Context : NGC 4815 is a populous \sim 500 Myr open cluster at R _ { gc } \sim 7 kpc observed in the first six months of the Gaia-ESO Survey .
Located in the inner Galactic disk , NGC 4815 is an important potential tracer of the abundance gradient , where relatively few intermediate age open clusters are found .

Aims : The Gaia-ESO Survey data can provide an improved characterization of the cluster properties , such as age , distance , reddening , and abundance profile .

Methods : We use the survey derived radial velocities , stellar atmospheric parameters , metallicity , and elemental abundances for stars targeted as potential members of this cluster to carry out an analysis of cluster properties .
The radial velocity distribution of stars in the cluster field is used to define the cluster systemic velocity and derive likely cluster membership for stars observed by the Gaia-ESO Survey .
We investigate the distributions of Fe and Fe-peak elements , alpha-elements , and the light elements Na and Al and characterize the cluster ’ s internal chemical homogeneity comparing it to the properties of radial velocity non-member stars .
Utilizing these cluster properties , the cluster color-magnitude diagram is analyzed and theoretical isochrones are fit to derive cluster reddening , distance , and age .

Results : NGC 4815 is found to have a mean metallicity of [ Fe/H ] = +0.03 \pm 0.05 dex ( s.d . ) .
Elemental abundances of cluster members show typically very small internal variation , with internal dispersions of \sim 0.05 dex .
The alpha-elements [ Ca/Fe ] and [ Si/Fe ] show solar ratios , but [ Mg/Fe ] is moderately enhanced , while [ Ti/Fe ] appears slightly deficient .
As with many open clusters , the light elements [ Na/Fe ] and [ Al/Fe ] are enhanced , [ Na/Fe ] significantly so , although the role of internal mixing and the assumption of LTE in the analysis remain to be investigated .
From isochrone fits to color-magnitude diagrams , we find a cluster age of 0.5 to 0.63 Gyr , a reddening of E ( B - V ) = 0.59 to 0.65 , and a distance modulus ( m - M ) _ { 0 } = 11.95 to 12.20 , depending on the choice of theoretical models , leading to a Galactocentric distance of 6.9 kpc .

Conclusions :