New results on flavor anomalies at LHCb

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1 New results on flavor anomalies at LHCb Paula Álvarez Cartelle on behalf of the LHCb collaboration Dark LHC Heidelberg, April 2018

2 The indirect approach Study processes that are suppressed or even forbidden in the SM - possible NP effects relatively large Precision measurement of observables that are very well predicted in the SM Access to higher mass scales, due to virtual contributions, in a model independent way 2 / P. Álvarez Cartelle (ICL) Flavour LHCb 2/38 25

3 Flavour anomalies A) Loop level b sl + l transitions Rates and angular observables in b sµ + µ Lepton Flavour Universality tests in µ/e ratios B) Tree level b clν transitions Lepton Flavour Universality tests in µ/τ ratios The following results are obtained using the full Run1 LHCb sample (3 fb 1 ) 3 / P. Álvarez Cartelle (ICL) Flavour LHCb 3/38 25

4 b sll transitions Flavour Changing Neutral Current (FCNC) b s(d)l + l decays, such as B 0 K 0 µ + µ, are forbidden at tree level in the SM Veto out charmonium resonances, where the hadronic process dominates 4 / P. Álvarez Cartelle (ICL) Flavour LHCb 4/38 25

$Branching fraction measurements Branching fractions$ processes SM predictions suffer from large hadronic

5 Branching fraction measurements Branching fractions consistently below the SM prediction for many b sµµ processes SM predictions suffer from large hadronic uncertainties 5 / P. Álvarez Cartelle (ICL) Flavour LHCb 5/38 25

Angular observables - B 0 K 0 µ + µ Complementary constraints on NP & orthogonal experimental systematics Good agreement with the SM in many of the observables Possibility to construct a

6 Angular observables - B 0 K 0 µ + µ Complementary constraints on NP & orthogonal experimental systematics Good agreement with the SM in many of the observables Possibility to construct a set of optimised observables with reduced dependence on form-factor at leading order [JHEP 1204 (2012) 104] P 5 = S 5/ F L(1 F L) 6 / P. Álvarez Cartelle (ICL) Flavour LHCb 6/38 25

$Altmannshofer et al. EPJC 77 (2017) 377 Best fit prefers shifted vector coupling C 9 (3 4σ depending on the group/observables included) Branching fractions and angular observables consistent 7 / P.$

7 Global fits to b sµ + µ observables Interpretation in effective theory, in terms of couplings (C i) and local operators (O i), describing e.g. photon (C 7), vector (C 9) or axial-vector (C 10) contributions W. Altmannshofer et al. EPJC 77 (2017) 377 Best fit prefers shifted vector coupling C 9 (3 4σ depending on the group/observables included) Branching fractions and angular observables consistent 7 / P. Álvarez Cartelle (ICL) Flavour LHCb 7/38 25

8 Hadronic effects or New Physics? Dependence of observables on the vector coupling enters through C eff 9 = C 9 + C λ 9 (q 2 ) where C λ 9 (q 2 ) contains all vector-like contributions Unaccounted for c c-loop contributions would mimic vector-like NP shifts in C 9 Big effort ongoing to improve both theory and experimental precision in order to solve this puzzle 8 / P. Álvarez Cartelle (ICL) Flavour LHCb 8/38 25

9 Lepton flavour universality tests In the Standard Model, couplings of the gauge bosons to leptons are independent of lepton flavour branching fractions of e, µ and τ differ only by phase space and helicity-suppressed contributions Free from QCD uncertainties that may affect other observables Any sign of lepton flavour non-universality would be a direct sign for new physics l γ,z 0 l + l l + b W s b LQ s NP models accomodating LFnU, often predict Lepton Flavour Violation too See Guido s talk tomorrow on the search for B eµ decays 9 / P. Álvarez Cartelle (ICL) Flavour LHCb 9/38 25

10 LFU in B + K + l + l [JHEP 07 (2007) 040] R SM K = BR(B+ K + µ + µ ) BR(B + K + e + e ) = 1 ± O(10 4 ) Measurement performed with 3 fb 1 of data, in 1 < q 2 < 6 GeV/c 2 R K = ± Compatible with SM at 2.6σ Clear motivation to explore related LFU ratios (R K 0, R φ,...) [LHCb, PRL 113 (2014) ] QED corrections can be O(10 2 ) [EPJC 76 (2016) 8,440] 10 / P. Álvarez Cartelle (ICL) Flavour LHCb 10/38 25

11 LFU in B 0 K 0 l + l [EPJC 76 (2016) 440, JHEP 04 (2017) 016, PRD 95 (2017) , EPJC 77 (2017) 377, PRD 93 (2016) ] R SM K 0 = BR(B0 K 0 µ + µ ) BR(B + K 0 e + e ) = 1 ± O(10 3 ) R K 0 is measured in 2 bins in q 2 Low: [0.045, 1.1] GeV/c 2 Central: [1.1, 6.0] GeV/c 2 QED corrections can be O(10 2 ) [EPJC 76 (2016) 8,440] 11 / P. Álvarez Cartelle (ICL) Flavour LHCb 11/38 25

12 Experimental challenge [LHCb, JHEP 08 (2017) 055] Differences between electrons and muons in the detector Electron Bremsstrahlung Degraded momentum, and mass/q 2 resolutions (bkg from B Kππee) Trigger less efficient for electrons Cancel most systematics arising from these differences by computing R K 0 as a double ratio B 0 K 0 µ + µ / B 0 K 0 e + e R K 0 = B 0 K 0 J/ψ(µ + µ ) B 0 K 0 J/ψ(e + e ) 12 / P. Álvarez Cartelle (ICL) Flavour LHCb 12/38 25

Cancel most systematics arising from these differences by computing R K 0 as a double ratio B 0 K 0 µ + µ / B 0 K 0

13 Experimental challenge [LHCb, JHEP 08 (2017) 055] Differences between electrons and muons in the detector Electron Bremsstrahlung Degraded momentum, and mass/q 2 resolutions (bkg from B Kππee) Trigger less efficient for electrons Cancel most systematics arising from these differences by computing R K 0 as a double ratio B 0 K 0 µ + µ / B 0 K 0 e + e R K 0 = B 0 K 0 J/ψ(µ + µ ) B 0 K 0 J/ψ(e + e ) 12 / P. Álvarez Cartelle (ICL) Flavour LHCb 12/38 25

14 R K 0 result [LHCb, JHEP 08 (2017) 055] 2.0 R K R K LHCb LHCb BIP CDHMV EOS flav.io JC q 2 [GeV 2 /c 4 ] LHCb LHCb BaBar Belle q 2 [GeV 2 /c 4 ] R K 0(0.045 < q 2 < 1.1 GeV/c 2 ) = ± 0.03 R K 0(1.1 < q 2 < 6.0 GeV/c 2 ) = ± 0.05 Compatibility with the SM is estimated to be at the level of σ for low q 2 and σ at central q 2 13 / P. Álvarez Cartelle (ICL) Flavour LHCb 13/38 25

15 Global fits with LFU observables Picture is consistent with b sµµ anomalies, if NP couples only to muons and not electrons [JHEP 01 (2018) 093] [PRD 96 (2017) ] 14 / P. Álvarez Cartelle (ICL) Flavour LHCb 14/38 25

16 s 0 B 0 (s) µ+ µ observation [PRL 118, (2017)] Sensitive to new (pseudo)scalar or axial vector operators and precisely predicted in the SM B SM (B 0 s µ + µ ) = (3.65 ± 0.23) 10 9 B SM (B 0 µ + µ ) = (1.06 ± 0.09) [PRL 112, (2014)] First single-experiment observation using Run1 (3 fb 1 ) + Run2 (2 fb 1 ) data B(B 0 s µ + µ ) = (3.0 ± ) 10 9 B(B 0 µ + µ ) < % CL ) µ + µ BF(B SM 68.27% BF(B µ + s µ ) 95.45% 99.73% 99.99% LHCb 9 10 First measurement of the effective lifetime for this decay (extremely clean theoretically and complementary sensitivity) τ µµ = 2.04 ± 0.44 ± 0.05 ps Decay time 15 [ps] / P. Álvarez Cartelle (ICL) Flavour LHCb 15/38 25 candidates / (1 ps) µ + µ 0 Weighted B LHCb Effective lifetime fit

Search for B 0 s K µ + µ [LHCb-PAPER-2018-004 in preparation] FCNC b dll transition, CKM-suppressed with respect to b sll in the SM (B O(10 8 )) Interesting to probe MFV nature of new physics First

17 Search for B 0 s K µ + µ [LHCb-PAPER in preparation] FCNC b dll transition, CKM-suppressed with respect to b sll in the SM (B O(10 8 )) Interesting to probe MFV nature of new physics First evidence of this decay is observed with a significance of 3.4σ The branching ratio is estimated using B 0 K J/ψ B(B 0 s K µ + µ ) = (3.0 ± 1.0(stat) ± 0.2(syst) ± 0.3(ext)) 10 8 Dataset: Run1 (3 fb 1 ) + Run2 (1.6 fb 1 ) 16 / P. Álvarez Cartelle (ICL) Flavour LHCb 16/38 25

18 LFU in trees - B 0 D + l ν l In the SM the only difference between the two decays is the mass of the lepton Theoretically clean R(D ) SM = BR( B 0 D + τ ν τ ) BR( B 0 D + µ ν = ± µ ) 2 measurements at LHCb Leptonic τ µ ν µν τ [PRL 115 (2015) ] Hadronic τ π π + π (π 0 )ν τ [arxiv: ] [S.Fajfer et al., PRD85 (2012) ] 17 / P. Álvarez Cartelle (ICL) Flavour LHCb 17/38 25

19 R(D ) experimental challenge Missing neutrinos No narrow peak to fit (in any distribution) Calculate m 2 missing, q 2 and E µ in approximate rest frame Main backgrounds are partially reconstructed B decays B D µν, B D µν, B D D(µX)X... Isolation MVA used to reject physics backgrounds with additional cuts and to select control samples of specific backgrounds 18 / P. Álvarez Cartelle (ICL) Flavour LHCb 18/38 25

R(D ) with τ µ ν µ ν τ [LHCb, PRL 115 (2015) 111803] Three dimensional template fit (m 2 missing, E µ, q 2 shown)

) Background from µ misid and combinatorial from data Shape and form factor dependence systematics included in the

20 R(D ) with τ µ ν µ ν τ [LHCb, PRL 115 (2015) ] Three dimensional template fit (m 2 missing, E µ, q 2 shown) Large MC samples for signal and physics backgrounds (data-driven syst.) Background from µ misid and combinatorial from data Shape and form factor dependence systematics included in the fit The obtained result R(D ) = ± ± is consistent with the SM at 2.1σ level 19 / P. Álvarez Cartelle (ICL) Flavour LHCb 19/38 25

21 R(D ) with τ π π + π (π 0 )ν τ [LHCb, arxiv: ] Measure the B(B 0 D τ + ν τ ) relative to the B 0 D 3π Use external inputs for B(B 0 D 3π) and B(B 0 D µ + ν µ) to compute R(D ) Similar experimental challenges associated with missing neutrino Main backgrounds are partially reconstructed B decays B D 3πX (τ lifetime), B DD (s) X (BDT) / P. Álvarez Cartelle (ICL) Flavour LHCb 20/38 25

22 R(D ) with τ π π + π (π 0 )ν τ [LHCb, arxiv: ] 3D template fit to τ lifetime, q 2 and BDT output Templates are extracted from simulation and validated in data control samples Candidates / (0.25ps) τ (ns) /c 4 ) 2 Candidates / (1.375GeV LHCb (GeV / c 4 ) q Result R(D ) = ± ± ± compatible with the SM at 1σ level Dominant systematic uncertainty comes from the size of the simulated samples t τ [ps] q 2 (GeV / c 4 ) Data Total model 50 B 0 D * τ + ν τ 40 B D ** τ + ν τ + B D * D s (X) + 30 B D * D (X) B D * 3π X 0 20 B D * D (X) Comb. bkg q 2 [GeV /c 4 ] 21 / P. Álvarez Cartelle (ICL) Flavour LHCb 21/38 25

23 R(D ( ) ) combination R(D*) BaBar, PRL109,101802(2012) 0.5 Belle, PRD92,072014(2015) LHCb, PRL115,111803(2015) Belle, PRD94,072007(2016) Belle, PRL118,211801(2017) LHCb, FPCP2017 Average χ = 1.0 contours SM Predictions R(D)=0.300(8) HPQCD (2015) R(D)=0.299(11) FNAL/MILC (2015) R(D*)=0.252(3) S. Fajfer et al. (2012) σ 4σ HFLAV FPCP 2017 P(χ 2 ) = 71.6% R(D) Latest HFAG average: 4.1σ from SM expectation (Recent theory input reduces tension [JHEP 11 (2017) 061]) 22 / P. Álvarez Cartelle (ICL) Flavour LHCb 22/38 25

24 LFU in B c J/ψl + ν l [LHCb, PRL 120, (2018)] R(J/ψ) SM = BR(B+ c J/ψτ + ν τ ) BR(B + c J/ψµ + ν µ ) [PLB 452 (1999) , arxiv:hep-ph/ , PRD 73 (2006) , PRD 74 (2006) ] [0.25, 0.28] FF parameters determined from fit to normalisation mode Use τ µ ν µ ν τ decays: similar exp. method as for leptonic R(D ) 23 / P. Álvarez Cartelle (ICL) Flavour LHCb 23/38 25

R(J/ψ) result [LHCb, PRL 120, 121801 (2018)] 3D template fit to m 2 miss, B+ c

in data control samples Result R(J/ψ) = 0.71 ± 0.17(stat) ± 0.

comes from the size of the simulated samples and the B c + J/ψ FF First

25 R(J/ψ) result [LHCb, PRL 120, (2018)] 3D template fit to m 2 miss, B+ c Z(Eµ, q 2 ) lifetime and Templates are extracted from simulation and validated in data control samples Result R(J/ψ) = 0.71 ± 0.17(stat) ± 0.18(syst) compatible with the SM at 2σ level Dominant systematic uncertainty comes from the size of the simulated samples and the B c + J/ψ FF First evidence fro the decay B c J/ψτ + ν τ 24 / P. Álvarez Cartelle (ICL) Flavour LHCb 24/38 25

26 Summary LHCb Run1 has left us with an interesting set of anomalies B s and angular observables in b sµµ transitions Hints of lepton non-universality in loop dominated b sll processes and in tree level b clν decays Many new measuremens expected at LHCb that will confirm or disprove these results 25 / P. Álvarez Cartelle (ICL) Flavour LHCb 25/38 25

27 Backup 26 / P. Álvarez Cartelle (ICL) Flavour LHCb 26/38 25

28 LHC schedule 26 / P. Álvarez Cartelle (ICL) Flavour LHCb 26/38 25

Angular observables In multibody final states, other observables sensitive to NP are accessible through the study of the angular distribution of the decay products Complementary constraints on NP &

29 Angular observables In multibody final states, other observables sensitive to NP are accessible through the study of the angular distribution of the decay products Complementary constraints on NP & orthogonal experimental systematics For B 0 K 0 µ + µ, the final state is described by three angles Ω = {θ K, θ l, φ} and q 2 = m 2 µµ 1 d 3 (Γ + Γ) d(γ + Γ)/dq 2 = 9 [ 3 dω 32π 4 (1 F L) sin 2 θ K + F L cos 2 θ K + F L, A F B and S i contain dependence with the Wilson coefficients (C 7, C 9, C 10) and hadronic form factors (1 F L) sin 2 θ K cos 2θ l F L cos 2 θ K cos 2θ l + S 3 sin 2 θ K sin 2 θ l cos 2φ + S 4 sin 2θ K sin 2θ l cos φ + S 5 sin 2θ K sin θ l cos φ A F B sin 2 θ K cos θ l + S 7 sin 2θ K sin θ l sin φ + S 8 sin 2θ K sin 2θ l sin φ + S 9 sin 2 θ K sin 2 θ l sin 2φ ] 27 / P. Álvarez Cartelle (ICL) Flavour LHCb 27/38 25

30 Interference with charmonia 28 / P. Álvarez Cartelle (ICL) LHCB-PAPER Flavour LHCb 28/38 25 At low q 2, main SM c c contribution comes from J/ψ and extends to q 2 = 0 Effect on C eff 9 strongly depends on the phase difference with the short distance process Fit B Kµµ data including resonance region with C eff 9 (q 2 ) = C 9 + j n j e iδj BW i (q 2 )

31 R K 0 systematics R K 0/R K 0 [%] low- q 2 central- q 2 Trigger category L0E L0H L0I L0E L0H L0I Corrections to simulation Trigger PID Kinematic selection Residual background Mass fits Bin migration r J/ψ ratio Total / P. Álvarez Cartelle (ICL) Flavour LHCb 29/38 25

32 R K 0 xchecks - control ratios Control the absolute scale of the efficiencies with the single ratio r J/ψ = B(B0 K 0 J/ψ(µ + µ )) B(B 0 K 0 J/ψ(e + e )) = ± ± Independent of the decay kinematics, such as and η of the B 0 candidate and final-state particles, and the charged-track multiplicity in the event Extra checks R ψ(2s) = B(B0 K 0 ψ(2s)(µ + µ )) / B(B 0 K 0 ψ(2s)(e + e )) B(B 0 K 0 J/ψ(µ + µ )) B(B 0 K 0 J/ψ(e + e )) [2%] r γ = B(B0 K 0 γ(e + e )) B(B 0 K 0 J/ψ(e + e )) [7%] B(B 0 K 0 γ(e + e )) in good agreement with [JHEP 04 (2017) 142] 30 / P. Álvarez Cartelle (ICL) Flavour LHCb 30/38 25

33 R K 0 x-checks - Brem. recovery Fraction of candidates [%] LHCb 0 B K *0 γ ( e + e ) Data Simulation Fraction of candidates [%] LHCb 0 B K *0 J/ψ Data Simulation 0 L0E L0H L0I L0E L0H L0I L0E L0H L0I 0 clusters 1 cluster 2 clusters 0 L0E L0H L0I L0E L0H L0I L0E L0H L0I 0 clusters 1 cluster 2 clusters 31 / P. Álvarez Cartelle (ICL) Flavour LHCb 31/38 25

34 R K 0 distributions - low q 2 Fraction of candidates [%] 0.5 LHCb <q 2 <1.1 [GeV /c 4 ] B Data Simulation 0 K *0 µ + µ 0.4 B Data Simulation 0 K *0 e + e Fraction of candidates [%] 0.5 LHCb <q 2 <1.1 [GeV /c 4 ] B Data Simulation 0 K *0 µ + µ 0.4 B Data Simulation 0 K *0 e + e Fraction of candidates [%] q 2 [GeV /c 4 ] 0.6 LHCb <q 2 <1.1 [GeV /c 4 ] 0.5 B Data Simulation 0 K *0 µ + µ B Data Simulation 0 K *0 e + e θ lepton [mrad] Fraction of candidates [%] m(k π ) [MeV/c 2 ] LHCb <q 2 <1.1 [GeV /c 4 ] B Data Simulation 0 K *0 µ + µ B Data Simulation 0 K *0 e + e [mm] z vertex 32 / P. Álvarez Cartelle (ICL) Flavour LHCb 32/38 25

35 R K 0 distributions - central q 2 Fraction of candidates [%] Fraction of candidates [%] LHCb 2 1.1<q 2 <6.0 [GeV /c 4 ] B Data Simulation 0 K *0 µ + µ B Data Simulation 0 K *0 e + e q 2 [GeV /c 4 ] LHCb 2 1.1<q 2 <6.0 [GeV /c 4 ] B Data Simulation 0 K *0 µ + µ B Data Simulation 0 K *0 e + e θ lepton [mrad] Fraction of candidates [%] Fraction of candidates [%] LHCb 2 1.1<q 2 <6.0 [GeV /c 4 ] B Data Simulation 0 K *0 µ + µ B Data Simulation 0 K *0 e + e m(k π ) [MeV/c 2 ] LHCb 2 1.1<q 2 <6.0 [GeV /c 4 ] B Data Simulation 0 K *0 µ + µ B Data Simulation 0 K *0 e + e [mm] z vertex 33 / P. Álvarez Cartelle (ICL) Flavour LHCb 33/38 25

LFU prospects For ratios of B s (e.g. R K, R K 0) we could reach 1-2% precision For comparison Belle 2 expects to reach a precision of 4-5% with a 50 ab 1 dataset [S.

36 LFU prospects For ratios of B s (e.g. R K, R K 0) we could reach 1-2% precision For comparison Belle 2 expects to reach a precision of 4-5% with a 50 ab 1 dataset [S. Sandilya at CKM 2016] Angular analyses with electrons have orthogonal systematics with respect to R X s and these can also be kept under control Expect good sensitivity to differences in the angular distributions for electron/muon final states [LHCb, EOI for phase II upgrade CERN-LHCC ] 34 / P. Álvarez Cartelle (ICL) Flavour LHCb 34/38 25

37 b dl + l transitions As for B d µ + µ /B s µ + µ and m d / m s, ratio of b s and b d decays is a test of MFV FNAL/MILC PRD93, (2016) EW penguins have additional uncertainty from ratio of form factors, will need improvements from Lattice too 35 / P. Álvarez Cartelle (ICL) Flavour LHCb 35/38 25

38 Baryonic decays Give access to different combinations of Wilson coefficients Unique sensitivity to these processes at LHCb Candidates / (8 MeV/c 2 ) Λ pk b µ + µ data Full fit Signal 80 Background LHCb Candidates / (8 MeV/c 2 ) Λ pk + b µ µ + data Full fit Signal 80 Background LHCb m(pk µ + µ ) [GeV/c 2 ] m(pk µ µ + ) [GeV/c 2 ] [JHEP 06 (2017) 108] 36 / P. Álvarez Cartelle (ICL) Flavour LHCb 36/38 25

39 Effective theory Can describe these interactions in terms of an effective Hamiltonian that describes the full theory at lower energies (µ) H eff i C i (µ)o i (µ) C i (µ) Wilson coefficient (integrating out scales above µ) O i Local operators with different Lorentz structures 37 / P. Álvarez Cartelle (ICL) Flavour LHCb 37/38 25

40 Effective theory Can describe these interactions in terms of an effective Hamiltonian that describes the full theory at lower energies (µ) H eff i C i (µ)o i (µ) C i (µ) Wilson coefficient (integrating out scales above µ) O i Local operators with different Lorentz structures Contributions from New Physics will modify SM contributions (Wilson coefficients) or introduce new operators H eff = c NP Λ NP O NP Depending on the choice of coupling c NP (e.g. MFV inherits SM CKM suppression), access to different NP scales Λ NP (up to hundreds of TeV) Complementarity with direct searches for new particles 37 / P. Álvarez Cartelle (ICL) Flavour LHCb 37/38 25

The LHCb detector Forward arm spectrometer to study b- and c-hadron decays (2 < η < 5) Good vertex and impact parameter resolution (σ(ip ) = 15 + 29/pT )m) Excellent momentum resolution (σ(mb ) 25

41 The LHCb detector Forward arm spectrometer to study b- and c-hadron decays (2 < η < 5) Good vertex and impact parameter resolution (σ(ip ) = /pT )m) Excellent momentum resolution (σ(mb ) 25 MeV/c2 for 2-body decays) Excellent particle ID (µ ID 97% for (π µ) misid of 1-3%) Versatile & efficient trigger [JINST 3 (2008) S080005] 38 P. A lvarez Cartelle (ICL) Flavour LHCb /25 38/38

Rare b and c decays at LHCb

Rare b and c decays at LHCb Rare b and c decays at Preema Pais, EPFL! on behalf of the Collaboration!! HQL 8 May 8, 8 Yamagata, Japan RARE DECAYS AT Diverse physics program studying decays of b,c,s hadrons (Non-exhaustive) sampling: