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KTeV KL ->eeee plots

Updated July 6, 2002.

[KL -> eeee Results]

Plots in Phys. Rev. Lett. 86, 5425 (2001)

"Measurements of the Rare Decay K_L -> e⁺e^-e⁺e^-"

• mpt2_datmc_paper.eps
  Top: The distribution of ${P_T}^{2}$ vs. $M_{e^{+} e^{-} e^{+} e^{-}}$ for candidate \(K_L \rightarrow e^+ e^- e^+ e^-\) events after all cuts except the ${P_T}^{2}$ and $M_{e^{+} e^{-} e^{+} e^{-}}$ cuts. There are 441 events in the signal region defined by the box.
  Bottom: The distribution of ${P_T}^{2}$ vs. $M_{e^{+} e^{-} e^{+} e^{-}}$ for reconstructed Monte Carlo simulated events, scaled to the data statistics. The filled circles represent the signal Monte Carlo and the open circles represent the $K_{L} \rightarrow \pi^{\pm} e^{\mp} \nu \: e^{+} e^{-}$ Monte Carlo. The box defines the signal region with an efficiency of $90\%$.
  
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• m4e_datmc_paper.eps
  The $M_{e^{+} e^{-} e^{+} e^{-}}$ distribution after all cuts except the invariant mass cut. The dots represent the data and the histogram represents the Monte Carlo simulation. The arrows indicate an intentionally wide mass window chosen to retain the low-side radiative tail visible in the data. The decay $K_{L} \rightarrow \pi^{\pm} e^{\mp} \nu \: e^{+} e^{-}$ is seen in the lower mass region.
  
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• mee_ff.eps
  (a) The $x$ distribution for data and for Monte Carlo using our measured value of $\alpha_{K^*}^{{\rm eff}}$ and using $f(x) = 1$. Since there are two $e^{+} e^{-}$ pairs in this decay, this is a double entry plot. The data/Monte Carlo ratio is shown for our measured value of $\alpha_{K^*}^{{\rm eff}}$ (b) and for a pointlike form factor (c). We measure $\alpha_{K^*}^{{\rm eff}} = -0.14 \pm 0.16({\rm stat}) \pm 0.15({\rm syst})$. Recall that $\alpha_{K^*} \approx 0.3$ best approximates a pointlike form factor.
  
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• betgam_paper_bms.eps
  The distribution of the angle $\phi$ between the planes of the two $e^{+} e^{-}$ pairs. In the bottom figure, the $\phi$ distribution from $90^{\circ}-180^{\circ}$ is folded into $0^{\circ}-90^{\circ}$. We fit these distributions to Eq.~\ref{eq:bg} and measure $\beta_{CP} = -0.23 \pm 0.09({\rm stat}) \pm 0.02({\rm syst})$ and $\gamma_{CP} = -0.09 \pm 0.09({\rm stat}) \pm 0.02({\rm syst})$. The dashed line shows the $CP=+1$($K_{1}$) prediction and further confirms that the decay proceeds predominantly through the $CP=-1$ ($K_{2}$) state.
  
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