1. Recent Results on  (3770) Physics at BES Ming-gang Zhao (For BES Collaboration) The 44 th Rencontres de Moriond, QCD and High Energy Interactions March 14-21, 2009, La Thuile, Italy

2.   Introduction Summary Measurements about  (3770)  non-DD Outline Anomalous line-shape of  e+e-  hadrons in energy region from 3.65 to 3.87 GeV   Measurement of  D+D- (s)/  D0D0 (s) 

3. Introduction Only exist one resonance:  (3770) Long standing  (3770) decay puzzle Knowledge about 3.70~3.87 GeV region [before BES-II and CLEO-c results] Theory prediction: nearly 100% DD decay Experiment measurement: unsaturation (nearly 40%) of  (3770) production and decay

4. Introduction  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 [pb -1 ] World  (3770) Samples  about 8 pb -1 data taken from 3.665 to 3.878 GeV  about 1 pb -1 data taken at 3.665 GeV BESII  (3770) data sample Data Samples  about 6.5 pb -1 data taken at 3.650 GeV

5. Several different methods and data samples ， and systematical studies on B[  (3770)→non-DD]. All first time measurements. Measurements about  (3770)  non-DD PDG 2008 PRD76, 122002PLB659, 74PRL97, 121801PLB641, 145

6. Anomalous line-shape high-energy sidelow-energy side One simple  (3770) resonance hypothesis is quite questionable to fit the current data. initial state radiation DD production threshold the energy dependence of the D D scattering amplitudes due to the Blatt-Weisskopt barrier    high energy slope steep than low energy slope low energy slope steep than high energy slope Two data sets taken in March and December 2003

7. Anomalous line-shape Solution 1: two amplitudes, no interference  Solution 2: two amplitudes, complete interference  Comparison: one  (3770) amplitude hypothesis  Solution 3:  (3770) amplitude + G(3900), interference  The expected cross section for e ＋ e －  hadrons: Rs(3770) means the full structure around 3.773 GeV, we use one or two pure P wave Breit-Wigner amplitude(s) with energy dependent to express Babar PRD76 (2007) 111105(R); Belle PRD77 (2008) 011103(R) PRL101 (2008) 102004

8. Anomalous line-shape Solution 1: two amplitudes, no interference Circles with error bars in black are the observed cross section; Red line: fitted values of cross section; Green line: the fit with one  (3770) hypothesis; Circles with error bars in red are the measured net cross sections after subtracting J/  and continuum contribution. The blue line shows the fits PRL101 (2008) 102004

9. Anomalous line-shape Circles with error bars in black are the observed cross section; Red line: fitted values of cross section; Green line: the fit with one  (3770) hypothesis; Circles with error bars in red are the measured net cross sections after subtracting J/  and continuum contribution. The blue line shows the fits Solution 2: two amplitudes, complete interference PRL101 (2008) 102004

10. Anomalous line-shape Solution 3:  (3770) amplitude + G(3900), interference Red line: Solution 3 Blue line: one  (3770) Yellow line: Solution 1 Green line: Solution 2 The ratio of the residual between the observed cross section and the fitted value for one  (3770) amplitude to the error of the observed cross section PRL101 (2008) 102004

11. Anomalous line-shape 2. Significance of the interference between the two amplitudes is 3.6  1. Significance of the two amplitudes is more than 7  3. 4. Solution with two amplitudes +G(3900) gives almost the same results with Solution 2 The hypothesis of  (3770) amplitude +G(3900) and interference does not significantly improve the fit from the one  (3770) amplitude hypothesis PRL101 (2008) 102004

12. Numbers of events and Detection efficiencies Measurement of  D+D- (s)/  D0D0 (s) PLB668 (2008) 263

13.  DD [nb] Measurement of  D+D- (s)/  D0D0 (s)  D+D- (s)/  D0D0 (s) PLB668 (2008) 263 Cross section for DD production

14. Summary Anomalous lineshape of  e+e-  hadrons (s) in energy region from 3.65 to 3.87 GeV  Measurement of  D+D- (s)/  D0D0 (s) in energy region from 3.74 to 3.80 GeV   Systematic study about B[  (3770)  non-DD]

15. Thank You !