439 research outputs found
Experimental Activities in Few-Body Physics
No full textUnderstanding the few-nucleon system remains one of the challenges in modern nuclear and hadron physics. Observables in few-nucleon scattering processes are sensitive probes to study the two and many-body interactions between nucleons in nuclei. In the past decades, several facilities provided a large data base to study in detail the three-nucleon interactions below the pion-production threshold by exploiting polarized proton and deuteron beams and large-acceptance detectors. Only since recently, the four-nucleon scattering process at intermediate energies has been explored. In addition, there is a focus to collect data in the hyperon-nucleon sector, thereby providing access to understand the more general baryon-baryon interaction. In this contribution, some recent results in the few-nucleon sector are discussed together with some of the preliminary results from a pioneering and exclusive study of the four-nucleon scattering process. Furthermore, this paper discusses the experimental activities in the hyperon sector, in particular, the perspectives of the hyperon program of PANDA
Nucleon resonance decay by the K0 Sigma+ channel
No full textWith the combined setup of the Crystal Barrel and TAPS photonspectrometers at ELSA in Bonn we have studied photonuclear reactions on protons and deuterons. From the series of experiments on single and multiple neutral meson emission we concentrate here on the hyperon production off protons and deuterons, and in particular on the K-0 Sigma(+) decay channel. The reaction is characterized by the final state of 6 photons and a forward emitted proton. We report on the first results from this channel.</p
Measurements of the absolute branching fractions of ω- Decays and test of the Δi=1/2 rule
No full textBased on a dataset of (27.12±0.10)×108 ψ(3686) events collected at the BESIII experiment, the absolute branching fractions of the three dominant ω- decays are measured to be Bω-→Ξ0π-=(25.03±0.44±0.53)%, Bω-→Ξ-π0=(8.43±0.52±0.28)%, and Bω-→ΛK-=(66.3±0.8±2.0)%, where the first and second uncertainties are statistical and systematic, respectively. The ratio between Bω-→Ξ0π- and Bω-→Ξ-π0 is determined to be 2.97±0.19±0.11, which is in good agreement with the PDG value of 2.74±0.15, but greater by more than four standard deviations than the theoretical prediction of 2 obtained from the ΔI=1/2 rule. © 2023 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.<br/
Measurement of the Exclusive D(p,ee)He and D(p,)He Reactions at 98 and 176 MeV
No full textA high resolution magnetic pair spectrometer for medium energy photons has been used for studies of the exclusive (p,e(+)e(-)) and (p, gamma) reactions on deuterium at 98 and 176 MeV. The (p, e(+)e(-)) cross sections, obtained at 40 degrees and 80 degrees, are compared with the corresponding data for the (p, gamma) reaction measured with the same apparatus. At small virtual photon masses the (p, e(+)e(-)) cross sections show significant enhancement over what is expected from model calculations, a behaviour which has earlier been observed also for the B-11(p, e(+)e(-))C-12 reaction. (C) 1998 Elsevier Science B.V.</p
Observation of Structures in the Processes e+e- →ωχc1 and ωχc2
No full textWe present measurements of the Born cross sections for the processes e+e-→ωχc1 and ωχc2 at center-of-mass energies s from 4.308 to 4.951 GeV. The measurements are performed with data samples corresponding to an integrated luminosity of 11.0 fb-1 collected with the BESIII detector operating at the Beijing Electron Positron Collider storage ring. Assuming the e+e-→ωχc2 signals come from a single resonance, the mass and width are determined to be M=(4413.6±9.0±0.8) MeV/c2 and Γ=(110.5±15.0±2.9) MeV, respectively, which is consistent with the parameters of the well-established resonance ψ(4415). In addition, we also use one single resonance to describe the e+e-→ωχc1 line shape and determine the mass and width to be M=(4544.2±18.7±1.7) MeV/c2 and Γ=(116.1±33.5±1.7) MeV, respectively. The structure of this line shape, observed for the first time, requires further understanding. © 2024 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.<br/
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