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 1/20

Jeroen van Tilburg Jeroen van Tilburg (Physikalisches Institut Heidelberg)(Physikalisches Institut Heidelberg)

On behalf of the LHCb On behalf of the LHCb collaborationcollaboration

CP violation in the charm and CP violation in the charm and beauty systems at LHCbbeauty systems at LHCb

CP violation in the charm and CP violation in the charm and beauty systems at LHCbbeauty systems at LHCb


IntroductionIntroduction

Tree – penguin interference in Tree – penguin interference in BB→→hh’hh’ allow to probe CKM angles allow to probe CKM angles

Tree – penguin interference in Tree – penguin interference in BB→→hh’hh’ allow to probe CKM angles allow to probe CKM angles

Focus on two new results today:

1. Time dependent CP violation in B0→+− and Bs→K+K−.• Sensitive to CKM angle γ and d, s.

2. Effective lifetime in Bs→K+K−

• Sensitive to ΔΓs and s

Unitarity triangleUnitarity triangleUnitarity triangleUnitarity triangle

ΔΓd ~ 0d = 2β

BBdd system systemBBdd system system

ΔΓs : lifetime difference of Bs systems : mixing phase

BBss system systemBBss system system


Time-dependent CPV in Time-dependent CPV in BB→hh’→hh’

where

Time-dependent CP asymmetryTime-dependent CP asymmetryTime-dependent CP asymmetryTime-dependent CP asymmetry

For For BB00→→ππ++ππ−− and and BBss→→KK++KK−− we have we haveFor For BB00→→ππ++ππ−− and and BBss→→KK++KK−− we have we have

• 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.

Adir(γ,d,θ) Adir(γ,d’,θ’)Amix(γ,d,d,θ) Amix(γ,s,d’,θ’)KK

KKππ

ππ


Current experimental statusCurrent experimental status

Only B0→π+π− measurements available from B-factories• Bare agreement for direct CP violation between BaBar and Belle• Third independent measurement essential.

Time-dependent CP asymmetry in Time-dependent CP asymmetry in BB00→→ππ++ππ−−Time-dependent CP asymmetry in Time-dependent CP asymmetry in BB00→→ππ++ππ−−

No measurements on Bs→K+K− yetNo measurements on Bs→K+K− yet

BaBar [arXiv:0807.4226]Belle [PRL 98 (2007) 211801]


LHCb analysisLHCb analysis

• 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 exampleFlavour tagging exampleFlavour tagging exampleFlavour tagging example

New result! Not shown before[LHCb-CONF-2012-007]

Preliminary

K+

K+

Bs

B-

μ-

DX

Signal

Sign of muon tags Bs

flavour at production


BBd,sd,s→K→K fit fit

B0→KπBs→πKB0→π+π−

Bs→K+K−

x-feed+3-bodycombinatorial

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 parameters: (Constrain Bs parameters)

Δmd = (0.484±0.019) ps-1

τ(B0) = (1.509±0.011) ps(only statistical errors)

• Tagging powerTagging power: : (2.3(2.3±±0.1)%0.1)%• Production asymmetryProduction asymmetry

AAPP((BB00) = (-1.5) = (-1.5±±1.3)%1.3)%

AAPP((BBss) = (-3) = (-3±±6)%6)%

• Tagging powerTagging power: : (2.3(2.3±±0.1)%0.1)%• Production asymmetryProduction asymmetry

AAPP((BB00) = (-1.5) = (-1.5±±1.3)%1.3)%

AAPP((BBss) = (-3) = (-3±±6)%6)%

Input to π+π− and K+K− fits.

Agreement with WA

[LHC

b-CO

NF

-2012-00

7]

BBdd oscillation plot oscillation plotBBdd oscillation plot oscillation plot


BBdd→→++−− fit fit

B0→KπB0→π+π−


5359±96 events

Input Δmd = (0.499±0.032) ps-1 [LHCb-CONF-2011-010]

First B0→π+π− CP asymmetry measurement at hadron collider

Extract from fit:

τ(B0) = (1.497±0.025) ps(only statistical error)

τ(B0) = (1.497±0.025) ps(only statistical error)

In agreement with WA

[LHC

b-CO

NF

-2012-00

7]


BBss→K→K++KK−− fit fit

B0→KπBs→K+K−


7155±97 events

First Bs→K+K− CP asymmetry measurement

Input Δms and Γs from LHCb measurements

Extract from fit:

ΔΓs = (0.076±0.019) ps-1

(only statistical error)

ΔΓs = (0.076±0.019) ps-1

(only statistical error)In agreement with[LHCb-PAPER-2011-021]

[LHC

b-CO

NF

-2012-00

7]


ResultsResults

(statistical correlation)

BB00→→ππ++ππ−−BB00→→ππ++ππ−−

Preliminary

• Adir favours BaBar result• Amix in agreement with WA

[LHC

b-CO

NF

-2012-00

7]

Main systematic uncer-tainty: input on Δmd


ResultsResults

(statistical correlation)

• Expect: • Assuming U-spin symmetry and neglecting penguin annihilation (small)

• SM prediction: • Assuming U-spin symmetry and SM predictions

[LHCb roadmap]

[LHCB-PAPER-2011-029]

BBss→→KK++KK−−BBss→→KK++KK−− [LHC

b-CO

NF

-2012-00

7]

Preliminary

Main systematic uncertainties: Decay time resolution & acceptance and input on Δms


Effective lifetime in CP eigenmodesEffective lifetime in CP eigenmodes

Alternative way to extract ΔΓs and s

→ Complementary to e.g. Bs → J/ → No flavour tagging needed

Untagged decay time distribution:Untagged decay time distribution:Untagged decay time distribution:Untagged decay time distribution:

Effective lifetime Effective lifetime BBss→→KK++KK−− Effective lifetime Effective lifetime BBss→→KK++KK−−

If no CPV then for CP eigenstates AΔΓ = ±1 :

with AΔΓ(γ,s,d’,θ’)

CP even: Bs→K+K− ΓL CP odd: Bs→ J/ f0 ΓH

CP even: Bs→K+K− ΓL CP odd: Bs→ J/ f0 ΓH

Expand in:


Current pictureCurrent picture

CDF [PRD84:052012, 2011]

LHCb [PLB 707 (2012)]

Using effective lifetimes to constrain Using effective lifetimes to constrain ΔΓΔΓss and and ssUsing effective lifetimes to constrain Using effective lifetimes to constrain ΔΓΔΓss and and ss

Including direct measurementsIncluding direct measurementsIncluding direct measurementsIncluding direct measurements

Fleischer, Knegjens, [arXiv:1109.5115]


Update on Update on ss

Γ = 0.6580 ± 0.0054(stat.)± 0.0066(syst.) ΔΓ = 0.116 ± 0.018(stat.) ± 0.006(syst.) s = -0.002 ± 0.083(stat.) ± 0.027(syst.)

[LHCb-CONF-2012-002]Preliminary

New result. Update using 1.0 fb−1

Only shown last week at Moriond EW (P. Clarke)

BBs s → → JJ// and and BBss→ → JJ// ππππ (incl. (incl. ff00) ) time-dependent analysistime-dependent analysisBBs s → → JJ// and and BBss→ → JJ// ππππ (incl. (incl. ff00) ) time-dependent analysistime-dependent analysis

[LHCb-PAPER-2012-006]

Note: Sign of ΔΓs resolved using P-wave – S-wave interference:

ΔΓs > 0 [LHCb-PAPER-2011-028]


Update on CP odd lifetimeUpdate on CP odd lifetime

Background

Using full CP odd sample:

Background


Statistical errors only.Detailed analysis of effective lifetime in preparation.

Using f0 resonance only:

Analysis of Analysis of BBss→ → JJ// ππππ (incl. (incl. ff00))Analysis of Analysis of BBss→ → JJ// ππππ (incl. (incl. ff00))


Effective Lifetime of Effective Lifetime of BBss→→KK++KK−−

New result!!! (not shown before)[LHCb-CONF-2012-001]PreliminaryMinimal 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

Previous analysis on 2010 dataPrevious analysis on 2010 dataPrevious analysis on 2010 dataPrevious 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−)

Now a third method is added and shown todayNow a third method is added and shown todayNow a third method is added and shown todayNow a third method is added and shown today


Mass distributionsMass distributions

Partially reconstructed B mesons B0→K+π−

Bs→K+K−

Partially reconstructed B mesons

B0→K+π−

Bs→K+K−

Final event selection• Use PID to isolate Bs→K+K− vs B0→K+π−.• Cut on proton ID to suppress contribution from Λ.

Signal: Signal: BBss→→KK++KK−−Signal: Signal: BBss→→KK++KK−−Control mode: Control mode: BB00→→KK++ππ−−Control mode: Control mode: BB00→→KK++ππ−−

[LHC

b-CO

NF

-2012-00

1]

Kaon mass assigned to both final state particles


Lifetime fitLifetime fit

Signal: Signal: BBss→→KK++KK−−Signal: Signal: BBss→→KK++KK−−Control mode: Control mode: BB00→→KK++ππ−−Control mode: Control mode: BB00→→KK++ππ−−

Agrees with WA (PDG):

Note: Trigger needs to cut at t>0.3 ps → Fit starts at t=0.5 ps

Note: Trigger needs to cut at t>0.3 ps → Fit starts at t=0.5 ps

Agrees well with previous result:

[LHC

b-CO

NF

-2012-00

1]


Effective lifetime Effective lifetime BBss→→KK++KK−−

In agreement with SM expectation:

Fleischer, Knegjens, [EPJC 71 (2011) 1532]

Final resultFinal resultFinal resultFinal result[LHCb-CONF-2012-001]Preliminary

Main systematic uncertainty from reconstruction efficiency

Main systematic uncertainty from reconstruction efficiency


Charm resultsCharm results

ΔΔAACPCP in in DD00→→hh++hh-- (CPV in decay) 0.6 fb (CPV in decay) 0.6 fb-1-1ΔΔAACPCP in in DD00→→hh++hh-- (CPV in decay) 0.6 fb (CPV in decay) 0.6 fb-1-1

inddir 1.0)()( CPCPCPCPCP aaAKKAA Production and detector asymmetry cancel.


Signifance 3.5

First evidence of CP violation in charm sector!

First evidence of CP violation in charm sector!

LHCb is currently updating for full 1.0 fb-1

yyCPCP and and AAГГ in in DD00→→KK++KK-- (CPV in mixing) 29 pb (CPV in mixing) 29 pb-1-1yyCPCP and and AAГГ in in DD00→→KK++KK-- (CPV in mixing) 29 pb (CPV in mixing) 29 pb-1-1

→ Combined with measurement of y gives access to CPV.



ConclusionsConclusions

• 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

• 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.

Time-dependent CPV in Time-dependent CPV in BB00→→ππ++ππ−− and and BBss→→KK++KK−− (0.7 fb(0.7 fb-1-1))Time-dependent CPV in Time-dependent CPV in BB00→→ππ++ππ−− and and BBss→→KK++KK−− (0.7 fb(0.7 fb-1-1))

Effective lifetime in Effective lifetime in BBss→→KK++KK−− (1.0 fb(1.0 fb-1-1))Effective lifetime in Effective lifetime in BBss→→KK++KK−− (1.0 fb(1.0 fb-1-1))



Charm resultsCharm resultsCharm resultsCharm results

• First evidence for CP violation in charm (ΔACP)• Expect large improvement for yCP and AΓ using 2011 data.


BackupBackup


Time-dependent asymmetriesTime-dependent asymmetries

For For BB00→→ππ++ππ−− and and BBss→→KK++KK−− we have we haveFor For BB00→→ππ++ππ−− and and BBss→→KK++KK−− we have we have

Jeroen van Tilburg (Physikalisches Institut Heidelberg) On behalf of the LHCb collaboration

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