Context :

Aims : We extend our previous work on the effects of the uncertainties on the main input physics for the evolution of low-mass stars .
We analyse the dependence of the cumulative physical uncertainty affecting stellar tracks on the chemical composition .

Methods : We calculated more than 6000 stellar tracks and isochrones , with metallicity ranging from Z = 0.0001 to 0.02 , by changing the following physical inputs within their current range of uncertainty : ^ { 1 } H ( p , \nu e ^ { + } ) ^ { 2 } H , ^ { 14 } N ( p, \gamma ) ^ { 15 } O and triple- \alpha reaction rates , radiative and conductive opacities , neutrino energy losses , and microscopic diffusion velocities .
The analysis was performed using a latin hypercube sampling design .
We examine in a statistical way – for different metallicities – the dependence on the variation of the physical inputs of the turn-off ( TO ) luminosity , the central hydrogen exhaustion time ( t _ { H } ) , the luminosity and the helium core mass at the red-giant branch ( RGB ) tip , and the zero age horizontal branch ( ZAHB ) luminosity in the RR Lyrae region .

Results : For the stellar tracks , an increase in the metallicity from Z = 0.0001 to Z = 0.02 produces a cumulative physical uncertainty error variation in TO luminosity from 0.028 dex to 0.017 dex , while the global uncertainty on t _ { H } increases from 0.42 Gyr to 1.08 Gyr .
For the RGB tip , the cumulative uncertainty on the luminosity is almost constant at 0.03 dex , whereas the one the helium core mass decreases from 0.0055 M _ { \sun } to 0.0035 M _ { \sun } .
The dependence of the ZAHB luminosity error is not monotonic with Z , and it varies from a minimum of 0.036 dex at Z = 0.0005 to a maximum of 0.047 dex at Z = 0.0001 .
Regarding stellar isochrones of 12 Gyr , the cumulative physical uncertainty on the predicted TO luminosity and mass increases respectively from 0.012 dex to 0.014 dex and from 0.0136 M _ { \sun } to 0.0186 M _ { \sun } .
Consequently , from Z = 0.0001 to Z = 0.02 for ages typical of galactic globular clusters , the uncertainty on the age inferred from the TO luminosity increases from 325 Myr to 415 Myr .

Conclusions :