Observables and anomalies in B K ( ) + decays Sam Cunliffe on - PowerPoint PPT Presentation

Observables and anomalies in B → K ( ∗ ) ℓ + ℓ − decays Sam Cunliffe on behalf of the LHCb collaboration. [stc09@ic.ac.uk] Frontiers in Fundamental Physics, Aix Marseille Universit ´ e 18th July 2014

Why study rare decays? The LHCb detector b → sℓℓ Theory The operator-product expansion Observables, observables, observables Isospin asymmetry of B → K ( ∗ ) µ + µ − Angular analysis of B 0 → K ∗ 0 µ + µ − Observables from the angular distribution LHCb measurement Interpretations Global fits Form factor uncertainties Lepton universality in B ± → K ± ℓ + ℓ − Something strange from charm Conclusions S.Cunliffe (Imperial) FFP14 2/21

Why study rare decays? ◮ ‘Rare’ F lavour- C hanging N eutral C urrent processes ◮ Forbidden at tree level = ⇒ proceed via loops (in SM) µ + Z 0 , γ µ − b s W − ◮ Searching for new particles via their indirect influence on rare processes ◮ Access to much higher mass scales (particles are virtual) ◮ Able to be model independent ◮ Search for broad classes of new particles at once ◮ For other flavour observables (and another perspective on b → sℓℓ ), see talk by F. Mescia , yesterday S.Cunliffe (Imperial) FFP14 Why study rare decays? 3/21

Why study rare decays? ◮ If you want to learn about space... ◮ If you want to find new particles... Very Large Array - Image courtesy of NRAO/AUI [Source] STS-I Launch - NASA/CC [Source] S.Cunliffe (Imperial) FFP14 Why study rare decays? 4/21

Why study rare decays? ◮ If you want to learn about space... ◮ If you want to find new particles... CMS Monojet candidate - [Source] S.Cunliffe (Imperial) FFP14 Why study rare decays? 4/21

Why study rare decays? ◮ If you want to learn about space... ◮ If you want to find new particles... ¯ ¯ ¯ q d d W − b s χ µ + Z 0 , γ µ − ¯ q χ S.Cunliffe (Imperial) FFP14 Why study rare decays? 4/21

Why study rare decays? ◮ If you want to learn about space... ◮ If you want to find new particles... ¯ ¯ ¯ q d d g ˜ b s χ µ + ˜ d H 0 ˜ µ − ¯ q χ S.Cunliffe (Imperial) FFP14 Why study rare decays? 4/21

Why study rare decays? ◮ If you want to learn about space... ◮ If you want to find new particles... ¯ ¯ q ¯ d d W − b s χ µ + Z ′ µ − ¯ q χ S.Cunliffe (Imperial) FFP14 Why study rare decays? 4/21

Why study rare decays? ◮ If you want to learn about space... ◮ If you want to find new particles... ¯ ¯ q ¯ d d b s χ µ + Z ′ µ − ¯ q χ S.Cunliffe (Imperial) FFP14 Why study rare decays? 4/21

Why study rare decays? The LHCb detector b → sℓℓ Theory The operator-product expansion Observables, observables, observables Isospin asymmetry of B → K ( ∗ ) µ + µ − Angular analysis of B 0 → K ∗ 0 µ + µ − Observables from the angular distribution LHCb measurement Interpretations Global fits Form factor uncertainties Lepton universality in B ± → K ± ℓ + ℓ − Something strange from charm Conclusions

The LHCb detector Beauty Experiment at Small Theta ◮ 2 < η < 5 ◮ Tracking: 0 . 4 < δp/p < 0 . 6% ◮ Vertexing: σ IP = 20 µ m ◮ Kaon ID = 95% (5% mis-ID) ◮ Muon ID = 98% (1% mis-ID) b θ 1 θ z 2 b ◮ Physics reach in other areas than rare b → sℓℓ LHCb MC s = 8 TeV observables... ◮ e.g. talks by J. Dalseno on CPV in multibody B 0 π /4 decays π θ /2 0 [rad] π 2 /4 π π 3 /4 /2 and B. Couturier on LHCb outreach/education π 3 /4 π θ [rad] π 1 S.Cunliffe (Imperial) FFP14 The LHCb detector 5/21

Why study rare decays? The LHCb detector b → sℓℓ Theory The operator-product expansion Observables, observables, observables Isospin asymmetry of B → K ( ∗ ) µ + µ − Angular analysis of B 0 → K ∗ 0 µ + µ − Observables from the angular distribution LHCb measurement Interpretations Global fits Form factor uncertainties Lepton universality in B ± → K ± ℓ + ℓ − Something strange from charm Conclusions

The operator-product expansion Or: how to be model independent ¯ ¯ ¯ ¯ d d d d W − b s b s W + µ + µ + W − Z 0 , γ ν µ µ − µ − b → sℓℓ Theory S.Cunliffe (Imperial) FFP14 6/21

The operator-product expansion Or: how to be model independent b s s b ℓ + γ ℓ − “ O 7 ” “ O 9 ”, “ O 10 ” “ C 7 ” “ C 9 ”, “ C 10 ” ◮ “Effective operators” O i ◮ “Wilson Coefficients” C i ◮ c.f. G F from 4 point β decay model ◮ Can predict C i ’s for SM and NP scenarios ◮ Have an effective Hamiltonian = ⇒ can calculate things e 2 H eff = − 4 G F 16 π 2 V tb V ∗ � C i O i + C ′ i O ′ � � √ + h . c . ts i 2 i =7 , 9 , 10 b → sℓℓ Theory S.Cunliffe (Imperial) FFP14 7/21

The operator-product expansion Or: how to be model independent b s s b ℓ + γ ℓ − “ O 7 ” “ O 9 ”, “ O 10 ” “ C 7 ” “ C 9 ”, “ C 10 ” ◮ “Effective operators” O i ◮ “Wilson Coefficients” C i ◮ c.f. G F from 4 point β decay model ◮ Can predict C i ’s for SM and NP scenarios ◮ Have an effective Hamiltonian = ⇒ can calculate things e 2 H eff = − 4 G F 16 π 2 V tb V ∗ � C i O i + C ′ i O ′ � � √ + h . c . ts i 2 i =7 , 9 , 10 b → sℓℓ Theory S.Cunliffe (Imperial) FFP14 7/21

The operator-product expansion Or: how to be model independent b s s b ℓ + γ ℓ − “ O 7 ” “ O 9 ”, “ O 10 ” “ C 7 ” “ C 9 ”, “ C 10 ” ◮ “Effective operators” O i ◮ “Wilson Coefficients” C i ◮ c.f. G F from 4 point β decay model ◮ Can predict C i ’s for SM and NP scenarios ◮ Have an effective Hamiltonian = ⇒ can calculate things e 2 H eff = − 4 G F 16 π 2 V tb V ∗ � C i O i + C ′ i O ′ � � √ + h . c . ts i 2 i =7 , 9 , 10 b → sℓℓ Theory S.Cunliffe (Imperial) FFP14 7/21

The operator-product expansion Or: how to be model independent b s s b ℓ + γ ℓ − “ O 7 ” “ O 9 ”, “ O 10 ” “ C 7 ” “ C 9 ”, “ C 10 ” ◮ “Effective operators” O i ◮ “Wilson Coefficients” C i ◮ c.f. G F from 4 point β decay model ◮ Can predict C i ’s for SM and NP scenarios ◮ Have an effective Hamiltonian = ⇒ can calculate things e 2 H eff = − 4 G F 16 π 2 V tb V ∗ � C i O i + C ′ i O ′ � � √ + h . c . ts i 2 i =7 , 9 , 10 b → sℓℓ Theory S.Cunliffe (Imperial) FFP14 7/21

A word on QCD Enter form factor uncertainty ◮ Observables also contain contributions Hadronic Form Factors. ◮ Different theorists use different versions/approximations. ˆ O = f ( C i , { form factors } ) ¯ ¯ d d W − b s µ + Z 0 , γ µ − b → sℓℓ Theory S.Cunliffe (Imperial) FFP14 8/21

A word on QCD Enter form factor uncertainty ◮ Observables also contain contributions Hadronic Form Factors. ◮ Different theorists use different versions/approximations. ˆ O = f ( C i , { form factors } ) ¯ ¯ ¯ ¯ d d d d W − b s b s µ + µ + Z 0 , γ µ − µ − b → sℓℓ Theory S.Cunliffe (Imperial) FFP14 8/21

O 7 J c b → sγ 1 P ′ C 7 | A R � | 2 V ( q 2 ) 5 C 9 b → sℓℓ ξ ⊥ A 2 ( q 2 ) cos θ K T 3 ( q 2 ) J s ¯ 2 A FB ξ � S 6 P ′ A L 4 ⊥ q 2 C NP 9 Nomenclature

O 7 J c b → sγ 1 P ′ C 7 | A R � | 2 V ( q 2 ) 5 q 2 = m 2 C 9 ℓℓ b → sℓℓ ξ ⊥ A 2 ( q 2 ) cos θ K Squared dilepton T 3 ( q 2 ) J s ¯ 2 A FB ξ � S 6 invariant mass P ′ A L 4 ⊥ q 2 C NP 9 Nomenclature

Observables, observables, observables ◮ Need to find measurable quantities that... ◮ ...are sensitive to the Wilson Coefficients ◮ ...cancel the QCD uncertainty (hadronic form factors) wherever possible Lepton-universality � B ± → K ± µ + µ − � B R K = � � B ± → K ± e + e − B Isospin asymmetry (spectator-model-asymmetry) � B 0 → K ( ∗ )0 µ + µ − � τ B 0 � B ± → K ( ∗ ) ± µ + µ − � B − τ B + B A I = � � τ B 0 � � B 0 → K ( ∗ )0 µ + µ − B ± → K ( ∗ ) ± µ + µ − B + τ B + B b → sℓℓ Theory S.Cunliffe (Imperial) FFP14 10/21

Why study rare decays? The LHCb detector b → sℓℓ Theory The operator-product expansion Observables, observables, observables Isospin asymmetry of B → K ( ∗ ) µ + µ − Angular analysis of B 0 → K ∗ 0 µ + µ − Observables from the angular distribution LHCb measurement Interpretations Global fits Form factor uncertainties Lepton universality in B ± → K ± ℓ + ℓ − Something strange from charm Conclusions