Title: Nachweis von B0sOszillationen mit dem ATLAS Detektor am LHC
1Nachweis 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
2Übersicht 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
3ATLAS installation schedule
4ATLAS cavern (Sept. 26, 2005)
Barrel Toroid
5Accuracy on Vtd is limited to 15 due to
theoretical uncertainties.
Can determine Vts/Vtd with 5 theoretical
uncertainty.
6Due to the size of the CKM matrix elements Dms
gtgt Dmd
7CKM Matrix
8Data Challenge 1
software chain
9Bs0 ? 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
10Ideal oscillation
11Oscillation in an experiment
?ms 14 ps1
resolution of t is very important
12Oscillation?
?ms 24 ps1
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14d c????t , ?? p/m
proper time resolution
15Oscillation signal significance
?
16Extracting 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)
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20A limit may be placed in regions of ?ms where
amplitudes of unityare excluded (at 95 C.L.).
21?md measurement CDF_at_Tevatron
At each value of ?ms in the interesting rangean
amplitude is measured, where an amplitude of
unity indicates a successful observation of
oscillation with that frequency.
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24CDF ?ms Semileptonic Channel
25CDF ?ms Hadronic Channel
26?ms CDF World Combined
27Conclusions
- Clean measurement of ?ms serves as input to fit
Bs0 ? J/? ? - determination of ??s (among other parameters)
- Already with 10 fb1 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