 (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）

Outline  Purely and semi leptonic decay of D meson  Summary  BF[  (3770) → D 0 D 0,D + D -,DD and non-DD]  Motivation

The effect of strong interaction can be parameterized by 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 | Motivation

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

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

Motivation Search for some exclusive non-DDbar decays No final answer from experiments. It is assumed S-D mixing,puzzle,Re-scattering mode, What is the total branching fraction for non-DDbar decays? Interference… 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 CLEO also observed some other non-DD-bar decay modes such as, … More works is being done…… PRL96(2005)082004

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

Near DD-bar production threshold region π–π– e+e+ e-e- D D K+K+ π–π– tag D+D+ D-D- π–π– e-e- e+e+ D D K+K+ Singly tagged D sample Absolute Measurements X+X+ X0X0 Throughout the talk, charge conjugation is implied Singly tagged D samples

Singly tagged D - modes: (a)K + π - π - ; (b) K 0 π - ; (c) K 0 K - ; (d) K + K - π - ; (e) K 0 π - π - π + ; (f) K + π - π - π 0 ; (g) K 0 π - π 0 ;(h) K + π - π - π - π + ; (i) π - π - π + ; (j) Sum Singly tagged D 0 modes: (a)K + π - ; (b) K + π - π - π + ; (c) K 0 π - π + ; (d) K + π - π 0 N D - Tag =5321±125±160N D 0 Tag =7584±198±241 Singly tagged D samples Mass[mKn π ]

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

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

CKM matrix elments Form factors PLB597(2004)39 BESII(%)CLEO(%) 3.83±0.40± ±0.10± ±0.13± ±0.025±0.008 PRL95(2005)181802

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

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

Candidates for Mass[mKn] Mass[K π ] Branching fractions Decay modesBESMARKIIIPDG04 support smaller ratio of D to V/P semileptonic decay of D mesons EPJC47(2006)31

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

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

E CM [GeV] σ obs had (nb) σ 0 had (nb) R PRL in press, hep/ Obtaining by fitting to the R values measured by BES in the range from 2.0 to 3.0 GeV PLB641(2006)145, hep-ex/

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

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

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, to identified DD-bar pair tagged one D meson tagged another D π+π+ π+π+ Double tag method K+K+ π - - K+K+ π+π+ Absolute measurement, does not depend on branching fractions of D meson decays  of data DD cross section

An absolute measurement NPB727(2005)395 D 0 D 0 (nb)D + D - (nb)DD(nb) BES single 3.58±0.09± ±0.08± ±0.12±0.50 BES double 3.47±0.32± ±0.33± ±0.46±0.35 MARKIII 2.90±0.25± ±0.30± ±0.39±0.34 CLEO Comparison of observed cross sections

Radiative correction factor Obtained from analysis of R Determination of Some systematic uncertainties can be canceled out Radiative correction factor obtained based on new  (3770) resonance parameters measured by BES-II, hep/ BF[  (3770) → D 0 D 0,D + D -,DD and non-DD] PLB641(2006)145, hep-ex/

Measurement of branching fractions for and 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.  Cross section scan experiment 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 

When scan over GeV Just before the scan experiment Mass [MeV] PDG04 BEPC BEPC energy calibration E BEPC is the energy of BEPC set in the experiment, E true is the true energy

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

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

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

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

Experiment MARK-I DELCO MARK-II PDG06 BES-II Comparison of  (3770) resonance parameters PRL in press, hep/

Comparison of  (3686) Resonance Parameters Experiment This measurement BES-II published (PLB550(2002)24) PDG2006 The measured partial width is consistent with PDG06 partial width of  (3686). PRL in press, hep/

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

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

Summary  BES measured the branching frations for inclusive non-DDbar decays of  (3770) using two different data sample and two different methods These are first measurements. 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. Thank You ！