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Dalitz plot of D0 0 EPS208

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EPS, July 2003. 1. Results on CP Violation from CLEO. Dalitz plot of D0 ... Uncertainties intrinsic to the fitter. M(Ds*(1-)) = 2.11 GeV. EPS, July 2003. 13 ... – PowerPoint PPT presentation

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Title: Dalitz plot of D0 0 EPS208


1

Results on CP Violation from CLEO
Searches for CP asymmetries in the
  • Dalitz plot of D0 ? ? -? ? 0 (EPS-208)
  • Kinematic distributions in ?c ? ?e? (EPS-138)
  • Decay rate of B0 ? K(892)? - (EPS-123)

Victor Pavlunin Purdue University the CLEO
collaboration EPS-2003, Aachen, Germany
2
The CLEO II and II.V detector
  • Tracking system
  • SVX (3 layers) or Gas Vertex Detector,
  • Vertex Detector, Drift Chamber
  • (B1.5T, Ar2C2H6 or He2C3H8)
  • (?p/p 0.6 for a 2 GeV track)
  • Time of Flight system
  • Scintillating 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.

3
CPV studies at CLEO
  • CESR is a symmetric (5.35.3) GeV ee
    collider.
  • On ?(4S),
  • ?B ?B ?Bc?B is 30 ?m,
  • ?D ?D?Dc?D is 120 - 320 ?m (assuming ?D?D 1
    ),
  • ?B lt Vertex resolution lt ?D
  • Time integrated asymmetries in B and D systems,
    and time dependent asymmetries in the D system
    are accessible.

All results reported today are on searches for
direct CP asymmetries
4
ACP in the Dalitz plot of D0 ? ? -? ?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.
  • ACP 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 D0 ? ? -? ? 0?

5
Event selection for D0 ? ? -??0 (CLEOII.V data
only)
D ? D0 ? slow , D0 ? ? -? ? 0 , ? 0 ? ??. The
sign of ? ?slow determines the flavor of the D0.
  • Standard criteria on charged tracks and ? 0s
  • Constrain D0 and ? slow to the beam spot
  • D0(? -? ? 0) and D(? -? ? 0 ? slow)
  • 1.841 GeV lt M(D0) lt 1.885 GeV
  • -0.604MeV lt Q Qexpected lt 0.691MeV, where Q ?
    M(D) - M(D0)
  • Xp ? P(D) / P(D) max gt 0.7

Signal yield 1.1K events in the signal box, of
which 20 are background.
6
The Dalitz plot of D0 ? ? -? ?0
7
Fit to the Dalitz plot of D0 ? ? -? ? 0
  • The likelihood function has the form
  • The matrix element is parameterized as
  • ACP across the Dalitz plot is obtained as

8
Results for ACP in D0 ? ? -? ? 0
  • The results of a fit with no CPV assumed
    (systematic errors are included)
  • The integrated ACP across the Dalitz plot

Fit fraction of ?(500) is consistent with zero.
  • Systematic errors (on-going)
  • Parameterization of efficiencies
  • Parameterization of background
  • Signal fraction
  • Event selection criteria.

All Preliminary
9
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 q2/q2max ,
    cos??, cos?W and ?.
  • The four-fold decay rate has the form
  • are helicity amplitudes containing
    the dependence on the form factors.

10
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 q2 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 f2/f1 and Mpole .

11
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/B3.7
12
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?Kl?.
  • 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 Rf2/f1 and Mpole
  • Major systematic errors
  • Background shapes in 4D,
  • Feeddown from modes ?c ? ?Xe? , X?0,
  • Background normalizations,
  • Uncertainties intrinsic to the fitter

M(Ds(1-)) 2.11 GeV
13
ACP in the kinematic distributions of ?c ? ?e?
  • 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.

for ltq2gt 0.67 GeV2.
All Preliminary
14
ACP in the decay rate of B0 ? 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

15
Event selection in B0 ? K(892)? -
K(892) is reconstructed in two submodes
K(892)? KS0? and K(892)? K? 0.
  • Standard cuts on tracks and showers
  • ?0s
  • P(? 0) gt 1.0 GeV
  • Beam constrained mass
  • B candidate energy
  • Veto some b ? c background
  • B ? D?, D ? K?
  • B ? J/?K0(or J/??0), J/? ? ??-
  • Example
  • Suppress background
  • .

16
UML fit for B0 ? K(892)? - and ACP
  • The likelihood function is given by
  • Variables (plot on the right) MB, EB, 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 B0 ? Rh, where h is ? - or
    K-, R can be any of the intermediate state
    resonances - K(1430), ?(770), or f0(980) and
    non-resonant (phase space) decays.
  • The fit is made for fjs and s, where
  • , for B0 ? 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 D0 ? K-? data
    and MC.

K(892)(KS0 ? -) ? -
17
Results for ACP in B0 ? K(892)? -
  • Fit to 30 free parameters (fjs and s)
  • Yield for B0 ? K(892)? -, K(892)? KS0?
  • Yield for B0 ? 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 ACP (Phys.Rev. D 68, 017101
    (2003))

B0 ? K(892)? -
18
SUMMARY
  • ACP in the Dalitz plot of D0 ? ? -? ? 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)

19
Additional slides
20
In the SM, the origin of CPV resides in flavor
changing quark transitions (VCKM)
CP violation in the Standard Model
  • 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.
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