereas the protons were measured by a combination of straw chambers and plastic scintillator planes in the forward hemisphere. About 6.9 x 10(4) and 9.3 x 10(4) events were found at Q = 40 MeV and Q = 72 MeV, respectively, with background contributions of less than 5%. A simple parametrization of the production cross section in terms of low partial waves was used to evaluate the acceptance corrections. Strong evidence was found for the influence of higher partial waves. The Dalitz plots show the presence of p waves in both the pp and the eta {pp} systems and the angular distributions of the eta in the center-of-mass frame suggest the influence of d-wave eta mesons.

  • 10. Schonning, K.
    et al.
    Bargholtz, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Bashkanov, M.
    Berlowski, M.
    Bogoslawsky, D.
    Calen, H.
    Clement, H.
    Demiroers, L.
    Ekstrom, C.
    Fransson, K.
    Geren, L.
    Stockholms universitet.
    Gustafsson, L.
    Hoistad, B.
    Ivanov, G.
    Jacewicz, M.
    Jiganov, E.
    Johansson, T.
    Keleta, S.
    Khakimova, O.
    Koch, I.
    Kren, F.
    Kullander, S.
    Kupsc, A.
    Kuzmin, A.
    Lindberg, K.
    Stockholms universitet.
    Marciniewski, P.
    Morosov, B.
    Oelert, W.
    Pauly, C.
    Pettersson, H.
    Petukhov, Y.
    Povtorejko, A.
    Ruber, R. J. M. Y.
    Scobel, W.
    Shafigullin, R.
    Shwartz, B.
    Skorodko, T.
    Sopov, V.
    Stepaniak, J.
    Tegner, P. -E
    Stockholms universitet.
    Engblom, P. Thorngren
    Tikhomirov, V.
    Turowiecki, A.
    Wagner, G. J.
    Wilkin, C.
    Wolke, M.
    Zabierowski, J.
    Zartova, I.
    Stockholms universitet.
    Zlomanczuk, J.
    Polarisation of the omega meson in the pd -> He-3 omega reaction at 1360 and 1450 MeV2008Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 668, nr 4, s. 258-262Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The tensor polarisation of omega mesons produced in the pd -> He-3 omega reaction has been studied at two energies near threshold. The 3 He nuclei were detected in coincidence with the pi(0)pi(+)pi(-) or pi(0)gamma decay products of the omega. in contrast to the case of phi-meson production, the omega mesons are found to be unpolarised. This brings into question the applicability of the Okubo-Zweig-lizuka rule when comparing the production of vector mesons in low energy hadronic reactions.

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