The Belle Experiment Belle recorded 711 fb 1 on the ( 4S ) - PowerPoint PPT Presentation

Search for B → ℓνγ and B → µν µ and Test of Lepton Universality with R ( K ∗ ) at Belle Moriond EW 2019 Markus Prim for the Belle Collaboration | 22nd March 2019 INSTITUT F ¨ UR EXPERIMENTELLE TEILCHENPHYSIK (ETP) www.kit.edu KIT – University of the State of Baden-W¨ urttemberg and National Laboratory of the Helmholtz Association

The Belle Experiment Belle recorded 711 fb − 1 on the Υ( 4S ) resonance. µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 2/23

B-Tagging at Belle Exclusive Tagging: The Full Event Interpretation (FEI) Inclusive Tag Keck, T., et al. Comput Softw Big Sci (2019) ǫ = O ( 100 )% ? Consistency of B tag Efficiency ǫ Semileptonic Tag D Purity ǫ = O ( 1 )% B ℓ Knowledge of B tag ν Hadronic Tag ǫ = O ( 0 . 1 )% B Exact knowledge of B tag µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 3/23

B → ℓνγ µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 4/23

B → ℓνγ M. Beneke and J. Rohrwild (2011) = α em G 2 F m 4 B | V ub | 2 d Γ Eur. Phys. J. C. 71:1818 x 3 γ ( 1 − x γ )[ F 2 A + F 2 V ] 48 π 2 dE γ upper limit Belle 2015 with x γ = 2 E γ / m B Previous Belle result (2015) b : ∆ B ( B + → ℓ + ν ℓ γ ) < 3 . 5 × 10 − 6 Form Factors (valid for large photon energies) Method λ B (GeV) � � Q u m B f B ξ ( E γ ) + Q b m B f B + Q u m B f B QCD factorization ≈ 0 . 2 F V ( E γ ) = R ( E γ , µ ) + ( 2 E γ ) 2 2 E γ λ B 2 E γ m b 0 . 46 ± 0 . 11 QCD sum rules BaBar (2009) a > 0 . 115 � � Q u m B f B ξ ( E γ ) − Q b m B f B − Q u m B f B ( 2 E γ ) 2 + Q ℓ f B Belle (2015) b F A ( E γ ) = R ( E γ , µ ) + > 0 . 238 2 E γ λ B 2 E γ m b E γ a: Phys. Rev. D 80, 111105 (2009) b: Phys. Rev. D 91, 112009 (2015) µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 5/23

B → ℓνγ : Analysis Strategy Control Region B + → π 0 ℓ + ν ℓ Background Reconstruction Suppression & Selection Multivariate Methods Signal Extraction B → ℓνγ B + → π 0 ℓ + ν ℓ with Likelihood Fit B + → ηℓ + ν ℓ hadronic tagging (FEI) e + e − → qq λ B Determination µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 6/23

B → ℓνγ : Fit on Data B + → e + ν e γ B + → µ + ν µ γ Previous results for B + → π 0 ℓ + ν ℓ B (B + → π 0 ℓ + ν ℓ ) ( 10 − 5 ) ∆ B (B + → ℓ + ν ℓ γ ) ( 10 − 6 ) ℓ σ B ( B + → π 0 ℓ + ν ℓ ) ( × 10 − 5 ) 8 . 3 + 0 . 9 1 . 7 + 1 . 6 − 0 . 8 ± 0 . 9 − 1 . 4 ± 0 . 7 e 1.1 Belle excl. a 8 . 0 ± 0 . 8 ± 0 . 4 1 . 0 + 1 . 4 7 . 5 ± 0 . 8 ± 0 . 6 − 1 . 0 ± 0 . 4 µ 0.8 7 . 80 ± 0 . 27 PDG e , µ 7 . 9 ± 0 . 6 ± 0 . 6 1 . 4 ± 1 . 0 ± 0 . 4 1.4 a: Sibidanov et al. , Phys. Rev. D 88, 032005 (2013) µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 7/23

B → ℓνγ : Results R π = ∆ B ( B + → ℓ + ν ℓ γ ) ∆Γ( λ B ) = B ( B + → π Γ( B + → π 0 ℓ + ν ℓ ) 0 ℓ + ν ℓ ) R π removes dependence of V ub . = ( 1 . 7 ± 1 . 4 ) × 10 − 2 measured R π based on theoretical input from: Beneke et al., JHEP 07:154 (2018) HFLAV, Eur. Phys. J., C77:895, (2017) a λ B > 0 . 24 GeV @ 90 % C . L . a: Phys.Rev. D98 (2018) no.11, 112016 Result of Belle (2015) was λ B > 0 . 238 GeV µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 8/23

B → µν µ µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 9/23

B → µν µ Standard Model B → µν µ (and B → e ν e ) yet to be observed. Both helicity and CKM suppressed. Pure leptonic channels are a golden mode to extract | V ub | . Highly sensitive to new physics. � 2 G 2 F m B m 2 � m 2 B | V ub | 2 τ B ℓ ℓ f 2 B ( B → ℓν ℓ ) SM = 1 − m 2 µ 8 π b B W + B ( B → µν µ ) SM = ( 4 . 26 ± 0 . 81 ) × 10 − 7 B + u ν µ Previous Belle result (2018) a : a: Phys. Rev. Lett. 121, 031801 (2018) B ( B → µν µ ) = ( 6 . 64 ± 2 . 22 ± 1 . 60 ) × 10 − 7 @ 2 . 4 σ µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 10/23

B → µν µ 2HDM New Physics Scenario: 2 Higgs Doublet Model. Change of experimental signature: Branching fraction due to interference. µ b 2 � B tan 2 β � W + m 2 � � Type II = B SM × B + B ( B → ℓν ℓ ) a � � 1 − � � m 2 � � H + ν µ � � u 2 � m 2 � µ b C R − C L Type III = B SM × � � B B ( B → ℓν ℓ ) b � 1 + � � H + � m b m ℓ C SM � B + � a: W.-S. Hou, Phys. Rev. D48, 2342 (1993) u ν µ b: Phys.Rev. D86 (2012) 054014 µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 11/23

B → µ N with a Sterile Neutrino New Physics Scenario: Sterile Neutrino in the final state. Change of experimental signature: Branching fraction due to additional decay channel: B ( B → µ + missing energy ) = B ( B → µν µ ) + B ( B → µ N ) . Shift in momentum spectrum due to sterile neutrino mass. µ µ b b b N W + H + B + B + B + LQ u ν µ u u µ N µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 12/23

B → µν µ : Analysis Strategy Control Region Classifier Sideband Control Channel B → D [ → K π ] π Reconstruction Background & Selection Suppression Signal Extraction B → µν µ Multivariate Method Likelihood Fit with e + e − → qq Inclusive Tagging BR Determination µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 13/23

B → µν µ : Fit on Data Signal Enriched I Signal Enriched II 150 Preliminary Continuum Preliminary Continuum 250 Entries / (0.050 GeV) Entries / (0.050 GeV) b c b c Rare 200 Rare B B 100 b u b u 150 Signal Signal sys. unc. 100 sys. unc. 50 Data Data 50 0 0 2.2 2.4 2.6 2.8 3.0 3.2 2.2 2.4 2.6 2.8 3.0 3.2 p B / (GeV) p B / (GeV) Background Enriched I Background Enriched II Preliminary Continuum Preliminary Continuum 1000 Entries / (0.050 GeV) Entries / (0.050 GeV) b c b c 600 Rare Rare 800 B B b u b u 400 600 Signal Signal sys. unc. sys. unc. 400 Data Data 200 200 0 0 2.2 2.4 2.6 2.8 3.0 3.2 2.2 2.4 2.6 2.8 3.0 3.2 p B / (GeV) p B / (GeV) µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 14/23

B → µν µ : (Preliminary) Result Extracted Signal Yield 5 stat. + sys. B ( B → µν µ ) stat. 4 sig = 117±48 4 . 26 × 10 − 7 SM 3 sig ) ( 6 . 6 ± 2 . 2 ± 1 . 6 ) × 10 − 7 @ 2 . 4 σ Belle (2018) a ( 2 ( 5 . 3 ± 2 . 0 ± 0 . 9 ) × 10 − 7 @ 2 . 8 σ Result (this) 1 < 8 . 64 × 10 − 7 @ 90% CL Frequentist UL Preliminary 0 50 100 150 200 a: Sibidanov et al. , Phys. Rev. Lett. 121, 031801 (2018) sig µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 15/23

B → µν µ 2HDM Type II Type III 95% CL 95% CL 300 0.2 B B 250 B B b s 0.1 200 150 tan 0.0 S R 100 0.1 50 Preliminary Preliminary 0 0 200 400 600 800 1000 0.2 0.2 0.1 0.0 0.1 0.2 m H + / (GeV) S L 2 � � B tan 2 β 2 m 2 � m 2 � � � C R − C L B ( B → ℓν ℓ ) = B SM × � � B ( B → ℓν ℓ ) = B SM × B � � 1 − � 1 + � � � � m 2 � m b m ℓ C SM � � � H + � � � µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 16/23

B → µ N with a Sterile Neutrino Sterile Neutrino Scan 10 0 1 local p 0 1 10 2 Preliminary B N stat. + sys. 2 10 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 Sterile Neutrino Mass m N / (GeV) µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 17/23

R ( K ∗ ) µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 18/23

R ( K ∗ ) Test of lepton flavor universality via: R K ∗ = B ( B → K ∗ µ + µ − ) ≈ 1 B ( B → K ∗ e + e − ) ℓ + W + ℓ − Z 0 / γ Clean theoretical predictions. s b B K ∗ Currently O ( 2 . 3 σ ) tension. d d ℓ + New physics can change this ratio. Z ′ ℓ − Decay modes used in this analysis: s K ∗ 0 → K + π − b B K ∗ B 0 → K ∗ 0 ℓ + ℓ − d d K ∗ + → K + π 0 B + → K ∗ + ℓ + ℓ − K ∗ + → K 0 S π + µ and Test of Lepton Universality with R ( K ∗ ) at Belle - Search for B → ℓν γ and B → µν Markus Prim 22nd March 2019 19/23