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New Results on ψ(3770) and D Mesons Production and Decays

This presentation discusses the measurements of the R parameters of ψ(3770) and the search for charmless decays of ψ(3770). It also presents new measurements of the resonance parameters and branching fractions of ψ(3770).

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New Results on ψ(3770) and D Mesons Production and Decays

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  1. New Results on (3770) and DMesons Production and Decays From BES Gang RONG (for BES Collaboration) Presented by Yi-Fang Wang Charm07 Cornell University, August 4-8 2007

  2. Outline Introduction Inclusive decays of D Mesons Measurements of R Parameters of (3770) B[(3770)non-DD] and Search for Charmless decays of (3770) Summary

  3. Introduction BESII (3770) data sample of about 33 pb-1 Data Samples • about 17.3 pb-1 data taken at 3.773 GeV • about 7 pb-1 data taken from 3.768 GeV to 3.778 GeV • about 8 pb-1 data taken from 3.665 to 3.878 GeV • about 6.5 pb-1 data taken at 3.650 GeV • about 1 pb-1 data taken at 3.665 GeV pb-1 World (3770) Samples (pb-1) (by summer,2005)

  4. D- and D0 tags Double tag analysis Absolute measurements

  5. D+X With the singly tagged D sample, we can do some absolute measurements of D decays on the side recoiling against the tags . K+ Singly tagged D sample D π– tag π– PT D- e+ e- 0.52-0.62 GeV D D+ P+ 0.62-0.72 GeV X=any particles 0.72-0.82 GeV 0.82-0.92 GeV P+ is any charged particle (, e, π and K) 0.92-1.02 GeV mKnπ(Dtag) Nμobs

  6. D+X μtrue etrue Ktrue πtrue εim= ratio of a particle “i” to be identified as “m” Nobsi =observed particle I; Ntruei = true particle i First measurements PDG

  7. De+X and DKX B(De+X) and B(DKX) Preliminary Comparison of Results

  8. The quantity R • Why are we interested in R(s) ? • Vacuum polarization correction needs the R(s) values, which plays an important role in the precision test of the Standard Model. • For evaluation of the electromagnetic coupling at the Z mass scale, • For determination of of the muon. • Evaluate • Non-DD decays of (3770) • important in open charm region for the understanding of 1-- resonance production, for searching for new states, and for studying dynamics …

  9. The quantity R • (3770) production & decays It is believed to be a mixture of and states of system. It is thought to decay almost entirely to pure DD-bar. Before BES-II & CLEO-c, previously published data indicate that more thanabout 35%of(3770)does not decay to DD-bar ? This conflicts with theoretical prediction.

  10. The quantity R • New Measurements Recently BES and CLEO-c measured the DD and (3770) production at 3.773 GeV based on the data taken below DD threshold and at 3.773 GeV. To uncover the puzzle, a better way is to make cross section scan A better way to measure the cross sections, the widths of the resonance and the DD branching fractions of (3770) is to analyze the line-shapes of (3770), (3686) and DD production simultaneously. BES made several fine cross section scans covering boththe(3686) and (3770) to measure the resonance parameters, branching fractions and search for non-DD decays …

  11. The quantity R The Previously Measured quantity R Precision measurement of the cross sections in this region Including all hadrons

  12. The quantity R Definition of different R above cc-bar threshold below cc-bar threshold hadrons [where q is the light (u,d,s) quarks] Ruds Evaluate Rhad(s)=Ruds(c)(s)+ΣRres,i(s), Rres,i(s) is R values due to all 1－－resonances decay to hadrons except Ψ(3770). hadrons calculate Rhad

  13. The quantity R ISR corrections Effective c.m. energy Moninal c.m. energy Kuraev & Fadin the electron equivalent radiator thickness

  14. The quantity R Vacuum polarization correction Vacuum polarization change the photon propagator results in Radiative correction factor

  15. The quantity R Ruds = 2.141±0.025±0.085 RpQCDuds = 2.15±0.03 Results PRL 97, 262001 (2006) above cc-bar threshold below cc-bar threshold Below DD-bar threshold

  16. The quantity R Comparison of R measurements from different experiments PLB 641 (2006) 145

  17. Resonance Parameters of (3770) New measurements 68 energy points Dec. 2003 data The paper is being in press (PLB)

  18. Resonance Parameters of (3770) New measurements Comparison with those measured by other experiments [Dec. 2003 data] [Dec. 2003 data] Ruds=2.121 0.023 0.084

  19. Resonance Parameters of (3770) What about World Average Comparison of measurements of the cross section for (3770) production Leptonic branching fraction PRL 97 (2006) 121801 Preliminary ! PRL 97 (2006) 121801 PDG04

  20. B[(3770)non-DD] PLB641 (2006) 145 Determined from analysis of R values and DD-bar cross sections PRL 97 (2006) 121801 Obtained by fitting to the inclusive hadron and the DD-bar production cross sections simultaneously. PDG07

  21. Search for Charmless Decays of (3770) Search for Charmless decays of(3770) We have searched for more than 40 modes for the light hadron decays. PLB650(2007)111

  22. Search for Charmless Decays of (3770) Preliminary Results Search for light-hadron decays of(3770)

  23. Search for Charmless Decays of (3770) Search for light-hadron decays of(3770) Preliminary Results Upper limits are set at 90% CL We searched for (3770)light hadrons over 40 channels, but no significant signals were found. This does not mean that (3770) does not decay into light hadrons. To extract the branching fractions for (3770)light hadrons from the observed cross sections, one need to make finer cross section scan covering both (3686) and (3770) with larger data samples (BES-III can do this well).

  24. SUMMARY • Inclusive decays of D mesons Measured BF(D+ mu+ X)=(17.6+-2.7+-1.3)% for the first time Measured BF(D+ K- X)=(24.7+-1.3+-1.2)% Improved measurements Measured BF(D+ K+ X)=(6.1+-0.9+-0.4)% Measured BF(D0 K- X)=(57.8+-1.6+-3.4)% • R value Improved measurements of R in the range from 3.65 to 3.88 GeV Measured Ruds = 2.121+-0.023+-0.085 Measured Ruds(c)+(3770) for the first time • (3770) parameters Precisely measured M(3770) =3772.3+-0.5 MeV; Γtot=28.5+-1.2 MeV; Γee=277+-16 eV Precisely measured BF(e+e-)=(0.97+-0.08+-0.05)x10-5 σobs(3770) = 7.15+-0.25+-0.25 nb [combined two measurements]

  25. SUMMARY Combined 49 energy point cross section scan results and 3 energy point cross section results (inclusive hadron and DD-bar cross sections) • BF[(3770)non-DDbar] Measured BF[(3770)non-DDbar] = (15+-5)% Measured BF[(3770)DDbar] = (85+-5)% PDG07 [BES] • Light hadron decays of (3770) No significant signals for (3770)light hadron were found in about 40 channels. • How to solve this problem ? Finer cross section scan over(3686) and (3770) to measure the cross sections for exclusive modes and fitting the cross sections to extract out the branching fractions (My comment only !)

  26. Thank You！

  27. Backup slides

  28. Comparison with those measured by CLEO-c BES-II CLEO-c (hep-ex/0512038); PRL 96 (2006) 092002 Based on analysis of inclusive hadron and DD-bar cross section scan data. PLB 141 (2006) 145 Actually, considering the errors, the two results are not in contradiction.

  29. Comparison with those measured by CLEO-c BES-II CLEO-c Assuming that there are interference between the two amplitudes of continuum and resonance Based on measured R values. Method: Method: BES measured near DD-bar threshold and R at 3.773 GeV with traditional method, then calculate the Born order cross section for (3770) production. By comparing the cross sections for DD-bar and (3770) production, BES obtained the branching fraction. BES used an ISR generator to simulate the decay e+e- hadrons and obtain theefficiency for e+e- hadrons. CLEO-c directly count the number of hadronic events observed at 3.773 GeV, and subtract the backgrounds from J/, (2S) radiative tails and continuum QED background. CLEO-c used the efficiency forthe decay (3770) J/ π+ π-to estimate the efficiency for e+e- hadrons. Use parameter Use parameter

  30. Comparison with those measured by CLEO-c BES-II CLEO-c Discussion Method: Method: CLEO-c did not consider the difference of ISR & vacuum polarization corrections for continuum hadron production at the two energy points (3.671 GeV and 3.773 GeV) when subtracting background at 3.773 GeV. if we use to calculate the ISR & vacuum polarization correction factor, and assuming that there are interference between the two amplitudes of the continuum and the resonance, we would obtain PRL 97 (2006) 121801

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