EPS, July 2003 1 Dalitz plot of D 0 - + 0 (EPS-208) Kinematic distributions in c e + (EPS-138) Decay rate of B 0 K * (892) + -
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EPS, July 2003 1 Dalitz plot of D 0 - + 0 (EPS-208) Kinematic distributions in c e + (EPS-138) Decay rate of B 0 K * (892) + - (EPS-123) Victor Pavlunin Purdue University the CLEO collaboration EPS-2003, Aachen, Germany Searches for CP asymmetries in the:
EPS, July 2003 2 CPV in decay (direct): Time integrated asymmetries; but strong phases are hard to calculate. CPV in mixing (indirect): Time integrated asymmetries ( e.g., like-sign di-lepton events); expected to be small in the SM. CPV in the interference between decays with and without mixing: Time dependent analyses; avoid hadronic uncertainties in some important cases. CP violation in the Standard Model In the SM, the origin of CPV resides in flavor changing quark transitions (V CKM ):
EPS, July 2003 3 The CLEO II and II.V detector Tracking system: SVX (3 layers) or Gas Vertex Detector, Vertex Detector, Drift Chamber (B=1.5T, Ar 2 +C 2 H 6 or He 2 +C 3 H 8 ) ( p/p ~ 0.6% for a 2 GeV track) Time of Flight system S cintillating plastic ( t ~ 170ps) Crystal Calorimeter CsI crystals( E/E ~ 2% for a 2 GeV photon Muon chambers Proportional chambers at 3, 5 and 7 I The size of the data sample is 13.7 fb -1. 2/3 (1/3) is taken with CLEOII.V (CLEOII). 2/3 (1/3) is taken ON (50 MeV OFF) (4S). ~10M of and ~18M of events.
EPS, July 2003 4 CPV studies at CLEO Type of CPV DirectMixingInterference Bottom Yes No Charm Yes All results reported today are on searches for direct CP asymmetries CESR is a symmetric (5.3+5.3) GeV e + e – collider. On (4S), B = B B c B is ~30 m, D = D D c D is 120 - 320 m (assuming D D = 1 ), B < Vertex resolution < D Time integrated asymmetries in B and D systems, and time dependent asymmetries in the D system are accessible.
EPS, July 2003 5 A CP in the Dalitz plot of D 0 - + 0 (EPS-208) Interference of different intermediate resonances in the Dalitz plot makes amplitudes and phases of the resonances accessible. Expected contributions are from resonant decays through 0, + and -, as well as a non-resonant contribution. A CP is predicted to be as large as 0.1% (F.Buccella et al., Phys.Lett.B 379, 249 (1996)). E791 found strong evidence for (500) in D + - + + ( PRL 86, 770 (2001)). Does (500) contribute in D 0 - + 0 ?
EPS, July 2003 6 Event selection for D 0 - + 0 (CLEOII.V data only) Standard criteria on charged tracks and 0 ’s Constrain D 0 and slow to the beam spot D 0 ( - + 0 ) and D* + ( - + 0 + slow ): 1.841 GeV < M(D 0 ) < 1.885 GeV -0.604MeV < Q – Q expected < 0.691MeV, where Q M(D *+ ) - M(D 0 ) X p P (D *+ ) / P (D *+ ) max > 0.7 D *+ D 0 + slow, D 0 - + 0, 0 . The sign of slow determines the flavor of the D 0. Signal yield: 1.1K events in the signal box, of which ~20% are background.
EPS, July 2003 7 The Dalitz plot of D 0 - + 0
EPS, July 2003 8 Fit to the Dalitz plot of D 0 - + 0 The likelihood function has the form The matrix element is parameterized as A CP across the Dalitz plot is obtained as
EPS, July 2003 9 All Preliminary Results for A CP in D 0 - + 0 Resonance AmplitudePhaseFit Fraction ++ 1.00 (fixed)0 (fixed)76.5±1.8±4.8 00 0.56±0.02±0.0710±3±323.9±1.8±4.6 0.65±0.03±0.04 4±3±4 32.3±2.1±2.2 Non res 1.03±0.17±0.3177±8±112.7±0.9±1.7 Systematic errors (on-going): Parameterization of efficiencies; Parameterization of background; Signal fraction; Event selection criteria. Fit fraction of (500) is consistent with zero. The results of a fit with no CPV assumed (systematic errors are included): The integrated A CP across the Dalitz plot:
EPS, July 2003 10 Form factor measurement and search for CPV in the decay c e + (EPS-138) In the heavy quark symmetry limit, particles with a heavy quark are subject to a larger symmetry group. The Lorentz structure of -type baryons is due to the polarization states of the heavy quark only (light quarks form a spin zero state). Due to this simplicity, the predictions of HQET for - type baryons are more reliable than for mesons. Four kinematic variables describe the decay sequence c e +, p + : t = q 2 /q 2 max, cos , cos W and . The four-fold decay rate has the form: are helicity amplitudes containing the dependence on the form factors.
EPS, July 2003 11 Form factor predictions for c e + Traditional parameterization of the hadronic current: HQET implies relations among form factors and reduces their number to two: In order to fit the data, the q 2 dependence of the form factors must be assumed. We follow the Korner-Kramer (KK) model (Phys.Lett. B 275, 495 (1992)) and assume the same dipole dependence for both form factors: The fit is made for R = f 2 /f 1 and M pole.
EPS, July 2003 12 Yields and Estimation of kinematic variables Event selection and background studies: Estimation of kinematic variables (neutrino is missing): kinematic constraints of the decay, the thrust vector of the event, the fragmentation function of c. ~3K of signal events and S/B=3.7
EPS, July 2003 13 ML fit for form factors in c e + The fitting method used in the analysis was first suggested in D.M.Schmidt, R.J.Morrison and M.S.Witherell, Nucl.Instr. and Methods A328 547 (1993), in the measurement of form factors in D K * l. The following samples are used as separate components in the fit (10 different components): c e + for CleoII/CleoII.V (2 components) c e - for CleoII/CleoII.V (2 components) c e + (2 components) fake positron background (3 components with different momentum ranges) fake background (1 component) Simultaneous fit for R=f 2 /f 1 and M pole : Major systematic errors Background shapes in 4D, Feeddown from modes c Xe +, X 0, Background normalizations, Uncertainties intrinsic to the fitter M(D s * (1 - )) = 2.11 GeV
EPS, July 2003 14 The fit results correspond to If CP is conserved then. Therefore, a CP violating parameter can be defined as. Fitting the charge conjugate states separately for and, and using the relation we obtain where correlations among systematic errors are taken into account. All Preliminary A CP in the kinematic distributions of c e + for = 0.67 GeV 2.
EPS, July 2003 15 A CP in the decay rate of B 0 K * (892) + - (EPS-123) In SU(3) symmetry limit: Measuring and allows the extraction of both and the strong phase, . CLEO measured ( PRL 89, 251801 (2002)): This study extends the previous analysis and measures:
EPS, July 2003 16 Event selection in B 0 K * (892) + - Standard cut on tracks and showers 0 ’ s: P( 0 ) > 1.0 GeV Beam constrained mass: B candidate energy: Veto some b c background : B D , D K ; B J/ K 0 (or J/ 0 ), J/ + - Example: Suppress background :. K * (892) + is reconstructed in two submodes: K * (892) + K S 0 + and K * (892) + K + 0.
EPS, July 2003 17 UML fit for B 0 K * (892) + - and A CP The likelihood function is given by Variables (plot on the right): M B, E B, the Fisher discriminant, cos( B ), dE/dx for the faster of the primary tracks ( h - = - or K - ) and Dalitz plot variables. Components: the signal, the continuum, the BBbar bckg, the B 0 R *+ h –, where h – is - or K -, R *+ can be any of the intermediate state resonances - K * (1430), (770), or f 0 (980) ; and non-resonant (phase space) decays. The fit is made for f j ’ s and ’s, where, for B 0 K * (892) + - PDFs are functions of the event location in the Dalitz plot (plot of the right) and are derived from the off-resonance data, the D 0 K - + data and MC. K * (892) + (K S 0 - ) -
EPS, July 2003 18 Results for A CP in B 0 K * (892) + - Fit to 30 free parameters ( f j ’s and ’s) Yield for B 0 K * (892) + -, K * (892) + K S 0 + : Yield for B 0 K * (892) + -, K * (892) + K + 0 : Combined significance 4.6 . Major systematic errors Dalitz PDF shapes Fitting method Interference among intermediate resonances Final results for A CP (Phys.Rev. D 68, 017101 (2003)): B 0 K * (892) + -
EPS, July 2003 19 SUMMARY A CP in the Dalitz plot of D 0 - + 0 (EPS-208):, No evidence for (500) is found. Form Factors and Search for CPV in c e + (EPS-138): Charge Asymmetry in B K * (892) + - (EPS-123):