M. Janusz

Jagiellonian University, Cracovia, Lesser Poland Voivodeship, Poland

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Publications (77)

  • [Show abstract] [Hide abstract] ABSTRACT: A brief experimental overview on the close-to-threshold η meson production in proton-proton interactions is presented and the available observables in measurements with unpolarized and polarized beam and target are discussed.
    Article · May 2012 · International Journal of Modern Physics A
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    [Show abstract] [Hide abstract] ABSTRACT: The Λ, Σ0 and Σ+ hyperon production in NN collisions is studied at the COSY – 11 installation in order to investigate the production mechanism as well as to extract information about the Y-N interaction.
    Full-text Article · May 2012 · International Journal of Modern Physics A
  • [Show abstract] [Hide abstract] ABSTRACT: The COSY-11 collaboration has conducted experiments aiming at the determination of the excitation function and phase-space population of the pp→ppη reaction close to the kinematical threshold. The precise data obtained with the stochastically cooled proton beam of the cooler synchrotron COSY and the high resolution zero-degree magnetic spectrometer allowed for the observation of the significant deviations – in the shape of the excitation function and two-particle invariant masses – from the predictions based on the assumption that the reaction phase space is homogenously populated. Comparison of the shape of the excitation function for the pp→ppη and pp→ppη′ reaction allows to distinquish in the model independent way an influence originating from the proton-proton and proton-η interaction. For the comparison the full data set from experiments performed at COSY and other laboratories is used.
    Article · May 2012 · International Journal of Modern Physics A
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    [Show abstract] [Hide abstract] ABSTRACT: Due to the high sensitivity of the NN→NNγ reaction to the nucleon–nucleon potential, Bremsstrahlung radiation is used as a tool to investigate details of the nucleon–nucleon interaction. Such investigations can be performed at the cooler synchrotron COSY in the Research Centre Jülich, by dint of the COSY–11 detection system. The results of the identification of Bremsstrahlung radiation emitted via the dp→dpγ reaction in data taken with a proton target and a deuteron beam are presented and discussed.
    Full-text Article · May 2012 · International Journal of Modern Physics A
  • Article · Jan 2012 · Physics Letters B
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    [Show abstract] [Hide abstract] ABSTRACT: The reaction pp -> pp pi(0)pi(0) has been investigated at a beam energy of 1.4 GeV using the WASA-at-COSY facility. The total cross section is found to be (324 +/- 21(systematic) +/- 58(normalization)) mu b. In order to study the production mechanism, differential kinematic distributions have been evaluated. The differential distributions indicate that both initial state protons are excited into intermediate Delta(1232) resonances, each decaying into a proton and a single pion, thereby producing the pion pair in the final state. No significant contribution of the Roper resonance N*(1440) via its decay into a proton and two pions is found.
    Full-text Article · Jan 2012 · Physics Letters B
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    [Show abstract] [Hide abstract] ABSTRACT: The reaction pp->pppi0pi0 has been investigated at a beam energy of 1.4 GeV using the WASA-at-COSY facility. The total cross section is found to be (324 +- 21_systematic +- 58_normalization) mub. In order to to study the production mechanism, differential kinematical distributions have been evaluated. The differential distributions indicate that both initial state protons are excited into intermediate Delta(1232) resonances, each decaying into a proton and a single pion, thereby producing the pion pair in the final state. No significant contribution of the Roper resonance N*(1440) via its decay into a proton and two pions is found
    Full-text Article · Jul 2011 · Physics Letters B
  • [Show abstract] [Hide abstract] ABSTRACT: We report on an exclusive and kinematically complete high-statistics measurement of the basic double-pionic fusion reaction pn→dπ(0)π(0) over the full energy region of the ABC effect, a pronounced low-mass enhancement in the ππ-invariant mass spectrum. The measurements, which cover also the transition region to the conventional t-channel ΔΔ process, were performed with the upgraded WASA detector setup at COSY. The data reveal the Abashian-Booth-Crowe effect to be uniquely correlated with a Lorentzian energy dependence in the integral cross section. The observables are consistent with a narrow resonance with m=2.37 GeV, Γ≈70 MeV and I(J(P))=0(3(+)) in both pn and ΔΔ systems. Necessary further tests of the resonance interpretation are discussed.
    Article · Jun 2011 · Physical Review Letters
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    [Show abstract] [Hide abstract] ABSTRACT: We report on a high-statistics measurement of the basic double pionic fusion reaction $pn \to d\pi^0\pi^0$ over the energy region of the so-called ABC effect, a pronounced low-mass enhancement in the $\pi\pi$-invariant mass spectrum. The measurements were performed with the WASA detector setup at COSY. The data reveal the ABC effect to be associated with a Lorentzian shaped energy dependence in the integral cross section. The observables are consistent with a resonance with $I(J^P) =0(3^+)$ in both $pn$ and $\Delta\Delta$ systems. Necessary further tests of the resonance interpretation are discussed.
    Full-text Article · Apr 2011 · Physical Review Letters
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    [Show abstract] [Hide abstract] ABSTRACT: In the first production run of the WASA experiment at COSY, the eta decay into three neutral pions was measured in proton-proton interactions at a proton beam kinetic energy of 1.4 GeV. The Dalitz plot of the three pious was Studied using 1.2 x 10(5) fully reconstructed events. and the quadratic slope parameter alpha was determined to be -0.027 +/- 0.008(stat) +/- 0.005(syst). The result is consistent with previous measurements and further corroborates the importance of pion-pion final state interactions.
    Full-text Article · Jun 2009 · Physics Letters B
  • Article · Jun 2009 · Physics Letters B
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    [Show abstract] [Hide abstract] ABSTRACT: Total cross sections for the quasifree pn→pnη reaction in the range from the kinematical threshold up to 20 MeV excess energy have been determined. At threshold they exceed corresponding cross sections for the pp→ppη reaction by a factor of about 3 in contrast to the factor of 6 established for higher excess energies. To large extent, the observed decrease of the ratio σ(pn→pnη)/σ(pp→ppη) toward threshold may be assigned to the different energy dependence of the proton-proton and proton-neutron final-state interactions. The experiment was conducted using a proton beam of the cooler synchrotron COSY and a cluster jet deuteron target. The proton-neutron reactions were tagged by the spectator proton whose momentum was measured for each event. Protons and neutron outgoing from the pn→pnη reaction have been registered by means of the COSY-11 facility, an apparatus dedicated for threshold meson production.
    Full-text Article · Jan 2009 · Physical Review C
  • C.F. Redmer · M. Janusz
    [Show abstract] [Hide abstract] ABSTRACT: We describe experimental studies of the decays η → π+π-γ(*), with the goal to test QCD anomalies and to search for flavor conserving CP violation.
    Article · Jan 2009 · Acta Physica Polonica B, Proceedings Supplement
  • [Show abstract] [Hide abstract] ABSTRACT: Studies of η meson decays with the WASA detector are a major goal of the experimental program at COSY-Jülich. In 2008 a sample of 107 η mesons was collected in pd →3He η reaction close to threshold without trigger bias on the decay channels. The status of the analysis of various decay channels is presented.
    Article · Jan 2009
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    [Show abstract] [Hide abstract] ABSTRACT: The near threshold production of K+K− pairs in proton-proton collisions has been investigated at the cooler synchrotron COSY below and above the threshold for the ϕ meson using the COSY-11 and ANKE facilities, respectively. The excitation function determined for the pp→ppK+K− reaction revealed a statistically significant enhancement close to the threshold which may plausibly be assigned to the influence of the K−p interaction. In addition, observed consistently by both groups, a strong enhancement at low values of the ratio of the K−p to K+p invariant mass distributions shows that the proton interacts much stronger with K− than with K+. In this report we focus on the measurements performed by the COSY-11 collaboration. We explain the experimental method used and present main results of completed analyses as well as a new qualitative elaboration of the ppK+K− events population on the Goldhaber plot. We conclude with the observation that event densities increase at the region where the influence from the K+K− interaction is expected.
    Full-text Article · Aug 2008 · Nuclear Physics B - Proceedings Supplements
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    [Show abstract] [Hide abstract] ABSTRACT: We present the results of measurements of the analysing power for the p(pol)p --> pp eta reaction at the excess energies of Q=10 and 36 MeV, and interpret these results within the framework of the meson exchange models. The determined values of the analysing power at both excess energies are consistent with zero implying that the eta meson is produced predominantly in s-wave.
    Full-text Article · Dec 2007
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    [Show abstract] [Hide abstract] ABSTRACT: We summarise measurements of the COSY-11 collaboration concerning the excitation functions of the near threshold pseudoscalar meson production in the proton-proton interaction. The results are discussed in the context of the meson-nucleon and hyperon-nucleon interactions. We conclude that the $\eta$-proton interaction is significantly stronger than the eta'-proton interaction. Similarly, we found that the hyperon Lambda interacts with the nucleon considerably stronger than the hyperon Sigma, and that the interaction of (K-)-proton is much stronger than this of the (K+)-proton.
    Full-text Article · Nov 2007
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    [Show abstract] [Hide abstract] ABSTRACT: Total and differential cross sections for the reaction have been measured near threshold for center-of-mass momenta in the range from 17.1 MeV/c to 87.5 MeV/c. The data were taken during a slow ramping of the COSY internal deuteron beam scattered on a proton target detecting the ejectiles with the COSY-11 facility. The forward–backward asymmetries of the differential cross sections deviate clearly from zero for center-of-mass momenta above 50 MeV/c indicating the presence of higher partial waves in the final state. Below 50 MeV/c center-of-mass momenta a fit of the final state enhancement factor to the data of the total cross sections results in the scattering length of |a|=4.3±0.5 fm.
    Full-text Article · Jun 2007 · Physics Letters B
  • [Show abstract] [Hide abstract] ABSTRACT: We have measured excitation functions for the d+p->3He+X, (X=pi0, eta) channels near the eta production threshold. The data were taken during a slow ramping of the COSY internal deuteron beam scattered on a proton target. The excitation function for the reaction d+p->3He+pi0 does not show any structure which could originate from the decay of 3He-eta bound state. We measured also the threshold excitation curve for the d+p->3He+X process, however, contrary to the SATURNE results, we observe no cusp near the eta threshold.
    Article · Jun 2007 · Nuclear Physics A
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    [Show abstract] [Hide abstract] ABSTRACT: Total and differential cross sections for the dp --> 3He eta reaction have been measured near threshold for 3He center-of-mass momenta in the range from 17.1 MeV/c to 87.5 MeV/c. The data were taken during a slow ramping of the COSY internal deuteron beam scattered on a proton target detecting the 3He ejectiles with the COSY-11 facility. The forward-backward asymmetries of the differential cross sections deviate clearly from zero for center-of-mass momenta above 50 MeV/c indicating the presence of higher partial waves in the final state. Below 50 MeV/c center-of-mass momenta a fit of the final state enhancement factor to the data of the total cross sections results in the 3He eta scattering length of a = |2.9 +/- 0.6| + i (3.2 +/- 0.4) fm.
    Full-text Article · Mar 2007

Publication Stats

743 Citations

Institutions

  • 2005-2011
    • Jagiellonian University
      • • Institute of Physics
      • • Department of Nuclear Physics
      Cracovia, Lesser Poland Voivodeship, Poland
  • 2004
    • University of Münster
      Muenster, North Rhine-Westphalia, Germany