Finally, we look at the fraction of candidates, after background subtraction, outside the signal mass region. We count the number of candidates in the range 1.036 < m KK < 1.05 GeV/c 2 and calculate the ratio of this number to the number of candidates in the signal region. This ratio is found to be 2.4% in **data** and 2.6% in Monte Carlo. This yields a difference of 0.2% on the number of φ candidates between **data** and Monte Carlo.