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Measurement of the weak phase γ

K.Akiba – UFRJOn behalf of the LHCb Collaboration

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CP Violation and CKM

CIPANP 2012Kazu Akiba

Wolfenstein parametrization

Unitarity

CKM mixing matrix MassWeak

eigenstates Unitary Complex CP Violation

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CP Violation and CKM

CIPANP 2012Kazu Akiba

CKM mixing matrix MassWeak

eigenstates Unitary Complex CP Violation

Wolfenstein parametrization

Unitarity

γ β

α

UFRJKazu Akiba

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Standard CP Violation

CIPANP 2012

Unitarity Triangle Constrained by all the CKM related measurementsCKMfitter Group (J. Charles et al.), Eur. Phys. J. C41, 1-131 (2005)

UFRJKazu Akiba

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The importance of γ

CIPANP 2012

Least precisely measured of the angles. (|Vub|<< 1)

Direct measurements: 66 ± 12 ° (CKM Fitter 2012) (-100.8 or 79.1) ± 9.2 °(UTFit post-Moriond 2012)

UFRJKazu Akiba

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How to measure γ

It’s a phase Interference.Needs bu transitions; Rare.Mainly 2 methods with tree level diagrams.

Time independent: B(u,d) D(*)K(*) Time dependent: Bs DsK

Requirements: A large sample of B mesons An excellent K / p identification Precise vertex reconstruction (time meas. And BG

suppr.)

CIPANP 2012

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The LHCb Experiment

Kazu Akiba CIPANP 2012

Large Hadron Collider beauty Experiment for CP violation and Rare B Decays.

TTSi

Muon

MWPCGEM

HCAL

ECAL RICH2 Outer Tracke

r straw Tubes

Magnet

RICH1

VELO&PUSi

Inner Tracke

r Si

+ TriggerHard &

Soft

Zoom in the vertex

region

Closes for

physics

Open during

injection

UFRJKazu Akiba

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BD0K : Time independent γ

Where f can be: Kπ, KK, ππ, Kπππ, Ksππ, KsKK, Kππ0 …

CIPANP 2012

→ f

→ f

(+ππ)

(+ππ)

UFRJKazu Akiba

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Gronau, London, Wyler (GLW)

CIPANP 2012

[Phys. Lett. B 253, 483 (1991), Phys. Lett. B 265, 172 (1991)]

Interference with D on a CP eigenstate: f = h+ h- , rD =1

Summarized in 2 observables, but 3 unknowns:

Similarly, B0 and K*0 can be used.

UFRJKazu Akiba

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Attwood, Dunietz, Soni (ADS)

Interference with D through Cabibbo favoured and supressed modes: f = K+ π- , rD ≈ 0.06 (rD=Γ(D0->K+π-)/Γ(D0->K-π+))

Need external input on δDKπ and rD.

Combined with GLW can provide a measurement of γ

CIPANP 2012

Phys.Rev.Lett. 78 (1997) 3257, axiv:hep-ph/9612433

UFRJKazu Akiba

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LHCb Results B(KK)D h (GLW)

CIPANP 2012

Mis-ID Kπ

Mis-ID πK

Difference in reconstructed candidates for different B charges

ACP+ = 0.145±0.032±0.010Phys. Lett. B Vol 712, Issue 3, 2012,, 203–212

BDK , BDπ, BDh+BG, ΛbΛc h (dashed)

UFRJKazu Akiba

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LHCb Results B(ππ)D h (GLW)

CIPANP 2012

Mis-ID Kπ

Mis-ID πK

Difference in reconstructed candidates for different B charges

RCP+ = 1.07±0.038±0.012Phys. Lett. B Vol 712, Issue 3, 2012,, 203–212

BDK , BDπ, BDh+BG, ΛbΛc h (dashed)

UFRJKazu Akiba

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LHCb Results B(hh')D h (ADS)

CIPANP 2012

Mis-ID Kπ

Mis-ID πK

Difference in reconstructed candidates for different B charges

Phys. Lett. B Vol 712, Issue 3, 2012,, 203–212

Favoured modesBDK , BDπ, BDh+BG, ΛbΛc h (dashed)

AADS(π)= (0.143±0.062±0.011)

AADS(K)= (-0.52±0.15±0.02)

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LHCb Results B(h'h)D h (ADS)

CIPANP 2012Kazu Akiba

Mis-ID KπMis-ID πK

Bs->D0Kπ

RADS(K) = (1.52±0.20±0.04)%B( B±→[π±K+]DK± ) ≈ (2.2 ± 0.3)×10−7

(10 σ) observation

RADS(π) = (0.410±0.025±0.005)%2σ higher than previous measurements

Phys. Lett. B Vol 712, Issue 3, 2012,, 203–212

Suppressed modes

UFRJKazu Akiba

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Global picture ADS/GLW (Kπ)Dπ

CIPANP 2012

B Factories still dominate most of the results but LHCb comes in with most precise measurements…

UFRJKazu Akiba

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Global picture ADS/GLW (Kπ)DK

CIPANP 2012

B Factories still dominate most of the results but LHCb comes in with most precise measurements…

UFRJKazu Akiba

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Global picture ADS/GLW (hh)DK

CIPANP 2012

B Factories still dominate most of the results but LHCb comes in with most precise measurements…

UFRJKazu Akiba

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Giri, Grossman, Soffer, Zupan (GGSZ)

Uses the same kind of interference but with a three-body final state B (Ks π π)D K and perform a Dalitz Analysis

Complementary to the previous methods, gives independent information on rB,δBγ.

No results fromLHCb just yet…

CIPANP 2012

Phys.Rev. D68 (2003) 054018, arXiv:hep-ph/0303187

UFRJKazu Akiba

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Effects on γ

CIPANP 2012

ADS/GLW do not provide unambiguous solution to γThe precision of the newest measurements does not translate directly to precision on γ.

LHCb gives more precise constraints on rB

UFRJKazu Akiba

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BsDsK : Time dependent γ

The Two diagrams interfere directly through the same final state time dependent analysis reveals γ-φs , where φs is the phase in the mixing.

Requires a good proper time calibration and tagging (BsDsπ).

Method unique to LHCb!CIPANP 2012

UFRJKazu Akiba

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Good proper time resolution ~50 ps (measured with Dsπ)

Well controlled tagging εD2 = (3.2 ±0.8) % (OS only) More from SST.

Milestones measurements Δms = 17.63 ±0.11 ± 0.02 1/ps

[arXiv:1112.4311]) BF (Bs DsK) =

(1.90 ±0.12(stat) ±0.13 (sys)+0.12

-0.14 (fd/fs) )

[arXiv:1204.1237]Basic ingredients ate there:

Time dependent analysis Flavour tagging Reconstruction and PID.

CIPANP 2012

BsDsK : towards a γ measurement

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ConclusionsDecays of BDh offer a rich programme to measure the CKM phase γ.

Main decay modes already measured 10 σ observation of suppressed ADS modes 5.8 σ measurements of CP violation B->DK modes

combinedMore and unique analyses to come

B0->D0K*0 modes to offer more information on GLW+ADS

Time dependent BsDsK way to measure γMultiple methods in LHCb can be combined for a best precision on γ!

CIPANP 2012Kazu Akiba

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