Z. Wilhelmi

Publications (45)26.15 Total impact

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  Available from: Janusz Zabierowski

  Article: The WASA detector facility at CELSIUS

  Chr. Bargholtz, M. Bashkanov, M. Berłowski, A. Bondar, D. Bogoslawsky, W. Brodowski, J. Brudvik, H. Calén, F. Capellaro, A. Chilingarov, [......], A. Turowiecki, G.J. Wagner, U. Wiedner, Z. Wilhelmi, M. Wolke, A. Yamamoto, H. Yamaoka, J. Zabierowski, I. Zartova, J. Złomańczuk
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  ABSTRACT: The WASA 4π multidetector system, aimed at investigating light meson production in light ion collisions and η meson rare decays at the CELSIUS storage ring in Uppsala is presented. A unique feature of the system is the use of hydrogen pellets as internal targets for the first time. A detailed description of the design, together with the anticipated and achieved performance parameters are given.
  Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 04/2008;
• Article: Deuteron breakup in the Δ-isobar region

  H Calén, S Carius, C Ekström, K Fransson, L Gustafsson, B Höistad, A Johansson, T Johansson, S Kullander, A Kupść, [......], A Mörtsell, A Nawrot, Z Pawlowski, U Schuberth, B Schwartz, J Stepaniak, Z Wilhelmi, J Zabierowski, I P Zieliński, J Zlomańczuk
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  ABSTRACT: The pd → npp charge exchange reaction has been studied at 1.15 GeV incident proton energy in a selected kinematical region. The distributions of two-proton invariant mass Mpp, of angle of a single proton and the differential cross section dσ/dt of the (p, n) reaction are presented and compared with model predictions corrected for the acceptance of the experimental apparatus. We see no evidence of narrow (Γ < 30 MeV/c2) peaks in the Mpp interval 2.1-2.3 GeV/c2. The production of an intermediate Δ isobar in the primary (p, n) charge exchange and its subsequent absorption in a final state ΔN → pp process together with the background from quasi-free charge exchange scattering reasonably reproduces the general trends of the data.
  Physica Scripta 08/2006; 48(1):86. · 1.20 Impact Factor
• Article: The CELSIUS/WASA Detector Facility

  Janusz Zabierowsk, C Bargholtz, D Bogoslawsky, A Bondar, H Calén, H Clement, L Demirörs, C Ekström, K Fransson, C-J Fridén, [......], P Thörngren Engblom, V Tikhomirov, A Turowiecki, G Wagner, U Wiedner, K Wilhelmsen, Z Wilhelmi, A Yamamoto, H Yamaoka, J Zlomańczuk
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  ABSTRACT: The 4π multidetector system for investigation of η-meson rare decays at the Uppsala CELSIUS storage ring is presented. A detailed description of the design, and achieved performance parameters is given.
  Physica Scripta 07/2006; 2002(T99):159. · 1.20 Impact Factor
• Article: First Results of the CELSIUS/WASA Experiment

  I Koch, C Bargholtz, D Bogoslawsky, A Bondar, H Calén, F Cappellaro, H Clement, J Comfort, L Demirörs, E Dorochkevitch, [......], V Tikhomirov, A Turowiecki, G Wagner, U Wiedner, K Wilhelmsen, Z Wilhelmi, A Yamamoto, H Yamaoka, J Zabierowski, J Zlomańczuk
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  ABSTRACT: The CELSIUS/WASA experiment is now finishing its commissioning phase and has started regular data taking in autumn 2001. Results from a first analysis of data samples from an experimental run at a beam energy of Tp = 1360 MeV in September 2001 are presented. The results show the ability to tag π0 and η production events. For 2π0 production a large data sample exists. The 2π0 and 3π0 production processes will be important sources of background for the η decays. They have until now been poorly measured, if at all, at this energy. The decay η → γγ will be used for normalization of all other η decays and the eta; → 3π0 decay will test the light quark mass ratio predicted by Chiral Perturbation Theory.
  Physica Scripta 07/2006; 2003(T104):29. · 1.20 Impact Factor
• Article: Report on the Charged Decay Products Identification Possibilities in WASA

  M Jacewicz, C Bargholtz, D Bogoslawsky, A Bondar, H Calén, F Cappellaro, H Clement, J Comfort, L Demirörs, E Dorochkevitch, [......], V Tikhomirov, A Turowiecki, G Wagner, U Wiedner, K Wilhelmsen, Z Wilhelmi, A Yamamoto, H Yamaoka, J Zabierowski, J Zlomańczuk
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  ABSTRACT: The WASA detector located at the CELSIUS storage ring of the The Svedberg Laboratory in Uppsala has recently finished its commissioning phase and is in full operation. An unique internal pellet-target system together with a detector covering a solid angle close to 4π steradians gives opportunities to study the rare decays of the π0 and the eta; meson in high-luminosity experiments. Another unique feature of the WASA setup is the thin-walled superconducting solenoid which provides the magnetic field for a mini drift chamber allowing highly efficient measurements of charged particles and minimal interference for particles entering the external electromagnetic calorimeter. The WASA setup is presented in this report with an emphasis on the ability to detect charged decay products. The results from the first experiments and performance of the detector are discussed together with the initial physics programme for charged decays of η mesons.
  Physica Scripta 07/2006; 2003(T104):98. · 1.20 Impact Factor
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  Available from: Janusz Zabierowski

  Article: Kinematically Complete Measurement of the pd → pdη Reaction

  J Zlomańczuk, R Bilger, W Brodowski, H Calén, H Clement, C Ekström, G Fäldt, K Fransson, L Gustafsson, B Höistad, [......], B Shwartz, V Sopov, J Stepaniak, A Sukhanov, P Thörngren-Engblom, A Turowiecki, G J Wagner, Z Wilhelmi, C Wilkin, J Zabierowski
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  ABSTRACT: The pd → pdη reaction has been measured in a kinematically complete experiment at 927, 961, 1032, and 1096 MeV. The CM angular distributions are quite flat and distributions of the pd and pη invariant mass are close to that of phase space. However, the dη invariant mass shows significant structure in the first few MeV above threshold. This behaviour is similar to that observed in the energy variation of the pn → dη total cross section and is a signal of strong η-deuteron scattering which has been predicted in many theoretical models.
  Physica Scripta 07/2006; 2003(T104):84. · 1.20 Impact Factor
• Article: Measurement of the pd→pdη cross section in complete kinematics

  R. Bilger, W. Brodowski, H. Calén, H. Clement, C. Ekström, G. Fäldt, K. Fransson, L. Gustafsson, B. Höistad, A. Johansson, [......], V. Sopov, J. Stepaniak, A. Sukhanov, P. Thörngren-Engblom, A. Turowiecki, G. J. Wagner, Z. Wilhelmi, C. Wilkin, J. Zabierowski, J. Złomańczuk
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  ABSTRACT: The pd→pdη reaction has been studied in a kinematically complete experiment at five beam energies 927, 961, 996, 1032, and 1096 MeV. In contrast to our measurement of the pd→3Heη at the same energies, all the c.m. angular distributions are consistent with isotropy. The energy dependence of the total cross section seems to follow a three-body phase space as modified by a proton-deuteron final-state interaction, and such an extrapolation is consistent with other near-threshold data. The distributions of the pd and pη invariant mass at fixed beam energy are both close to those of phase space. However, this is not the case for the dη invariant mass, which shows significant structure in the first few MeV above threshold. This behavior is similar to that observed in the energy variation of the pn→dη total cross section and is the sign of a large η-deuteron scattering length that has been predicted in many theoretical models.
  Phys. Rev. C. 01/2004; 69(1).
• Article: Study of baryon and search for dibaryon resonances by the reaction

  E. Doroshkevich, M. Bashkanov, W. Brodowski, R. Bilger, H. Calén, H. Clement, C. Ekström, K. Fransson, J. Greiff, S. Häggström, [......], J. Pätzold, R.J.M.Y. Ruber, W. Scobel, J. Stepaniak, A. Sukhanov, A. Turowiecki, G.J. Wagner, Z. Wilhelmi, J. Zabierowski, J. Zlomanczuk
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  ABSTRACT: Exclusive measurements of the two-pion production channel pp ® ppp+ p-pp \rightarrow pp\pi^ + \pi^- have been carried out near threshold at CELSIUS with the PROMICE/WASA detector. They reveal pp ® pp*(1440)® pps® pp(p+ p-)I = l = 0pp \rightarrow pp^*(1440)\rightarrow pp\sigma \rightarrow pp(\pi^ + \pi^-)_{I = \ell = 0} as the dominant process at these energies, however, the data exhibit also significant contributions from p*(1440) ® Dp® p(p+ p-)I = l = 0p^*(1440) \rightarrow \Delta \pi \rightarrow p(\pi^ + \pi^-)_{I = \ell = 0} . From the observed interference of these Roper decay routes their relative branching ratio is derived. The status on the search for NN-decoupled NNpNN\pi -resonances is reviewed with regard to recent experimental searches in the pionic double charge exchange in nuclei, the two-pion production in nucleon-nucleon collisions, the photo pion-production on the deuteron and the electro pion-production in nuclei.
  European Physical Journal A 10/2003; 18(2):171-176. · 2.19 Impact Factor
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  Available from: Janusz Zabierowski

  Article: Study of the p p -> p p pi+ pi- Reaction in the Low-Energy Tail of the Roper Resonance

  J. Paetzold, M. Bashkanov, R. Bilger, W. Brodowski, H. Calen, H. Clement, C. Ekstrom, K Fransson, J. Greiff, S. Haggstrom, [......], R. J. M. Y. Ruber, M. Schepkin, W. Scobel, J. Stepaniak, A Sukhanov, A. Turowiecki, G. J. Wagner, Z. Wilhelmi, J. Zabierowski, J. Zlomanczuk
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  ABSTRACT: Exclusive measurements of the p p -> p p pi+ pi- reaction have been carried out at Tp = 775 MeV at CELSIUS using the PROMICE/WASA setup. Together with data obtained at lower energy they point to a dominance of the Roper excitation in this process. From the observed interference of its decay routes N* -> N sigma and N* -> Delta pi -> N sigma their energy-dependent relative branching ratio is determined.
  01/2003;
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  Available from: Janusz Zabierowski

  Article: Search for Narrow NNpi Resonances in Exclusive p p -> p p pi+ pi- Measurements

  W. Brodowski, J. Paetzold, R. Bilger, H. Calen, H. Clement, C. Ektrom, K Fransson, J. Greiff, S. Haggstrom, B. Hoistad, [......], R. J. M. Y. Ruber, M. Schepkin, W. Scobel, J. Stepaniak, A Sukhanov, A. Turowiecki, G. J. Wagner, Z. Wilhelmi, J. Zabierowski, J. Zlomanczuk
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  ABSTRACT: Narrow structures in the range of a few MeV have been searched for in p p pi+ and p p pi- invariant mass spectra obtained from exclusive measurements of the p p -> p p pi+ pi- reaction at Tp = 725, 750 and 775 MeV using the PROMICE/WASA detector at CELSIUS. The selected reaction is particularily well suited for the search for NN and / or N Delta decoupled dibaryon resonances. Except for a possible fluctuation at 2087 MeV/c^2 in Mpppi- no narrow structures could be identified neither in Mpppi+ nor in Mpppi- on the 3 sigma level of statistical significance, giving an upper limit (95% C.L.) for dibaryon production in this reaction of sigma < 20 nb for 2020 MeV/c^2 < m(dibaryon) < 2085 MeV/c^2 Comment: 3 pages, 4 figures
  06/2002;
• Article: Exclusive measurement of the pp --> pppi(+)pi(-) reaction near threshold.

  W Brodowski, R Bilger, H Calén, H Clement, C Ekström, K Fransson, J Greiff, S Häggström, B Höistad, J Johanson, [......], M Schepkin, W Scobel, I Seluzhenkov, J Stepaniak, A Sukhanov, A Turowiecki, G J Wagner, Z Wilhelmi, J Zabierowski, J Zlomanczuk
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  ABSTRACT: The pp-->pp pi(+) pi(-) reaction has been measured exclusively near threshold at CELSIUS. The total cross sections are nearly an order of magnitude lower than expected from previous inclusive measurements. The differential cross sections reveal pp-->pp(*)(1440)-->pp sigma = pp(pi(+)pi(-))(I = l = 0) as the dominant process as well as significant contributions from p(*)-->Delta(++)pi(-)-->psigma. The observed anisotropy in the proton angular dependence is consistent with heavy-meson exchange. In the invariant mass spectra, no narrow structures of statistical relevance (3sigma) are found.
  Physical Review Letters 06/2002; 88(19):192301. · 7.37 Impact Factor
• Article: Measurement of the pd⃗3Heη cross section between 930 and 1100 MeV

  R. Bilger, W. Brodowski, H. Calén, H. Clement, C. Ekström, G. Fäldt, K. Fransson, L. Gustafsson, B. Höistad, A. Johansson, [......], B. Shwartz, J. Stepaniak, A. Sukhanov, P. Thörngren-Engblom, A. Turowiecki, G. J. Wagner, Z. Wilhelmi, C. Wilkin, J. Zabierowski, J. Złomańczuk
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  ABSTRACT: The differential cross section for the pd⃗3Heη reaction has been measured at four beam energies 930, 965, 1037, and 1100 MeV. The total cross section is nearly constant throughout the whole energy region, despite the c.m. angular distribution becoming more anisotropic with increasing energy. The data join smoothly onto the results of near-threshold measurements, which are dominated by the S-wave η3He final state interaction. At all the energies the differential cross section is maximal for cosθη≈+0.5 and this may provide a clue to the reaction mechanism and, in particular, to two-step contributions.
  Phys. Rev. C. 03/2002; 65(4).
• Article: Differential cross sections of the pp -> ppπ0 reaction from 310 to 425 MeV

  J. Zlomańczuk, R. Bilger, W. Brodowski, H. Calén, H. Clement, J. Dyring, C. Ekström, G. Fäldt, K. Fransson, L. Gustafsson, [......], P. Sundberg, B. Shwartz, J. Stepaniak, A. Sukhanov, A. Turowiecki, G. J. Wagner, Z. Wilhelmi, C. Wilkin, J. Zabierowski, A. Zernov
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  ABSTRACT: Measurements of the differential cross sections of the pp -> ppπ0 reaction at 310, 320, 340, 360, 400 and 425 MeV have been carried out at the CELSIUS storage ring in Uppsala. An attempt has been made to describe the distributions obtained in terms of the five partial waves Ss, Ps, Pp, Sd and Ds. The relative contributions from the different states depend significantly upon the energy. For instance, that of the Ss state drops from about 80% at 310 MeV to around 10% at 425 MeV.
  Nuclear Physics A 12/1999; 663:452-452. · 1.54 Impact Factor
• Article: Neutron orbit radii in 89Sr from the (d,p) sub-Coulomb reaction

  A Saganek, V Meyer, S Mirowski, M Oteski, M Sieminski, E Wesolowski, Z Wilhelmi
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  ABSTRACT: Root-mean-square radii of 2d5/2, 2d3/2 and 3s1/2 neutron orbits in 89Sr have been determined from a DWBA analysis of angular distributions and absolute cross sections of the reaction 88Sr(d,p). The data were taken at sub-Coulomb deuteron energies of 3.4, 3.8 and 4.0 MeV. With spectroscopic factors obtained from a sum-rule analysis of existing 88Sr(d,p) and 88Sr(p,d) data it was possible to determine the RMS radii for the 2d5/2, 2d3/2 and 3s1/2 states.
  Journal of Physics G Nuclear Physics 12/1998; 10(4):549.
• Article: Neutron distribution differences of nickel isotopes

  E Wesolowski, A Saganek, E Gierlik, V Meyer, M Sieminski, A Turowiecki, Z Wilhelmi
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  ABSTRACT: The differences between the neutron distributions of nickel isotopes were determined by the single-particle potential method using single particle wavefunctions determined by the sub-Coulomb (d,p) reaction and occupation numbers deduced from one-neutron transfer reactions at higher energies. The RMS radii of single particle orbits of valence neutrons, the RMS radii of excess neutrons and of the neutron distribution differences were determined.
  Journal of Physics G Nuclear and Particle Physics 12/1998; 17(6):955. · 4.18 Impact Factor
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  Available from: Janusz Zabierowski

  Article: Higher Partial Waves in p+p->p+p+eta near Threshold

  H. Calen, J. Dyring, G. Faldt, K Fransson, L. Gustafsson, S. Haggstrom, B. Hoistad, J. Johanson, A Johansson, T. Johansson, [......], B. Morosov, A. Povtorejko, A. Zernov, A. Kupsc, P. Marciniewski, J. Stepaniak, J. Zabierowski, A. Turowiecki, Z. Wilhelmi, C. Wilkin
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  ABSTRACT: Exclusive measurements of the production of eta mesons in the p+p->p+p+eta reaction have been carried out at excess energies of 16 and 37 MeV above threshold. The deviations from phase space are dominated by the proton-proton final state interaction and this influences particularly the energy distribution of the eta meson. However, evidence is also presented at the higher energy for the existence of an anisotropy in the angular distributions of the eta meson and also of the final proton-proton pair, probably to be associated with D-waves in this system interfering with the dominant S-wave term. The sign of the eta angular anisotropy suggests that rho-exchange is important for this reaction.
  12/1998;
• Article: Higher Partial Waves in . . .

  J. Dyring, G. Faldt, K Fransson, L. Gustafsson, S. Haggstrom, B. Hoistad, J. Johanson, A Johansson, T. Johansson, S. Kull, [......], A. Povtorejko, A Sukhanov, A. Zernov, A. Kupsc, P. Marciniewski, J. Stepaniak, J. Zabierowski, A. Turowiecki, Z. Wilhelmi, C. Wilkin
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  ABSTRACT: Exclusive measurements of the production of j-mesons in the pp ! ppj reaction have been carried out at excess energies of 16 and 37 MeV above threshold. The distributions are dominated by the proton-proton final state interaction and this influences particularly the energy distribution of the j meson. However, evidence is also presented at the higher energy for the existence of an anisotropy in the angular distributions of the j-meson and also of the final proton-proton pair, probably to be associated with D-waves in this system interfering with the dominant S-wave term. The sign of the j angular anisotropy suggests that ae-exchange is important for this reaction. PACS: 13.60.Le, 13.75.Cs Keywords: j-mesons, threshold production, angular distribution. Draft 24/10/98 Corresponding author: T. Johansson, Department of Radiation Sciences, Uppsala University, S-751 21 Uppsala, Sweden. E-mail: tord.johansson@tsl.uu.se The production of j mesons in proton-proton collisions near thresh...
  11/1998;
• Article: Near-Threshold Pion Production in pN Collisions at CELSIUS

  J. Zlomanczuk, R. Bilger, W. Brodowski, H. Calen, H. Clement, J. Dyring, C. Ekstroem, G. Faeldt, K. Fransson, L. Gustafsson, [......], B. Shwartz, J. Stepaniak, A. Sukhanov, P. Sundberg, A. Turowiecki, G. J. Wagner, Z. Wilhelmi, C. Wilkin, J. Zabierowski, A. Zernov
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  ABSTRACT: The pp→ ppπ0 and pn→ ppπ- reactions have been measured at 310, 320 and 340 MeV using the CELSIUS proton beam and 1H and 2H internal cluster-jet targets. The π0 production at 310 MeV has been fully analyzed and a significant deviation from isotropy found in the pion angular distributions. This increases at small excitation energies of the final proton pair, suggesting that d-wave pion production is important even close to threshold. Evidence is also found for some P-wave excitation in the final p--p system.
  Acta Physica Polonica Series B 10/1998; 29:3141. · 0.90 Impact Factor
• Article: Threshold Structure of the Quasi-Free

  J. Dyring, K Fransson, L. Gustafsson, S. Haggstrom, B. Hoistad, J. Johanson, A Johansson, T. Johansson, A. Khoukaz, S. Kull, [......], A. Bondar, A. Kuzmin, B. Shwartz, V. Sidorov, A Sukhanov, A. Turowiecki, Z. Wilhelmi, K. Kilian, W. Oelert, T. Sefzick
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  ABSTRACT: The quasi-free p+n!d+j reaction cross section has been measured at threshold using 1295 MeV protons in the CELSIUS storage ring and an internal cluster-jet deuterium target. The kinematics is chosen such that the target proton can be assumed to be a spectator. The Fermi momentum of the target neutron is used to extract the energy dependence of the cross section by reconstructing the kinematics on an event-by-event basis. The data cover excess energies from threshold to 10 MeV in the center of mass of the final dj system. Approaching the threshold the cross section is enhanced compared to what is expected from phase-space. This behaviour is typical for a strong final-state interaction. PACS numbers: 13.75.cs 14.20.Gk 25.10.+s 25.40.Ve Typeset using REVT E X Over the last few years, the interest in j-meson physics has increased considerably. The strength of the j-N interaction has lead to speculations on the existence of a quasi-bound j-nuclear state even in the two-nucleon system [1-...
  10/1998;
• Article: Measurement of the Quasi-Free

  J. Dyring, K Fransson, L. Gustafsson, S. Haggstrom, B. Hoistad, A Johansson, T. Johansson, S. Kull, A. Mortsell, R. Ruber, [......], P. Marciniewski, J. Stepaniak, V. Dunin, B. Morosov, A. Povtorejko, A Sukhanov, A. Zernov, J. Zabierowski, A. Turowiecki, Z. Wilhelmi
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  ABSTRACT: The first measurement of the quasi-free p+n!p+n+j reaction cross section has been made at the CELSIUS storage ring using a deuterium internal cluster jet target. The energy dependence of the cross section is extracted using a fixed incident proton energy of T p = 1350 MeV and exploiting the Fermi momentum of the struck neutron. The data cover a range of centre-of-mass excess energies from 16 MeV to 109 MeV. The shape of the excitation function is broadly similar to that of the p+p!p+p+j reaction, though with a cross section about a factor of 6.5 larger. PACS numbers: 13.75.-n 13.60.Le 13.75.cs 13.85.Lg Production of j mesons in nucleon-nucleon collisions, N+N!N+N+j, can be described by two independent partial cross sections oe 0 and oe 1 , where the subscripts refer to the total isospin of the two nucleons (0 or 1) in the initial state. The p+p!p+p+j reaction, which corresponds to a pure oe 1 cross section, is reasonably well measured in the threshold region [1-3]. To learn about the...
  10/1998;