Dalitz plot of D0 0 EPS208

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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
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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.

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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
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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?

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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.
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The Dalitz plot of D0 ? ? -? ?0
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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

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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
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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.

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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 .

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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
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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
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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
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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

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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
• .

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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 ? -) ? -
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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)? -
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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)

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Additional slides
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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.