  We present the abundance analysis of 82 red giant branch stars in the dense,
metal-poor globular cluster NGC 6093 (M 80), the largest sample of stars
analyzed in this way for this cluster. From high resolution UVES spectra of 14
stars and intermediate resolution GIRAFFE spectra for the other stars we
derived abundances of O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,
Zn, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, Eu. On our UVES metallicity scale the mean
metal abundance of M 80 is [Fe/H]=-1.791+/-0.006+/-0.076 (+/-statistical
+/-systematic error) with rms=0.023 (14 stars). M 80 shows star to star
variations in proton-capture elements, and the extension of the Na-O
anticorrelation perfectly fit the relations with (i) total cluster mass, (ii)
horizontal branch morphology, and (iii) cluster concentration previously found
by our group. The chemistry of multiple stellar populations in M 80 does not
look extreme. The cluster is also a typical representative of halo globular
clusters for what concerns the pattern of alpha-capture and Fe-group elements.
However we found that a significant contribution from the s-process is required
to account for the distribution of neutron-capture elements. A minority of
stars in M 80 seem to exhibit slightly enhanced abundances of s-process
species, compatible with those observed in M 22 and NGC 1851, although further
confirmation from larger samples is required.
