Semileptonic Branching Ratios and Moments

Transcription

1 Semileptonic Branching Ratios and Moments Giuseppe Della Ricca University and INFN Trieste, Italy 9 th International Conference on B Physics at Hadron Machines October 14-18, 18, 003 Pittsburgh, PA, USA

2 BEAUTY 03 October 14-18, 18, 003 Motivations semileptonic decays are relatively simple theoretically at parton level accessible experimentally sensitive to quark couplings to W ± (i.e. CKM matrix elements V ub and V cb ) probe the dynamics of the decay probe the impact of strong interactions b W Vub,cb l - u,c ν l two possible approaches exclusive measurements need form-factors to describe the transition of the B meson to a lighter one inclusive measurements need OPE and b-quark mass to extract V xb from the total rate

3 Target BEAUTY 03 October 14-18, 18, 003 in naïve spectator picture the process is analogous to muon decay Γ G m 19π 5 F b ( b ulν, clν) V 3 ub, cb f( parameters) x Vub, cb but QCD (perturbative and non-perturbative) corrections are needed to extract weak decay physics comparison of results from different measurements provides a test of the consistency of OPE predictions and of underlying assumptions use many different approaches/techniques CKM CERN 3

4 BEAUTY 03 October 14-18, 18, 003 Framework sinβ η B d mixing: m d kaon decays: ε K b ulν: V ub D*lν: V cb B s mixing: m s / m d ρ measurements of V ub and V cb provide stringent tests of the unitarity triangle 4

5 Outline exclusive measurements BR(B ρeν) [BaBar] BEAUTY 03 October 14-18, 18, 003 BR(B πlν), BR(B ρ lν), BR(B ωlν) [BaBar, Belle, Cleo] BR(B D * lν) [BaBar] BR(B πlν) [Cleo] BR(B D **0 lνx) [Opal] V cb or V ub b q far too much interesting material to include in 0 min [apologies in advance] inclusive measurements <M xn >, <E ln >in B X c lν [BaBar, Cleo, Delphi] BR(B X u lν) [BaBar] BR(B X u lν) [Belle] W - e, µ, ν c or u q my own selection of recent result τ 5

6 BEAUTY 03 October 14-18, 18, 003 BR(B 0 ρ + e - ν) [1] signal (ISGW) HILEP HILEP crossfeed b ueν downfeed (ISGW+DeFazio Neubert) b ceν (HQET + Goity Roberts) [1] M ρ± E HILEP:.3< E electron <.7 GeV (large continuum backgrounds) LOLEP:.0< E electron <.3 GeV (large b ceν backgrounds) Γ(B 0 ρ - e + ν) = Γ(B + ρ 0 e + ν) Γ(B 0 π - e + ν) = Γ(B + π 0 e + ν) Γ(B + ρ 0 e + ν)= Γ(B + ωe + ν) (isospin-constrained average of ρ ± and ρ 0 ) LOLEP M ρ± LOLEP E 6

7 BR(B 0 ρ + e - ν) [] BEAUTY 03 October 14-18, 18, 003 extrapolate partial branching fraction to entire lepton-energy spectrum using five different form-factor calculations combined result: unweighted mean theoretical error on the combined result: full spread seen between the different form-factors combined result (unweighted mean): PRL 90 (003) BR=(3.9 ± 0.4 ± 0.47 ± 0.55 ) x

8 BR(B π 0 lν, ρ 0 lν, ωlν) BEAUTY 03 October 14-18, 18, 003 very high purity but small statistics loose cuts: small model dependence ρ 0 : 0.65<m ππ <0.95 GeV/c π 0 ρ 0 ω BR(B π 0 lν) = (0.78 ± 0.3 ± 0.13 ) x 10-4 BR(B ρ 0 lν) = (0.99 ± 0.37 ± 0.19 ) x 10-4 BR(B ωlν) = (.0 ± 0.9 ± 0.57 ) x 10-4 new CLEO results: see next talk! preliminary 8

9 BEAUTY 03 October 14-18, 18, 003 B D * lν: motivations B D * lν represents 10% (5% e +5% µ channel) of the total B 0 decays, so a precise understanding of this decay improves the overall knowledge of the B branching ratios the study of the differential decay rate can be used to extract V cb D *± D 0 π ± D 0 Kπ, K s ππ, Kππ 0, Kπππ δm [= M(D * )-M(D 0 )] used to fit signal and background components (except D ** ) B 0 π s D 0 e/µ K π constrained vertex fit on D 0 decay products, soft pion and lepton data control samples are used to estimate the background components (7 samples) 9

10 BEAUTY 03 October 14-18, 18, 003 Background characterization: fit to δm [= M(D * )-M( M(D 0 )] continuum from data control samples uncorrelated fake lepton fake D* 10

11 Separation of D ** component once other backgrounds are estimated from the global fit, B 0(+) D * Xlν events are separated using the angle between the B 0 and the D * l direction. can be written as: m m Xν Xν = > 0 0 if B 0 D * lν if B 0(+) D * Xlν D ** shape different from the D * one fitted in each D 0 mode and e/µ subsample p B θ BY BEAUTY 03 October 14-18, 18, 003 electrons-kπ mode D*lν (73.5%) D**lν (7.5%) Real D*, Fake (0.3%) Uncorrelated D* (6.%) Correlated D*(1.5%) Continuum D*(3.%) Fake D*(7.75%) p ν p miss θ min p Y = p ρ + p lept 11

12 Results for BR(B D * lν) BEAUTY 03 October 14-18, 18, 003 hep-ex/ BR(B 0 D* - l + ν)= (4.69±0.0 stat.data ±0.0 stat.mc ±0.4 syst.data )% comparison with other results 1

13 Orbitally excited D mesons (D ** ) BEAUTY 03 October 14-18, 18, 003 D **0 are L=1 orbitally excited charm mesons narrow J q = 3/, J p =1 +, + states (D 0 1, D *0 ) wide J q = 1/, J p =0 +,1 + states (not visible with statistics) motivation investigate the difference between measured inclusive and exclusive semileptonic branching ratios reduce uncertainty in V cb test HQET predictions 13

14 BEAUTY 03 October 14-18, 18, 003 Method identify high p lepton (µ,e) high efficiency and purity for p µ >3 GeV/c, p e >GeV/c exclusively reconstruct D **0 D **0 D *+ π **- D 0 π + slow K - π + (π + π - ) background cuts to remove fake π **- (π from fragmentation) main background from b D *0 lν decays plus fake π **- lx ANN (p, p T, d0/σ d0 ) to select π **- 3 mm 14

15 D **0 D *+ mass difference BEAUTY 03 October 14-18, 18, 003 combine D 0 Kπ and K3π channels to reduce uncertainty due to background unbinned ML fit to determine number of D 1 and D * events (B.-W. Gaussian) BR(b B) BR(B D l ν X) BR(D 0 1 D * + - π ) = = (. 64 ± 0. 79(stat) ± 0. 39(syst)) 10-3 number of wrong sign and right sign background events fit simultaneously BR(b B) BR(B D * 0 - l ν X) BR(D * 0 D * + - π ) ( 95% C.L.) CERN-EP

16 BEAUTY 03 October 14-18, 18, 003 B o & B + semileptonic decays accurate, separate BR sl for B o & B +, tagged by fully reconstructing one B BR(B + Xlν)/B(B 0 Xlν)=1.14±0.04±0.01 preliminary BR sl (%) Γ sl (ns -1 ) B o 10.3± ± ±.8 B ± ± ±.5 ½(B o +B + ) 11.19± ± ±1.9 Y(4S) ± ±1.8 Γ sl (B + )/Γ sl (B o )=1.063±

17 Semileptonic B decays average BR on Y(4S), use high momentum lepton to tag flavor of 1 st B BR sl BEAUTY 03 October 14-18, 18, 003 CLEO BR(B Xeν)= (10.89±0.08 stat ±0.33 syst )% preliminary, EPS 03 7 LEP(most recent EW fit)=(10.59±0.)% 10.76% at Y(4S) 17

18 BEAUTY 03 October 14-18, 18, 003 Parameters of HQE parameterization of decay rate in terms of Operator Product Expansion in HQET in powers of α s (m b )β 0 and Λ/m B: Γ sl G F Vcb 5 αs c3 αs c5 1 αs = mb c1{ 1 c + Λ (1 c4 ) + (Λ + c6λ1 + c7λ) + O( ) + O( ) π π m π m m π B B B } Λ, λ 1, λ, are non-perturbative parameters pole mass expansion λ 1 : (-) kinetic energy of the motion of the b-quark λ : chromo-magnetic coupling of b-quark spin to gluon (from B*-B mass difference, λ =0.1GeV ) Λ= m B m b + (λ 1-3λ )/m B + + additional parameters enter at higher orders (ρ 1, ρ, τ 1, τ, τ 3, τ 4 ) use theoretical estimates 1/m 3 B 18

19 OPE parameter extraction BEAUTY 03 October 14-18, 18, 003 first derivations of OPE parameters from spectral moments used the pole mass expansion and photon energy spectrum in B X s γ, hadronic mass spectrum and lepton energy spectrum in B X c lν E γ M PRL 87 (001) X PRL 87 (001) E PRD 67 (001) l E γ = m B Λ ( M ) = M + ( Λ, λ1, λ) +... X md 0 M1 m m B B 19

20 BEAUTY 03 October 14-18, 18, 003 Moments of lepton energy spectrum and hadronic mass spectrum in Z bb Z events B d0 D ** lν decays exclusively reconstructed in three channels: D ** D *+ π -, D 0 π +, D + π - B Z qq 3mm B l - D ** π* K - π + D 0 D π* π - ν l π + first measurements of moments performed at LEP exploiting advantage of Z 0 kinematics good secondary vertex reconstruction and signal/background separation Γ bb / Γ hadrons % E B 0.7 E beam 30 GeV signal: 0

21 Hadronic mass spectrum in B D ** BEAUTY 03 October 14-18, 18, 003 ** lν D ** D *+ π - D ** D 0 π + D ** D + π - M = M(D (*) π) - M(D (*) ) distributions fitted including contributions of resonant (narrow, broad) and non resonant states, D * Xlν floating BR(B 0 D ** lν)=(.7 ± 0.7 ± 0.) % DELPHI

22 BEAUTY 03 October 14-18, 18, 003 Interpretations moments of hadronic mass spectrum and of lepton energy spectrum are sensitive to the non-perturbative parameters of the Heavy Quark Expansion. at order 1/m b Λ, λ 1, λ (λ 0.1 GeV ), at order1/m b3 ρ 1, ρ,τ 1-4 two possible approaches: 1) pole mass expansions M n = f n ( λ 1, Λ, λ, Τ1, Τ,...) (Falk, Luke, Gambino) ) running quark masses M n = fn ( µ π, m b (1 GeV ), µ G, ρ 3 D, ρ 3 LS,...) (Bigi, Shifman, Uraltsev, Vainshtein)

23 Pole mass scheme multi-parameter fit: BEAUTY 03 October 14-18, 18, 003 λ 1 (GeV ) ρ 1 (GeV 3 ) M 1 (M x ) M (M x ) M 3 (M x ) M 1 (E l ) M (E l ) M 3 (E l ) Λ (GeV) Λ = fit sys GeV λ 1 = fit sys GeV ρ 1 = fit sys GeV 3 ρ = fit sys GeV 3 Λ (GeV) good consistency of all measurements (χ /d.o.f.=0.4) results compatible with CLEO similar results with m b 1S -λ 1 formalism applied to CLEO and DELPHI data (C.W.Bauer, Z.Ligeti, M.Luke, A.V.Manohar hep-ph/01007) 3

24 Non-perturbative parameter extraction BEAUTY 03 October 14-18, 18, 003 makes use of low scale running quark masses and does not rely on a 1/m c expansion M n 3 3 m ρ b α µ µ ρ s π G D LS E l) = ϕn( r) + an( r) + bn( r) + c ( ) + ( ) + ( ) +... n r d n r s 3 n r π mb mb mb mb n( 3 m b (µ), m c (µ) are independent parameters and two operators only mc ( µ ) r = contribute to 1/m b3 corrections : ρ D3, ρ 3 LS m ( µ ) first applied to fit DELPHI data multi-parameter χ fit to first three moments of lepton energy spectra and hadronic mass spectra (higher moments used to get sensitivity to 1/m b3 parameters) use expressions for non-truncated lepton spectra simultaneous use of leptonic and hadronic moments in order to leave enough free parameters in the fit Phys. Lett. B556 (003) 41 b 4

25 Kinetic mass scheme BEAUTY 03 October 14-18, 18, 003 M 1 (M x ) M (M x ) M 3 (M x ) M 1 (E l ) M (E l ) M 3 (E l ) µ π (GeV ) ρ D 3 (GeV 3 ) 4-parameter fit input constraints: µ G = GeV ρ LS3 = GeV 3 m c = 1.05 ± 0.30 GeV m b = 4.57 ± 0.10 GeV m b (GeV) m b (GeV) equivalent to that derived from E γ in B X s γ m b,kin (1GeV)= fit sys GeV m c,kin (1GeV)= fit sys GeV µ π (1GeV) = fit sys GeV ρ D 3 (1GeV) = fit sys GeV 3 good consistency of all measurements (χ /d.o.f.=0.9) within present accuracy no need to introduce higher order terms to establish agreement with data 5

26 Generalized energy moments BEAUTY 03 October 14-18, 18, 003 hep-ex/01051 using ratios of truncated lepton spectra (Gremm et al. PRL ) R 0 = 1.7 GeV 1.5 GeV dγsl de de l dγsl de de l l l R 1 = 1.5GeV 1.5GeV Γsl E d l l de de l dγsl del del R R 0 1 = ± ± GeV = ± ± GeV 1σ theoretical ellipse Λ = 0.39±0.03 stat ±0.06 sys ±0.1 th GeV λ 1 = 0.5±0.0 stat ±0.05 sys ±0.14 th GeV parameters extracted from lepton spectra are in agreement with those extracted from M X and E γ 6

27 [1] Hadronic mass moments [1] ~ measured M X differs from true M X for each interval in M X, full detector simulation gives < M X > and <M X > ~ calibration curves applied to data: no model dependence! p min* dependence study ~ <M X > D BEAUTY 03 October 14-18, 18, 003 non-res D** D* <M X > <M X -mb > <M X > TRUE p min * p min * 7

28 Hadronic mass moments [] BEAUTY 03 October 14-18, 18, 003 fit OPE _ for <M X > to data and extract the two leading HQE parameters Λ and λ 1 (MS scheme) all correlations taken into account <M X > OPE fit CLEO b sγ OPE prediction using CLEO data only <Mx > and <Eγ> from b sγ p min * all hadron mass moments are consistent (overlap from bands and BABAR ellipse) but χ =1 contour does not overlap with <Eγ> band from CLEO b sγ 8

29 Hadronic mass moments [3] BEAUTY 03 October 14-18, 18, 003 extraction of m b 1s, and λ 1 1s from a fit to the HQE in the 1s mass scheme (O(1/m b3 ) parameters are fixed in the fit) χ =1 contour of hadron moments and lepton moments do not overlap indication for large O(1/m b3 ) corrections, duality violation, or maybe even more? m λ 1s b 1 = ± = 0. 6 ± exp exp ± ± dim BLM dim BLM ± ± /m 3 B 1/m 3 B GeV GeV hep-ex/

30 BEAUTY 03 October 14-18, 18, 003 Hadronic mass moments the neutrino 4-vector is inferred using the detector hermeticity <M X -M D > El>1.0 GeV = 0.456±0.014±0.045± (GeV/c ) <M X -M D > El>1.5 GeV = 0.93±0.01±0.033±0.048 (GeV/c ) 4 hep-ex/

31 BEAUTY 03 October 14-18, 18, 003 Summary Huge efforts/progress in this area!! Large theoretical progress over the last decade (HQET & OPE) Fully reconstructed B meson recoil tag, neutrino reconstruction Many complementary observables Inclusive studies yield crucial informations for Heavy Quark physics, even for exclusive decays 31

32 BEAUTY 03 October 14-18, 18, 003 Start of Backup Slides 3

33 BEAUTY 03 October , 003 The BaBar detector 1.5 T solenoid Čerenkov Detector (DIRC) 144 quartz bars PMTs e- (9 GeV) Instrumented Flux Return iron/rpcs (muon/neutral hadrons) SVT: SVT+DCH: DIRC: EMC: ElectroMagnetic Calorimeter 6580 CsI(Tl) crystals e+ (3.1 GeV) Drift CHamber 40 stereo layers Silicon Vertex Tracker 5 layers, double sided strips 97% efficiency, 15 µm z hit resolution (inner layers, tracks) σ(pt)/pt = 0.13 % pt % K-π separation 3.0 GeV/c 4.0 GeV/c σe/e =.3 % E-1/4 1.9 % 33

34 BEAUTY 03 October 14-18, 18, 003 The BELLE detector SC solenoid 1.5T CsI(Tl) 16X 0 Aerogel Cherenkov cnt. n=1.015~ GeV e + TOF counter 8 GeV e Central Drift Chamber small cell +He/C H 5 Si vtx. detector µ / K L detection 14/15 lyr. RPC+Fe 3 lyr. DSSD vtx σ xy,z 55µm@1GeV mom σ pt /p t =0.19p t (+) 0.34 % E σ E PID: ACC+TOF+dE/dx(CDC) ε~90%, η~6% up to 3GeV e-id: ε>90%, η~0.3% (>1GeV) µ-id: ε>90%, η <% (>1GeV) [ε=efficiency, η=fake rate] 34

35 BEAUTY 03 October 14-18, 18, 003 The CLEO detector 35

36 BEAUTY 03 October 14-18, 18, 003 The DELPHI detector 36

37 BEAUTY 03 October , 003 The OPAL detector 37

38 BEAUTY 03 October 14-18, 18, 003 Inclusive b clν rather than focusing on one hadronic final state, sum over all states and compare to quark level calculation i Γ( B X lν) =Γ( b relies on assumption of quark-hadron duality ( i) c clν) constrain theory parameters and test consistency 38

39 Inclusive BR(B X c l ν) and τ B BEAUTY 03 October 14-18, 18, 003 Y(4S) BR(B X c l ν) = (10.83± 0.5) x10 τ B = (1.598 ± 0.01) ps Γ B Xc l ν = (1 ±0.03 ±0.007)x10 10 MeV LEP BR(B X l ν) = (10.59±0.) x10 BR(B X u l ν) = ( 0.17±0.05) x10 BR(B X c l ν) = (10.4±0.6) x10 τ b = (1.573 ± 0.01) ps Γ B Xc l ν = (1 ±0.0 ±0.014)x10 10 MeV word average Γ B Xc l ν = (1 ±0.018) x10 10 MeV 39

40 Reconstruction and cuts BEAUTY 03 October 14-18, 18, 003 D * /D 0 are reconstructed in the following modes: decay mode BR (%) D *± D 0 π ± 67.7 ± 0.5 D 0 Kπ D 0 Kπππ 3.80 ± 0.09 D 0 K s ππ.96 ± 0.18 D 0 Kππ ± ±

41 Moments of lepton energy spectrum and hadronic mass spectrum in Z bb Z events BEAUTY 03 October 14-18, 18, 003 large momentum of b-hadrons (E B ~30 GeV) gives sensitivity to full lepton energy spectrum in B rest frame: measure first, second and third moment lepton spectrum in B X c l ν e+µ p (GeV/c) background subtracted B system reconstructed from lepton+neutrino+charm vertex lepton boosted in B rest frame DELPHI

42 Results for M n BEAUTY 03 October 14-18, 18, 003 <m n H>= p D m n D +p D* m n D* + (1-p D -p D* )<m n D**> moments of the hadronic mass M 1 = <m H -m D > = 0.647±0.046±0.093 (GeV/c ) measured M = <(m H -m D ) > = 1.98±0.3±0.9 (GeV/c ) 4 M =<(m H -<m H >) > = 1.56±0.18±0.17 (GeV/c ) 4 M 3 =<(m H -<m H >)3 > = 4.05±0.74±0.31 (GeV/c ) 6 moments of the lepton energy spectrum <E l* > = 1.383±0.01±0.009 GeV DELPHI 03-8 unfolded spectrum <(E l* -<E l* >) > = 0.19±0.005±0.008 GeV <(E l* -<E l* >) 3 > =-0.09±0.005±0.006 GeV 3 4

43 BEAUTY 03 October 14-18, 18, 003 Lepton endpoint from the partial branching ratio B( B X u eν ) = (0.15 ± ± 0.014) 10 3 with f u from CLEO (b sγ measurement) B f u ( p) = = ± ± B B( B X eν ) u = (.05 ± exp ± 0.46 ) 10 f u Electron Momentum [GeV/c] hep-ex/

44 BEAUTY 03 October 14-18, 18, 003 Hadronic moments - info 44

45 BEAUTY 03 October 14-18, 18, 003 End of Backup Slides 45