An Updated Measurement of the CP Violating Phase beta

Primary Authors: F. Azfar, J. Boudreau, N. Bousson, M. Feindt, J.P. Fernandez, K. Gibson, G.Giurgiu, G. Gomez- Ceballos, T. Kuhr, M. Kreps, L. Oakes, J. Morlock, M. Paulini, E. Pueschel, A.Schmidt

Introduction

This webpage summarizes the CDF preliminary result updating the flavor-tagged determination of CP violation in B_s → J/ψ φ decays corresponding to 5.2 fb^-1 data. In addition to doubling the previous sample size, several improvements have been made to the analysis. These include fully incorporating potential contamination of the B_s → J/ψ φ signal by B_s → J/ψ KK or B_s → J/ψ f₀(980) (where the non-resonant KK and f₀(980) are S-wave states) into the likelihood fit, improvements to the NN selection and optimization, and full calibration of particle ID and flavour tagging. This analysis uses the updated and recalibrated Same Side Kaon Tagger.

This result is described in this public note
This result was first presented at FPCP2010, the slides are here
The slides from the Fermilab Wine and Cheese talk for this update are here

See also the previous results at First Flavor-Tagged Determination of Bounds on CP Violation in B_s → J/ψ φ Decays with L = 1.3 fb^-1 published in PRL 100, 161802 (2008)
and Updated measurement of CP violating phase β_s^{J/ψ φ} with 2.8 fb^-1

Results

We present 68% and 95% confidence regions in the β_s-ΔΓ plane:

Assuming the standard model predictions of β_s and ΔΓ, the probability of a deviation as large as the level of the observed data is 44%, corresponding to 0.8 σ .

Additionally we present a confidence interval in β_s, where ΔΓ is treated as a nuisance parameter, and find that β_s is within [0.02,0.52] U [1.08,1.55] at the 68% CL and within [-π/2, -1.44] U [-0.13, 0.68] U [0.89, π/2] at the 95% CL.

Assuming no CP violation (β_s^{J/ψ φ} = 0), we also measure the mean lifetime,the decay width difference, the transversity amplitudes and the strong phase φ_⊥ :

cτ_s = 458.6 ± 7.6 (stat) ± 3.6 (syst) μm
ΔΓ_s = 0.075 ± 0.035 (stat) ± 0.01 (syst) ps^-1
|A_||(0)|² = 0.231 ± 0.014 (stat) ± 0.015 (syst)
|A₀(0)|² = 0.524 ± 0.013 (stat) ± 0.015 (syst).
φ_⊥ = 2.95 ± 0.64 (stat) ± 0.07 (syst)

These results give the world's most precise single measurement of the B_s lifetime and decay width difference. We find the S-wave contamination of the signal φ meson to be < 6.7% at the 95% CL

The likelihood

We provide the information for use of the CDF 35-dimensional likelihood in global fits and combinations in two formats. One is a statistics consisting in coverage-corrected profile-likelihood ratios as a function of β_s and ΔΓ in which the likelihood has been profiled over the other 33 parameters. The other is the full multidimensional likelihood function, as a function implemented on a server, and its representation as a Markov chain in a root file. Instructions on how to use this information are here

Figures

Below are all figures meant for download.

Likelihood contours

(eps), (gif): 2D β_s - ΔΓ likelihood profile with full coverage adjustment
(eps), (gif): 1D β_s likelihood profile with full coverage adjustment
(eps), (gif): 2D β_s - ΔΓ likelihood profile with non-Gaussian error adjustment only (no systematics)
(eps), (gif): 1D β_s likelihood profile with non-Gaussian error adjustment only (no systematics)
(eps), (gif): 2D β_s - ΔΓ likelihood profile with no coverage adjustment
(eps), (gif): 1D β_s likelihood profile with no coverage adjustment

Coverage adjustment
(eps), (gif): Distribution of 1-CL for coverage adjustment of tagged 2D likelihood profile
(eps), (gif): Distribution of 1-CL for coverage adjustment of tagged 1D likelihood profile
(eps), (gif): Distribution of 1-CL for coverage adjustment of untagged 2D likelihood profile

Selection, yield, angular efficiencies
(eps), (gif): B_s yield
(eps), (gif): B_s mass distribution with ct>60μm
(eps), (gif): KK invariant mass distribution
(eps), (gif): KK invariant mass distribution with ct>60μm
(eps), (gif): B_s NN training
(eps), (gif): NN signal efficiency
(eps), (gif): NN signal purity
(eps), (gif): NN output
(eps), (gif): NN sensitivity, toy MC with β_s=0.0
(eps), (gif): NN sensitivity, toy MC with β_s=0.3
(eps), (gif): NN sensitivity, toy MC with β_s=0.5
(eps), (gif): NN significance curve
(eps), (gif): Angular efficiencies in re-weighted realistic MC
(eps), (gif): Starting background angular functions
(eps), (gif): Starting background angular functions overlaid with angular efficiencies

Flavor tagging (see also SSKT)
(eps), (gif): B⁺ yield (for OST calibration)
(eps), (gif): OST measured vs. predicted dilution for B⁺ decays
(eps), (gif): OST measured vs. predicted dilution for B^- decays

S-wave studies
(eps), (gif): S-wave KK fraction of signal
(eps), (gif): 2D β_s - ΔΓ likelihood profile comparison between fit including and without S-wave KK component (no coverage adjustment)
(eps), (gif): B_s mass fit with wide KK invariant mass window, to get fractions of signal, combinatorial bkg and B⁰ reflections for KK mass study
(eps), (gif): KK invariant mass with projections of signal φ, combinatorial bkg and B⁰ reflection fractions
(eps), (gif): KK invariant mass with projections of signal φ, combinatorial bkg and B⁰ reflection fractions and S-wave f₀ component fixed to central value from full likelihood fit

Fit cross checks
(eps), (gif): untagged fit: 2D β_s - ΔΓ likelihood profile with full coverage adjustment
(eps), (gif): overlay of fully adjusted 2D β_s - ΔΓ likelihood profile for tagged and untagged fits
(eps), (gif): untagged fit: 2D β_s - ΔΓ likelihood profile with full coverage adjustment
(eps), (gif): untagged fit: 2D β_s - ΔΓ likelihood profile with non Gaussian adjustment (no systematics)
(eps), (gif): untagged fit: 2D β_s - ΔΓ likelihood profile with no adjustment
(eps), (gif): untagged fit: 1D β_s - ΔΓ likelihood profile with no adjustment
(eps), (gif):tagged fit: 2D β_s - ΔΓ likelihood profile for L=0-1.35fb^-1
(eps), (gif):tagged fit: 2D β_s - ΔΓ likelihood profile for L=1.35-2.8fb^-1
(eps), (gif):tagged fit: 2D β_s - ΔΓ likelihood profile for L=2.8-5.2fb^-1

Fit projections
(eps), (gif): Bs lifetime projection in signal region
(eps), (gif): Bs lifetime projection in sideband region
(eps), (gif): Bs lifetime error projection in signal region
(eps), (gif): Bs lifetime error projection in sideband region
(eps), (gif): Bs signal angular projection
(eps), (gif): Bs background angular projection