J/b→y+元nObservationofX(1835)in房双世“晨光杯”论文报告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 𝐽/𝜓 → 𝛾𝜋 +𝜋 −𝜂 ′ 房双世 “晨光杯”论文报告
OutlineIntroductionEyent SelectionBackground StudyResultsSummary and Discussion
Outline ➢ Introduction ➢ Event Selection ➢ Background Study ➢ Results ➢ Summary and Discussion
IntroductionA narrow enhancement is observed in .JAssuming thatthe system is in anps-wave resulted in a resonancemass of Mev and a total width of MeV.=1859+3+5-10-25150M-1859100T<30 MeV/c2 (90% CL)500.3M(pp)-2m,(GeV)-2
➢ 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. 𝐽/𝜓 → 𝛾𝑝𝑝LJ 𝑝𝑝LJ 𝑚 = 1859 −10−25 +3+5 𝛤 < 30 M=1859 MeV/c2 < 30 MeV/c2 (90% CL) +3 +5 −10 −25 M(pp)-2mp (GeV) 0 0.1 0.2 0.3 Introduction
IntroductionIt can be interpreted as a ppbar bound state.Insuch a case,it is desirable to observe such a statein other decay modesN-→ VT+元=n'Many possible decay modes suggested inC. S. Cao and S.L. Zhu Commun. Theory. Phys. 42, 844(2004)C. J. Ding and M. L. Yan, Phys. Rev. C72(2005)OnepossibledecaymodesneverstudiedbeforeatBEsneasy to tag using
Introduction 𝑝𝑝LJ 𝐽/𝜓 → 𝛾𝜋 +𝜋 −𝜂 ′ ➢ 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) 𝐽/𝜓 → 𝛾𝜋 +𝜋 −𝜂 ′ ➢ One possible decay modes, ✓ never studied before at BES ✓ easy to tag using 𝜂 ′
Event Selection>Charged tracks4goodchargedtrackswithlcosol<o.8inMDC:The total charge is required to be O;PID: at least three of them are identified as pions with TOFanddE/Dx;>Photon selectionEnergy deposited in BSC greater than 60 MeVIsolated from charged tracks by more than 5J/ → +n'(nN=3for+元)N%=2 forJ / →元+元*n'(n' → yp)
➢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 Event Selection 𝐽/𝜓 → 𝛾𝜋 +𝜋 −𝜂 ′ (𝜂 ′ → 𝜋 +𝜋 −𝜂) 𝐽/𝜓 → 𝛾𝜋 +𝜋 −𝜂 ′ (𝜂 ′ → γρ)