CP Violation in the B(s) meson system at LHCb Julian Wishahi on behalf of the LHCb collaboration

Transcription

1 CP Violation in the B(s) meson system at Julian Wishahi on behalf of the collaboration 5th Rencontres de Moriond, Electroweak Session, 2th of March 215

2 CPV in Interference of Mixing/Decay interference between direct decay and decay after oscillation phase difference φ q = φ mix 2 φ dec phases related to CKM angles golden modes (dominant b cc s tree decay) - B s J/ψ h + h (φ s = 2β s ) - B J/ψ K S (φ d = 2β) precise constraints from other measurements - sin φ d = J. Charles et al. - sin φ s = arxiv: excellent probe for NP contributions 2

3 CPV in Interference of Mixing/Decay CPV leads to a decay-time dependent asymmetry observables CP observables S, C, A ΔΓ mixing parameters Δm=m H m L and ΔΓ=Γ H Γ L 3

4 Asymmetry measurement A meas (t) = N B (t) N q B q (t) N B (t)+n q B q (t) D A CP (t)+a exp with D (1 2!) e m t trigger efficiency 9% for μμx channels track reconstruction efficiency >96% PV K + /! + SS kaon/pion u q Bq decay-time resolution 4 5 fs q b b x determine initial B flavour, εtag 36% need to control rate of wrong tags (ω 38%) t=lm/p SV b c b X l OS vertex charge c s same side opposite side K l OS kaon OS muon OS electron tagging power εtag(1 2ω) 2 3% 4

5 φs from Bs J/ψ K + K 96 signal candidates in 3 fb 1 analysis decay-time dependent (resolution 46 fs) flavour tagged (tagging power 3.7%) angular analysis in 6 bins of m KK - describe three P-wave and an S-wave state - disentangle CP-even and -odd P-wave contributions results (polarization-independent) Candidates / (.5π rad) CP even CP odd S-wave -2 2 ϕ h [rad] Candidates / most precise! Candidates / cosθ µ Candidates / (.2 ps) Candidates / S-wave! 3PRD 87, 112 (213) Decay time [ps] cosθ K Candidates / (.67 π rad) cosθ K 5 Phys. Rev. Lett. 114, 4181 (215) CP CP -2

6 φs from (Bs J/ψ K + K /π + π ) CDF 9.6 fb 1 DØ 8fb 1 CMS 2 fb 1 3fb 1 Combined SM 68% CL contours ( ) ATLAS 4.9 fb Phys. Rev. Lett. 114, 4181 (215) Phys. Lett. B736 (214) 6

7 Penguin Control for φs measure an effective phase separate higher-order SM contributions (penguins) SU(3) flavour symmetry: constrain Δφ s in B J/ψρ B J/ψ π + π 175 candidates in dataset of 3 fb 1 (2 MeV around the B mass) s = 2 s + NP + s angular + mass analysis to identify resonant π + π contributions Phys. Lett. B 742 (215), expected phase shift of s =(.5 ±.56) =[ 1.5, ] at 95% CL small compared to current exp. uncertainties exp s =.15 ±.35 = (.86 ± 2.1) 7

8 sin2β from B J/ψ K S time-dependent asymmetry (ΔΓ ) A J/ K S (t) = (B (t)! J/ K S ) (B (t)! J/ K S ) (B (t)! J/ K S )+ (B (t)! J/ K S ) = S J/ K S sin( m d t) C J/ K S cos( m d t) golden channel CPV in the decay negligible C J/ K S ) S J/ K S =sin2 precisely measured at B factories benchmark for TD CPV interesting prospects for sin(2β) sin(2φ 1 ) BaBar PRD 79 (29) 729 BaBar χ c K S PRD 8 (29) 1121 BaBar J/ψ (hadronic) K S PRD 69 (24) 521 Belle PRL 8 (212) ALEPH PLB 492, 259 (2) OPAL EPJ C5, 379 (1998) CDF PRD 61, 725 (2) PLB 721 (213) 24 Belle5S PRL 8 (212) Average HFAG HFAG Moriond 214 PRELIMINARY.69 ±.3 ±.1.69 ±.52 ±.4 ± ±.42 ± ±.2 ± ±.16 ± ±.7 ±.4.57 ±.58 ±.6.68 ±.2 8

9 sin2β from B J/ψ K S Run I dataset of 3 fb B J/ψ K S decays decay time resolution negligible dilution (slow B oscillation) improved flavour tagging Candidates / (1 MeV/c 2 ) (a) preliminary m (MeV/c 2 ) -PAPER-215-4, in preparation 35 tagging power (3.2 ±.5)% tagged 25 decays 2 Candidates / (1 MeV/c 2 ) analysis (a) 15 account for production and tagging 5 asymmetries correct for K effects m (MeV/c 2 ) Candidates / (.2ps) (b) preliminary 5 15 t (ps) Julian Wishahi Figure (TU Dortmund) 1: Distribution CPV in of the (a) B(s) thesystem reconstructed at mass Moriond and EW (b) logarithmic 2th March215 distribution of the decay 9 time of tagged B! J/ K S candidates. The solid black lines show the fit projections, while the

10 Signal yield asymmetry sin2β from B J/ψ K S Results preliminary results preliminary 5 15 t (ps) precision similar to B factories! BaBar.662 ±.39 ±.12 PRD 79, 729 (29) Belle.67 ±.29 ±.13 PRL 8, (212).731 ±.35 ±.2 Run I Average.688 ±.18 naive, all S b ccs BaBar PRD 79, 729 (29) Belle PRL 8, (212) S J/ψK S.26 ±.25 ± ±.21 ± ±.32 ±.5 Run I Average.3 ±.14 naive, all C b ccs C J/ψK S -PAPER-215-4, in preparation

11 β from B J/ψ K S 11

12 β from B J/ψ K S see Alexis talk see William s talk 12

13 Penguin control for B J/ψ K S measurement of β in B J/ψ K S precision on β - current world avg..8 - upgrade.2 (see -PUB-212-6) penguin contributions negligible? sin 2 B!J/ K S = S p 1 C 2 =sin(2 + d + NP d ) B b W + c c s J/ψ d K controlling SM penguins mandatory d U-spin symmetry: B J/ψ K S B s J/ψ K S same decay topologies B b W + colour singlet exchange u, c, t c c s J/ψ d K d 13

14 CPV in Bs J/ψ K S analysis of 3 fb 1 dataset x fewer B s than B decays multivariate selection trained on B proxy 9 selected B s decays ( 8k B ) tagging different treatment of B and B s comp. tagging power in B s 3.8% (2.6% in B ) Candidates / (.15 ps ) Pull Events / ( 2 MeV/c 2 ) comb. bkg. preliminary Downstream K S (MeV/c 2 ) B J/ψKS comb. bkg. B J/ψKS m J/ψ KS Bs J/ψKS Downstream preliminary K S -PAPER-215-5, in preparation likelihood fit for B s, B, comb. bkg. Pull 1 5 Bs J/ψKS t (ps) 14

15 CPV in Bs J/ψ K S preliminary results A Bs! J/ K S AC dir Bs! J/ K S A mix S Bs! J/ K S AΔΓ =.49 ± (stat.) ±.6 (syst.) =.28 ±.41 (stat.) ±.8 (syst.) =+.8 ±.4 (stat.) ±.8 (syst.) First measure ment! -PAPER-215-5, in preparation theory prediction (see arxiv: ) AΔΓ Bs! J/ K S =.957 ±.61 A dir C Bs! J/ K S =.3 ±.21 A mix S Bs! J/ K S =.29 ±.2 successful proof of concept 15

16 Summary time-dependent, tagged CP analyses with Run I precise measurements of CPV observables unique access to the B s meson system starting to reach the precision of the B factories good agreement with the Standard Model, so far still large room for improvement in experimental sensitivity further precision with more data and improved measurements control of penguin contributions will become mandatory a lot of interesting prospects for Run II & the upgrade! 16

17 D. Brady, Life ring, CC BY 2. Backup

18 Detector Vertex Detector reconstruct vertices decay time resolution: 45 fs IP resolution: 2 µm Tracking system momentum resolution Δp/p =.4%.6% RICH detectors K/π/p separation Dipole Magnet normal conducting bending power: 4 Tm regular polarity switches Calorimeters energy measurement particle identification Muon System 18

19 Prospects for Run II & Upgrade Type Observable Current Upgrade Theory precision 218 (5 fb 1 ) uncertainty Bs mixing 2 s (Bs! J/ ). [138] s (Bs! J/ f (98)).17 [214] a s sl [43] Gluonic 2 s e (Bs! ) penguins 2 s e (Bs! K K ).13.2 <.2 2 e (B! KS ).17 [43] s e (Bs! ).9.2 <.1 Right-handed currents e (Bs! )/ B s 5% 1%.2% Electroweak S 3 (B! K µ + µ ;1<q 2 < 6GeV 2 /c 4 ).8 [67] penguins s A FB (B! K µ + µ ) 25% [67] 6% 2% 7% A I (Kµ + µ ;1<q 2 < 6GeV 2 /c 4 ).25 [76] B(B +! + µ + µ )/B(B +! K + µ + µ ) 25% [85] 8% 2.5% % Higgs B(Bs! µ + µ ) [13] penguins B(B! µ + µ )/B(Bs! µ + µ ) % 35 % 5% Unitarity (B! D ( ) K ( ) ) 12 [244, 258] 4.9 negligible triangle (Bs! D s K) negligible angles (B! J/ K S ).8 [43].6.2 negligible Charm A [43] CP violation A CP [18] PUB

20 φs from Bs J/ψ K + K analysis decay-time dependent (resolution 46 fs) flavour tagged (tagging power 3.7%) angular analysis in 6 bins of m KK - disentangle CP-even and -odd contributions - describe three P-wave and an S-wave state results (polarization-independent) Candidates / (.5π rad) ϕ h [rad] Candidates / most precise! Candidates / cosθ µ Candidates / (.2 ps) Candidates / S-wave! 3PRD 87, 112 (213) Decay time [ps] cosθ K Candidates / (.67 π rad) cosθ K Phys. Rev. Lett. 114, 4181 (215) CP CP -2

21 φs from Bs J/ψ K + K select 96 signal candidates in 3 fb 1 ) 2 Candidates / (1. MeV/c (a) m(k K ) [MeV/c ] ) 2 Candidates / (2.5 MeV/c 15 5 (b) m(j/ψ K K ) [MeV/c ] Phys. Rev. Lett. 114, 4181 (215) 21

22 φs from Bs J/ψ K + K PRL 114, 4181 (215) P H Y S I C A L R E V I E W L polarisation-independent results Parameter Value Γ s (ps 1 ) ΔΓ s (ps 1 ) ja j ja j δ (rad) þ.þ.6 δ (rad) 3.8 þ ϕ s (rad) jλj Δm s (ps 1 ) þ.55 Phys. Rev. Lett. 114, 4181 (215) 22

23 φs from Bs J/ψ K + K syst. uncertainties (polarisation-independent) Source Γ s (ps 1 ) ΔΓ s (ps 1 ) ja j 2 ja j 2 δ (rad) δ (rad) ϕ s (rad) jλj Δm s (ps 1 ) þ. þ.14 þ.55 Total statistical uncertainty Mass factorization Signal weights (statistical) b-hadron background B þ c feed down.5 þ.2 Angular resolution bias Angular efficiency (reweighting) Angular efficiency (statistical) Decay-time resolution Trigger efficiency (statistical).11.9 þ.1 Track reconstruction (simulation) Track reconstruction (statistical) Length and momentum scales.2.5 S-P coupling factors Fit bias Quadratic sum of systematics þ Phys. Rev. Lett. 114, 4181 (215) 23

24 ay-time and ata points) e solid blue composed green), and φs from Bs J/ψ K + K polarisation-dependent results TABLE II. Values of the polarization-dependent parameters ϕ k s and jλ k j determined from the polarization-dependent fit. Parameter Value jλ j jλ =λ j jλ =λ j jλ S =λ j ϕ s (rad) ϕ s ϕ s (rad) ϕ s ϕ s (rad) ϕ S s ϕ s (rad) Phys. Rev. Lett. 114, 4181 (215)

25 φs from Bs J/ψ K + K syst. uncertainties (polarisation-dependent) TABLE IV. Statistical and systematic uncertainties for the polarization-dependent result. Source jλ j jλ jj =λ j jλ =λ j jλ S =λ j ϕ s (rad) ϕ jj s ϕ s (rad) ϕ s ϕ s (rad) ϕ S s ϕ s (rad) Total statistical uncertainty Mass factorization b-hadron background Angular efficiency (reweighting) Angular efficiency (statistical) Decay-time resolution S-P coupling factors.6 Quadratic sum of systematics Phys. Rev. Lett. 114, 4181 (215) 25

26 ± ±.24 ps ±.9 ps 1 B J/ψ π + π ±.1 ps ±.3 ps ± ps candidates in dataset of 3 fb 1 (2 MeV around the B mass) angular + Dalitz analysis to identify resonant contributions ±.424 Table 4 Fit and transversity fractions of contributing resonances from Fit 1. Uncertainties are statistical only. These results are presented only as a cross-check. Phys. Lett. B 742 (215), he se a- Component Fit fraction (%) Transversity fractions (%) ρ(77) 65.6 ± ± ± ± 1.7 f (5) 2.1 ±.7 1 f 2 (127) 7.8 ±.6 64 ± 4 9± 5 27 ± 5 ω(782) ± ± ρ(145) 9. ± ± ± ± 8 ρ(17) 3.1 ±.7 29 ± ± ± 15 26

27 B J/ψ π + π CP observables CP phase First measure ment! Phys. Lett. B 742 (215), e d (B! J/ ) = (41.7 ± 9.6 (stat) (syst)) constraint on penguin shift s =(.5 ±.56) =[ 1.5, ] at 95% CL small compared with exp. uncertainy on world average exp s =.15 ±.35 = (.86 ± 2.1) 27

28 B J/ψ π + π systematic uncertainties Systematic uncertainties on CP-violating phases 2β eff i Fit Sources ( ). Statistical uncertainties are also shown. Fit 1 Fit 2 ρ other ρ ρ ρ ρ ρ ρ other ρ Resonance model Resonance parameters ±1.21 ±.43 ±1.35 ±.68 ±.57 ±.6 Mass and angular acceptance ±.27 ±.5 ±.28 ±.21 ±.16 ±.5 Angular acc. correlation ±.22 ±.3 ±.22 ±.21 ±.8 ±.3 Decay time acceptance ±.5 ±.2 ±.6 ±.4 ±.4 ±.3 Bkg. mass and angular PDF ±.43 ±.9 ±.47 ±.22 ±.26 ±.11 Bkg. decay time PDF ±.14 ±.5 ±.12 ±.6 ±.8 ±.7 Bkg. model ±.49 ±.23 ±.15 ±.97 ±.38 ±.13 Flavor Tagging ±1.46 ±.3 ±1.66 ±.44 ±.86 ±.1 Production asymmetry ±.17 ±.5 ±.28 ±.9 ±.49 ±.42 Total systematic uncertainty Statistical uncertainty ±9.6 ±3.6 ±.2 ±6.5 ±7.2 ± Phys. Lett. B 742 (215),

29 sin2β from B J/ψ K S systematic uncertainties Origin S C Background tagging asymmetry.179 (2.5%).15 (4.5%) Tagging calibration.62 (.9%).24 (7.2%).47 (.6%) Fraction of wrong PV component.21 (.3%).11 (3.3%) z-scale.12 (.2%).23 (7.%) m.34 (.3%) Upper decay time acceptance.12 (3.6%) Correlation between mass and decay time Decay time resolution calibration Decay time resolution o set Low decay time acceptance Production asymmetry Sum.2 (2.7%).5 (15.2%) -PAPER-215-4, in preparation 29

30 CPV in Bs J/ψ K S systematic uncertainties Long Downstream Source A C dir S mix R 5 R 5 Mass modelling Decay-time resolution Decay-time acceptance Tagging calibration Mass resolution Mass time correlation Total PAPER-215-5, in preparation 3