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(3770) and D physics at BESII

(3770) and D physics at BESII. Ma HaiLong [For BES Collaboration] CCAST & IHEP 中国物理学会 2006 年秋季会议（北京） 2006.9.15-17. Outline. Motivation. Purely and semi leptonic decay of D meson. BF[ (3770) → D 0 D 0 ,D + D - ,DD and non-DD]. Summary. Motivation.

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(3770) and D physics at BESII

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  1. (3770) andD physics at BESII Ma HaiLong [For BES Collaboration] CCAST & IHEP 中国物理学会2006年秋季会议（北京） 2006.9.15-17

  2. Outline • Motivation • Purely and semi leptonic decay of D meson • BF[(3770) → D0D0,D+D-,DD and non-DD] • Summary

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

  4. Motivation • Branching fractions The decay rates can be related to the CKM matrix elements and form factors • Isospin conservation implies The called “Longstanding puzzle” in Charm decay! PDG04 BF • Ratio of partial widths of vector to pseudoscalar semileptonic decays of D mesons Early theories: 0.9-1.3 Measurements: smaller Recent theories:0.5-0.7 There are controversies from both experiment and theoretical prediction

  5. Motivation (3770)is thought to decay almost entirely to pure DDbar, but there is large discrepancy between and Cross section at peak (PDG04 parameters) before BES-II & CLEO-c (Mark-III) Long-standing puzzle of (3770) production and decays 1, Systematic shift in the measured cross sections 2, There may be some other effects 3, There may be substantial non-DDbar decays • Simultaneously measusing both and • Precisely measuring the energy dependent cross sections for both inclusive hadrons and DDbar events production simutanmeously, directly measure • and

  6. Motivation • Search for some exclusive non-DDbar decays BES observed 12 signal events for the decay measured the branching fraction to be CLEO confirmed BES observation of the decay, and measured the branching fractions to be PLB 605(2005)63 PRL96(2005)082004 CLEO also observed some other non-DD-bar decay modes such as , … More works is being done…… • What is the total branching fraction for non-DDbar decays? No final answer from experiments. It is assumed Interference… S-D mixing, puzzle, Re-scattering mode,

  7. (3770) data sample ~17.3 pb-1 data taken at 3.773 GeV ~7 pb-1 data taken at the region from 3.768 GeV to 3.778 GeV ~8 pb-1 data taken in the energy region from 3.665 to 3.878 GeV The total Luminosity is about 33 pb-1

  8. Singly tagged D samples Near DD-bar production threshold region Singly tagged D sample K+ K+ D D π– tag tag π– π– D- e+ e- e+ e- D D D+ Absolute Measurements X0 X+ Throughout the talk, charge conjugation is implied

  9. Singly tagged D samples ND-Tag=5321±125±160 ND0Tag=7584±198±241 Mass[mKnπ] Singly tagged D- modes: (a)K+π-π-; (b) K0 π-;(c) K0 K-; (d) K+K-π-; (e) K0π-π-π+; (f) K+π-π-π0; (g) K0π-π0;(h) K+π-π-π-π+; (i) π-π-π+; (j) Sum Singly tagged D0 modes: (a)K+π-; (b) K+ π-π-π+; (c) K0 π-π+; (d)K+ π-π0

  10. Purely leptonic decay • Fully reconstruct one D- K+ background estimation D- π- tag π- D- 0.33±0.11 background events is estimated from 3 candidate events, 2.67±1.74 is retained e+ e- D+ D+ PLB610(2005)283 Theory Comparison[from Matt Shepherd’s Meson06 Talk] Neutrino carries energy and momentum away PRL95(2005)251801 Should be around zero Require one additional charged track and no additional photons

  11. Semileptonic Decays Singly tagged D sample K+ D tag Should be around zero due to the mass of the missing neutrino is zero Umiss=Emiss-pmiss π– e+ e- D |Umiss|<2[3]σUmiss No surplus charged track and good photon on the recoiling side

  12. CKM matrix elments • Form factors PLB597(2004)39 PRL95(2005)181802

  13. Preliminary Results The first error is statistical, the second systematic, and the third arises from PDG branching fractions for the normalizing modes BESII CLEO E687-1 E687-2 E653 FOCUS PDG06

  14. Preliminary Results PLB608(2005)24 Support isospin conservation holds in the D semileptonic decays! PRL95(2005)181801

  15. Candidates for Mass[mKn] Mass[Kπ] • Branching fractions EPJC47(2006)31 support smaller ratio of D to V/P semileptonic decay of D mesons

  16. Candidates for No signal event is observed 90%CL EPJC47(2006)39

  17. Measurement of R R is one of the most fundamental quantities in particle physics, which counts directly the charges, the flavors andthe colors of quarks involved. pQCD calculates the R ratio Experimentally, one measures : # of hadronic events : Luminosity : Eff. : radiative correction factor

  18. PLB641(2006)145, hep-ex/0605105 Obtaining by fitting to the R values measured by BES in the range from 2.0 to 3.0 GeV PRL in press, hep/0605107

  19. (3770) cross section Taking the R for light hadron production to be a constant, then We obtain It is consistent with My calculation obtained based on PDG04 (3770) resonance parameters PLB 603(2004)130

  20. DD cross section • of data @ 3.773 GeV Single tag method Using Kinematic fit method to improve momentum resolution and select the singly tagged D meson K- D π+ tag π+ D+ e+ e- Observed cross sections for DD-bar production at 3.773 GeV D D- Requiring PLB 603(2004)130

  21. DD cross section • of data Absolute measurement, does not depend on branching fractions of D meson decays Using ‘double tag’ method, pioneered by MARK-III, to identified DD-bar pair Double tag method Near DD-bar production threshold region tagged one D meson K- K- D D π+ tag tag π+ π+ D0 D+ e+ e- e+ e- D0 D D- D K+ K+ π- - π- - π- - π- - tagged another D π+

  22. Comparison of observed cross sections An absolute measurement NPB727(2005)395

  23. Determination of BF[(3770) → D0D0,D+D-,DD and non-DD] Obtained from analysis of R Radiative correction factor Some systematic uncertainties can be canceled out Radiative correction factor obtained based on new (3770)resonance parameters measured by BES-II, hep/0605107. PLB641(2006)145, hep-ex/0605105

  24. Measurement of branching fractions for and • Cross section scan experiment The data were collected at 49 energy points from 3.66 to 3.89 GeV, which begin from off-resonance, cover (2S), (3770) and stop at DD* threshold . Separated beam collision data at 3 energy points were collected to study beam associated background. Some J/, (2S) data were also taken to calibrate BEPC energy and determine trg Integrated luminosities Luminosities were measured by using large angle Bhabha scattering events About 5.4 pb-1 of data were collected for the experiment (for hadron events) Monte Carlo Developed a inclusive hadronic event generator with high order ISR corrections to simulate the hadronic event production (including Lorentz boost due to initial state photon emission) in the full energy region

  25. BEPC energy calibration Just before the scan experiment EBEPC is the energy of BEPC set in the experiment, Etrue is the true energy When scan over 3.770GeV

  26. D.Zhang,G.Rong,J.C.Chen, PRD74(2006)054012 MC generator & simulation Full energy range ISR Generator KNO Nch φ cosθ Thrust Oblateness Aplanarity Density [nb/GeV] Sphericity Jet axis cosθ x Y η Pt <PTin2> <PTout2>

  27. Energy dependent hadron cross sections : # of hadronic Inclusive hadrons events : Luminosity : Eff. Hadron efficiency vs C.M. energy Observed cross section for hadron production [nb] Inclusive hadrons (Kuraev and Fadin)

  28. Energy dependent DDbar cross sections Distributions of invariant masses of combinations at different c.m.energyies

  29. Line shape of the cross sections for hadron and DD-bar production Inclusive hadrons Inclusive hadrons Inclusive hadrons PRL in press, hep/0605107 Simultaneously.fitting to the inclusive hadron and the DD-bar production cross sections • Branching fractions

  30. Comparison of (3770) resonance parameters PRL in press, hep/0605107

  31. Comparison of (3686) Resonance Parameters PRL in press, hep/0605107 The measured partial width is consistent with PDG06 partial widthof (3686).

  32. Summary • BES measured branching fraction for pure leptonic decay • BES measured branching fractions of exclusive semileptonic decays of D mesons • CKM matrix elments and form factors • The ratio of Preliminary Support isospin conservation holds in the D semileptonic decays. • The ratio of support smaller ratio of D to V/P semileptonic decay of D mesons • BES search for and

  33. Summary • BES measured DDbar cross sections at 3.773 GeV Singly tagged D analysis Doubly tagged D analysis • BES measured R at 3.773 GeV and Ruds around 3.65 and 3.6648 GeV In the range from 3.67 to 3.89 GeV, obtained from fitting to (3686) and (3770)

  34. Summary • BES measured the branching frations for inclusive non-DDbar decays of (3770) using two different data sample and two different methods Determined from analysis of R values and DD-bar cross sections Obtained from fitting to the inclusive hadron and the DD-bar production cross sections simultaneously. These are first measurements. Thank You！

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