Penguin decays at LHCb Paula Álvarez Cartelle Universidade de Santiago de Compostela XL International Meeting on Fundamental Physics, Benasque May 31, 2012
Outline 1 Introduction 2 LHCb results Bs 0 K 0 K 0 Bs 0 φφ 3 Outlook 4 Conclusions Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 2 / 19
Introduction Introduction Loops are particularly sensitive to New Physics: New heavy particles entering the loops Observable deviations from SM CP-violation: Weak phases sin(2β) (B 0 φk S ) or φ S (B 0 s K 0 K 0, B 0 s φφ) B VV polarization puzzle: Observed f T /f L 1 in B 0 φk 0, in opposition to the expectation that f T f L Bd penguin decays studied at other experimens (B-factories, CLEO), new interest in Bs penguin decays. Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 3 / 19
LHCb results B 0 s K 0 K 0 B 0 s K 0 K 0 Very interesting for precision CP-violation studies, where B 0 K 0 K 0 channel is used to control the theoretical error (Ciuchini, Pierini and Silvestrini, hep-ph/0703137 ; Bhattacharya, Datta, Imbeault and London, hep-ph/1203.3435 (2011); Descotes-Genon, Matas and Virto, hep-ph/1111.4882 (2011)) Standard Model Negligibly small φ S. U-spin rotations, d s, are genuine flavour symmetries. Standard EW and QCD physics predict small breaking ( 10%) Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 4 / 19
) B 0 s LHCb results K 0 K 0 : Observation B 0 s K 0 K 0 First observation with 35pb 1 of 2010 data with very good signal to background ratio B(B 0 s K 0 K 0 ) = (2.81 ± 0.46(stat) ± 0.45(syst) ± 0.34(f s /f d )) 10 5 S-wave component in ±150 MeV/c 2 window around K 0 mass 15% Events / (30 MeV/c 2 ) 40 35 30 25 20 15 10 LHCb Events / ( 30 MeV/c 2 30 LHCb 20 10 5 0 5000 5200 5400 5600 5800 + - - M(K π K π + ) (MeV/c 2 ) 0 800 900 1000 M(Kπ) (MeV/c 2 ) LHCb Collaboration, R. Aaij et al., Phys. Lett. B709 (arxiv:1111.4183) Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 5 / 19
B 0 s LHCb results K 0 K 0 : Angular Analysis B 0 s K 0 K 0 B VV decay: Three polarization amplitudes A 0, A and A Untagged, time-integrated angular fit to helicity angles. A 0 2 = 0.30±0.12(stat)±0.04(syst) A 2 = 0.38±0.11(stat.)±0.04(syst.) dγ dcosθ Γ 1 0.4 0.2 LHCb Remarkable difference with its U-spin partner B 0 K 0 K 0 (BaBar: A 0 2 = 0.80 ± 0.12(stat) ±0.04(syst)). dϕ Γ 1 dγ 0-1 -0.8-0.6-0.4-0.2 0 0.2 0.4 0.6 0.8 1 cosθ 0.4 LHCb 0.2 0 0 1 2 3 4 5 6 ϕ Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 6 / 19
2 2 B 0 s φφ LHCb results B 0 s φφ Golden mode for measurement of φ s (Raidal, arxiv, hep-ph/0209091) 801 ± 29 candidates in the full 2011 dataset (1fb 1 ). S-wave component in ±25 MeV/c 2 window around φ mass 1.3% Candidates / 5 MeV/c 120 LHCb 100 80 60 Candidates / 2 MeV/c 3 10 2 10 10 LHCb 40 1 20 5100 5200 5300 5400 5500 5600 2 m KKKK (MeV/c ) -1 10 1000 1010 1020 1030 1040 2 m KK (MeV/c ) Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 7 / 19
LHCb results B 0 s φφ: Angular Analysis B 0 s φφ Polarization amplitudes in good agreement with CDF measurement. A 0 2 = 0.365 ± 0.022(stat) ± 0.012(syst) A 2 = 0.291 ± 0.024(stat) ± 0.010(syst) cos(δ ) = 0.844±0.068(stat)±0.029(syst) LHCB-PAPER-2012-004 (arxiv:1204.2813) Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 8 / 19
LHCb results B 0 s φφ B 0 s φφ: Triple Product Asymmetries Search for NP with no need of tagging or time-dependent analysis (Datta and London, arxiv:hep-ph/0303159) Interference terms I(A 0 A ) and I(A A ) are proportional to the tripple products: U: sin ϕ = (ˆn 1 ˆn 2 ) ˆp 1 V: sin(2ϕ)/2 = (ˆn 1 ˆn 2 )(ˆn 1 ˆn 2 ) ˆp 1 TP are odd under time reversal: Non zero TP asymmetries measurement may be a sign of CP-violation (CPT conservation) A U = Γ(U > 0) Γ(U < 0) Γ(U > 0) + Γ(U < 0) A V = Γ(V > 0) Γ(V < 0) Γ(V > 0) + Γ(V < 0) Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 9 / 19
LHCb results B 0 s φφ B 0 s φφ: Triple Product Asymmetries Candidates / 0.2 350 300 250 200 150 100 50 0 LHCb -0.4-0.2 0 0.2 0.4 U Candidates / 0.4 350 300 LHCb 250 200 150 100 50 0-1 -0.5 0 0.5 1 V Results are in good agreement with CDF and consistent with the hypothesis of CP conservation. A U = 0.055 ± 0.036(stat) ± 0.018(syst) A V = 0.010 ± 0.036(stat) ± 0.018(syst) Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 10 / 19
Outlook Ongoing work and future plans 2011 data: Bs 0 K 0 K 0 : M(Kπ)-dependent angular analysis to ensure 1% level S-wave contribution systematics Test of U-spin symmetry with simultaneous analysis of Bs 0 K 0 K 0 and B 0 K 0 K 0 B 0 φk 0 : Angular analysis, TP analysis Search for Bs 0 φk 0 2011 + 2012 data: Tagged, time-dependent angular analysis to measure φ S Key channels for LHCb upgrade: 50 fb-1 & improved hadron trigger, precision of 0.02 rad in φ S Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 11 / 19
Conclusions Conclusions First observation of Bs 0 and BR measurement. K 0 K 0 with 2010 data. Polarization amplitudes Analysis of B 0 s φφ with 2011 data. Polarization amplitudes and Triple Products analysis. Extension of these analysis and new ones (B 0 φk 0 and B 0 s φk 0 ) expected with 2011 (&2012) data. Hadronic penguin decays are key channels for LHCb CP-violation analysis. Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 12 / 19
Backup BACKUP Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 13 / 19
Polarization puzzle Backup Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 14 / 19
Angular distribution Backup I (θ 1, θ 2, ϕ) = d 3 ( Γ 1 d cos θ 1 d cos θ 2 dϕ = A 0 2 cos 2 θ 1 cos 2 θ 2 + Γ L 1 A 2 1 Γ L 2 sin2 θ 1 sin 2 θ 2 cos 2 ϕ + 1 A 2 1 Γ H 2 sin2 θ 1 sin 2 θ 2 sin 2 ϕ + ) 1 1 A 0 A cos δ Γ L 2 2 sin 2θ 1 sin 2θ 2 cos ϕ A 0 = H 0 A = 1 2 (H +1 + H 1 ) A = 1 2 (H +1 H 1 ) Normalization A 0 2 + A 2 + A 2 = 1 Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 15 / 19
B 0 s K 0 K 0 systematics Backup Table: Estimated systematic error sources in the B (BsKstKst) measurement. Systematic effect Error (%) Trigger efficiency 11 Global angular acceptance 7.2 S-wave fraction 5 Background subtraction 4.7 Bs 0 J/ψ K 0 and J/ψ µµ BR uncertainty 4.6 Selection efficiency 3.4 Total 15.9 Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 16 / 19
Backup Polarization amplitudes B 0 s φφ Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 17 / 19
B 0 s φφ systematics Backup Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 18 / 19
B 0 s φφ systematics Backup Paula Álvarez Cartelle (USC) Penguin decays at LHCb 31/05/2012 19 / 19