Measurement of Bs &rarr &Phi &Phi Branching Ratio with 2.9 fb-1 data
Primary authors: Benedetto di Ruzza, Mirco Dorigo, Lorenzo Ortolan,
Marco Rescigno, Anna Maria Zanetti, Giacomo Artoni
This web page summarizes the results of the ratio of the BR(Bs0 &rarr &Phi &Phi) to the BR(Bs0 &rarr J/&psi &Phi). The measurement is done with 2.9 fb-1 of Two Track Trigger data.
The results have been approved by B Group Meeting as of June 19, 2009.
A more detailed description of the results can be found:
- Cdf Public Note 10064 here
The analysis
The measurement consists in the evaluation of this ratio:
where:
- N&Phi &Phi: number of Bs &rarr &Phi &Phi events;
- NJ/&psi &Phi: number of Bs &rarr J/&psi &Phi events;
- &epsilon(Bs &rarr &Phi &Phi): efficiency of Bs &rarr &Phi &Phi evaluated with Monte Carlo;
- &epsilon(Bs &rarr J/&psi &Phi): efficiency of Bs &rarr J/&psi &Phi evaluated with Monte Carlo;
- &epsilon&mu: muon efficiency.
The optimized cuts for the two signals are summarized in the following table:
The signal yields are shown in the figures:
The final result of the ratio is:
from which, using the Branching Ratio of Bs &rarr J/&psi &phi, modified according
to the updated measurements of the ratio of production cross section of Bs and Bd
mesons, we have:
BR(Bs &rarr &Phi &Phi) = [2.40 ± 0.21(stat) ± 0.27(syst) ± 0.82(BR)] 10 &minus 5
where the last error is due to the uncertainty in the Bs &rarr J/&psi &Phi Branching Ratio.
The blessed figures are:
- KKKK invariant mass after reconstruction and trigger confirmation only .eps .gif
-
- Sideband subtracted signal, Monte Carlo simulation and Bs mass sidebands for the following observables:
- fit vertex &Chi2xy in the plane transverse to the beam. .eps .gif
- Lxy, transverse decay length of Bs candidates. .eps .gif
- d0, Reconstructed impact parameter with respect the primary vertex of Bs candidates. .eps .gif
-
- d0&Phimax, reconstructed impact parameter for the highest momentum &Phi . .eps .gif
-
- PTKmin, minimum transverse momentum among the 4 kaons in the Bs candidates decays. .eps .gif
- d0&Phimin, reconstructed impact parameter for the lowest momentum &Phi . .eps .gif
-
- Bs &rarr &Phi &Phi signal yield .jpg .eps .pdf
- Bs &rarr J/&psi &Phi signal yield .jpg .eps .pdf
- Bs &rarr J/&psi &Phi signal yield exclusively triggered by dispaced track trigger. .jpg .eps .pdf
- CMX muon efficiency .jpg .eps .pdf
- CMP muon efficiency .jpg .eps .pdf
- Invariant Mass for the highest momentum K+K- pairs for Bs &arr &Phi &Phi candidates. .eps .gif
- Invariant Mass for the lowest momentum K+K- pairs for Bs &arr &Phi &Phi candidates. .eps .gif
- Sideband subtracted K+K- pair mass (two entries for candidates). .eps .gif
Theory Prediction
- B. Souza de Paula, Y. Xie; LHCb's sensitivity to New CP Violating Phases in the decay Bs &rarr &Phi &Phi, LHCb public Note.
