2. 1 Chen Jiangchuan (for BES Collaboration) Institute of High Energy Physics, Beijing 100039, P.R. C. The International Conference on QCD and Hadronic Physics June 16—20, 2005 Recent Results on  (3770) Resonance and D Mesons Production & Decays from BES

3. 2 D 0 & D + Meson Decays  (3770) production & decays Outline Summary   

4. 3 ~18 pb -1 of data taken at 3.773 GeV ~7 pb -1 of data taken at the region from 3.768 GeV to 3.778 GeV ~8 pb -1 of data taken in the energy region from 3.665 to 3.878 GeV about 33 pb -1 of data collected around 3.773 GeV in total. 2004 Jan.5 BES completed total  (3770) data collection. BES  (3770) data Sample

5. 4  (3770) production & decays  (3770) resonance parameters DD-bar cross cection at 3.773 GeV Search for charmless decays of Evidence for    

6. 5 Since its mass is above open charm-pair threshold and its width is two order of magnitude larger than that of,  (3770) is thought to decay almost entirely to pure DD-bar.  (3770) is believed to be a mixture of and states of system  (3770) production cross section at peak Using mass and branching fraction (PDG02): (Mark-III) Non-saturate decay ? About 39% of  (3770) does not decay to DD-bar ? Puzzle of  (3770) production and decays

7. 6 Added all above numbers up ! There are some theoretical calculations about non-DD-bar decays Theoretical prediction There are some theoretical arguments about decays Lipkin pointed out that could decay to non-DD-bar final states with a large branching fraction.  (3770)

8. 7  (3770) resonance parameters To understand this long-standing puzzle,  (3770) and production cross section should be measured more precisely. The cross section of  (3770) can be obtained based on the  (3770) resonance parameters.  (3770) resonance parameters can be extracted from a fit to the observed hadonic cross sections in the energy range which cover  (3770) resonance (-- scan experiment).

9. 8 Events Recorded by BESII Cosmic-ray and beam associated background Distributions of the vertex of events physics background could be estimated based on cross sections, luminosities and acceptances

10. 9 Monte Carlo production The ISR (Initial State Radiation) return. The histogram show the hadronic event production due to ISR when nominal center-of-mass energy at 3.78 GeV.

11. 10 Monte Carlo production Shadows are experimental data, lines are MC sample, (E cm = 3.773 GeV). (Nch, KNO, Thrust, Sphericity, Aplanarity, x p, η,, distributions)

12. 11 Hadron efficiency vs C.M. energy (Kuraev and Fadin) Observed cross section

13. 12 When scan over 3.770 GeV Just before the scan experiment Mass [MeV] PDG02 BEPC BEPC energy calibration E BEPC is the energy of BEPC set in the experiment, E true is the true energy

14. 13  (3770) production To get right resonance parameters, the two resonance productions and decays should be considered simultaneously. In this way the “correct” QED background ( ) can be determined correctly ! BES-II Preliminary !

15. 14 (preliminary !) Experiment MARK-I DELCO MARK-II PDG02 BES-II Comparison of  (3770) Resonance Parameters

16. 15 Comparison of  (2s) Resonance Parameters experiment This measurement (preliminary !) BES-II published (PLB550(2002)24) PDG2002 Using a constant for vacuum polarization correction

17. 16 e+e+ e-e- D D K-K- tag D-D- D+D+ π+π+ π+π+ Single tag analysis Using kinematical fit method to improve momentum resolution and select the singly tagged D meson Requiring PDG02 Br From Monte Carlo DD-bar Cross Section at 3.773 GeV  BES-II: of data @ 3.773 GeV Single tag method

18. 17 Observed cross sections for DD-bar production at 3.773 GeV

19. 18 Near DD-bar production threshold region e+e+ e-e- D D K-K- π+π+ tag D-D- D+D+ e-e- e+e+ D D K-K- D0D0 D0D0 Using ‘double tag’ method, pioneered by MARK-III DD-bar Cross Section at 3.773 GeV  BES-II: of data @ 3.773 GeV Singly tagged D sample Doubly tagged D π+π+ π+π+ Double tag method

20. 19 绝对测量绝对测量 Preliminary !

21. 20 Assuming that decay exclusively into  (3770) Radiative correction PR D62 (2000)012002-1 Initial State Radiation correction factor

22. 21 Obtained based on PDG02  (3770) resonance parameters : Radiative correction factor Due to the uncertainties in resonance parameters and vaccum polarization

23. 22 and The contribution to R in the charm threshold region from the light quarks is estimated to be, which is obtained by fitting to the R values from 2.0 to 3.0 GeV measured by BES-II. The theoretical expectation is that is approximately independent of center of mass energy in this region. yielding The open square is charm counting method of R measurement Assuming that decays exclusively into DD-bar Squares are the BES-II direct R measurements by counting inclusive hadronic events  (3770) which is obtained in measurement of  (3770) resonance parameters or

24. 23 4-prong with net charge zero Selection criteria Data taken around  (3770) peak Neutral mode Charged mode Search for charmless decays of

25. 24 Data taken off-resonance (@ 3.65 GeV) Normalized to the luminosity and phase space of ψ(3770) production Check if there are continuum production ?

26. 25 Resonance productions and decays QED process Observed in experiment Charmless final states observed around 3.77 GeV Three gluon annihilation process

27. 26 A detailed maximum likelihood analysis based on above observed event numbers gives giving a significance of

28. 27 Those yield the branching fraction and upper limit to be and partial width to be (preliminary !)

29. 28 Evidence for Decay it is an interesting question if transitions inside the charmonium system exist.

30. 29  Examine the recoil mass of Projecting the events on to the vertical scale (recoil mass of ), the evidence for is observed (mainly) Due to ISR Evidence for ( cont’d)

31. 30 Evidence for ( cont’d) and Data MC signal events Analysis of the recoil mass out of events in total 20 times large than the data

32. 31 Evidence for ( cont’d) analysis of the fitted dilepton masses of Open histogram is for e+e- channel, histogram in yellow is for mu+mu- channel mainly The histogram is psi(3686), while error bars are the psi(3686) + psi(3770 ) signal events obtained out of signal events data MC 20 times large than the data

33. 32 It has been quoted 21 times.  (3770) It is an interesting question if transitions inside the charmonium system exist. It is very important in elucidating the exact nature of the  (3770) and help us understand why the  (3770) does not seem to be saturated by DD-bar decays. Before BES-II one knows the decays BES-II established the transition at level ! Paper published in PLB605 (2005)63 Comments by Referees of the paper

34. 33 D 0 & D + Meson Decays Exclusive Semileptonic D Decays Purely Leptonic D + Decay D absolute hadronic decay branching fractions Singl tag samples      (3770) is a good laboratory for study D meson decays

35. 34 Invariant mass distribution for tags Singly tagged D samples

36. 35 Semileptonic D Decays e+e+ e-e- D D tag D-D- D+D+ π+π+ K-K- π+π+ π+π+ e-e- e+e+ D D K-K- D0D0 D0D0 Singly tagged D sample

37. 36  Branching fractions for and To measure the standard model parameters Vcs, Vcd Probing the hadronic current Understand the dynamics of semileptonic decays Where is a vector form factor, and are the four momenta of the initial and final mesons, respectively, and is the squared mass of the virtual W. As an example (“nearest pole dominance”) Motivation

38. 37  Branching fraction for To test if the Isospin conservation is still held in D semileptonic decays. Isospin conservation requires and From PDG Br It is called “Longstanding puzzel” in Charm decay ! Longstanding Puzzle in charm decay Is isospin conservation held in the D semileptonic decays? Motivation

39. 38 Distribution of the Inv. masses of Combinations for the events in which the are observed in the recoil side Distribution of the momentum of the electron from the events of

40. 39 Experiment BES MARK III PDG 04 Results Phy. Let. B597(2004)39-46Phy. Let. B608(2005)24-30

41. 40 QCDSR LQCD(1) LQCD(2) BES Phys.Rev.D66,114002,2000 Nucl.Phys.Prog.Suppl.83,28 6,2000 Nucl.Phys.B619,565,2001 Theoretical predictions are in the range from 0.7 to 1.4. See J.D. Richman et al., Rev. Mod. Phys., Vol. 67, No 4, 1995 Different theoretical predictions  Form factors PDG04 inserting Average MARK-III and CLEO gives

42. 41 BES( QCDSR ) BES( LQCD(1) ) BES( LQCD(2) ) BES MARK III Input  CKM matrix elements Input theoretical predictions for the form factors

43. 42 BES MARK IIIPDG04  Ratio of partial width Obtained based on the branching fractions quoted from PDG02 Solve the longstanding puzzle in Charm decays ! BES-II results support isospin conservation is held in the D semileptonic decays!

44. 43 Purely Leptonic D + Decay e+e+ e-e- D D K-K- tag D-D- D+D+ π+π+ π+π+ Phy. Let. B610(2005)183-191

45. 44 Motivation Lattice gauge, potential models bag model, QCD sum rule …, calculation predict the value of The f D measurement will allow comparison with the theoretical calculation to improve the theory. Lattice predicts f B /f D with small errors. Precision measurement of f D  precision estimate of f B and precision determination of V td Mixing experiment It is very difficult to measure the f D due to |V cd | is small The effect of strong interaction can be parameterized by

46. 45 MARK-III set an upper limit of f D < 290 MeV BES-I observed 1 event for and measured Physics Letters B 429(1998) 188-194 Previous measurements

47. 46 e+e+ e-e- D D K+K+ tag D+D+ D-D- π-π- π-π- Neutrino carries energy and momentum away Should be around zero  Fully reconstruct one D  Require one additional charged track and no additional photons Total

48. 47 Monte Carlo sample 150 times more than data 3 events in the signal region Monte Carlo simulation

49. 48 Estimation of background The main background are 3 X 100 times more Monte Carlo samples for each of the modes  Nb = 0.22 Analysis of 320 pb -1 Monte Carlo sample  Nb = 0.33+/-0.11 13 events in the tagged D - mass region  Method 1  Method 2  Method 3 1 hadronic track in the recoil of the tags Nb=0.31±0.09 1 muon is fund in the recoil of the tags, and the events satisfied the requirements for selection of

50. 49 Search for the decay e+e+ e-e- D D K+K+ π-π- νeνe Singly tagged D- Candidate tag D+D+ D-D- π-π- 2.67±1.74 Events

51. 50 e+e+ e-e- D D K-K- π+π+ tag D-D- D+D+ π+π+ Double-tag D absolute hadronic decay branching fractions π+π+ e-e- e+e+ D D K-K- tag D0D0 D0D0 Singly tagged D sample

52. 51 They are two very important constants to normalize all other branching fractions for the D mesons decays, B mesons and Z 0 decays. They enter into CKM matrix elements determinations. So more precisely measuring the both branching fractions can directly improve the CKM matrix elements: determine from and Methods of measuring and at  (3770) --- B decay double tag analysis  Absolute branching fractions for and

53. 52 : Singly tagged D sample Mass inv GeV/c Mass inv D0D0 D+D+

54. 53 Double tag Mass inv

55. 54 χ 2 minimization fit Tag-N single Tag-N double Produced DD Br.(i-mode) Efficiency A χ 2 minimization fit to  (with tagged D.vs.D) R double conout

56. 55 D absolute hadronic decay branching fractions PDG04 (preliminary !)

57. 56 SUMMARY BES measured  (3770) resonance parameters BES measured the DD-bar Cross Section at 3.773 GeV to be . Experiment BES-II PDG02 (preliminary !) ( ISR based on PDG02 ) ( ISR based on BES-II parameters ) (preliminary !)  (3770) From 3.66 to 3.87 GeV

58. 57 BES observed the charmless decay events of measured the partial width of BES observed hadronic transition of to and measured the partial width to be  (3770) . and set its upper limit to be (preliminary !) SUMMARY

59. 58 SUMMARY Measured the form factors & ratio of partial widths Observed 3 D + purely leptonic decay events, and obtained . Theory: from 0.7 to 1.4 Solve the longstanding puzzle in Charm decays Measured absolute hadronic branching fractions for Those would improve the normalization constants used in Charm and B physics !

60. 59 谢 谢！ Thank You ！

61. 60 Comparing the BES Results with that from CELO-c Near DD-bar Threshold Experiments

62. 61 LP03 关于       J/  的讨论 ? e  e  →  2S   2S  →      J  E cm -Mass recoiling      3770  →      J  mainly BES-II CLEO-c BES-II 结果成为热门话题， 被广泛关注，讨论和引用！ 这是 BES-II 与 CLEO-c 的物 理结果第一次被 CLEO 成员 所做的对比。 (at LP03)

63. 62 DAPHNE’04 06/08/04 Hanna Mahlke-Krueger, Cornell (RG mdfy) e  e  →  2S   2S  →      J  ? 232 events E cm -Mass recoiling     5.2±0.2 pb -1, (4.5±0.4)10 4  ’’  decays efficiency: 37%  < 4.75 events @ 90%CL B R  3770     J  ( 1S )) <0.26% @ 90% CL 17.8±4.8 events incl 6.0±0.8 bgd (0 from cont) BR  3770  →     J  ) = (0.34±0.14±0.08) %  = (80 ±32±21) keV BESIICLEO-c T. Skwarnicki, QWG03 e  e  →  2S   2S  →      J  M( ℓ + ℓ  ) GeV hep-ex/0307028 已 21 次 被引用

64. 63 DAPHNE’04 06/08/04 Hanna Mahlke-Krueger, Cornell       J/  e  e  →  2S   2S  →      J  ? 232 events E cm -Mass recoiling     5.2±0.2 pb -1, (4.5±0.4)10 4  ’’  decays efficiency: 37%  < 4.75 events @ 90%CL B R  3770     J  ( 1S )) <0.26% @ 90% CL 28 pb -1 (3.783-3.885GeV), 1.85  10 5  ’’  decays efficiency: 16%  17.8±4.8 events incl 6.0±0.8 bgd (0 from cont) BR  3770  →     J  ) = (0.34±0.14±0.08) %  = (80 ±32±21) keV BESIICLEO-c T. Skwarnicki, QWG03 e  e   →  2S   2S  →      J  M( ℓ + ℓ  ) GeV hep-ex/0307028

65. 64 Results given at international conference from BES-II & CLEO-c Moriond EW04 (2004 年 3 月 )APS (2004 年 5 月 ) 无报道 N/A 这是 BES-II 的物理结果与 CLEO-c 的第二次对比。 2 个月之后

66. 65 Results given at international conference from BES-II & CLEO-c BES -- Moriond EW04 (March, 2004) CLEO-c -- APS (May, 2004) 无报道 Dalitz analysis of N./A. Branching fractions CLEO-c 原计划要在 Moriond ’ 04 国际会议 上正式报道物理结果。 但最后却什么也没讲。 Rosner 主要根据 BES Moriond ’ 04 结果, 提出 rescattering 模型, 来解释 衰变. 他在文章中先后 5 次引用 BES 结 果.

67. 66 BES-II DD-bar Cross section in good agreement with CLE-c 与 CLEO-c 物理结果的对比及国际反 响 在 1.3% 的范围内一致！

68. 67

69. 68

70. 69 BES-II Final result

71. 70

72. 71 Heavy Quarkonia 8 类典型的热点问题 3 大不解之迷 ? 有 2 个主要起源于 BES 的 近期研究工作！ QQ-bar 的热点问题和不解之迷？ 国际反响  (3770)

73. 72 几乎是常数效率，早年的辐射修正， … MARK-I, DELCO, MARK-II 平滑效率； ( 相对 scale) BES-II 效率曲线

74. 73 依赖于 目前 PDG 采用 MARK-III 的 依赖于 CLEO measured 绝对 测量 软 标记 实验状况 It is important to accurately measure the cross sections for DD-bar production !

75. 74 CKM matrix elements & Form factors & Branching fractions * * * Motivation Isospin conservation implies longstanding puzzle in Charm decays ! From PDG Br