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Recent Results on  (3770) Physics at BES

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. Outline. . Introduction. . Measurements about  (3770) non-DD. .

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Recent Results on  (3770) Physics at BES

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

  2. Outline  Introduction  Measurements about (3770)non-DD  Anomalous line-shape of se+e-hadrons in energy region from 3.65 to 3.87 GeV  Measurement of sD+D-(s)/sD0D0(s)  Summary

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

  4. Introduction Data Samples BESII (3770) data sample • 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

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

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

  7. Anomalous line-shape PRL101 (2008) 102004 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  Solution 1: two amplitudes, no interference  Solution 2: two amplitudes, complete interference  Solution 3: y(3770) amplitude + G(3900), interference Babar PRD76 (2007) 111105(R); Belle PRD77 (2008) 011103(R)  Comparison: one y(3770) amplitude hypothesis

  8. Anomalous line-shape PRL101 (2008) 102004 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 y(3770) hypothesis; Circles with error bars in red are the measured net cross sections after subtracting J/y, y(3686) and continuum contribution. The blue line shows the fits

  9. Anomalous line-shape PRL101 (2008) 102004 Solution 2: two amplitudes, complete 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 y(3770) hypothesis; Circles with error bars in red are the measured net cross sections after subtracting J/y, y(3686) and continuum contribution. The blue line shows the fits

  10. Anomalous line-shape PRL101 (2008) 102004 Solution 3: y(3770) amplitude + G(3900), interference Red line: Solution 3 Blue line: one y(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 y(3770) amplitude to the error of the observed cross section

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

  12. Measurement of sD+D-(s)/sD0D0(s) Numbers of events and Detection efficiencies PLB668 (2008) 263

  13. Measurement of sD+D-(s)/sD0D0(s) Cross section for DD production PLB668 (2008) 263 sDD [nb] sD+D-(s)/sD0D0(s)

  14. Summary  Systematic study about B[(3770)non-DD]  Anomalous lineshape of se+e-hadrons(s) in energy region from 3.65 to 3.87 GeV  Measurement of sD+D-(s)/sD0D0(s) in energy region from 3.74 to 3.80 GeV

  15. Thank You !

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