code: def _get_asym_alpha(self,a,b):
          
          
          # just  use AL0
          try:
              a = a[2:4]
          except IndexError:
              a = a[:2]
              
          # sum counts in alpha detectors
          asum = np.sum(a,axis=0)
          
          # sum counts in beta detectors
          bsum = np.sum(b,axis=0)
          
          # check for dividing by zero 
          asum[asum == 0] = np.nan
          bsum[bsum == 0] = np.nan
          
          # asym calcs
          asym = asum/bsum
          
          # errors
          dasym = asym*np.sqrt(1/asum + 1/bsum)
          
          return [asym,dasym]
docs: Find alpha diffusion ratios from cryo oven with alpha detectors. 
              a: list of alpha detector histograms (each helicity)
              b: list of beta  detector histograms (each helicity)