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Recent results on light hadron spectroscopy at BES

Recent results on light hadron spectroscopy at BES. Hongxun Yang (for BES Collaboration) Moriond QCD and High Energy Interactions March 13-20 2010. Outline. Introduction of BES at BEPC analysis of charged  at BESII Confirmation of ppbar mass threshold structure at BESIII

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Recent results on light hadron spectroscopy at BES

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  1. Recent results on light hadron spectroscopy at BES Hongxun Yang (for BES Collaboration) Moriond QCD and High Energy Interactions March 13-20 2010

  2. Outline Introduction of BES at BEPC analysis of charged  at BESII Confirmation of ppbar mass threshold structure at BESIII Confirmation of X(1835) at BESIII Summary 2 2014/9/5

  3. Beijing Electron Positron Collider (BEPC) at IHEP Beijing Spectrometer I: 1989 -1998 BESII: 1999 -2004 L ~ 5*1030cm-2s-1@ J/ Ebeam~ 1-2.5 GeV BESIII: 2008 (Physics run from March 2009)- , L~3.2*1032cm-2s-1@(3770)~30% of designed value 3 2014/9/5

  4. 4 2014/9/5

  5. Milestones of BESIII 5 2014/9/5

  6. Observation of charged  at BESII •  was first found in K scattering data • However, its phase shift is much less than 180o and it cannot be filled into any nonets of ordinary mesons. There have been hot debates on the existence of . • In recent years: • FNAL E791 found evidence of neutral  in D+ K-++. • CLEO D0 K-+0 data find no evidence of . • FOCUS data on D+K-++ require K*0 interfere with either a constant amplitude or a broad 0+ resonance in K. • BESII observed neutral  in J/  K*0K  KK in 2006. • neutral  pole: 6 2014/9/5

  7. The existence of charged  is expected ! • CLEO reported the necessity of in . • However, no charged  is needed in BABAR data. • BESII studied charged  in BESII Preliminary BESII Preliminary K*(1410), K*(1430) M(K0) GeV/c2  7 2014/9/5

  8. Partial wave analysis results BESII Preliminary BESII Preliminary M(K) (GeV/c2) M(K*(892)) (GeV/c2) BESII Preliminary BESII Preliminary M(K*(892)K) (GeV/c2) 8 2014/9/5

  9. Resonance parameters of charged  For reference, resonance parameters of neutral  • Different parameterizations of  give consistent results on the • pole of charged  . • The pole position for charged  is consistent with that for • neutral  within the error. arXiv:1002.0893 [hep-ex] 9 2014/9/5

  10. Observation of an anomalous enhancement X(1860) near the threshold of pp mass spectrum PRL 91, 02201 (2003) BESII 0.3 0.2 0 0.1 Mpp-2mp (GeV) • theoretical speculation: • bound state (baryonium) • FSI effects • …… 10 2014/9/5

  11. The narrow threshold enhancement is NOT observed in those channels PR D73, 032001 (2006) EPJ C53 ,15 (2008) PRL 99, 011802 (2007) No significant narrow strong enhancement near threshold (~2 if fitted with X(1860)) Mpp(GeV/c2) 11 2014/9/5

  12. Observation of an anomalous enhancement near the threshold of mass spectrum at BES III CPC(HEP & NP), 2010, 34(4): 421-426 BESIII preliminary BESIII preliminary Fitted with a S-wave BW, M=1861+6-13 (stat)+7-26 (syst) MeV/c2 G < 38 MeV/c2 (90% CL) 12 2014/9/5

  13. This narrow threshold enhancement is “NOT” observed in at BESIII No significant narrow strong enhancement near threshold Pure FSI interpretation disfavored 13 2014/9/5

  14. Statistical Significance ~6  Statistical Significance ~5.1  Observation of X(1835) J/’+- at BESII PRL 95,262001(2005) To be confirmed with ~220M J/ data at BESIII 14 14 2014/9/5

  15. Mass spectrum of ’+- in J/’+-, ’ BESIII preliminary BESIII preliminary • Significant peak at M~1835MeV • Statistic significance of X(1835) is about 18σ 15 2014/9/5

  16. Mass spectrum of ’+- in J/’+-, ’+- BESIII preliminary BESIII preliminary • Significant peak at M~1835MeV • Statistic significance of X(1835) is about 9σ 16 2014/9/5

  17. Structures at higher mass region??? ??? Combined mass spectrum of the two decay modes BESIII preliminary X(1835) is confirmed in BESIII and the significance increases as statistics increases BESII 17 2014/9/5

  18. Summary BEPCII/BESIII is a major upgrade of the BESII experiment at the BEPC accelerator for studies of hadron spectroscopy and -charm physics. BESIII has been in operation since 2008: ~110M ’ and ~220M J/ events have been collected Recent results at on light hadron BES are presented: Partial wave analysis of charged  at BESII Confirmation of ppbar mass threshold structure at BESIII Confirmation of X(1835) at BESIII More Exciting results are expected. 18 2014/9/5

  19. THANK YOU!

  20. Data Accumulated @ BESIII Pb-1 Pb-1 Pb-1 20 2014/9/5

  21. A unique e+e- machine in the -charm energy Tau charm physics with BEPCII/BESIII: From PDG The Y’s are here! 21 In transition region between pQCD and non-pQCD. 21 2014/9/5

  22. Physics potential at BESIII • The physics window is precision charm physics and the search for new physics. • High statistics: high luminosity machine + high quality detector. • Small systematic error: high quality detector. 22 2014/9/5

  23. BEPCII: a high luminosity double–ring collider 23 2014/9/5

  24. Achieved Luminosity 24 2014/9/5

  25. Detector Performance and Calibration 25 2014/9/5

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