To evaluate the background subtraction for A_LL, an alternate method is the after-the-fact estimate, where one subtracts the background asymmetry from the raw (or total) asymmetry rather than subtracting the background from the yield for each spin state.  The formula is



with s being the signal fraction. 

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Fitting other mass range

As an initial guess, one can estimate the background as 0 \pm some max value.  To guess at what this max value for the background asymmetry might be, the asymetry is computed in the mass region 0.35 to 0.45 GeV.  The result is:

A_L Blue

A_L Yellow

A_LL

Fitting to a line yields

Chi2                      =      14.5942
NDf                       =            6
p0                        =    0.0277576   +/-   0.0489465

 

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New Results

From the above side mass fits, we conclude 0 +/- 0.1 is a reasonable estimate of the background.  Using this estimate and the top formula results in
 

A_L Blue

A_L Yellow

A_LL

 

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Discussion

Whether this method is any more or less scientific than using the Monte Carlo background shapes is not obvious.  The other method is much more careful, but also prone to instabilities.  This method is less fancy, and more stable, but possibly less accurate.