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1.
  • Adlarson, Patrik, et al. (author)
  • Investigation of the dd -> (3)Hen pi(0) reaction with the FZ Julich WASA-at-COSY facility
  • 2013
  • In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 88:1, s. 014004-
  • Journal article (peer-reviewed)abstract
    • An exclusive measurement of the dd -> (3)Hen pi(0) reaction was carried out at a beam momentum of p(d) = 1.2 GeV/c using the WASA-at-COSY facility. Information on the total cross section as well as differential distributions was obtained. The data are described by a phenomenological approach based on a combination of a quasifree model and a partial wave expansion for the three-body reaction. The total cross section is found to be sigma(tot) = ( 2.89 +/- 0.01(stat) +/- 0.06(sys) +/- 0.29(norm)) mu b. The contribution of the quasifree processes ( with the beam or target neutron being a spectator) accounts for 38% of the total cross section and dominates the differential distributions in specific regions of phase space. The remaining part of the cross section can be described by a partial wave decomposition indicating the significance of p-wave contributions in the final state.
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2.
  • Adlarson, Patrik, et al. (author)
  • Measurement of the pn -> pp pi(0)pi(-) reaction in search for the recently observed resonance structure in d pi(0)pi(0) and d pi(+)pi(-) systems
  • 2013
  • In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 88:5, s. 055208-
  • Journal article (peer-reviewed)abstract
    • Exclusive measurements of the quasifree pn -> pp pi(0)pi(-) reaction have been performed by means of pd collisions at T-p = 1.2 GeV using the wide angle shower apparatus (WASA) detector setup at the cooler synchrotron COSY (Institut fur Kernphysik, Julich). Total and differential cross sections have been obtained covering the energy region root s = (2.35-2.46) GeV, which includes the region of the ABC effect and its associated resonance structure. NoABCeffect, i.e., low-mass enhancement is found in the pi(0)pi(-) -invariant mass spectrum, in agreement with the constraint from Bose statistics that the isovector pion pair can not be in relative s wave. At the upper end of the covered energy region t-channel processes for Roper, Delta(1600) and Delta Delta excitations provide a reasonable description of the data, but at low energies the measured cross sections are much larger than predicted by such processes. Adding a resonance amplitude for the resonance at m = 2.37 GeV with Gamma = 70 MeV and I (J(P)) = 0(3(+)) observed recently in pn -> d pi(0)pi(0) and pn -> d pi(+)pi(-) reactions leads to an agreement with the data also at low energies.
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3.
  • Adlarson, Patrik, et al. (author)
  • Abashian-Booth-Crowe Effect in Basic Double-Pionic Fusion : A New Resonance?
  • 2011
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:24, s. 242302-
  • Journal article (peer-reviewed)abstract
    • We report on an exclusive and kinematically complete high-statistics measurement of the basic double-pionic fusion reaction pn -> d pi(0)pi(0) over the full energy region of the ABC effect, a pronounced low-mass enhancement in the pi pi-invariant mass spectrum. The measurements, which cover also the transition region to the conventional t- channel Delta Delta 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, Gamma approximate to 70 MeV and I(J(P)) = 0(3(+)) in both pn and Delta Delta systems. Necessary further tests of the resonance interpretation are discussed.
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4.
  • Adlarson, Patrik, et al. (author)
  • Cross section ratio and angular distributions of the reaction p + d -> He-3 + eta at 48.8MeV and 59.8MeV excess energy
  • 2014
  • In: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 50:6, s. 100-
  • Journal article (peer-reviewed)abstract
    • We present new data for angular distributions and on the cross section ratio of the p+d -> He-3+eta reaction at excess energies of Q - 48.8MeV and Q - 59.8 MeV. The data have been obtained at the WASA-at-COSY experiment (Forschungszentrum Julich) using a proton beam and a deuterium pellet target. While the shape of obtained angular distributions show only a slow variation with the energy, the new results indicate a distinct and unexpected total cross section fluctuation between Q = 20MeV and Q = 60 MeV, which might indicate the variation of the production mechanism within this energy interval.
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5.
  • Adlarson, Patrik, et al. (author)
  • Differential cross sections for neutron-proton scattering in the region of the d* (2380) dibaryon resonance
  • 2020
  • In: Physical Review C. Nuclear Physics. - : AMER PHYSICAL SOC. - 0556-2813 .- 1089-490X. ; 102:1
  • Journal article (peer-reviewed)abstract
    • Differential cross sections have been extracted from exclusive and kinematically complete high-statistics measurements of quasifree polarized (n) over barp scattering performed in the energy region of the d* (2380) dibaryon resonance covering the range of beam energies T-n = 0.98-1.29 GeV (root s = 2.32-2.44 GeV). The experiment was carried out with the WASA-at-COSY setup having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process dp -> np + p(spectator). In this way the np differential cross section sigma (Theta) was measured over a large angular range. The obtained angular distributions complement the corresponding analyzing power A(y)(Theta) measurements published previously. A SAID partial-wave analysis incorporating the new data strengthens the finding of a resonance pole in the coupled D-3(3) - (3)G(3) waves.
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6.
  • Adlarson, Patrik, et al. (author)
  • Evidence for a New Resonance from Polarized Neutron-Proton Scattering
  • 2014
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 112:20, s. 202301-
  • Journal article (peer-reviewed)abstract
    • Exclusive and kinematically complete high-statistics measurements of quasifree polarized (n) over right arrowp scattering have been performed in the energy region of the narrow resonancelike structure d* with I(J(P)) = 0(3(+)),M approximate to 2380 MeV, and Gamma approximate to 70 MeV observed recently in the double-pionic fusion channels pn -> d pi(0)pi(0) and pn -> d pi(+)pi(-). 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 (d) over right arrowp -> np + p(spectator). This allowed the np analyzing power, A(y), to be measured over a broad angular range. The obtained A(y) angular distributions deviate systematically from the current SAID SP07 NN partial-wave solution. Incorporating the new A(y) data into the SAID analysis produces a pole in the D-3(3) - (3)G(3) waves in support of the d* resonance hypothesis.
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7.
  • Adlarson, P., et al. (author)
  • Isospin decomposition of the basic double-pionic fusion in the region of the ABC effect
  • 2013
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 721:4-5, s. 229-236
  • Journal article (peer-reviewed)abstract
    • Exclusive and kinematically complete high-statistics measurements of the basic double-pionic fusion reactions pn -> d pi(0)pi(0), pn -> d pi(+)pi(-) and pp -> d pi(+)pi(0) have been carried out simultaneously over the energy region of the ABC effect using the WASA detector setup at COSY. Whereas the isoscalar reaction part given by the d pi(0)pi(0) channel exhibits the ABC effect, i.e. a low-mass enhancement in the pi pi-invariant mass distribution, as well as the associated resonance structure in the total cross section, the isovector part given by the d pi(+)pi(0) channel shows a smooth behavior consistent with the conventional t-channel Delta Delta process. The d pi(+)pi(-) data are very well reproduced by combining the data for isovector and isoscalar contributions, if the kinematical consequences of the isospin violation due to different masses for charged and neutral pions are taken into account.
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8.
  • Adlarson, Patrik, et al. (author)
  • Neutron-proton scattering in the context of the d*(2380) resonance
  • 2014
  • In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 90:3, s. 035204-
  • Journal article (peer-reviewed)abstract
    • 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.
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9.
  • Adlarson, Patrik, et al. (author)
  • Search for eta-mesic He-4 with the WASA-at-COSY detector
  • 2013
  • In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 87:3, s. 035204-
  • Journal article (peer-reviewed)abstract
    • An exclusive measurement of the excitation function for the dd -> (3)Hep pi(-) reaction was performed at the Cooler Synchrotron COSY-Julich with the WASA-at-COSY detection system. The data were taken during a slow acceleration of the beam from 2.185 to 2.400 GeV/c crossing the kinematic threshold for the eta-meson production in the dd -> He-4 eta reaction at 2.336 GeV/c. The corresponding excess energy with respect to the He-4-eta system varied from -51.4 to 22 MeV. The integrated luminosity in the experiment was determined using the dd -> (3)Hen reaction. The shape of the excitation function for the dd -> (3)Hep pi(-) reaction was examined. No signal of the He-4-eta bound state was observed. An upper limit for the cross section for the bound state formation and decay in the process dd -> (He-4-eta)(bound) -> (3)Hep pi(-) was determined on the 90% confidence level and it varies from 20 to 27 nb for the bound state width ranging from 5 to 35 MeV, respectively. 
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10.
  • Curceanu, C., et al. (author)
  • Kaonic deuterium measurement with Siddharta-2 on daΦNE
  • 2020
  • In: Acta Physica Polonica B. - 0587-4254. ; 51:1, s. 251-257
  • Journal article (peer-reviewed)abstract
    • The interaction of antikaons with nucleons and nuclei in the low-energy regime represents an active research field in hadron physics with still many important open questions. The investigation of light kaonic atoms is, in this context, a unique tool to obtain precise information on this interaction. The most precise kaonic hydrogen measurement to date, together with an exploratory measurement of kaonic deuterium, were carried out by the SIDDHARTA Collaboration at the DAΦNE electron–positron collider of LNF-INFN, by combining the excellent quality kaon beam delivered by the collider with new experimental techniques, as fast and precise Silicon-Drift X-ray detectors. The measurement of kaonic deuterium will be realized in the near future by SIDDHARTA-2, a major upgrade of SIDDHARTA.
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11.
  • Miliucci, M., et al. (author)
  • Kaonic Deuterium Precision Measurement at DA Φ NE : The SIDDHARTA-2 Experiment
  • 2020
  • In: Recent Progress in Few-Body Physics : Proceedings of the 22nd International Conference on Few-Body Problems in Physics, FB22 2018 - Proceedings of the 22nd International Conference on Few-Body Problems in Physics, FB22 2018. - Cham : Springer International Publishing. - 0930-8989 .- 1867-4941. - 9783030323561 - 9783030323578 ; 238, s. 965-969
  • Book chapter (peer-reviewed)abstract
    • Light kaonic atoms spectroscopy offers the unique opportunity to perform experiments equivalent to scattering at vanishing relative energies. This allows the determination of the antikaon-nucleus interaction at threshold, without the need of extrapolation to zero energy, as in the case of scattering experiments. In this framework, the SIDDHARTA-2 collaboration aims to perform the first measurement of kaonic deuterium transition to the fundamental level, which is mandatory to extract the isospin dependent antikaon—nucleon scattering lengths. The experiment will be carried out at the DA(formula presented)NE collider of LNF-INFN in 2019–2020.
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12.
  • Saito, T. R., et al. (author)
  • Studies of three-and four-body hypernuclei with heavy-ion beams, nuclear emulsions and machine learning
  • 2023
  • In: Journal of Physics, Conference Series. - : Institute of Physics (IOP). - 1742-6588 .- 1742-6596. ; 2586
  • Journal article (peer-reviewed)abstract
    • Interests on few-body hypernuclei have been increased by recent results of experiments employing relativistic heavy ion beams. Some of the experiments have revealed that the lifetime of the lightest hypernucleus, hypertriton, is significantly shorter than 263 ps which is expected by considering the hypertriton to be a weakly-bound system. The STAR collaboration has also measured the hypertriton binding energy, and the deduced value is contradicting to its formerly known small binding energy. These measurements have indicated that the fundamental physics quantities of the hypertriton such as its lifetime and binding energy have not been understood, therefore, they have to be measured very precisely. Furthermore, an unprecedented Lambda nn bound state observed by the HypHI collaboration has to be studied in order to draw a conclusion whether or not such a bound state exists. These three-body hypernuclear states are studied by the heavy-ion beam data in the WASA-FRS experiment and by analysing J-PARC E07 nuclear emulsion data with machine learning.
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13.
  • Sekiya, R., et al. (author)
  • Search for η'-mesic nuclei in 12C(p, dp) reaction with the WASA detector at GSI-FRS
  • 2024
  • In: Nuovo cimento della societa italiana de fisica. C, Geophysics and space physics. - : Società Italiana di Fisica. - 1124-1896 .- 1826-9885. ; 47:4
  • Journal article (peer-reviewed)abstract
    • We conducted an experimental search for η′-mesic nuclei, bound systems of an η′ meson and a nucleus, in 12C(p, dp) reactions. We measured the missing mass in the (p, d) reaction to obtain the mass spectrum of the reaction product near the η′ emission threshold. Forward-emitted deuterons were momentum-analyzed in the FRS of GSI. We installed a nearly 4π detector WASA near the 12C target to effectively select formation and decay of the η′-mesic nuclei. We are presently finalizing the analysis.
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14.
  • Adlarson, Patrik, et al. (author)
  • Measurement of the eta -> pi(+)pi(-)pi(0) Dalitz plot distribution
  • 2014
  • In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 90:4, s. 045207-
  • Journal article (peer-reviewed)abstract
    • The Dalitz plot distribution of the eta -> pi(+)pi(-)pi(0) decay is determined by using a data sample of 1.2 x 10(7) eta mesons from the pd -> He-3 eta reaction at 1 GeV collected by the WASA detector at COSY.
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15.
  • Adlarson, Patrik, et al. (author)
  • pi(0)pi(0) Production in proton-proton collisions at T-p=1.4 GeV The WASA-at-COSY Collaboration
  • 2012
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 706:4-5, s. 256-262
  • Journal article (peer-reviewed)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.
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16.
  • De Paolis, L., et al. (author)
  • Kaonic atoms measurement at DA Φ NE : SIDDHARTA and SIDDHARTA-2
  • 2019
  • In: Basic Concepts in Nuclear Physics : Theory, Experiments and Applications - 2018 La Rábida International Scientific Meeting on Nuclear Physics - Theory, Experiments and Applications - 2018 La Rábida International Scientific Meeting on Nuclear Physics. - Cham : Springer International Publishing. - 9783030222031 ; 225, s. 191-195
  • Conference paper (peer-reviewed)abstract
    • Light kaonic atoms studies provide the unique opportunity to perform experiments equivalent to scattering at threshold, being their atomic binding energies in the keV range. High precision atomic X-rays spectroscopy ensures that the energy shift and broadening of the lowest-lying states of the kaonic atoms, induced by the strong interaction between the kaon and nucleus, can be detected. Kaonic hydrogen and kaonic deuterium are the lightest atomic systems and their study deliver the isospin-dependent kaon-nucleon scattering lengths. The SIDDHARTA collaboration was able to perform the most precise kaonic hydrogen measurement to date, together with an exploratory measurement of kaonic deuterium. The measurement of the kaonic deuterium will be realized in the near future by a major upgrade of SIDDHARTA: SIDDHARTA-2. In this paper an overview of the main results obtained by SIDDHARTA together with the future plans are presented.
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17.
  • Saito, T. R., et al. (author)
  • The WASA-FRS project at GSI and its perspective
  • 2023
  • In: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier. - 0168-583X .- 1872-9584. ; 542, s. 22-25
  • Journal article (peer-reviewed)abstract
    • A novel technique to study bound states of exotic hadrons in subatomic nuclei, such as hypernuclei and mesic nuclei, has been developed by employing the Fragment Separator FRS and the WASA central detector at GSI. Two experiments, S447 for studying light hypernuclei, especially hypertriton and a Ann bound state, and S490 for searching for ri' mesic-nuclei, were recently performed. Data analyses are currently in progress, and light charged particles such as protons and x & PLUSMN; are clearly observed and identified in the both experiments. For S447, light nuclear fragments that can also be residual nuclei from decays of hypernuclei of interests have been analysed by the FRS, and a momentum resolution, Ap/p, of 5 x 10-4 has been achieved. Further data analyses are to be completed. The WASA-FRS project will be continued and extended with the FRS at FAIR Phase 0, and upgrading of the WASA magnet and detectors is currently in progress. Furthermore, construction of a larger detector system with the Super-FRS at FAIR Phase 1 is also under consideration.
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18.
  • Tanaka, Y. K., et al. (author)
  • WASA-FRS EXPERIMENTS IN FAIR PHASE-0 AT GSI
  • 2023
  • In: ACTA PHYSICA POLONICA B PROCEEDINGS SUPPLEMENT. - : Jagiellonian University.
  • Conference paper (peer-reviewed)abstract
    • We have developed a new and unique experimental setup integrating the central part of the Wide Angle Shower Apparatus (WASA) into the Fragment Separator (FRS) at GSI. This combination opens up possibilities of new experiments with high-resolution spectroscopy at forward 0 and measurements of light decay particles with nearly full solid-angle acceptance in coincidence. The first series of the WASA-FRS experiments have been successfully carried out in 2022. The developed experimental setup and two physics experiments performed in 2022 including the status of the preliminary data analysis are introduced.
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19.
  • Adlarson, Patrik, et al. (author)
  • ABC effect and resonance structure in the double-pionic fusion to He-3
  • 2015
  • In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 91:1, s. 015201-
  • Journal article (peer-reviewed)abstract
    • Exclusive and kinematically complete measurements of the double pionic fusion to He-3 have been performed in the energy region of the so-called ABC effect, which denotes a pronounced low-mass enhancement in the pi pi-invariant mass spectrum. The experiments were carried out with the WASA detector setup at COSY (the cooler synchrotron at Forschungszentrum Julich). Similar to the observations in the basic pn -> d pi(0)pi(0) reaction and in the dd -> He-4 pi(0)pi(0) reaction, the data reveal a correlation between the ABC effect and a resonance-like energy dependence in the total cross section. Differential cross sections are well described by the hypothesis of d* resonance formation during the reaction process in addition to the conventional t-channel Delta Delta mechanism. The deduced d* resonance width can be understood from collision broadening due to Fermi motion of the nucleons in initial and final nuclei.
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20.
  • Adlarson, Patrik, et al. (author)
  • Charge symmetry breaking in dd -> He-4 pi(0) with WASA-at-COSY
  • 2014
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 739, s. 44-49
  • Journal article (peer-reviewed)abstract
    • Charge symmetry breaking (CSB) observables are a suitable experimental tool to examine effects induced by quark masses on the nuclear level. Previous high precision data from TRIUMF and IUCF are currently used to develop a consistent description of CSB within the framework of chiral perturbation theory. In this work the experimental studies on the reaction dd -> He-4 pi(0) have been extended towards higher excess energies in order to provide information on the contribution of p-waves in the final state. For this, an exclusive measurement has been carried out at a beam momentum of p(d) = 1.2GeV/c using the WASA-at-COSY facility. The total cross section amounts to sigma(tot) =(118 +/- 18(stat) +/- 13(sys) +/- 8(ext)) p band first data on the differential cross section are consistent with s-wave pion production.
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21.
  • Adlarson, Patrik, et al. (author)
  • Exclusive measurement of the eta -> pi(+) pi(-) gamma decay
  • 2012
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 707:2, s. 243-249
  • Journal article (peer-reviewed)abstract
    • An exclusive measurement of the decay eta -> pi(+) pi(-) gamma has been performed at the WASA facility at COSY. The eta mesons were produced in the fusion reaction pd -> He-3 X at a proton beam momentum of 1.7 GeV/c. Efficiency corrected differential distributions have been extracted based on 13 960 +/- 140 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 -> pi(+) pi(-) 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(+) pi(-) system.
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22.
  • Adlarson, Patrik, et al. (author)
  • Measurements of branching ratios for eta decays into charged particles
  • 2016
  • In: PHYSICAL REVIEW C. - 2469-9985. ; 94:6
  • Journal article (peer-reviewed)abstract
    • The WASA-at-COSY experiment has collected 3 x 10(7) events with eta mesons produced via the reaction pd -> He-3 eta at T = 1.0 GeV. Using this data set, we evaluate the branching ratios of the decays eta -> pi(+)pi(-)gamma, eta -> e(+)e(-)gamma, eta -> pi(+)pi(-)e(+)e(-), and eta -> e(+)e(-)e(+)e(-). The branching ratios are normalized to the eta -> pi(+)pi(-) pi(0) decay. In addition an upper limit on a CP-violating asymmetry in eta -> pi(+)pi(-)e(+)e(-) is extracted.
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23.
  • Adlarson, Patrik, et al. (author)
  • Search for eta-mesic He-4 in the dd -> (3)Hen pi(0) and dd -> (3)Hep pi(-) reactions with the WASA-at-COSY facility
  • 2017
  • In: Nuclear Physics A. - : ELSEVIER SCIENCE BV. - 0375-9474 .- 1873-1554. ; 959, s. 102-115
  • Journal article (peer-reviewed)abstract
    • The search for He-4-eta bound states was performed with the WASA-at-COSY facility via the measurement of the excitation function for the dd -> (3)Hen pi(0) and dd -> (3)Hep pi(-) processes. The deuteron beam momentum was varied continuously between 2.127 GeV/c and 2.422 GeV/c, corresponding to the excess energy for the dd -> He-4 eta reaction ranging from Q = 70 MeV to Q = 30 MeV. The luminosity was determined based on the dd -> (3)Hen reaction and the quasi-free proton proton scattering via dd -> ppn(spectator)n(spectator) reactions. The excitation functions, determined independently for the measured reactions, do not reveal a structure which could be interpreted as a narrow mesic nucleus. Therefore, the upper limits of the total cross sections for the bound state production and decay in dd -> (4He-eta)(bound) -> (3)Hen pi(0) and dd -> (He-4-eta)(bound) -> (3)Hep pi(-) processes were determined taking into account the isospin relation between the both of the considered channels. The results of the analysis depend on the assumptions of the N* (1535) momentum distribution in the anticipated mesic-He-4. Assuming, as in the previous works, that this is identical with the distribution of nucleons bound with 20 MeV in He-4, we determined that (for the mesic bound state width in the range from 5 MeV to 50 MeV) the upper limits at 90% confidence level are about 3 nb and about 6 nb for n pi(0) and p pi(-) channels, respectively. However, based on the recent theoretical findings of the N*(1535) momentum distribution in the N*-He-3 nucleus bound by 3.6 MeV, we find that the WASA-at-COSY detector acceptance decreases and hence the corresponding upper limits are 5 nb and 10 nb for n pi(0) and p pi(-) channels respectively. (C) 2017 Elsevier B.V. All rights reserved.
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24.
  • Adlarsona, Patrik, et al. (author)
  • Measurement of the np -> np pi(0)pi(0) reaction in search for the recently observed d* (2380) resonance
  • 2015
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 743, s. 325-332
  • Journal article (peer-reviewed)abstract
    • Exclusive measurements of the quasi-free np --> np pi(0)pi(0) reaction have been performed by means of dp collisions at T-d = 2.27 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region root s = (2.35-2.46) GeV, which includes the region of the ABC effect and its associated d* (2380) resonance. Adding the d* resonance amplitude to that for the conventional processes leads to a reasonable description of the data. The observed resonance effect in the total cross section is in agreement with the predictions of Faldt and Wilkin as well with those of Albadajedo and Oset. The ABC effect, i.e. the low-mass enhancement in the pi(0)pi(0)-invariant mass spectrum, is found to be very modest - if present at all, which might pose a problem to some of its interpretations.
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25.
  • Curceanu, C., et al. (author)
  • Low-energy kaon-nuclei interaction studies at DAΦNE : Siddharta-2 and amadeus
  • 2017
  • In: Acta Physica Polonica B. - 0587-4254. ; 48:10, s. 1855-1860
  • Journal article (peer-reviewed)abstract
    • The DAΦNE electron-positron collider of the Laboratori Nazionali di Frascati of INFN has made available a unique quality low-energy negatively charged kaons "beam", which is being used to study the kaon-nucleon/nuclei interactions by the SIDDHARTA-2 experiment and the AMADEUS Collaboration. The dynamics of the strong interaction processes in the nonperturbative regime is approached by lattice calculations and effective field theories (ChPT) which are still lacking experimental results in the lowenergy regime, fundamental for their good understanding. The studies of kaonic atoms and of the kaonic nuclear processes performed by SIDDHARTA- 2 and AMADEUS play in this context a key-role.
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