Rare b and c decays at LHCb

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1 Rare b and c decays at Preema Pais, EPFL! on behalf of the Collaboration!! HQL 8 May 8, 8 Yamagata, Japan

2 RARE DECAYS AT Diverse physics program studying decays of b,c,s hadrons (Non-exhaustive) sampling: EW penguins Lepton flavor universality tests Radiative.3 decays Ratio of candidate yields..... c 4 ] - GeV -8 [ φµµ)/dq db(bs R K q SM pred. Data [GeV /c 4 ] q [GeV /c 4 ] Data Fit SM t [ps] BIP CDHMV EOS flav.io JC Baryonic decays Very rare decays Many recent results - will only cover a few in this talk! Searches for lepton flavor violation ) Candidates / ( MeV/c 3 Total Bs µ 3 µ BDT >. B µ µ B(s) h h' B π (K (s) )µ ν µ () () B π µ µ Λb pµ ν µ B c J/ψµ ν µ [MeV/c ] Rare charm decays Candidates per MeV/c CL s m µ µ 8 Low-m(µ µ ) ρ /ω B(τ µ µ µ ) [ ] 8 9 (Diego Martinez Santos will cover recent results on LFV and rare kaon decays) η Data Fit m(d ) [MeV/c ] D K K µ µ D K K π π Comb. backg. 8 9

3 RARE DECAYS Flavor-changing neutral current (FCNC) transitions Proceed via electroweak loops; suppressed in the SM New particles could also contribute at loop level Potential effects observed via: Anomalies in decay rates, differential branching fraction measurements Analyses of angular distributions Tests of lepton flavor universality and lepton flavor violation 3

4 B(S) µ µ - DECAYS b ll transitions are additionally helicity-suppressed PRL 8 98 Very rare in the SM; excellent probes of NP Search for B(s) μ μ - carried out with 4.4 fb - of data Theoretically and experimentally clean First single-experiment observation of Bs μ μ - decays (at 7.8 σ) Limit set on B μ μ - BF Measurement of effective lifetime in Bs μ μ - decays offers complementary probe of NP effects ) Candidates / ( MeV/c 3 Total 3 BDT > [MeV/c ] s B µ µ B µ µ B h h' B B (s) (s) () Λb B c π (K )µ π pµ () ν µ J/ψµ ν µ m µ µ µ µ ν µ In the SM, only heavy mass eigenstate decays to μ μ - All results consistent with SM expectations 4 candidates / ( ps) µ µ s Weighted B Effective lifetime fit Decay time [ps]

5 ANOMALIES IN b sll BF MEASUREMENTS Consistent pattern of deviations from SM predictions JHEP 6 (4) 33 JHEP 6 () ] [c 4 /GeV db/dq... 6 JHEP (6) 47 B K*μμ q [GeV /c 4 ] c 4 ] - GeV -8 db(bs φµµ)/dq [ JHEP 9 () 79 B S φμμ q SM pred. Data [GeV /c 4 ]

6 LFU IN b sll TRANSITIONS: R(K*) Ratios of B hll decays are clean probes of NP JHEP 8 (7) Hadronic uncertainties cancel Analysis performed with B K* ll decays (where K*(89) K π - and l=e,μ) in two bins of invariant mass squared Double ratio with B K* J/ψ reduces systematic uncertainties However, extremely challenging due to differences in trigger/reconstruction for electrons and muons 6

7 LFU IN b sll TRANSITIONS: R(K*) Electron reconstruction challenging due to bremsstrahlung; momentum and mass resolution degraded Recover by adding ECAL clusters to extrapolated upstream electron track Limited by calorimeter acceptance, energy threshold (ET > 7 MeV) Worse B mass resolution in the electron channel JHEP 8 (7) J/ψ backgrounds leak into signal region /c 4 ] [GeV q m(k π µ µ ) [MeV/c ] 4 3 /c 4 ] [GeV q m(k π e e ) [MeV/c ]

8 LFU IN b sll TRANSITIONS: R(K*) Analysis strategy: JHEP 8 (7) Keep selection as similar as possible for electron, muon channels Multivariate classifier to reject combinatorial background Veto for peaking backgrounds Signal efficiencies determined from simulation corrected using data-driven techniques Normalisation channel used to correct signal mass shapes Hardware trigger ET thresholds are higher for electrons than for muons Analysis performed for three exclusive trigger categories Compatible with the SM at.σ -.3σ (.4σ -.σ) in the low (central) q bin Measurement is statistically dominated 7

9 GLOBAL FITS Results from b sll, b ll and b sγ transitions interpreted by global fits to Wilson coefficients Includes ~ observables from multiple experiments All fits require additional (non-sm) contribution NP in C9-C favored at ~3.σ from R(K ( * ) ) results considered alone Adding in other results, C9 favored at ~σ arxiv:7.674 JHEP 6 (6) 9 arxiv:

10 PHASE DIFFERENCE IN B K µ µ - DECAYS Vector-like resonances that produce di-muon pairs could mimic NP: EPJC 77: 6 (7) Perform a full fit of the di-muon invariant mass spectrum: Candidates / ( MeV/c ) Resonances described by sum of relative Breit-Wigners, short-distance contribution modeled with EFT description of decay Magnitudes, relative phases between short-distance component and resonances allowed to vary in fit Four ~degenerate solutions for unknown J/ψ and ψ(s) phases Measured phases of J/ψ, ψ(s) indicate that interference with short-distance component in regions away from their pole masses is small Exclusion of C9= hypothesis at σ 4 3 Signal Specific backgrounds Partially reconstructed background background Data 6 6 m [MeV/c Kµµ ] Candidates / (44 MeV/c ) 3 data total short-distance resonances interference background 3 4 m rec µ µ [MeV/c ]

11 _ SEARCH FOR B S K* µ µ - DECAYS b dll transitions are additionally suppressed by CKM factor arxiv: Provide information complementary to studies of b sll decays Search for Bs K* μ μ - carried out with 4.6 fb - of data collected in, and 6 Bs K* J/ψ [ μ μ - ] decays used as a normalization channel First evidence (at 3.4 σ) for this decay, with a measured breaching fraction ) Candidates / (. MeV/c m(j/ψ K Data Fit * Bs J/ψ K * B J/ψ K B K * µ µ Λb J/ψ pk B J/ψ K Comb. bkg. π ) [MeV/c ] ) Candidates / (. MeV/c m(k Data Fit Bs K * µ µ B K * µ µ Λb pk µ µ Comb. bkg. π µ µ ) [MeV/c ]

12 SEARCH FOR Λ C pµ - µ DECAYS Search for rare charm baryonic decay Λc pμ - μ performed with 3 fb - of data BR of short distance c ull contribution expected to be ~ -9 in the SM Expected long-distance contribution via intermediate dimuon resonance enhanced in the SM (~ -6 ) Analysis performed in three regions of di-muon invariant mass: Λc pφ decays used as a normalization channel Searches performed in region around ω invariant mass region, and non-resonant region No significant excess seen in non-resonant channel, limits set at 9% (9%) CL: First observation of the Λc pμ - μ decay at σ in the ω/ρ invariant mass region: Candidates / (7 MeV/c ) Candidates / (7 MeV/c ) Candidates / (7 MeV/c ) arxiv: a) nonresonant b) c) φ region ω region 3 4 m(pµ µ ) [MeV/c ]

13 ASYMMETRIES IN D h h - µ µ - DECAYS Total amplitude dominated by longdistance contributions from decays via intermediate resonances Study of decay asymmetries increases sensitivity to short-distance effects -PAPER-8-! System can be characterized in terms of two invariant masses (mhh and mμμ) and three angles (θh, θμ and φ) Forward-backward asymmetry AFB, charge asymmetry ACP, and tripleproduct asymmetry Aφ could have high sensitivity to NP effects 3

14 ASYMMETRIES IN D h h - µ µ - DECAYS Analysis performed with fb - of data collected in -6 -PAPER-8- Signal studied in regions of di-muon invariant mass defined by resonances Asymmetry computed only in regions where significant yield was previously observed (arxiv: ) BDT used to reject combinatorial background, peaking backgrounds from double mis-id in D hhππ decays suppressed with muon ID criteria Measurements consistent with SM predictions: 4

15 SUMMARY Wide variety of measurements and searches performed with the Run dataset No direct evidence of NP (yet) from a single measurement/search Consistent anomalies seen in LFU measurements, BF measurements, angular analyses of b sll transitions Analyses are statistically limited - Run dataset will more that double existing statistics Enables the study of very rare baryonic decays and b dll processes, offering complementary information on potential NP effects First analyses ready, more results to come soon!

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17 THE DETECTOR Single-arm spectrometer instrumented in the forward ( < η <) region 7

18 THE DETECTOR Trigger system:!! Initial hardware trigger (L), using information from calorimeters and muon system!! Software trigger split into two stages: fast partial event reconstruction subsequent full reco.!! Low luminosity can trigger on relatively low pt objects! 8

19 THE DETECTOR 3 fb - collected in Run Dataset used for most analyses shown today To date, a total of ~7 fb - has been collected Measurements/searches with Run data underway 9

20 PARAMETRIZING FCNC TRANSITIONS Effective Hamiltonian described by an operator product expansion Operators (Oi) - long-distance effects (non-perturbative) Wilson coefficients (Ci) - perturbative, short-distance physics different regions of q probe different processes

21 R(K*) Yields obtained from fit to the invariant mass JHEP 8 (7) Precision dominated by statistics in electron channel Candidates per MeV/c low q central q normalisation channel B K * µ µ.4<q <. [GeV /c 4 ] m(k π µ µ ) [MeV/c ] m(k π µ µ ) [MeV/c ] Candidates per MeV/c B K * µ µ.<q <6. [GeV /c 4 ] m(k π µ µ ) [MeV/c ] m(k π µ µ ) [MeV/c ] Candidates per MeV/c * B K J/ψ Λ K b pj/ψ * K J/ψ m(k π µ µ ) [MeV/c ] m(k π µ µ ) [MeV/c ] (8 ± 8) (33 ± ) ~74, B s Candidates per per MeV/c B Signal K * e e B Xe e B Xe e.4<q <. [GeV /c 4 ] 4 6 m(k π e e ) [MeV/c ] m(k m(k π e π e 6 e) ) [MeV/c ] Candidates per per MeV/c m(k π e e ) [MeV/c ] m(k m(k π e π e 6 e) ) [MeV/c ] BSignal K * e e B Xe e * B X( YK )ee * * B K J/ ψ( ee) J/ψ.<q <6. [GeV /c 4 ] Candidates per per MeV/c * B K *J/ψ 6 K J/ψ Λ K b pj/ψ 4 Λ b * B pj/ψ s K * 3 K J/ψ m(k m(k π e π e 6 e) ) [MeV/c ] (89 ± ) ( ± 4) ~8, B s

22 R(K*) Yields obtained from fit to the invariant mass JHEP 8 (7) Precision dominated by statistics in electron channel Candidates per MeV/c low q central q normalisation channel B K * µ µ.4<q <. [GeV /c 4 ] m(k π µ µ ) [MeV/c ] m(k π µ µ ) [MeV/c ] Candidates per MeV/c B K * µ µ.<q <6. [GeV /c 4 ] m(k π µ µ ) [MeV/c ] m(k π µ µ ) [MeV/c ] Candidates per MeV/c * B K J/ψ Λ K b pj/ψ * K J/ψ m(k π µ µ ) [MeV/c ] m(k π µ µ ) [MeV/c ] (8 ± 8) (33 ± ) ~74, B s Candidates per per MeV/c B Signal K * e e B Xe e B Xe e.4<q <. [GeV /c 4 ] 4 6 m(k π e e ) [MeV/c ] m(k m(k π e π e 6 e) ) [MeV/c ] Candidates per per MeV/c m(k π e e ) [MeV/c ] m(k m(k π e π e 6 e) ) [MeV/c ] BSignal K * e e B Xe e * B X( YK )ee * * B K J/ ψ( ee) J/ψ.<q <6. [GeV /c 4 ] Candidates per per MeV/c * B K *J/ψ 6 K J/ψ Λ K b pj/ψ 4 Λ b * B pj/ψ s K * 3 K J/ψ m(k m(k π e π e 6 e) ) [MeV/c ] (89 ± ) ( ± 4) ~8, B s

23 R(K) Analysis performed with 3 fb - of data [GeV /c 4 ] q (a) PRL 3 (4) Signal in q range [,6] GeV /c 4 R K R(K) value compatible with SM at.6σ.. BaBar Belle SM [GeV /c 4 ] q (b) m(k µ µ ) [MeV/c ] 3 q [GeV /c 4 ] m(k e e ) [MeV/c ]