$\mathrm{{D}}^\mathbf {0}\rightarrow \mathrm{{K}}^\mathbf {-}{\pi }^\mathbf {+}$ Decay Reconstruction

Abstract

The chapter is devoted to the description of the $\mathrm{D^0}$ analysis in Pb–Pb and p–Pb collisions. The aim of the analysis is to extract the elements that are needed to measure the elliptic flow in Pb–Pb collisions, the production cross section and nuclear modification factor in both Pb–Pb and p–Pb collisions. In the first part of the chapter, Sect. 5.1, the Pb–Pb and p–Pb data samples are described. In Sect. 5.2 the event-plane determination for the azimuthal anisotropy measurement is explained. Section 5.3 is devoted to the description of the reconstruction and selection strategy for D mesons. The strategy exploits the displacement (from the primary vertex) of the secondary vertices originating from the weak decay of the D mesons. The variables allowing to select the ${\mathrm{D^0}\rightarrow \mathrm{K}^-{\pi }^+}$ topology will be introduced, together with the particle identification procedure to improve the rejection of the combinatorial background. A description of the invariant mass analysis used to extract the yields is given in Sect. 5.4. The invariant mass distributions together with the fits performed to obtain the raw signals are shown for both Pb–Pb and p–Pb systems. Section 5.5 describes the study of the $\mathrm{D^0}$ reflections, defined as the signal candidates that pass the cuts both as $\mathrm{D^0}$ and $\overline{\mathrm{D^0}}$. The last two Sects. 5.6 and 5.7, are devoted to the description of the efficiency calculation and feed-down correction, respectively.