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Veröffentlicht von:Lothar Kranz Geändert vor über 8 Jahren
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Nachweis von B 0 s -Oszillationen mit dem ATLAS Detektor am LHC B. Epp 1, V.M. Ghete 2, E. Kneringer 1, D. Kuhn 1, A. Nairz 3 1 Institut für Experimentalphysik, Universität Innsbruck 2 jetzt: Institut für Hochenergiephysik, ÖAW, Wien 3 jetzt: CERN, Genf ÖPG-Jahrestagung Wien, 28. 9. 2005
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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
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3 ATLAS installation schedule
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4 ATLAS cavern (Sept. 26, 2005) Barrel Toroid
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5 Accuracy on |V td | is limited to ~15 % due to theoretical uncertainties. Can determine |V ts |/|V td | with ~5 % theoretical uncertainty.
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6 Due to the size of the CKM matrix elements: m s >> m d
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7 CKM Matrix
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8 Data Challenge 1 software chain
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9 B s 0 D s + Fully reconstruct B s decay – Tag B s or B s at production and decay production sign of lepton of decay of (non oscillating) B-hadron in opposite hemisphere (level 1 trigger ): B – – B s 0 decay sign of D-meson: B s 0 D s – _ How to know if an oscillation occurred?
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10 Ideal oscillation
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11 Oscillation in an experiment m s = 14 ps –1 resolution of t is very important
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12 Oscillation? m s = 24 ps –1
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14 d = c t, = p/m proper time resolution
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15 Oscillation signal significance ?
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16 Extracting information on m s from data How to extract the oscillation frequency m s 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 ( m s t) 1 + A cos ( m s t)
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20 A limit may be placed in regions of m s where amplitudes of unity are excluded (at 95% C.L.).
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21 m d – measurement: CDF@Tevatron At each value of m s in the interesting range an amplitude is measured, where an amplitude of unity indicates a successful observation of oscillation with that frequency.
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24 CDF: m s – Semileptonic Channel
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25 CDF: m s – Hadronic Channel
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26 m s : CDF + World Combined
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27 Conclusions Clean measurement of m s serves as input to fit B s 0 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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