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KTeV KL -> pi0 gamma gamma plots

Updated August 18, 2008.

[KL->pi0 gamma gamma Results]

Plots in Phys. Rev. D 77, 112004 (2008) .

det_2D.eps, det_2D.pdf
FIG.1: Schematic of the KTeV detector.

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csi_schem.eps, csi_schem.pdf
FIG.2: Transverse view of the KTeV CsI calorimeter. The smaller blocks are located in the central region with larger blocks located in the outer region.

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fuse99.eps, fuse99.pdf
FIG.3: The photon shape chi² variable. a) The photon shape chi² variable for K_L->pi⁰pi⁰ with the dots representing the data and the solid histogram the Monte Carlo simulation. The Monte Carlo simulation was generated using our GEANT-based shower library. b) The photon shape chi² variable for K_L->pi⁰pi⁰ events. The dots are the data and the histogram represents the Monte Carlo simulation using our data-based shower library. The data-based Monte Carlo simulation shows marked improvement over the GEANT-based shower library.

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pggzdk.eps, pggzdk.pdf
FIG.4: The reconstructed decay vertex position from four photons for all events (histogram) prior to imposing the decay vertex cut. All cuts except for the decay vertex and photon shape chi² have been applied. The shaded histogram indicates K_L->pi⁰pi⁰ and K_L->pi⁰gamma gamma candidates. The rise at large values is doue to K_L->pi⁰pi⁰pi⁰ decays in which one or more photons misses the CsI calorimeter. The position of the cut is indicated by the two vertical lines.

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fuserecut.eps, fuserecut.pdf
FIG.5: The photon shape chi² variable. The solid histogram shows the K_L->pi⁰gamma gamma signal Monte Carlo simulation is the shaded histogram. The sum of the signal plus background Monte Carlo simulation agrees well with the data.

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mgg_final2.eps, mgg_final2.pdf
FIG.6: The m₃₃₄ distribution for after all selection cuts. The dots show the data, the histogram the sum of the signal and background Monte Carlo samples, and the shaded histogram the scaled background Monte Carlo simulation.

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ekzdk_2p.eps, ekzdk_2p.pdf
FIG.7: The a) energy and b) decay vertex for K_L->pi⁰pi⁰ decays. The dots are the data and the histogram is the Monte Carlo simulation.

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ydalitz.eps, ydalitz.pdf
FIG.8: The Y_Dalitz distribution for after all selection cuts. The dots show the data, the histogram the sum of the signal and background Monte Carlo simulation, and the shaded histogram the scaled background Monte Carlo simulation.

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Plots in Phys. Rev. Lett. 83, 917 (1999)

"Measurement of the Decay K_L -> pi⁰ gamma gamma"

pgg_fig0.eps
Fig.1. Theoretical predictions for $m_{34}$ for various values of $a_V$.

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pgg_fig1.eps
Fig.2. Plan view of the KTeV detector as configured for the E832 experiment. The arrows indicate the decay region considered for this analysis.

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pgg_fig2.eps
Fig.3. The maximum shape $\chi^2$ after all requirements except for the shape $\chi^2$ cut. The dots are the data and the histogram is the $3pi0$ Monte Carlo. The excess at low $\chi^2$ is due to $K_L->pi0 gamma gamma $ events and the arrow indicates the position of our cut. The inset shows the same distribution for events with $m_{34}<0.240$ GeV/$c^2$, indicating the existence of a low-mass tail in $K_L->pi0 gamma gamma $ events.

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pgg_fig3a.eps
Fig.4a) The $m_{34}$ mass distribution. The $2pi0$ events are removed from the $m_{34}$ distribution by cutting events between 0.10 GeV/$c^2$ and 0.16 GeV/$c^2$. The dots are the data, the histogram is the sum of the background and $K_L->pi0gamma gamma $ Monte Carlo and the dashed histogram is the normalized background Monte Carlo. The $K_L->pi0 gamma gamma $ MC is an ${\cal O}(p^6)$ calculation with $a_V = -0.7$. The inset shows the data and Monte Carlo for events in the mass region between 0.10 GeV/$c^2$ and 0.16 GeV/$c^2$ which are dominated by $K_L->pi0 pi0$ events.

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pgg_fig3b.eps
Fig.4b) The y parameter.

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