1. CP violation in the charm and beauty systems at LHCb
Jeroen van Tilburg
(Physikalisches Institut Heidelberg)
On behalf of the LHCb collaboration
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

2. Tree – penguin interference in B→hh’ allow to probe CKM angles
Introduction
Focus on two new results today:
Time dependent CP violation in B0→+− and Bs→K+K−.
Sensitive to CKM angle γ and d, s.
Effective lifetime in Bs→K+K−
Sensitive to ΔΓs and s
Tree – penguin interference in B→hh’ allow to probe CKM angles
Bs system
Unitarity triangle
ΔΓs : lifetime difference of Bs system
s : mixing phase
Bd system
ΔΓd ~ 0
d = 2β
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

3. Time-dependent CPV in B→hh’
Time-dependent CP asymmetry
where
For B0→π+π− and Bs→K+K− we have
Adir(γ,d,θ) Adir(γ,d’,θ’)
Amix(γ,d,d,θ) Amix(γ,s,d’,θ’) ππ KK ππ KK
Assuming U-spin symmetry: d=d’ and θ=θ’
Use d as input: extract γ and s.
[Fleischer, PLB459 (1999) 306]
[LHCb roadmap]
Complementary to γ from pure tree decays using B→DK: ADS+GLW method.
→ see new nice results on AADS shown by Chris Jones yesterday.
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

4. Current experimental status
Time-dependent CP asymmetry in B0→π+π−
Only B0→π+π− measurements available from B-factories
Bare agreement for direct CP violation between BaBar and Belle
Third independent measurement essential.
No measurements on Bs→K+K− yet
BaBar [arXiv: ]
Belle [PRL 98 (2007) ]
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

5. LHCb analysis New result! Not shown before Data sample:
[LHCb-CONF ]
Preliminary
Data sample:
Integrated luminosity of 0.69 fb-1
Event selection:
Common kinematics cuts for B→Kπ, B0→π+π− and Bs→K+K−
PID cuts to distinguish various final states
Decay time resolution
Use resolution from B→J/X: t=50 fs
Decay time acceptance from MC
Flavour tagging
Use OS tagging only
Use B→Kπ to calibrate efficiency and mistag rate
Flavour tagging example K+
Signal Bs K+ DX B-
Sign of muon tags Bs flavour at production μ-
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

6. Bd,s→K fit Extract from fit: Bd parameters: (Constrain Bs parameters)
B0→Kπ
Bs→πK
B0→π+π−
Bs→K+K−
x-feed+3-body
combinatorial
[LHCb-CONF ]
Extract from fit:
Bd parameters: (Constrain Bs parameters)
Δmd = (0.484±0.019) ps-1
τ(B0) = (1.509±0.011) ps
(only statistical errors)
Bd oscillation plot
Agreement with WA
Tagging power: (2.3±0.1)%
Production asymmetry
AP(B0) = (-1.5±1.3)%
AP(Bs) = (-3±6)%
Input to π+π− and K+K− fits.
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

7. Bd→+− fit Input Δmd = (0.499±0.032) ps-1 [LHCb-CONF-2011-010]
5359±96 events
B0→Kπ
B0→π+π−
x-feed+3-body
combinatorial
[LHCb-CONF ]
Input Δmd = (0.499±0.032) ps-1 [LHCb-CONF ]
Extract from fit:
First B0→π+π− CP asymmetry measurement at hadron collider
τ(B0) = (1.497±0.025) ps
(only statistical error)
In agreement with WA
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

8. Bs→K+K− fit Extract from fit: First Bs→K+K− CP asymmetry measurement
7155±97 events
B0→Kπ
Bs→K+K−
x-feed+3-body
combinatorial
[LHCb-CONF ]
Input Δms and Γs from LHCb measurements
Extract from fit:
First Bs→K+K− CP asymmetry measurement
ΔΓs = (0.076±0.019) ps-1
(only statistical error)
In agreement with [LHCb-PAPER ]
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

9. Results B0→π+π− Adir favours BaBar result Amix in agreement with WA
[LHCb-CONF ]
Main systematic uncer-tainty: input on Δmd
(statistical correlation)
Preliminary
Adir favours BaBar result
Amix in agreement with WA
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

10. Results Bs→K+K− Expect: SM prediction: [LHCb-CONF-2012-007]
Main systematic uncertainties: Decay time resolution & acceptance and input on Δms
[LHCb-CONF ]
(statistical correlation)
Preliminary
[LHCB-PAPER ]
Expect:
Assuming U-spin symmetry and neglecting penguin annihilation (small)
SM prediction:
Assuming U-spin symmetry and SM predictions
[LHCb roadmap]
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

11. Effective lifetime in CP eigenmodes
Untagged decay time distribution:
with AΔΓ(γ,s,d’,θ’)
If no CPV then for CP eigenstates AΔΓ = ±1 :
CP even: Bs→K+K− ΓL
CP odd: Bs→ J/ f0 ΓH
Effective lifetime Bs→K+K−
Expand in:
Alternative way to extract ΔΓs and s
→ Complementary to e.g. Bs → J/ 
→ No flavour tagging needed
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

12. Current picture Using effective lifetimes to constrain ΔΓs and s
Fleischer, Knegjens, [arXiv: ]
Including direct measurements
LHCb [PLB 707 (2012)]
CDF [PRD84:052012, 2011]
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

13. Update on s New result. Update using 1.0 fb−1
Only shown last week at Moriond EW (P. Clarke)
Bs → J/  and Bs→ J/ ππ (incl. f0) time-dependent analysis
[LHCb-CONF ]
Preliminary
[LHCb-PAPER ]
Γ = ± (stat.)± (syst.)
ΔΓ = ± 0.018(stat.) ± (syst.)
s = ± 0.083(stat.) ± 0.027(syst.)
Note: Sign of ΔΓs resolved using P-wave – S-wave interference:
ΔΓs > 0
[LHCb-PAPER ]
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

14. Update on CP odd lifetime
Analysis of Bs→ J/ ππ (incl. f0)
[LHCb-PAPER ]
Background
Background
Using f0 resonance only:
Using full CP odd sample:
Statistical errors only.
Detailed analysis of effective lifetime in preparation.
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

15. Effective Lifetime of Bs→K+K−
Previous analysis on 2010 data
[PLB 707 (2012)]
Two approaches to counter lifetime biasing effects in trigger and selection
“Swimming” method (determine trigger acceptance event-by-event )
Relative method (Bs→K+K− vs B0→K+π−)
New result!!! (not shown before)
[LHCb-CONF ]
Preliminary
Now a third method is added and shown today
Minimal lifetime bias method
No cuts on lifetime, impact parameters, etc.
Dedicated trigger line
Trigger and event selection all based on neural networks
Flat acceptance (verified on MC)
Using full 1.0 fb−1 from 2011 data set
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

16. Mass distributions Signal: Bs→K+K− Control mode: B0→K+π− B0→K+π−
[LHCb-CONF ]
Partially reconstructed B mesons
Partially reconstructed B mesons
B0→K+π−
Bs→K+K−
Kaon mass assigned to both final state particles
Final event selection
Use PID to isolate Bs→K+K− vs B0→K+π−.
Cut on proton ID to suppress contribution from Λ.
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

17. Lifetime fit Signal: Bs→K+K− Control mode: B0→K+π−
[LHCb-CONF ]
Note: Trigger needs to cut at t>0.3 ps
→ Fit starts at t=0.5 ps
Agrees well with previous result:
Agrees with WA (PDG):
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

18. Effective lifetime Bs→K+K−
[LHCb-CONF ]
Preliminary
Final result
Main systematic uncertainty from reconstruction efficiency
In agreement with SM expectation:
Fleischer, Knegjens, [EPJC 71 (2011) 1532]
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

19. Charm results ΔACP in D0→h+h- (CPV in decay) 0.6 fb-1
[LHCb-PAPER ]
Production and detector asymmetry cancel.
Signifance 3.5
First evidence of CP violation in charm sector!
yCP and AГ in D0→K+K- (CPV in mixing) 29 pb-1
[LHCb-PAPER ]
→ Combined with measurement of y gives access to CPV.
LHCb is currently updating for full 1.0 fb-1
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

20. Conclusions Time-dependent CPV in B0→π+π− and Bs→K+K− (0.7 fb-1)
[LHCb-CONF ]
Preliminary
B0→π+π− CP asymmetries in good agreement with world average
Amix yields first 3 evidence of time-dependent CPV at hadron collider
CP asymmetry in Bs→K+K− measured for the first time
[LHCb-CONF ]
Preliminary
Effective lifetime in Bs→K+K− (1.0 fb-1)
Effective Bs→K+K− lifetime measured using novel technique
Minimal lifetime bias in trigger and selection using neural networks
Significant improvement over 2010 result
Analyses using different techniques in progress and expect to reduce further uncertainty.
Charm results
First evidence for CP violation in charm (ΔACP)
Expect large improvement for yCP and AΓ using 2011 data.
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

21. Backup Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg

22. Time-dependent asymmetries
For B0→π+π− and Bs→K+K− we have
Moriond QCD, 13 March 2012
CP violation in the charm and beauty systems at LHCb, Jeroen van Tilburg