The V ub puzzle The V ub puzzle Λ b B PDG version 4 6 8 1 1 14 d b u W Vub d u Eclusive π + l νl p b Inclusive W.5.3.35.4.45.5.55 V ub Vub u Xu l νl Longstanding discrepancy between eclusive and inclusive V ub. V ub / V cb constrains the length of the unitarity triangle opposite the angle β. ecluded area has CL sin β α ε K V ub V ud V cb V cd γ γ α m d ρ V ub β Summer 14 sol. w/ cos β < (ecl. at CL >.95).4....4.6.8 1. α Recent results on R(D William ) and Sutcliffe V ub October 7, 15 / 13
The V ub puzzle V ub from Λ b pµ ν µ decays Normalise Λ b pµ ν µ to Λ b Λ c µ ν µ in the high q (= m µν) region where theory uncertainty is lowest: R theory ( V ub / V cb N(Λ b pµ ν µ ) ) = N(Λ b (Λ c pkπ)µ ν µ ) B(Λ c pkπ) ǫ rel 1 Dataset ( fb 1 ) Relative efficiency ǫ rel = 3.5±. determined from simulation. Branching fraction B(Λ c pkπ) from Belle PRL 113, 4 (14) R theory = qma 15GeV /c 4 dγ(λ b pµ ν µ) dq / V ub dq q ma dγ(λ b Λ cµ ν µ) 7GeV /c 4 dq / V cb dq = 1.471±.95(stat)±.19(syst) W. Detmold, C. Lehner and S. Meinel [Phys.Rev. D9 (15) 3, 3453] Recent results on R(D William ) and Sutcliffe V ub October 7, 15 3 / 13
The V ub puzzle Selection Reconstruct q up to a -fold ambiguity. Require both solutions > q cut. selection efficiency [%] q 9 8 7 6 5 4 3 1 LHCb simulation both solutions one solution 5 1 15 q [GeV/c Boosted decision tree removes backgrounds with additional charged tracks that could verte with pµ candidate. ] X b X b PV Λ b p µ ν µ PV Λ b Λ + c ν µ p µ Recent results on R(D William ) and Sutcliffe V ub October 7, 15 4 / 13
The V ub puzzle Signal and normalisation fits Candidates / (5 MeV/c ) 18 15 1 9 6 3 Combinatorial Mis-identified D pµ ν * Λ + c µ ν + Λcµ ν * N µ ν pµ ν LHCb Candidates / (4 MeV/c ) 4 3 1 LHCb + Λcµ ν *+ µ Λ c ν Combinatorial 3 4 5 Corrected pµ mass [MeV/c ] 4 45 5 55 Corrected pk π + µ mass [MeV/c ] N(Λ b pµ ν µ ) = 17687±733 Nature Physics 11, 743-747 (15) N(Λ b (Λ c pkπ)µ ν µ ) = 3455±571. First observation of Λ b pµ ν µ decays: B(Λ b pµ ν µ ) = (4.1±1.) 1 4. Recent results on R(D William ) and Sutcliffe V ub October 7, 15 6 / 13
The R(D ) Anomaly R(D ) selection Signal (B D + τ ν τ ) Normalisation (B D + µ ν µ ) X b X b PV B π + ν µ D τ K π + ν µ µ ν τ PV B π + ν µ D µ K π + Take τ µ ν τ ν µ. Reconstruct D + π + (D K π + ) Boosted decision tree removes backgrounds with additional charged tracks originating from the D µ verte. Recent results on R(D William ) and Sutcliffe V ub October 7, 15 9 / 13
The R(D ) Anomaly Finding an approimate B rest frame y B p B = (,,?) z boost (p z ) B mb m(d µ) (p z ) D µ mmiss D + B q = (p B p D ) νs µ E µ Arbitrary units.15.1.5 5 1 (GeV/c ) mmiss Arbitrary units.8.6.4. 5 1 15 5 E (MeV/c mu ) Arbitrary units.6.4. 5 1 q (GeV/c ) B D + τ ν τ B D + µ ν µ Recent results on R(D William ) and Sutcliffe V ub October 7, 15 1 / 13
) The R(D ) Anomaly ) R(D ) fit 7 1 LHCb 3 6 18 5 5 16 14 4 1 15 3 1 Data 8 B D*τν 1 6 B D*H c ( lνx')x 1 5 4 B D**lν B D*µν - 4 6 8 1 5 1 15 5 4 6 8 1 1 Combinatorial 4 mmiss (GeV /c ) E µ* (MeV) 4 q (GeV /c ) m Misidentified µ 3.85 < q < 6.1 GeV /c 4 LHCb 1 1 1 8 6 4 4 6 8 1 miss (GeV /c ) E 4.85 < q < 6.1 GeV /c 4 LHCb 3 1 5 1 15 5 4 6 8 1 5 1 15 5 4 m (GeV /c ) miss 4 E * * (MeV) 9.35 < q < 1.6 GeV /c 4 LHCb 4 9.35 < q 3 1 LHCb < 1.6 GeV /c 4 4 6 8 1 5 1 15 5 4 6 8 1 5 1 15 5 (MeV) m (GeV /c ) miss E * (MeV) Three dimensional fit to mmiss, q and E µ. Candidates / (.3 GeV /c 4 ) 4 /c Candidates / (.3 GeV Pulls Candidates / (75 MeV) Candidates / ( 75 MeV ) LHCb Pulls ) 4 /c Candidates / (.3 GeV Pulls Candidates / ( 3.5 GeV /c 4 LHCb B D + τ ν τ contribution most prominent at high q. Candidates / (75 MeV) Pulls Control various backgrounds using control samples in data. Recent results on R(D William ) and Sutcliffe V ub October 7, 15 11 / 13
The R(D ) Anomaly Prel. EPS15 The first R(D ) from a hadron collider R(D ) =.336±.7(stat)±.3(syst) PRL 115, 11183 (15) Belle PRD 8 (1) 75 6 657 1 BB (Inclusive Tag) BaBar PRD 88 (13) 71 6 471 1 BB (Hadronic Tag) Belle Presented at FPCP15 6 77 1 BB (Hadronic Tag) LHCb LHCb-PAPER-15-5 -1 3. fb (τ µ νν).1.15..5.3.35.4.45 Standard Model R(D*) Fajfer et al, PRD 85 (1) 945 R(D*).5.45.4.35.3.5 BaBar, PRL19,118(1) Belle, arxiv:157.333 LHCb, arxiv:156.8614 Average SM prediction χ = 1. HFAG P(χ ) = 55%...3.4.5.6 R(D) Combining results for R(D ) from Belle, BaBar and LHCb gives a 3.9σ discrepancy with the Standard Model. Recent results on R(D William ) and Sutcliffe V ub October 7, 15 1 / 13
Conclusion Conclusion LHCb has peformed two measurements using semileptonic decays which were unepected from a hadron collider: V ub = (3.7±.3) 1 3. This measurement is 3.5σ below the inclusive measurement but agrees well with current eclusive average using B πlν decays. R(D ) =.336±.7(stat)±.3(syst) Together with measurements from the B factories this is an eciting hint of lepton flavour universality violation and hence new physics. Recent results on R(D William ) and Sutcliffe V ub October 7, 15 13 / 13