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Observation of an Anomalous Line Shape of the eta 'pi(+)pi(-) Mass Spectrum near the p(p)over-bar Mass Threshold in J/psi -> gamma eta 'pi(+)pi(-)
Inst High Energy Phys, Beijing 100049, Peoples R China..
Novosibirsk State Univ, Novosibirsk 630090, Russia..
Helmholtz Inst Mainz, Johann Joachim Becher Weg 45, D-55099 Mainz, Germany..
Inst High Energy Phys, Beijing 100049, Peoples R China..
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2016 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 117, no 4, 042002Article in journal (Refereed) PublishedText
Abstract [en]

Using 1.09 x 10(9) J/psi events collected by the BESIII experiment in 2012, we study the J / psi -> gamma eta'pi(+)pi(-) process and observe a significant abrupt change in the slope of the eta'pi(+)pi(-) invariant mass distribution at the proton-antiproton (p (p) over bar) mass threshold. We use two models to characterize the eta'pi(+)pi(-) line shape around 1.85 GeV/c(2): one that explicitly incorporates the opening of a decay threshold in the mass spectrum (Flatte formula), and another that is the coherent sum of two resonant amplitudes. Both fits show almost equally good agreement with data, and suggest the existence of either a broad state around 1.85 GeV/c(2) with strong couplings to the c final states or a narrow state just below the p (p) over bar mass threshold. Although we cannot distinguish between the fits, either one supports the existence of a p (p) over bar moleculelike state or bound state with greater than 7 sigma significance.

Place, publisher, year, edition, pages
2016. Vol. 117, no 4, 042002
National Category
Subatomic Physics
Identifiers
URN: urn:nbn:se:uu:diva-301422DOI: 10.1103/PhysRevLett.117.042002ISI: 000380123400003PubMedID: 27494467OAI: oai:DiVA.org:uu-301422DiVA: diva2:954637
Funder
Swedish Research Council
Available from: 2016-08-23 Created: 2016-08-23 Last updated: 2016-08-23Bibliographically approved

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Johansson, TordKupsc, AndrzejLi, CuiPettersson, JoachimSchönning, KarinWolke, Magnus
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