[KTeV HOME] [Results] [Publications] [Theses] [Talks]

KTeV KL->pi⁰pi⁰pi⁰ plots

Updated August 18, 2008

[KL->pi⁰pi⁰pi⁰ Dalitz Plot Results]

Plots in Phys. Rev. D 78, 032009 (2008)

• xydal_model.eps, xydal_model.pdf
  FIG.1: Expected deviation from K_L->pi⁰pi⁰pi⁰ phase-space based on (a) h₀₀₀ = -0.005 and no contribution from rescattering, and (b) K_L->pi⁺pi^-pi⁰ with rescattering as calculated by Cabibbo and Isidori [6], with h₀₀₀ = 0. The intensity scales are slightly different to better illustrate the relateive shapes.
  
  -------------------------------------------------------
• detector.eps, detector.pdf
  FIG.2: Plan view of the KTeV (E832) detector. The evacuated decay volume ends with a thin vacuum window at Z=159m. Only decays from the vacuum beam are used to measure h₀₀₀.
  
  -------------------------------------------------------
• csilayout.eps, csilayout.pdf
  FIG.3: Layout of CsI calorimeter. The two neutral beams go through the 15 x 15 cm² beam holes (into page) shown by the two inner squares. The fiducial cut, indicated by the dark lines, rejects K_L->pi⁺pi^-pi⁰ decays in which any photon hits a crystal adjacent to a beam hole or at the outer boundary.
  
  -------------------------------------------------------
• m3pi0.eps, m3pi0.pdf
  FIG.4: (a) Invariant pi⁰pi⁰pi⁰ mass with all selection requirements except for the pi⁰pi⁰pi⁰-mass and chi_E². The pi⁰pi⁰pi⁰ mass resolution (from Gaussian fit) is 0.94 MeV/c². (b) shows chi_E² distribution with all other selection requirements; last bin includes all events with chi_E² > 200. Dots are data and the histogram is MC. Vertical arrows show the selection requirements.
  
  -------------------------------------------------------
• xydal_data.eps, xydal_data.pdf
  FIG.5: Dalitz plot density, Y_D vs. X_D, for 68.3. million K_L->pi⁰pi⁰pi⁰ decays in the KTeV data sample after all selection requirements. the color-scale at right shows the number of events in each 0.05 x 0.05 pixel. The reconstruction resolution on X_D and Y_D is sigma ~ 0.01 as determined by the MC; the box in the lower-left corner shows 10 sigma x 10sigma for illustration.
  
  -------------------------------------------------------
• m2p0rsq.eps, m2p0rsq.pdf
  FIG.6: For the 68.3 million K_L->pi⁰pi⁰pi⁰ in the KTeV sample, projected Dalitz distributions are shown for (a) R_D² and (b) m^min_pi0_pi0. The average reconstruciton resolution determined by the simulation is sigma(R_D² ~ 0.014 and sigma (min m_pi0_pi0) ~ 0.3MeV/c⁰: these resolution are indicated by a 10 sigma marker on each plot. The data/MC (phase-space) ratio is shown as a function of (c) R_D² and (d) m^min_pi0_pi0 (points with eror bars). The solid curve is the prediction from our best fit h₀₀₀ The dashed curve is the prediction using h₀₀₀ (PDG06) = (-5.0 +- 1.4) x 10^-3. The arrow in (d) shows the selection requirements m^min_pi0_pi0 > 0.274 GeV/c². Note that previous analysis [4,5] ignored rescattering and excluded R_D² > 1.9; the corresponding data/MC ratio was assumed to be a straight line with slope of -0.005.
  
  -------------------------------------------------------
• crosschecks.eps, crosschecks.pdf
  FIG.7: Crosscheck measurement of h₀₀₀: data-taking years (96,97,99), left and right vacuum beams (L,R), and min/max photon-energy ratio (E_gamma^min/ E_gamma^max) as discussed in the text. Measurements with each category (between vertical lines) are statistically independent. Error bars reflect the statistical uncertainties from the data and MC samples.
  
  -------------------------------------------------------
• m2p0rsq_2d.eps, m2p0rsq_2d.pdf
  FIG.8: Same as Fig.6c-d, except a₀-a₂ is floated in the fit instead of fixed to the NA48 value.
  
  -------------------------------------------------------

Send comments/corrections to Taku