Observation of Bs Oscillations

Observation of B_s - B_s Oscillations

We report the observation of B_s - B_s oscillations from a time-dependent measurement of the B_s - B_s oscillation frequency Δm_s. Using a data sample of 1 fb^-1 of pp collisions at sqrt(s) = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron, we find signals of 5600 full reconstructed hadronic B_s decays, 3100 partially reconstructed hadronic B_s decays, and 61500 partially reconstructed semileptonic B_s decays. We measure the probability as a function or proper decay time the that B_s decays with the same, or opposite, flavor as the flavor at production, and we find a signal for B_s - B_s oscillations. The probability that random fluctuations could produce a comparable signal is 8x10^-8, which exceeds 5σ significance. The results are as follows:

Δm_s

= 17.77

± 0.10(stat)

± 0.07(sys)

|V_td|

|V_ts|

= 0.2060

± 0.0007(exp)

+0.0081
- 0.0060

(theor)

This result has been published in PRL: PRL 97, 242003 2006.
This result supersedes the previous measurement set using 1 fb^-1: PRL 97, 062003 2006.

Figures

Below are eps and gif versions of the most interesting figures.

Hadronic decay modes

Figure 1: gif - eps : Mass Projection Bs &rarr Ds(3)&pi
Figure 2: gif - eps : Mass Projection Bs &rarr Ds &pi with Ds &rarr &phi&pi
Figure 3: gif - eps : Mass Projection Bs &rarr Ds &pi with Ds &rarr K*K
Figure 4: gif - eps : Mass Projection Bs &rarr Ds &pi with Ds &rarr 3&pi
Figure 5: gif - eps : Mass Projection Bs &rarr Ds 3&pi with Ds &rarr &phi&pi
Figure 6: gif - eps : Mass Projection Bs &rarr Ds 3&pi with Ds &rarr K*K
Figure 7: gif - eps : Mass Projection Bs &rarr Ds 3&pi with Ds &rarr 3&pi(new mode)
Figure 9: gif - eps : ct Projection Bs &rarr Ds &pi with Ds &rarr &phi&pi
Figure 9: gif - eps : ct Projection Bs &rarr Ds &pi with Ds &rarr K*K
Figure 10: gif - eps : ct Projection Bs &rarr Ds &pi with Ds &rarr 3&pi
Figure 11: gif - eps : ct Projection Bs &rarr Ds 3&pi with Ds &rarr &phi&pi
Figure 12: gif - eps : ct Projection Bs &rarr Ds 3&pi with Ds &rarr K*K
Figure 13: gif - eps : ct Projection Bs &rarr Ds 3&pi with Ds &rarr 3&pi
Figure 14: gif - eps : Illustrative plots of the improvement from NN based selection

Semileptonic decay modes

Figure 15: gif - eps : Ds Mass from Bs &rarr Ds l &nu X, Ds &rarr &phi&pi decays
Figure 16: gif - eps : Ds Mass from Bs &rarr Ds l &nu X, Ds &rarr K*K decays
Figure 17: gif - eps : Ds Mass from Bs &rarr Ds l &nu X, Ds &rarr 3&pi decays
Figure 18: gif - eps : l Ds Mass from Bs &rarr Ds l &nu X, Ds &rarr &phi&pi decays
Figure 19: gif - eps : l Ds Mass from Bs &rarr Ds l &nu X, Ds &rarr K*K decays
Figure 20: gif - eps : l Ds Mass from Bs &rarr Ds l &nu X, Ds &rarr 3&pi decays
Figure 21: gif - eps : Combined D and l Ds Mass from Bs &rarr Ds l &nu X, Ds &rarr &phi&pi decays
Figure 22: gif - eps : Combined D and l Ds Mass from Bs &rarr Ds l &nu X, Ds &rarr K*K decays
Figure 23: gif - eps : Combined D and l Ds Mass from Bs &rarr Ds l &nu X, Ds &rarr 3&pi decays
Figure 24: gif - eps : ct Projection Mass from Bs &rarr Ds l &nu X, Ds &rarr &phi&pi decays
Figure 25: gif - eps : ct Projection Mass from Bs &rarr Ds l &nu X, Ds &rarr K*K decays
Figure 26: gif - eps : ct Projection from Bs &rarr Ds l &nu X, Ds &rarr 3&pi decays
Figure 27: gif - eps : ct distribution(TTT trigger where lepton is SVT Track)
Figure 28: gif - eps : ct distribution(TTT trigger where lepton is not SVT Track)
Figure 29: gif - eps : ct distributions(Lepton + SVT track trigger)

ct resolution

Figure 30: gif - eps : Hadronic decay modes ct resolution
Figure 31: gif - eps : Semileptonic decay modes ct resolution
Figure 32: gif - eps : Semileptonic and partially reconstructed decay mode K factors
Figure 33: gif - eps : Semileptonic and partially reconstructed decay mode ct resolutions vs. K factor
Figure 34: gif - eps : ct resolution calibration sample

Amplitude Scans

Figure 35: gif - eps : Combined amplitude scan
Figure 36: gif - eps : Combined amplitude scan(statistical errors only)
Figure 37: gif - eps : Amplitude scan: Golden Mode
Figure 38: gif - eps : Amplitude scan: Other Hadronic Modes
Figure 39: gif - eps : Amplitude scan: Partially Reconstructed Hadronic Modes
Figure 40: gif - eps : Amplitude scan: Semileptonic Modes
Figure 41: gif - eps : Amplitude scan: OST Tags Only
Figure 42: gif - eps : Amplitude scan: SST Tags Only
Figure 43: gif - eps : Amplitude scan on combinatorial background
Figure 44: gif - eps : Systematic uncertainties for the hadronic decays modes
Figure 45: gif - eps : Systematic uncertainties for the semileptonic decays modes
Figure 46: gif - eps : Systematic and statistical uncertainties for the semileptonic decays modes

Likelihood Plots

Figure 47: gif - eps : Wide range likelihood plot
Figure 48: gif - eps : Wide range likelihood plot with no signal and signal hypothesis lines
Figure 49: gif - eps : Narrow range likelihood plot
Figure 49: gif - eps : Narrow range likelihood plot: Hadronic decay modes
Figure 50: gif - eps : Plot of signal vs. fluctuation toys
Figure 51: gif - eps : Plot of signal vs. fluctuation toys with expected signal distribution
Figure 52: gif - eps : Log Scale plot of signal vs. fluctuation toys

Oscillation Plots

Figure 53: gif - eps Time domain oscillation plot
Figure 54: gif - eps Time domain oscillation plot: Modulo frequency 16
Figure 55: gif - eps Time domain oscillation plot: Modulo frequency 21
Figure 56: gif - eps Time domain oscillation plot from the B_d OST calibration analysis

Bonus Event Display

Figure 56: gif - eps Example golden event with muon tag

Technical measurements

Experimental Status

Below is a comparison of this result to other relevant experimental work:

2005 World average limit

m_s

^-1

D0 PRL 97, 021802 (2006)

m_s

^-1

Belle PRL 96, 221601 (2006)

b &rarr d&gamma

_td

_ts

CKMFitter

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