Gr. I, 10/9/01 Luca Lista L.Lista INFN Sezione di Napoli Results of B A B AR experiment on CP violation and B physics
Gr. I, 10/9/01 Luca Lista Outline (4S) Experimental set-up CP asymmetries sin2 sin2 eff B Mixing and lifetime Rare B decays Conclusions (Many topics will be skipped)
Gr. I, 10/9/01 Luca Lista Low Energy Ring [e +, 3.1GeV] High Energy Ring [e -, 9.0GeV] PEP-II at SLAC center of mass energy M (4S) =10.58 GeV/c 2 = 0.56 BaBar The PEP-II B-Factory
Gr. I, 10/9/01 Luca Lista Integrated Luminosity 32 Million Y(4S) decays recorded BaBar recorded: 37.7fb fb -1 off peak Top luminosity: 3.4x10 33 cm -2 s -1 Design: 3x10 33 cm -2 s -1
Gr. I, 10/9/01 Luca Lista The BaBar detector Electromagnetic Calorimeter 6580 CsI(Tl) crystals Instrumented Flux Return 19 iron / RPC layers Drift Chamber 40 axial stereo layers 1.5T solenoidDIRC (PID) 144 quartz bars PMTs e-e- e+e+ Silicon Vertex Tracker 5 layers, 2-sided Si strips
Gr. I, 10/9/01 Luca Lista Unitarity relations on matrix elements lead to a triangle in the complex plane The Unitarity Triangle 1 B=(1,0) C=(0,0) A=( , ) Quark mixing is described by the CKM matrix
Gr. I, 10/9/01 Luca Lista CP violation at asymmetric B factory CP violation via mixing t=0 B0B0 B0B0 t (ps) FF FF B0B0B0B0 f CP f CP B0B0B0B0 b d WW d b t t B0B0 B0B0 For “golden” b ccs modes: f CP eigenvalue e -2i
Gr. I, 10/9/01 Luca Lista sin2 : Improvements w.r.t. run I More data! Added new modes c1 K S, J/ K *0 Improved reconstruction efficiency Improved tracking ~ +30% K S reconstruction eff. Improved vertex resolution New alignments More elaborated vertex algorithm Optimized K L selection taking into account the background CP asymmetry Maximize (S+A B /A S B) 2 /(S+B), not S 2 /(S+B)
Gr. I, 10/9/01 Luca Lista All sin2 CP modes N=724 B 0 J/ K 0 S B 0 (2S)K 0 S B 0 c K 0 S B 0 J/ K 0 L IFR EMC CP = -1 CP = +1 K L momentum not measured E determined from B mass and beam energy constraints N=129 (65% pur.) N=128 (56% pur.) Golden modes: ~30% higher efficiency than run 1: K S efficiency improved
Gr. I, 10/9/01 Luca Lista Fully reconstructed B flavor modes Cabibbo favored decays: B 0 D a B + D ( )0 +, J/ K +, (2S)K +
Gr. I, 10/9/01 Luca Lista CP modes: F CP ( t) e -| t|/ B ( 1 CP sin2 sin m d t ) Flavour specific modes: F flav ( t) e -| t|/ B ( 1 cos m d t ) B 1 = B 0 zz e - e + B 0 1 partially reconstructed flavor tagged B 0 2 fully reconstructed D *+ - or J/ K 0 S B 1 = B 0 unmixed B 0 B 0 mixed B 0 B 0 or B 0 B 0 Mixing and CP asymmetry of B 0 /B 0
Gr. I, 10/9/01 Luca Lista Imperfect tagging and resolution B 0 unmixed mixed e -| t|/ B (1 CP sin2 sin m d t) e -| t|/ B (1 cos m d t) e -| t|/ B (1 CP D sin2 sin m d t) e -| t|/ B (1 D cos m d t) e -| t|/ B (1 CP D sin2 sin m d t) R( t) e -| t|/ B (1 D cos m d t) R( t) D = 1-2w = dilution, w = wrong tag fraction R( t) = resolution function Imperfect tagging Imperfect resolution
Gr. I, 10/9/01 Luca Lista Fitting Procedure Parameter#sample sin2 1CP w and w 8Flavor t resolution 16Flavor, CP Bkgd w8Sidebands Bkgd t 12Sidebands Unbinned maximum likelihood fit Mistag and resolution: empirical distribution fitted from data fixed in the fit: m d = ps -1 (was extracted from the same fit in Run-I analysis) t B = ps Separate for Run I & II Largest correlation With sin2 : 13%
Gr. I, 10/9/01 Luca Lista Flavor misid. measurement D=1-2w Q= (1-w) 2 (sin2 1/( Q ) w Neural network mainly to recover unidentified leptons and use soft pions from D*
Gr. I, 10/9/01 Luca Lista sin2 result sin2 = 0.59 ± 0.14 stat ± 0.05 syst
Gr. I, 10/9/01 Luca Lista Comparison of different samples Submitted to Phys. Rev. Lett. On July
Gr. I, 10/9/01 Luca Lista Unitarity triangle 22 11 sin2 = 0.59 ± 0.14 stat ± 0.05 syst sin2 = 0.59 ± 0.14 stat ± 0.05 syst
Gr. I, 10/9/01 Luca Lista Search for direct CP violation Assuming more than one amplitude dominate the decay: | | may be 1 Only CP = -1 used High purity, no assumption needed on CP of the background No evidence found (none expected from SM) | |=0.93 ± 0.09 ± 0.03
Gr. I, 10/9/01 Luca Lista 0.03 from vertexing 0.03 from tagging 0.02 from background Total 0.05 Systematic errors
Gr. I, 10/9/01 Luca Lista m d measurement m d = ± stat ± syst ps -1 preliminary Run I only
Gr. I, 10/9/01 Luca Lista Lifetime results 0 = 0.032(stat) 0.022(syst) ps = 0.032(stat) 0.022(syst) ps 0 / = 0.026(stat) 0.011(syst ) common resolution t (ps) background BB B 0 /B 0
Gr. I, 10/9/01 Luca Lista Charmless Hadronic Decays Physics motivations b u d(s) V ub V ud(s) B0B0 { } } } (K ) dd u b B0B0 { d u d(s) } } } (K ) d u t WW WW V tb V td(s) Cabibbo suppressed tree diagram Penguin diagram Significant penguin contribution Direct CP violation studies Measurement of from time-dependent asymmetry + isospin analysis Possible field for new physics…
Gr. I, 10/9/01 Luca Lista Two body Branching fractions control sample: D* D 0, D 0 K > 3 sigma p (GeV/c) Run I only
Gr. I, 10/9/01 Luca Lista CP violation in B 0 : sin2 eff Neglecting penguin pollution: = f e -2i( ) = f e 2i C =0, S = sin2 Considering penguin diagrams: | | 1 C 0, S = sin2 eff = sin2 f (Penguin / Tree) Extraction of sin2 requires the study of B 0 and B 0 Fitted simultaneously with branching fractions Dilutions and time resolutions taken from sin2 fit S = 0.11 C = 0.14 A CP (K ) = 0.08 0.02 preliminary expected ~0.3 Run I + II
Gr. I, 10/9/01 Luca Lista Radiative Penguin: B K* Signal: B 0 K* 0 , K* 0 K + - Backgrounds: e + e - qq e + e - qq X 0 Sensitive to top quark couplings CKM matrix elements V td,V ts Sensitive to New Physics SUSY, Charged Higgs No CP asymmetry in the Standard Model (< 1%) Possible sources beyond SM
Gr. I, 10/9/01 Luca Lista B 0 K* 0 : yield and branching ratio N signal = 13.1 events Br(B 0 K *0 ) = (43.9 4.1 2.7) Br(B Kl + l - ) < 0.6 (90% C.L.) Br(B K*l + l - ) < 25.7 (90% C.L.) B 0 K* 0 K* 0 K +
Gr. I, 10/9/01 Luca Lista B K, B K* Penguin dominated B + K + = ( 0.8) B + < 1.4 (90% C.L.) B + K* + = ( 1.7) Possible measure of sin2 B 0 K* 0 = ( 1.1) B 0 K 0 = ( 0.8) Max Lik. Fit projections
Gr. I, 10/9/01 Luca Lista B + + = ( 0.7 ) B 0 K 0 < 12 B + K + = ( 70 8 5 ) B 0 K 0 = ( 4 ) B + K* + = ( 3.3 ) B 0 K* 0 = ( 1.7 ) B 0 K* 0 < 28 B + 0 K + < 39 B + 0 + < 39 B + K + < 54 B + + < 22 B 0 = ( 49 ) B 0 a 0 (980) Br(a 0 = ( 1.3 ) Quasi 2-body and 3-body decays Potential for sin2 First Observation
Gr. I, 10/9/01 Luca Lista Search for direct CP violation
Gr. I, 10/9/01 Luca Lista B D*D ( * ) K Study of the b ccs transition Experimental inclusive estimate from from B D S X, (cc)X, C X, C X (ALEPH, CLEO) Br(b ccs) ~ 15.8 2.8 % Theoretical calculation can’t determine this low value together with inclusive s.l. branching ratio (b cW) Three-body B DDK can contribute Study of color suppressed modes (B D* D* K ) Color allowed Color suppressed
Gr. I, 10/9/01 Luca Lista B D*D ( * ) K B 0 (all modes) N S = 180 21 B + (all modes) N S = 117 15 B D* D* K N S = 8.2 3.5 Reconstructed decays: D *+ D 0 + D *0 D 0 0 D *0 D 0 D 0 K - + D 0 K - + 0 D 0 K - + - + D + K - + + Br(B D* D 0 K ) = (0.28 0.07 0.05) Br(B D* D* K ) = (0.68 0.17 0.17) Br(B D* D* K ) = (0.34 0.16 0.11) First observation of color suppressed mode other than B (charmonium)X
Gr. I, 10/9/01 Luca Lista Conclusions sin2 extracted from 37.7 millions of BB events sin2 = 0.59 ± 0.14 stat ± 0.05 syst CP violation established at 4.1 level First measurement of CP violation in B 0 High precision measurements of mixing parameter and lifetimes High precision measurements of B decays branching fractions Many newly observed decays Most of the results are still statistically limited
Gr. I, 10/9/01 Luca Lista Backup slides
Gr. I, 10/9/01 Luca Lista J/ K* angular analysis |A | 2 = CP odd, P wave |A || | 2 = CP even, S+D wave |A 0 | 2 = CP even, S+D wave = arg(A /A 0 )= 0.17 0.16 0.07 || = arg(A || /A 0 )=2.50 0.20 0.08 Time dependent CP asymmetry dilution factor: D = 1 – 2 |A | 2 = 0.68 0.10 L=0,1,2 waves Both CP even and odd amplitudes are present Measurement of sin2 is possible from angular analysis Channels with 0 Channels without 0 f ( cos tr, cos K*, tr ) = f 1 |A 0 | 2 + f 2 |A || | 2 + f 3 |A | 2 + f 4 Im(A || * A ) + f 5 Re (A 0 * A || ) + f 6 Im (A 0 * A ) J/ rest frame K* decay plane
Gr. I, 10/9/01 Luca Lista B 0 D* + D* Cabibbo suppressed decay A measurement in b ccd of CP violating time-dependent asymmetry can be performed from angular analysis Possible penguin contamination Measurement of sin2 independent from B 0 J/ K S Significant deviations from B 0 J/ K S measurement of sin2 may be indication of new physics Branching ration measurement of B D ( * )+ D ( * )- : Tree diagram Penguin contribution
Gr. I, 10/9/01 Luca Lista B 0 D* + D* Br(B 0 D* + D* - ) = (8.0 1.6 1.2) Background sample (6.24 0.49 expected in signal box) Signal box (38 events)
Gr. I, 10/9/01 Luca Lista Inclusive Charmonium decays Inclusive J/ branching ratio: Br(B J/ X) = (1.044 0.028) Br(B J/ X dir.) = (0.789 0.034) Inclusive (2S) branching ratio: Br(B (2S) X) = (0.275 0.029) (2S) l l branching ratio: (2S) e e (7.8 0.9 0.8) (2S) (6.7 0.8 0.7) Inclusive c branching ratios: Br(B c1 X) = ( ) Br(B c1 X dir.)= ( ) Br(B c2 X) < 0.21 10 90% C.L. = ( ) Br( (2S) J/ assumed from PDG p* J/ < 2 GeV/c J/ e e J/ b s, d B 0, B X J/ , (2S), c d,u c c W-W-
Gr. I, 10/9/01 Luca Lista Main motivation: Channels are used for CP violation measurements Kinematics selection: Energy substituted mass Independent on particle mass hypotheses Energy difference in the center of mass Exclusive B decays B 0 J/ 0 First observation: B 0 c1 K* 0 First observation: B 0 c1 K* 0
Gr. I, 10/9/01 Luca Lista J/ production in continuum Color singles prediction: 0.8 pb A –0.8, NRQCD (c.o.) prediction: 2.8 pb 0.6<A<1.0 Angular distribution 1+A cos 2 * First observation of J/ production in continuum (4S) events with p* J/ >2 GeV/c Off-resonance events A (all E*) = 0.25 0.19 A (p*>3.5 GeV) l= 0.62 0.39
Gr. I, 10/9/01 Luca Lista Branching ratios results Mode Br ( ) B 0 J/ 0.06 0.02 B 0 J/ K* 0.5 0.9 B + J/ K* 13.7 0.9 1.1 B + J/ K 10.1 0.3 0.5 B 0 J/ K K L 6.8 0.8 0.8 B 0 J/ K K S 0 0 9.6 1.5 0.7 B 0 J/ K K S + 8.5 0.5 0.6 B 0 J/ K All 8.3 0.4 0.5 B 0 c1 K* 4.8 1.4 0.9 B 0 c1 K 5.4 1.4 1.1 B + c1 K 0.8 0.8 B + (2S) K 0.5 0.8 B 0 (2S) K 1.0 1.1 Br(B + J/ )/ Br(B + J/ K ) = (3.91 0.78 0.19) RUN 1: 22.7 MBB
Gr. I, 10/9/01 Luca Lista m d measurement: the di-lepton analysis e - e + zz l + or l - N + –, – + – N + +, – – N + –, – + + N + +, – – A( z)= Asymmetry m d = ± ± ps -1
Gr. I, 10/9/01 Luca Lista Semileptonic B decays Determine the sign of the B from a sample of ~14000 fully reconstructed B B 0 D (*) , D (*) , D (*) a 1 , J/ K *0 B D (*) , J/ K , (2S)K Lepton identified in the decay of the other B B+B+ B0B0 Mixing corrected
Gr. I, 10/9/01 Luca Lista b s , B 0 Semi-exclusive study Sum of exclusive modes K+n (n=1,2,3) m ES for 0.6 <m had < 2.0 GeV Theoretical exp.: ~ 10 Br(B 0 ) < 1.7 x % C.L. PDG: Br(B 0 ) < 3.9 x % C.L. (L3) Branching ratio measurement coming soon… B 0