Measurement of charm production at central rapidity in proton-proton collisions at

The pt-differential production cross sections of the prompt (B feed-down subtracted) charmed mesons D0, D+, and D*+ in the rapidity range |y| < 0.5, and for transverse momentum 1 < pt  < 12 GeV/c, were measured in proton-proton collisions at $$ \sqrt {s} = 2.76\;{\text{TeV}} $$ with the ALICE detector at the Large Hadron Collider. The analysis exploited the hadronic decays D0 → K−π+, D+ → K−π+π+, D*+ → D0π+, and their charge conjugates, and was performed on a $$ {\mathcal{L}_{{{\rm int} }}} = 1.1\;{\text{n}}{{\text{b}}^{{ - 1}}} $$ event sample collected in 2011 with a minimum-bias trigger. The total charm production cross section at $$ \sqrt {s} = 2.76\;{\text{TeV}} $$ and at 7 TeV was evaluated by extrapolating to the full phase space the pt-differential production cross sections at $$ \sqrt {s} = 2.76\;{\text{TeV}} $$ and our previous measurements at $$ \sqrt {s} = 7\;{\text{TeV}} $$. The results were compared to existing measurements and to perturbative-QCD calculations. The fraction of $$ {\text{c}}\overline {\text{d}} $$ D mesons produced in a vector state was also determined.