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Nachweis von B 0 s -Oszillationen mit dem ATLAS Detektor am LHC

Nachweis von B 0 s -Oszillationen mit dem ATLAS Detektor am LHC. ÖPG -Jahrestagung Wien, 28. 9. 2005. B. Epp 1 , V.M. Ghete 2 , E. Kneringer 1 , D. Kuhn 1 , A. Nairz 3 1 Institut f ü r Experimentalphysik, Universit ä t Innsbruck 2 jetzt: Institut f ü r Hochenergiephysik, Ö AW, Wien

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Nachweis von B 0 s -Oszillationen mit dem ATLAS Detektor am LHC

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  1. Nachweis von B0s-Oszillationen mit dem ATLAS Detektor am LHC ÖPG-JahrestagungWien, 28. 9. 2005 B. Epp1, V.M. Ghete2, E. Kneringer1, D. Kuhn1, A. Nairz3 1Institut für Experimentalphysik, Universität Innsbruck 2jetzt: Institut für Hochenergiephysik, ÖAW, Wien 3jetzt: CERN, Genf

  2. Übersicht über den Vortrag • Einführung • ATLAS Detektor • Theorie, Motivation • Hauptteil • Analyse • Genauigkeit experimenteller Messgrössen • Masse, Zerfallseigenzeit • Monte-Carlo Programm • Amplituden-Scan/Fit • Sensitivität der Analyse • Ausblick • aktuelle Experimente • CDF, D0

  3. ATLAS installation schedule

  4. ATLAS cavern (Sept. 26, 2005) Barrel Toroid

  5. Accuracy on |Vtd| is limited to ~15 %due to theoretical uncertainties. Can determine |Vts|/|Vtd| with ~5 % theoretical uncertainty.

  6. Due to the size of the CKM matrix elements: Dms >> Dmd

  7. Data Challenge 1 software chain

  8. Bs0 Ds + –  • Fully reconstruct Bs decay How to know if an oscillation occurred? _ • Tag Bs or Bs at production and decay • production • sign of lepton of decay of (non oscillating) B-hadron in opposite hemisphere (level 1 trigger ): B– –  Bs0 • decay • sign of D-meson: Bs0 Ds–

  9. Ideal oscillation

  10. Oscillation in an experiment ms = 14 ps–1 resolution of t is very important

  11. Oscillation? ms = 24 ps–1

  12. d = ct ,  = p/m proper time resolution

  13. Oscillation signal significance ?

  14. Extracting information on ms from data • How to extract the oscillation frequency ms from the measurements • Max. Likelihood method (for parameter estimation) • was found to have several disadvantages • needs lots of MC • sensitivity of analysis not easy to define or estimate • combination of several analyses is difficult • ln L w.r.t. minimum or infinity? (different results) • Amplitude method • invented by H.G. Moser from ALEPH 1 + 1cos (mst)  1 + Acos (mst)

  15. A limit may be placed in regions of mswhere amplitudes of unityare excluded (at 95% C.L.).

  16. md – measurement: CDF@Tevatron At each value of msin the interesting rangean amplitude is measured, where an amplitude of unity indicates a successful observation of oscillation with that frequency.

  17. CDF: ms – Semileptonic Channel

  18. CDF: ms – Hadronic Channel

  19. ms: CDF + World Combined

  20. Conclusions • Clean measurement of ms serves as input to fit Bs0  J/  • determination of s (among other parameters) • Already with 10 fb–1 Atlas is capable to achieve the sensitivity that is obtained by the SM-fit to all available data today • The analysis is also sensitive in the SUSY regime

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