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First Events from BELLE

First Events from BELLE. Daniel Marlow Princeton University for the Belle Collaboration 200 People 50 Institutions 10 Countries. Physics Motivation.

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First Events from BELLE

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  1. First Events from BELLE Daniel Marlow Princeton University for the Belle Collaboration 200 People 50 Institutions 10 Countries XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  2. Physics Motivation Our goal is to measure the phases of the KM mixing matrix elements by observing interference between direct and mixing-induced decays of the form where f is a CP eigenstate, e.g., XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  3. The KEK-B Asymmetric Collider KEK-B is similar to PEP-II in many ways, although there is a (potentially) important difference in the way in which the beams are brought into collision. XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  4. Beam Crossing Schemes By colliding the beams at an angle, the KEK-B design achieves a simplified interaction region. Moreover, every RF bucket (2 ns spacing) can be filled to achieve maximum luminosity. However, this approach risks destabilizing couplings between transverse and longitudinal modes of the machines. A crab-crossing cavity is under development in case this proves to be a problem. XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  5. Linac Parameters XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  6. Ring Parameters XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  7. Motivation for Detector Parameters • Vertex Measurement • Need to measure decay vertices to <50m to get proper time distribution. • Tracking… • Would like p/p.5% to help distinguish B decays from BK and BKK decays. • Provide dE/dx for particle ID. • EM calorimetry • Detect g’s from slow, asymmetric p0’s  need efficiency down to 20 MeV. • Hadronic Calorimetry • Tag muons. • Tag direction of KL’s from decay BKL . • Particle ID • Tag strangeness to distinguish B decays from Bbar decays (low p). • Tag ’s to distinguish B decays from BK and BKK decays (high p). XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  8. Particle ID needs XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  9. XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  10. Key Belle Milestones • Early 1990’s - Japanese groups begin working. • January 1994 - Collaboration forms. • April 1995 - TDR Submitted. …lots of work by lots of people in lots of places... • Dec 18, 1998 - Belle detector completed (including SVD) • Jan 26, 1999 - First cosmic ray with full detector. • May 1, 1999 - Belle rolled into place. • June 1, 1999 - First hadronic event!!!!! • June 1999 About 1200 hadron events obtained before vacuum pipe mishap. XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  11. June 1, 1999: Our First Hadronic Event XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  12. More Fun: SVD Included XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  13. First J/y Candidate • J/yee • M(ee) = 3.1 GeV XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  14. SVD Performance XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  15. SVD Tomography X-Z distribution of primary vertices for all triggers, including beam gas. The IP, the beam crossing angle, and various flanges etc in the IR are clearly evident. XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  16. CDC Performance (Cosmic Rays) XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  17. CDC Performance Hadronic sampled di-pion invariant mass. Close to MC value XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  18. ACC Efficiency XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  19. CsI Performance XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  20. CsI Performance Hadronic sample XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  21. More CsI XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  22. KLM Performance XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  23. Detection XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  24. We observed a dimuon event • J/y • M() = 3.1 GeV • both muons tracks clearly evident in magnet return yoke • This events is consistent with • although there were no hits in the RPCs XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  25. Truth in Advertising • CDC backgrounds higher than expected • Wire currents somewhat high • Crosstalk raises effective occupancy • Problem under study, one option is to reduce Q/T converter ramp-down time • Significant beampipe heating observed • adding cooling in short term • smooth HOM-inducing discontinuity on inside of beampipe in longer term XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  26. Conclusions & Outlook • The KEK-B accelerator is working. • The entire Belle detector, including the DAQ and offline reconstruction software, is working. • We face daunting challenges in terms of increasing the luminosity while keeping the backgrounds under control. • The months ahead should be interesting! XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

  27. Run Plan XIth Rencontres de Blois on Frontiers of Matter, July 1, 1999

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