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unlike-sign and like-sign background invariant mass spec- tra are shown in Fig. 10. 

In this analysis, we cannot resolve individual states of the Υ family due to the limited statistics, finite mo- mentum resolution, and electron bremsstrahlung result- ing from the large material budget during the 2006 run. Therefore, the yield reported here is for the combined Υ(1S+2S+3S) states. The total dielectron unlike-sign yield after like-sign background subtraction has three contributions. 

1. The Υ states. 

2. The Drell-Yan continuum. 

3. The b - ¯ b continuum. 

In order to separate these three contributions, we ob- tain parametrizations for the expected shapes of each of the three components of the dielectron unlike-sign yield. The contribution from the Υ states is obtained by the same simulations that were used to obtain the detec- tor efficiency. The reconstructed invariant mass shape for the 1S, 2S, and 3S states are individually obtained. Each of the shapes from the simulation is fit with a functional form introduced by the Crystal-Ball experi- ment [31], which can accommodate detector resolution 

## A. Υ Line Shape 

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and losses due to bremsstrahlung in the detector mate- rial, and has the form: 

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Requiring that the function and its derivative be contin- uous constrains the constants A and B to be: 

We fix the parameters of the three Crystal-Ball functions representing the three Υ states and then adjust the rela- tive scales according to the average branching ratios and according to the ratios of cross sections shown in Ta- ble II. The overall integral of the Crystal-Ball functions combined this way is left as a free parameter in the fit, which allows us to obtain the Υ yield. 

Figure 11 shows the data used to obtain the Υ and continuum yields. The data points are the unlike-sign e $^{+}$e − signal after subtracting the like-sign combinatorial background. The background subtraction is done bin-by- bin. The error bars shown are statistical. The fit includes the contributions from the Υ(1S+2S+3S) states and the continuum contributions from Drell-Yan and b - ¯ b shown as the solid-line function. The Υ states are modeled with 

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