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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.

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Presentation on theme: "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."— Presentation transcript:

1 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

2 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)

3 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

4 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

5 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

6 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

7 Gr. I, 10/9/01 Luca Lista CP violation at asymmetric B factory CP violation via mixing t=0 B0B0 B0B0  t (ps) FF FF 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 

8 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)

9 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

10 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 +

11 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 zz 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

12 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

13 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%

14 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*

15 Gr. I, 10/9/01 Luca Lista sin2  result sin2 = 0.59 ± 0.14 stat ± 0.05 syst

16 Gr. I, 10/9/01 Luca Lista Comparison of different samples Submitted to Phys. Rev. Lett. On July

17 Gr. I, 10/9/01 Luca Lista Unitarity triangle 22 11 sin2 = 0.59 ± 0.14 stat ± 0.05 syst sin2 = 0.59 ± 0.14 stat ± 0.05 syst

18 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

19 Gr. I, 10/9/01 Luca Lista 0.03 from vertexing 0.03 from tagging 0.02 from background Total 0.05 Systematic errors

20 Gr. I, 10/9/01 Luca Lista  m d measurement  m d = ± stat ± syst ps -1 preliminary Run I only

21 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 BB B 0 /B 0

22 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 WW WW 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…

23 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

24 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

25 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

26 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 +  

27 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

28 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

29 Gr. I, 10/9/01 Luca Lista Search for direct CP violation

30 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

31 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

32 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

33 Gr. I, 10/9/01 Luca Lista Backup slides

34 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

35 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

36 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)

37 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-

38 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

39 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 0.62 GeV/c  Off-resonance events A (all E*) = 0.25  0.19 A (p*>3.5 GeV) l= 0.62  0.39

40 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

41 Gr. I, 10/9/01 Luca Lista  m d measurement: the di-lepton analysis e -  e + zz l + or l - N + –, – + – N + +, – – N + –, – + + N + +, – – A(  z)= Asymmetry  m d = ± ± ps -1

42 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

43 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


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