Observation of an Anomalous Line Shape of the η′π<SUP>+</SUP>π<i><SUP>-</SUP></i> Mass Spectrum near the <i>p(p)over-bar</i> Mass Threshold in <i>J</i>/ψ → γη′π<SUP>+</SUP>π<SUP>-</SUP>


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Ablikim M., Achasov M. N., Ahmed S., Ai X. C., Albayrak O., Albrecht M., ...Daha Fazla

PHYSICAL REVIEW LETTERS, cilt.117, sa.4, 2016 (SCI-Expanded) identifier identifier identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 117 Sayı: 4
  • Basım Tarihi: 2016
  • Doi Numarası: 10.1103/physrevlett.117.042002
  • Dergi Adı: PHYSICAL REVIEW LETTERS
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Bursa Uludağ Üniversitesi Adresli: Hayır

Özet

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.