1. Martin Heck, for the CDF II collaboration
New Measurement of
the Bs mixing phase
at CDF II
Martin Heck, for the CDF II collaboration
KIT
Susy 2010

2. Outline Motivation Analysis Strategy Results Other CDF flavor results
Conclusions and Outlook

3. Motivation Decay without mixing Ф J/ψ Decay after mixing J/ψ Ф
One possible way of CP violation:
Interference of decays with and without mixing
Only for channels, that are accessible for both particle/antiparticle
CP violation comes in phase βs
In SM βs is predicted to be small
J/ψ
Decay after mixing
J/ψ
β 𝑠 𝑆𝑀 =𝑎𝑟𝑔 − 𝑉 𝑡𝑠 𝑉 𝑡𝑏 ∗ 𝑉 𝑐𝑠 𝑉 𝑐𝑏 ∗ ≈0.02 Ф
βs value in SM indistin-guishable from 0 for us.
Significant measurement of phase -> New Physics!
Top quark dominant contribution.
Are there SuSy particles in the loop, too?

4. Status with 2.8 fb-1 of Tevatron data
See
Combination of
Abazov et al. D0 Collaboration
PRL 101, (2008)
CDF public note 9458
Looked promising...
Confidence region instead of value + uncertainty, because of non-Gaussian uncertainty behavior
βs analysis often cited by SuSy papers, random examples:
Biggio, Calibbi, arXiv
Wang, Zu, Li, arXiv:
Kubo, Lenz, arXiv:
Altmannshofer et. al.,arXiv:

5. Analysis Strategy Measure CDF public note 10206 Bs life time
Decay width ΔΓ difference between CP even and odd Bs
CP violation phase βs
CDF public note 10206
Di-muon Trigger μ+ μ-
J/ψ Bs Ф
NN Selection K+ K-

6. multidimensional likelihood-fit Angles
separate CP even and odd final states
𝑓 𝑠 𝑃 𝑠 𝑚∣ σ 𝑚 𝑃 𝑠 𝑡,ρ,ξ∣𝐷, σ 𝑡 𝑃 𝑠 σ 𝑡 𝑃 𝑠 𝐷
ρ= θ,ϕ,ψ
tagging
flavour of initial Bs state
Mass
discriminate signal/background
ξ=  −1for 𝐵 𝑠 ˉ +1for 𝐵 𝑠 at production time
Lifetime
lifetime of each mass eigenstate

7. Reconstruct Bs candidates in 5
Reconstruct Bs candidates in 5.2 fb-1 of data triggered on a di-muon pattern with J/ψ characteristics.
Combine kinematic and particle ID variables in neural network to enrich signal.
Chose cut based on simulation in such a way, that uncertainty on βs is
minimized.
~6500 Bs mesons compared with ~3150 in old analysis.

8. μ- K+ J/ψ Bs Ф φ J/ψ K- Bs μ+ Ф K- θ ψ K+
- Propagating Bs mesons are almost CP eigenstates.
- This dominates the lifetime difference (think as well Kshort, Klong )
- CP violation means, sometimes dominantly CP even decays in CP odd final state and vice versa (like Klong decaying into 2 pions) ==> necessary to know CP value of final state.
CP even (light if no New Physics) states decay in S- or D-waves
CP odd (heavy) states decay in P-waves This allows statistical discrimination by measuring the angular distribution ( ρ= (θ,φ,ψ) )
Kaons define xy plane μ-
Ψ: K angle in Ф rest frame K+ Ф Bs
J/ψ
φ: μ angle of
projection to Ф plane
in J/ψ rest frame
x defined by Ф φ
J/ψ Bs K- μ+ Ф K-
θ: μ angle relative to z direction in J/ψ rest frame θ ψ K+
orthogonal to xy plane Z

9. We are searching for effect in mixing
We are searching for effect in mixing. Tagging production flavor tells us, if mixing happened or not.
Tagging is possible due to two effects
1. dominant b production is in bottom anti-bottom pairs
-> find flavour of “opposite side” bottom
2. fragmentation means, the strange quark has usually a nearby kaon partner
-> find the fragmentation partner on the “same side”
At correct ε D2 amplitude scan reaches exactly 1
Output of flavour tagger
- flavour decision
- probability that the decision is correct
For the first time the CDF II same side kaon Tagger has been calibrated on data for this analysis.
Efficiency times Dilution2 (ε D2) is measured as 3.2 ± 1.4% (~reduced statistics)

10. Results
Lifetime and decay width difference Assuming no CP violation, most precise single measurements
τ 𝑠 =1.530±0.025 (stat)±0.012 (sys) ps
Δ Γ 𝑠 =0.075±0.035 (stat)±0.01 (sys) ps
CP even lifetime
CP odd lifetime

11. Polarization amplitudes
∣ 𝐴 ∣∣ 0 ∣ 2 =0.231±0.014 𝑠𝑡𝑎𝑡 ±0.015 𝑠𝑦𝑠𝑡
∣ 𝐴 0 0 ∣ 2 =0.524±0.013 𝑠𝑡𝑎𝑡 ±0.015 𝑠𝑦𝑠𝑡
Φ  =2.95±0.64 𝑠𝑡𝑎𝑡 ±0.07 𝑠𝑦𝑠𝑡
Signal fit projections
background fit projections

12. CP violating phase
Allowed are βs [0.02, 0.52] or [1.08,1.55] at 68% CL
Improvement in this analysis:
S-wave contributions with Bs -> J/ψ K+ K- are included.
The effect of the contributions is as expected rather small, so old analysis still OK.
Improved agreement with standard model.

13. Other CDF Flavour Results
First measurement of polarization angles in Bs-> ΦΦ
Confirms puzzling behavior in b->s penguin polarizations
CDF public note 10064

14. Updated measurement B-> K*μμ CDF public note 10047
competitive B factory results
CDF public note 10047
A 𝐹𝐵 q 2 =1−6 GeV 2 = 0.43 − (stat)±0.06(syst)
More details on this analysis and many more on

15. Conclusion CP violation measurement updated with 5.2 fb-1
Tightened constraints in βs space [0.02, 0.52] or [1.08, 1.55] at 68% CL
Agreement with SM has increased
Best measurement of
Bs life time
ΔΓs
Polarization amplitudes
Several other measurement
Bs-> ΦΦ polarization
B-> K*μμ:
A 𝐹𝐵 q 2 =1−6 GeV 2 = 0.43 − (stat)±0.06(syst)

16. Outlook
Possible further improvements with more data and channels: factor ~2-3
βs measurement is one of the most promising B physics cases today (see as well D0 ASL measurement) ==> stay tuned for updates
Update on Bs -> μμ is going to be ready soon.

17. Backup

18. One dimensional likelihood profile