中国高能物理学会第十届全国粒子物理学术会议,南京

1、中国高能物理学会第十届全国粒子物理学术会议中国高能物理学会第十届全国粒子物理学术会议, 南京南京 Observation of X(1835) in Observation of X(1835) in J房双世房双世“晨光杯晨光杯”论文报论文报告告Outline Introduction Event Selection Background Study Results Summary and Discussion A narrow enhancement is observed in . Assuming that the system is in an S-wave resulted in

2、a resonance mass of MeV and a total width of MeV. ppJpp5325101859m30M=1859 MeV/c2 30 MeV/c2 (90% CL) +3 +5 10 25M(pp)-2mp (GeV)00.10.20.3IntroductionIntroductionppJ 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 possib

3、le 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)J One possible decay modes, never studied before at BES easy to tag using Charged tracks4 good charged tracks with |cos |0.8 in MDC;The total charge is required to be

4、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 MeVIsolated from charged tracks by more than 5oN =3 forN =2 for Event Selection)(J)(J used to improve the mass resolution Event Selection for )(J824CGeVMM05. 0|1525CMGeV

5、MM015. 0| Analysis of)(JX(1835) Event Selection for )(J224KKC824C GeVMGeVmMGeVM82. 072. 005. 0|22. 0GeVMM025. 0|0 Analysis of )(JX(1835) mass-sideband events Main background, 60M decays by LUND model Check efficiency curve phase space Background Study0JJJBkg. study for )(JLUND MC)(0J sidebandsdatada

6、ta Bkg. Study for )(JPhase space eventsEfficiency curveMCBkg. Study for )(JLUND MC)(0J sidebandsdatadata)(J Bkg. Study for Efficiency curvePhase space eventsMC)(JObservation of X(1835) in The sum + - mass spectrum for decaying into + - and JJ Mass spectrum fitting 2668obsNMeVm1 . 84 .1827MeV5 .342 .

7、54 410)7 . 08 . 1 ()()(XBXJB5.1 The + - mass spectrum for )(J Mass spectrum fitting 43193obsNMeVm9 . 73 .1836MeV1 .233 .70 410)5 . 03 . 2()()(XBXJB6.0 The + - mass spectrum for )(J Mass spectrum fitting 54264obsNMeVm7 . 21 . 67 .1833MeV7 . 73 .207 .67 410)4 . 04 . 02 . 2()()(XBXJB7.7 The sum + - mas

8、s spectrum for decayinginto + - and 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/c2The sum of mass spectrum for two decay modes m=1833.7 6.1 2.7MeV/c2 , =67.7 20.3 7.7MeV/c2)(J)(J The sum of mass spectrum for two decay modes )(J410)

9、7 . 08 . 1 ()()(XBXJB)(J410)4 . 04 . 02 . 2()()(XBXJB410)5 . 03 . 2()()(XBXJBqThe mass, width and branching fractions obtained from two different decay modes are consistent with each other.Results of mass spectrum fittingPaper published inPhys. Rev. Lett. 95,262001(2005)(Received 11 August 2005; pub

10、lished 28 December 2005) SPIRES-HEP search(2008-04-01) 39 times cited 首次在以我国科学家为主首次在以我国科学家为主进行的北京谱仪实验中发进行的北京谱仪实验中发现新粒子。现新粒子。国际权威粒国际权威粒子数据手册子数据手册PDG2006首首次收录次收录以中国科学家为主以中国科学家为主发现的新粒子发现的新粒子X(1835)等。等。强烈反响和广泛的认同强烈反响和广泛的认同 (I) 粒子数据手册在粒子数据手册在2006年版的年版的“非常规介子非常规介子”综综合评述部分，合评述部分，因因BES实验实验的新发现而首次加入有关的新发现而首次

11、加入有关“质子反质子束缚态质子反质子束缚态”的评述。的评述。强烈反响和广泛的认同强烈反响和广泛的认同 (II) 在国内，在国内，“北京电子对撞机上发现北京电子对撞机上发现X1835新粒子新粒子”被评为被评为 “2006年度中国基础研究十大新闻年度中国基础研究十大新闻”第一名第一名 “2006年度国内十大科技新闻年度国内十大科技新闻”第二名。第二名。 Summary and DiscussionqA new resonance X(1835) observed in qThe mass, width and branching fractions obtained from two differ

12、ent decay modes are consistent with each other. J 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.

13、PDG2006 takes it as a possible ppbar bound state.Fit to J/ pp including FSIInclude FSI curve from A.Sirbirtsev et al.(hep-ph/ 0411386) in the fit (I=0)M = 1830.6 6.7 MeV = 0 93 MeVpppmM2In good agreement with X(1835)Summary and Discussionq Other interpretations are not excluded. q Glueball? N. Koche

14、lev, D. P. Min Phys. Lett. B633:283(2006); B.A. Li, Phys. Rev. D74:034019(2006); C. F. Qiao Phys. Lett. B642:53(2006) q radial excitation ? T. Huang S. L. Zhu Phys. Rev D73:014023(2006)Determination of its IGJPC helps 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 ! Summary and Discussion谢谢 谢谢Back u