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中国高能物理学会第十届全国粒子物理学术会议 , 南京

中国高能物理学会第十届全国粒子物理学术会议 , 南京. Observation of X(1835) in. 房双世. “晨光杯”论文报告. Outline. Introduction Event Selection Background Study Results Summary and Discussion. Introduction.

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中国高能物理学会第十届全国粒子物理学术会议 , 南京

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  1. 中国高能物理学会第十届全国粒子物理学术会议, 南京 Observation of X(1835) in 房双世 “晨光杯”论文报告

  2. Outline • Introduction • Event Selection • Background Study • Results • Summary and Discussion

  3. Introduction • A narrow enhancement is observed in . Assuming that the system is in an S-wave resulted in a resonance mass of MeV and a total width of MeV. +3 +5 -10 -25 M=1859 MeV/c2 G < 30 MeV/c2 (90% CL) 0 0.1 0.2 0.3 M(pp)-2mp (GeV)

  4. Introduction • It can be interpreted as a ppbar bound state. In such a case, it is desirable to observe such a state in other decay modes. • Many possible decay modes suggested in C. S. Cao and S.L. Zhu Commun. Theory. Phys. 42, 844(2004) C. J. Ding and M. L. Yan, Phys. Rev. C72(2005) • One possible decay modes, • never studied before at BES • easy to tag using

  5. Event Selection • Charged tracks • 4 good charged tracks with |cos|<0.8 in MDC; • The total charge is required to be 0; • PID: at least three of them are identified as pions with TOF and dE/Dx ; • Photon selection • Energy deposited in BSC greater than 60 MeV • Isolated from charged tracks by more than 5o • N =3 for • N=2 for

  6. Event Selection for used to improve the mass resolution

  7. Analysis of X(1835)

  8. Event Selection for

  9. Analysis of X(1835)

  10. Background Study • mass-sideband events • Main background, • 60M decays by LUND model • Check efficiency curve • phase space

  11. Bkg. study for LUND MC data  sidebands data

  12. Bkg. Study for Efficiency curve Phase space events MC

  13. Bkg. Study for LUND MC data  sidebands data

  14. Bkg. Study for Phase space events Efficiency curve MC

  15. Observation of X(1835) in The sum +- mass spectrum for  decaying into +- and  

  16. Mass spectrum fitting The +- mass spectrum for 5.1

  17. Mass spectrum fitting The +- mass spectrum for 6.0 

  18. Mass spectrum fitting The sum +- mass spectrum for  decaying into +- and   7.7

  19. Results of mass spectrum fitting • Mass and width from m=1827.48.1MeV/c2 , =54.234.5MeV/c2 • Mass and width from m=1836.37.9MeV/c2 , =70.323.1MeV/c2 • The sum of mass spectrum for two decay modes m=1833.76.12.7MeV/c2 , =67.720.37.7MeV/c2 • The sum of mass spectrum for two decay modes The mass, width and branching fractions obtained from two different decay modes are consistent with each other.

  20. Paper published inPhys. Rev. Lett. 95,262001(2005)(Received 11 August 2005; published 28 December 2005)SPIRES-HEP search(2008-04-01)39times cited

  21. 强烈反响和广泛的认同 (I) • 首次在以我国科学家为主进行的北京谱仪实验中发现新粒子。国际权威《粒子数据手册》PDG2006首次收录以中国科学家为主发现的新粒子X(1835)等。 • 《粒子数据手册》在2006年版的“非常规介子”综合评述部分，因BES实验的新发现而首次加入有关“质子－反质子束缚态”的评述。

  22. 强烈反响和广泛的认同 (II) 在国内，“北京电子对撞机上发现X1835新粒子”被评为 • “2006年度中国基础研究十大新闻”第一名 • “2006年度国内十大科技新闻”第二名。

  23. Summary and Discussion A new resonance X(1835) observed in The mass, width and branching fractions obtained from  two different decay modes are consistent with each other. • X(1835) could be the same structure as ppbar mass threshold enhancement. • It could be a ppbar bound state since it dominantly decays to ppbar when its mass is above ppbar mass threshold. • Its spin-parity should be 0-+: this would be an important test. • PDG2006 takes it as a possible ppbar bound state.

  24. Fit to J/pp including FSI Include FSI curve from A.Sirbirtsev et al.(hep-ph/ 0411386) in the fit (I=0) M = 1830.6  6.7 MeV  = 0  93 MeV In good agreement with X(1835)

  25. Summary and Discussion • Other interpretations are not excluded. • Glueball? N. Kochelev, D. P. Min Phys. Lett. B633:283(2006); B.A. Li, Phys. Rev. D74:034019(2006); C. F. Qiao Phys. Lett. B642:53(2006) •  radial excitation ? T. Huang S. L. Zhu Phys. Rev D73:014023(2006)

  26. Summary and Discussion • Determination of its IGJPChelps us to understand this resonance • Confirmation of X(1835) in other decay modes needed • With 100 times high quality data, may BESIII issue a new “birth certificate” for X(1835) soon !

  27. 谢 谢

  28. Back up

  29. BCK subtracted PS corrected

  30. BCK subtracted PS corrected

  31. Photon angular distributions in • For Data – it is not inconsistent with 0-+ -- statistics is too low. Sideband Subtracted & Eff. corrected X(1835) region X(1835) sideband

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