KTeV KL > pi0 gamma gamma plots
Updated August 18, 2008.
[KL>pi0 gamma gamma Results]

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


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.


fuse99.eps,
fuse99.pdf
FIG.3: The photon shape chi^{2} variable. a) The photon shape chi^{2} variable for K_{L}>pi^{0}pi^{0} with the dots representing the data and the solid histogram the Monte Carlo simulation. The Monte Carlo simulation was generated using our GEANTbased shower library. b) The photon shape chi^{2} variable for K_{L}>pi^{0}pi^{0} events. The dots are the data and the histogram represents the Monte Carlo simulation using our databased shower library. The databased Monte Carlo simulation shows marked improvement over the GEANTbased shower library.


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 chi^{2} have been applied. The shaded histogram indicates K_{L}>pi^{0}pi^{0} and K_{L}>pi^{0}gamma gamma candidates. The rise at large values is doue to K_{L}>pi^{0}pi^{0}pi^{0} decays in which one or more photons misses the CsI calorimeter. The position of the cut is indicated by the two vertical lines.


fuserecut.eps,
fuserecut.pdf
FIG.5: The photon shape chi^{2} variable. The solid histogram shows the K_{L}>pi^{0}gamma gamma signal Monte Carlo simulation is the shaded histogram. The sum of the signal plus background Monte Carlo simulation agrees well with the data.


mgg_final2.eps,
mgg_final2.pdf
FIG.6: The m_{334} 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.


ekzdk_2p.eps,
ekzdk_2p.pdf
FIG.7: The a) energy and b) decay vertex for K_{L}>pi^{0}pi^{0} decays. The dots are the data and the histogram is the Monte Carlo simulation.


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.

"Measurement of the Decay K_{L} >
pi^{0} gamma gamma"

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


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.


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 lowmass tail in $K_L>pi0 gamma gamma $ events.


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.


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

Send corrections to Taku Yamanaka