CP Violation at the LHC - workshop 2017

Transcription

1 CP Violation at the LHC - SM@LHC workshop 217 Sarah Karodia on behalf of the LHCb collaboration, including results from ATLAS, CMS and LHCb University of Glasgow May 2, 217 Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

2 Introduction CKM matrix describes charged-current weak interactions. CKM matrix has 3 angles and 1 phase- the only source of CPV in SM quark sector is this phase. V ud V ub + V cd V cb + V td V tb = Deviations from the CKM picture of the standard model could show signs of new physics. Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

3 Introduction CPV is an important part of the LHCb physics program. Many analysis measure CPV at the LHC. Topics include: - Measuring the B s mixing phase φ s - The unitary triangle angle γ - CPV in charm - Time dependent CP asymmetry measurements in B-mesons - CPV from B-meson lifetimes - CPV in Λ b baryons - CP asymmetry measurements in top-quark events Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

4 Overview 1 Time dependent CP violating asymmetries in B d and B s mesons 2 Combined measurement of CKM angle γ 3 CPV in Λ b baryon decays 4 Measurements of the phase φ s 5 V ub status and prospects Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

5 Time dependent CP violating asymmetries in Bd and Bs mesons Sarah Karodia (UoG) 217 May 2, / 23

6 Time dependent CP violating asymmetries in B d and B s mesons Talk includes two separate time dependent asymmetry measurements. One result from a decay dominated by tree level processes and one where the decay is dominated by loop processes. These measurements can be used to determine the CKM the angle γ, Eur.Phys.J.C71:1532,211, Nucl.Phys. B671 (23) For final state f, CP asymmetry A(t) = Γ(B (s) f (t)) Γ(B (s) f (t)) Γ(B (s) f (t)) + Γ(B (s) ) f (t)) = C f cos( mt) + S f sin( mt) cosh Γ t + 2 A Γ f sinh Γ t, 2 This condition is not imposed in fits. (S f ) 2 + (C f ) 2 + (A Γ f ) 2 = 1. Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

7 Time dependent CP violating asymmetries in B s D s K ± LHCb-CONF s s b u, c, t s B s b c D + s B s s W ± u, c, t W ± b u K V cb V us λ 3 u s K V ub V cs λ 3 c s D + s Standard model measurements from tree topology. CPV in interference beween mixing and decay amplitudes. Can extract γ 2β S from decay-time evolution of decay rates. Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

8 2 2 Time dependent CP violating asymmetries in B s D s K ± LHCb-CONF Analysis was performed with 3 fb 1 run 1 data, and uses flavour tagging to determine initial flavour of B s. Flavour tagging calibrated with B s D s π +, OS and SS neural network taggers used (Eur. Phys. J. C (212) 77:22,Eur. Phys. J. C (217) 77:238). Ongoing work to improve tagging efficiencies in LHCb. High tagging power. Mistag rate against the average predicted mistag rate η, (left) OS and (right) SS taggers: ω LHCb Preliminary grint Entries 3 χ / ndf 7.14 / 5 Mean.3937 p.3898 ±.557 RMS.1456 p1 1 ±.5981 η _mean.3698 ± η ω LHCb Preliminary grint Entries 3 χ / ndf Mean / 7 p.4458 ±.4241 RMS.1396 p ±.6527 η _mean.4374 ± η Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

9 - + Time dependent CP violating asymmetries in B s D s K ± LHCb-CONF LHCb Preliminary BeautyMass m(d K ± ) [MeV/c 2 s ] Candidates / ( 5. MeV/c 2 ) + sk D A mix.4 LHCb Preliminary.2 ± Candidates / (.85 MeV/c 2 ) - sk D A mix 7 LHCb Preliminary CharmMass m(k + K π ±, π + π π ±, K ± π π + ) [MeV/c 2 ].4 LHCb Preliminary.2 C f = C f =.735 ±.142 ±.48 S f =.518 ±.22 ±.73 S f =.496 ±.197 ±.71 A Γ f =.395 ±.277 ±.122 A Γ =.314 ±.274 ±.17 f Using 2β s φ s =.1 ±.39 from Phys. Rev. Lett. 114, 418. gives γ = ( ) with 68.3% C.L. Im LHCb prel, 3 fb, B s D s K 2 -iγ 2λ f / (1+ λ ) = ( A Γ, S)~ e 2 +iγ 2λ / (1+ λ ) = ( A Γ, S)~e f τ modulo (2π/ m ) [ps] s τ modulo (2π/ m ) [ps] s γ ( A Γ,S) ( A Γ,S) 2 radius = 1 C Re Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

10 Time dependent CP violating asymmetries in Bd π + π and Bs K + K LHCb-CONF fb 1 run 1 data Only OS flavour taggers used, Calibrated with Bd K + π and Bs π + K Cπ+ π =.24 ±.7 ±.1 Sπ+ π =.68 ±.6 ±.1 CK + K =.24 ±.6 ±.2 SK + K =.22 ±.6 ±.2 A Γ K + K =.75 ±.7 ±.11 Most precise measurement of CPV in Bs K + K. Future improvements on precision on run 1 with SS tagger included, and run 2 data analysis. γ and φs extracted from U-spin symmetry. Hadronic uncertainties can be controlled using a combined analysis. Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

11 Combined measurement of CKM angle γ Sarah Karodia (UoG) 217 May 2, / 23

12 Combined measurement of CKM angle γ JHEP 12 (216) 87 1-CL Direct measurement from interference between b cw (V cb ) and b uw (V ub ). Performed with LHCb run 1 data. Time-integrated measurements: B u + Dh +, B u + DK +, Bd DK, Bd DK + π and B u + Dh + π + π. (see backup) Time-dependent measurement: Bs Ds K ± (used the 1fb 1 measurement). ( B h + h not included) Frequentist treatment (Bayesian procedure agrees). 68.3% LHCb 95.5% γ [ ] decays B s B decays + B decays Combination Results: γ = ( ) Most precise direct measurement. Future improvements: Including latest B s D s K ± (Discussed previously). Time-integrated analysis of B u ± DK ±, two body D decays. LHCb-CONF Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

13 CPV in Λ b baryon decays Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

14 Evidence of CPV in Λ b pπ π + π Nature Phys. 13 (217) 391 In SM, CPV is predicated in baryon decays. Direct measurement of CPV, difficult to determine SM prediction. 3 fb 1 run 1 data. CP odd observables are scalar triple products of final-state particle momenta, Λ b c.o.m. frame: C T = p p ( p h p h + ) 1 2 In figure (h 1, h+ 2 ) = (π fast, π+ ) A T (C T ) = N(C T >) N(C T <) N(C T >)+N(C T <) A T (C T ) = N( C T >) N( C T <) N( C T >)+N( C T <) P and CP violating observables defined: ( ) A T + A T a T -odd P = 1 2 a T -odd CP = 1 2 ( A T A T ) Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

15 Evidence of CPV in Λb pπ π + π Nature Phys. 13 (217) 391 Λb pπ π + π asymmetries measured with two binding schemes. Scheme A: binned in phase space corresponding to dominate resonances. Scheme B: 1 uniform bins in Φ. CPV at 3.3σ. 1st evidence of CPV in Λb baryons. Λb pπ K + K asymmetries measured with two regions of phase space. No evidence of P or CP violation. Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

16 Measurements of the phase φ s Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

17 Measurements of the phase φ s JHEP 8 (216) 147, Phys. Lett. B 757 (216) 97, arxiv: Most sensitivity coming from B s J/Ψφ(12)( K + K ). Mixture of CP-even and CP-odd final state particles, separated by angular analysis. 14.3fb 1 ATLAS run1 data: φ s =.9 ±.78 ±.41 rad Γ s =.85 ±.11 ±.7 ps 1 Γ s =.675 ±.3 ±.3 ps fb 1 CMS run1 data: φ s =.75 ±.97 ±.31 rad Γ s =.95 ±.13 ±.7 ps 1 LHCb run 1, latest result: m KK above φ(12) mass. φ s =.199 ±.17 ±.34 rad. 3fb 1 LHCb run 1 combination: φ s =.1 ±.37 rad Γ s =.813 ±.73 ±.36 ps 1 Γ s =.6588 ±.22 ±.15 ps 1 All results agree with SM prediction, ( )mrad. Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

18 V ub status and prospects Sarah Karodia (UoG) 217 May 2, / 23

19 V ub from Λ b pµ ν µ and Λ b Λ + c µ ν µ Candidates / (5 MeV/c 2 ) Nature Phys. 1 (215) Exclusive measurement on 2 fb 1 LHCb data. Combinatorial Mis-identified D pµ ν * Λ + c µ ν + Λcµ ν * N µ ν pµ ν LHCb Corrected pµ mass [MeV/c 2 ] corrected mass m corr = Candidates / (4 MeV/c 2 ) V ub 2 V cb 2 = B(Λ b pµ ν µ) B(Λ b Λ + c µ ν µ) R FF LHCb + Λcµ ν *+ Λ c µ ν Combinatorial Corrected pk π + µ mass [MeV/c 2 ] m 2 hµ + p2 + p V ub V cb =.83 ±.4 ±.4 computed with R FF =.68 ±.7 (Phys. Rev. D 92, 3453 (215)). Using V cb world average gives: V ub = (3.27 ±.15 ±.16 ±.6) V ub V ub V ub inclusive exclusive exclusive * D V cb exclusive D V cb inclusive V cb 3 2 Indirect (HFAG) V ub /V cb Λb V cb 1 3 Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

20 V ub prospects Λ b pµ ν µ measurement is systematics limited. Future improvements: Current measurement limited by LQCD predictions on form factors, expect uncertainty to reduce. Improvements on uncertainties from the normalisation mode branching fraction could come from BES and BELLE. Changes to tracking and trigger implemented in run 2 will reduce uncertainties from these efficiencies. Difficult to numerically predict how these improvements will increase sensitivity. Use Bs K µ + ν mu to measure V ub. Branching fraction of Bs K µ + ν mu is lower than in Λ b case. Smaller form factor uncertainty. Normalisation mode branching fraction Bs Ds µ + ν mu has small uncertainties. Potentially lower systematics than Λ b channel. Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

21 Conclusions Latest results of time-dependent asymmetries in Bd and Bs improves precision of CPV variables and γ = ( ). Most precise direct measurement of γ = ( ), already new measurements done to improve sensitivity. First evidence of CPV in baryonic Λ b decays at 3.3σ. All run 1 measurements of φ s consistent with SM. Plans to improve exclusive V ub with LHCb run 2 data and a new physics channel. Many other interesting CPV results that this talk did not have time to cover including: -CP asymmetry measurements in top-quark events, JHEP 2 (217) 71. -CPV in Λ b pk µ + µ, arxiv: Time-dependent asymmetries in charm, arxiv: Submitted to Phys. Rev. Lett. Thanks for listening! Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

22 Backup Slides: Combination γ JHEP 12 (216) 87 B decay D decay Method Ref. Status since last combination [28] B + Dh + D h + h GLW/ADS [44] Updated to 3 fb 1 B + Dh + D h + π π + π GLW/ADS [44] Updated to 3 fb 1 B + Dh + D h + h π GLW/ADS [45] New B + DK + D K S h + h GGSZ [46] As before B + DK + D K S K π + GLS [47] As before B + Dh + π π + D h + h GLW/ADS [48] New B DK D K + π ADS [49] As before B DK + π D h + h GLW-Dalitz [5] New B DK D K S π + π GGSZ [51] New Bs Ds K ± D s + h + h π + TD [52] As before List of LHCb measurements used in combination including methods used to determine γ. References correspond to those in paper. Sarah Karodia (UoG) SM@LHC 217 May 2, / 23

23 Backup Slides: Λ b pπ π + π Nature Phys. 13 (217) 391 Phase space bin m(pπ + ) m(pπ slow ) m(π+ π slow ), m(π+ π fast ) Φ 1 (1.7, 1.23) (, π 2 ) 2 (1.7, 1.23) ( π 2, π) 3 (1.23, 1.35) (, π 2 ) 4 (1.23, 1.35) ( π 2, π) 5 (1.35, 5.34) (1.7, 2.) m(π + π slow ) <.78 or m(π+ π fast ) <.78 (, π 2 ) 6 (1.35, 5.34) (1.7, 2.) m(π + π slow ) <.78 or m(π+ π fast ) <.78 ( π 2, π) 7 (1.35, 5.34) (1.7, 2.) m(π + π slow ) >.78 and m(π+ π fast ) >.78 (, π 2 ) 8 (1.35, 5.34) (1.7, 2.) m(π + π slow ) >.78 and m(π+ π fast ) >.78 ( π 2, π) 9 (1.35, 5.34) (2., 4.) m(π + π slow ) <.78 or m(π+ π fast ) <.78 (, π 2 ) 1 (1.35, 5.34) (2., 4.) m(π + π slow ) <.78 or m(π+ π fast ) <.78 ( π 2, π) 11 (1.35, 5.34) (2., 4.) m(π + π slow ) >.78 and m(π+ π fast ) >.78 (, π 2 ) 12 (1.35, 5.34) (2., 4.) m(π + π slow ) >.78 and m(π+ π fast ) >.78 ( π 2, π) Definition of binning scheme A. Sarah Karodia (UoG) SM@LHC 217 May 2, / 23