Abstract
Abstract The p t-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 < p t < 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 p t-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.
Highlights
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 t√ransverse momentum 1 < pt < 12 GeV/c, were measured in proton-proton collisions at s = 2.76 TeV with the ALICE detector at the Large Hadron Collider
The study of charm production was performed by reconstructing D0, D+, and D∗+ charmed hadrons via their hadronic decays D0 → K−π+ (BR of 3.87 ± 0.05% [33]), D+ → K−π+π+ (BR of 9.13±0.19% [33], including the resonant channels via a K∗0), and D∗+(2010) → D0π+ (BR of 67.7 ± 0.5% [33]) with D0 → K−π+, and their charge conjugates
The extrapolated cross sections for D mesons are given in tables 5 and 6 with uncertainties resulting from the yield extraction, the quadratic sum of the experimental uncertainty in D-meson reconstruction and the uncertainty in subtracting the contribution of D mesons originating from beauty production, a 1.9% (3.5%) uncertainty in the absolute luminosity at 2.76 TeV (7 TeV), the uncertainty in the branching ratios (BR), and the uncertainty due to extrapolation to the full phase space
Summary
The D mesons are reconstructed in the central rapidity region using the central barrel detectors of the ALICE experiment. The Time-Of-Flight (TOF) detector, based on Multi-gap Resistive Plate Chambers (MRPCs), is positioned in the region between 377 to 399 cm from the beam axis and covers |η| < 0.9 and full azimuth. In this analysis, the TOF complemented the hadron identification capability of the TPC, ensuring an efficient track by track kaon/pion separation up to a momentum of about 1.5 GeV/c. Minimum-bias collisions were triggered by requiring at least one hit in either of the VZERO scintillator hodoscopes (one located at z = 328 cm covering 2.8 < η < 5.1, and the other at z = −86 cm covering −3.7 < η < −1.7) or in the SPD (|η| < 2), in coincidence with the arrival of proton bunches from both sides of the interaction region. The systematic uncertainty of 1.9% was assigned upon considering the uncertainties on the beam intensities and on the analysis procedure
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