Feasibility study of intrinsic charm meausurement with ALICE at CERN Large Hadron Collider

Abstract

Quantum ChromoDynamics (QCD) predicts that the proton can have up to five valence quarks, with the additional quark-antiquark pair being an intrinsic component. It is expected that, with a probability in the order of one percentage, the two additional intrinsic quarks can be charm quarks. This is explained by non-perturbative QCD. Previous research shows that this component is expected to overtake perturbative contributions at higher Bjorken x. Although relevant for testing QCD, the study of intrinsic charm is also important to correctly model the background in the discovery measurement of astronomical neutrinos performed by the IceCube Collaboration. In this thesis, a topology involving a central gluon jet, a central D meson and a forward muon from heavy-flavour hadron decays is proposed as a viable measurement strategy, and simulated whilst keeping in mind the ALICE detector acceptance. To do this, C++ framework ROOT is used along with Pythia8 and LHAPDF6 to simulate five different parton distribution functions (PDF) with varying levels of intrinsic charm, and compared to a PDF set with no intrinsic charm by means of ratios. The results of these simulations show that the proposed topology works in tagging intrinsic charm events. In particular, it is possible, my tuning the transverse momentum (p_T) range of the D meson, to enhance the intrinsic charm contribution of the intermediate muon p_T, allowing one to separate this contribution from the one of the perturbative charm production. This indicates that forward muons are a promising candidate for an intrinsic charm trigger once produced in association with a D meson at central rapidity.