We have applied a new method to analyze the horizontal branch ( HB ) morphology in relation to the distribution of stars near the red giant branch ( RGB ) tip for the globular clusters M22 , M5 , M68 , M107 , M72 , M92 , M3 and 47 Tuc .
This new method permits determination of the cluster ages to greater accuracy than conventional isochrone fitting .
Using the method in conjunction with our new high-quality photometric data for RGB and HB stars in the first five of these clusters , we discuss the origins of the spread in color on the HB and its relation to the ‘ second parameter ’ problem .
The oldest clusters in our sample are found to have relatively low ages ( 13.5 \pm 2 Gyr ) .
A 1 \sigma uncertainty in each of the parameters of mass and helium content combined with the effects of helium diffusion gives a lower limit for the age of the oldest clusters of 9.7 Gyr .