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First Steps in Radiative Return Studies at Belle: Exploring Particle Interactions

This study at Belle focuses on radiative return physics with charged particle events. Comparison to VEPP-2000 project and the importance of new Bhabha trigger implementation for improved efficiency are discussed.

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First Steps in Radiative Return Studies at Belle: Exploring Particle Interactions

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  1. First steps to radiative return studies at Belle B.A.Shwartz BINP, Novosibirsk TAU-04, NARA

  2. Plan This is our first steps to see what can be done at Belle for radiative return physics. The events with 2 charged particles were studied • Basic things • A sample for first study • What’s seen for: gmm, gpp, gKK and gp pp0 TAU-04, NARA

  3. e+e   0 1 30 TAU-04, NARA

  4. Comparison to VEPP-2000 project, ee up to 2 GeV (under construction at BINP) TAU-04, NARA

  5. A sample to study • The Tau-pair sample (skim) is used ( 2<Ntrk<8, Pch<9GeV, Eecl<9GeV) • Then the following cuts were applied: • Ntrk=2 • 10<Erec<11　GeV • Ptot <0.5 GeV • Ng>0 • Egmax>3 GeV • 0.7<<2.6 • Pmin >0.7 GeV (charged) 25.9 fb-1 is used study TAU-04, NARA

  6. Ptot Pg Erec Minv Eg2<0.2 (for 2 particles modes) TAU-04, NARA

  7. Two particle events All events  , (p1m/p, p2m/p >0.5) Minv(2tr), GeV Minv(2tr), GeV TAU-04, NARA

  8.   calculation   background TAU-04, NARA

  9. Npp/Nmm ratio By a simple separation procedure the number of pp and mm events are obtained and ratio is calculated (just demonstration, not for usage!) The difference 5% can be caused by the different trigger efficiency for pion and muon events. This is a measure of systematics. TAU-04, NARA

  10. How to compare with BaBar? N=183093 M =31061 MeV =16.30.9 MeV 71 J/ per 1 fb-1 From BaBar J/  paper – 7800 J/  event at 88.4 fb-1  88.2 J/  per 1 fb-1 TAU-04, NARA

  11. 0 KK ECM – (｜pgmax ｜+｜p+ ｜+p ｜)>1 GeV TAU-04, NARA

  12. Conclusion • Events with radiative return can be seen at Belle with reasonable efficiency. • New Bhabha trigger implementation should improve the trigger efficiency at low invariant mass area TAU-04, NARA

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