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Investigation of Charm Production and Annihilation at 4 GeV

This study explores the region of interest in charm production and annihilation around 4 GeV, focusing on cross sections and multi-body production. Data from the CLEO Collaboration and simulations are used to analyze the charm states and their contributions. The inclusive cross sections and radiative corrections are also considered.

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Investigation of Charm Production and Annihilation at 4 GeV

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  1. Charm – Production in e+e- Annihilation around 4 GeV Brian Lang University of Minnesota on behalf of the CLEO Collaboration Charm 2007 Cornell University, August 5th-8th 2007

  2. Region of Interest The region which is being investigated. Fit to Continuum Cross section as a function of Ecm from the 2005 PDG Brian Lang University of Minnesota and the CLEO Collaboration

  3. Why investigate this region: • The cross sections to DD, D*D, and D*D* are not well known at the energies of interest. • The only previous measurements of Ds yields in this region: • BES measured the production cross section times branching ratio to fp at 4030 MeV as 11.2 pb, due to DsDs. • Mark III measured the production cross section times branching ratio to fp at 4140 MeV as 26 pb, production is largely DsDs*. • Optimal Ecm for Ds decay physics: balance of total production against event complexity. • Test of theoretical predictions from Eichten et al in 1980 Phys. Rev. D21 203 • Coupling of open charm channels to cc states Brian Lang University of Minnesota and the CLEO Collaboration

  4. Using the scan data which was collected between Aug. and Oct. of 2005. At each energy the data sample was sufficient to determine the cross sections for all expected charm states. Total integrated Luminosity Scan (12 energy points) ~ 60 pb-1 4170 MeV ~ 180 pb-1 Data Sample from CLEO Scan Brian Lang University of Minnesota and the CLEO Collaboration

  5. MbcMD and E0 for DD Cross Sections MC Simulation ECM=4160 MeV • Do not reconstruct D* since the momentum, in terms of Mbc, indicates event type Brian Lang University of Minnesota and the CLEO Collaboration

  6. Multi-Body Production PRELIMINARY • There is no reason why, for example, there can not exist multi-body events like e+e-DD*p or any other allowed combination of D-mesons and pions. • First, are there events outside our two-body D(s)(*)D(s)(*) exclusive event categories? Yes! Ecm=4170 MeV • Assuming only two body kinematics, NO D0 mesons with a momenta below ~350 MeV. • Data shows a clear D0 peak in the mass distribution for K-p+ candidates with momenta below 250 MeV. PD < 250 MeV Brian Lang University of Minnesota and the CLEO Collaboration

  7. Momentum Spectrum of D0 at 4170 MeV • D0K-p+ momentum spectrum after sideband subtraction D0 D*D* D*D PRELIMINARY DD What populates this region? Brian Lang University of Minnesota and the CLEO Collaboration

  8. Ecm = 4170 MeV Multi-Body Production PD* < 400 MeV X p- e+ e- Combining a D* and a p- D+* p0 D+ PRELIMINARY PD < 250 MeV X p+ Combining a D and a p+ e+ e- D0 Brian Lang University of Minnesota and the CLEO Collaboration

  9. Multi-Body Production Ecm = 4260 MeV PRELIMINARY X p+ PD* < 400 MeV e+ e- Combining a D* and a p+ D0* D0* p0 D0 Brian Lang University of Minnesota and the CLEO Collaboration

  10. Momentum Fits using MC • How do we get a handle on the multi-body contribution? • It is possible to estimate the contribution of multibody events by fitting the observed D momentum spectrum with MC predictions for the two-body processes and some representation of multi-body. Brian Lang University of Minnesota and the CLEO Collaboration

  11. Momentum Fits using MC Ecm = 4170 MeV ~ 180 pb-1 PRELIMINARY Only assuming D*Dp multi-bodyis present. D+K-p+p+Momentum Spectrum after sideband subtraction D0K-p+Momentum Spectrum after sideband subtraction D0 D+ D*D D*D* D*D D*D* DD DD D*Dp D*Dp Brian Lang University of Minnesota and the CLEO Collaboration

  12. Exclusive Cross Section Results • No theoretical predictions for multi-body. • No evidence of DDp in this region PRELIMINARY Brian Lang University of Minnesota and the CLEO Collaboration

  13. Check of the Total Charm Cross Section • One can perform an inclusive measurement as a cross check on the total charm cross section. • The invariant mass used to extract the yields. • Only using D0K-p+, D+K-p+p+ and the high yield mode of Ds+K+K-p+. • Also, one can count the number of hadronic events above the uds continuum background as an additional check to the total charm cross section. Brian Lang University of Minnesota and the CLEO Collaboration

  14. Comparison: Exclusive from Momentum Fits vs. Inclusive PRELIMINARY • Exclusive: Sum of the two-body charmed mesons and multi-body • Inclusive charm: D0 + D+ + Ds • Inclusive Hadrons: Excess over uds Includes multi-body Brian Lang University of Minnesota and the CLEO Collaboration

  15. Radiative Corrections PRELIMINARY • In order to compare the observed cross sections to theory and previous experiments the cross sections need to be corrected for the effects of initial-state radiation. • Using theoretical treatment of Kuraev and Fadin (Sov. J. Nucl. Phys. 41 466) and Crystal Ball R measurement R R = Ruds+Rcharm Ruds=2.29 0.03 m Brian Lang University of Minnesota and the CLEO Collaboration

  16. Inclusive Cross Section PRELIMINARY • These inclusive measurements can be compared to other experiments by the cross section times branching ratio for D0K-p+ and D+K-p+p+. CLEO-c CLEO-c Brian Lang University of Minnesota and the CLEO Collaboration

  17. Most noticeable difference in D*D* channel. Still reasonable qualitative agreement. Comparison with Updated Eichten et al. E. Eichten, International Workshop on Heavy Quarkonium (BNL 2006) and personal communication PRELIMINARY Brian Lang University of Minnesota and the CLEO Collaboration

  18. R is proportion to the cross section. Fit assumes only a single resonance. Introduction of another narrow resonance can explain the ‘dip’ in DD at 4015 MeV Near D*D* Threshold PRELIMINARY DD DsDs R1 R2 D*D* NO DD R4 R3 D*D Updating S. Dubynskiy and M.B. Voloshin’s results hep-ph/0608179 Brian Lang University of Minnesota and the CLEO Collaboration

  19. Comparison with the Belle Collaboration D*+D*- D*D* Phys. Rev. Lett. 98, 092001 (2007) D*+D- D*D PRELIMINARY DD DD P.Pakhlov, EPS-HEP 2007 Brian Lang University of Minnesota and the CLEO Collaboration

  20. Conclusions • Exclusive charm production above threshold have been measure. • s(DsDs) peaks at 4010 MeV • s(Ds*Ds) peaks at 4170 MeV and is used by CLEO-c for Ds decay studies • Interesting absence of DD at 4015 MeV (possibly a new resonance?) • These studies will lead to a better understanding of QCD Brian Lang University of Minnesota and the CLEO Collaboration

  21. Backup Slides Brian Lang University of Minnesota and the CLEO Collaboration

  22. Momentum Fits to Data Ecm = 4170 MeV ~ 180 pb-1 Ds+fp momentum spectrum after sideband subtraction Brian Lang University of Minnesota and the CLEO Collaboration

  23. Comparison with the BaBar Collaboration DD Brian Lang University of Minnesota and the CLEO Collaboration

  24. Theoretical Predictions • Determined partial widths at two ECM energies. Partial widths in units of MeV hep-ph/0412057 Brian Lang University of Minnesota and the CLEO Collaboration

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