Summer student project report: Search for the decay ∗ ± ∗± 퐷푠(2317) → 퐷푠 훾 at the LHCb experiment Lukas Calefice1,2,* and Supervisor: Ricardo Vázquez Gómez2,** 1Fakultät Physik, Technische Universität Dortmund, 2LHCb collaboration, CERN, *
[email protected], **
[email protected] September 2018 Abstract ∗ ± ∗± The summer student project treated the search for the radiative decay 퐷푠(2317) → 퐷푠 훾 with the 2016 and 2017 data sets collected by the LHCb experiment corresponding to 3.3 fb−1 at a centre- ∗ ± ∗± ∗ ± of-mass energy of 13 TeV. For the search the ratio BR(퐷푠(2317) → 퐷푠 훾)/BR(퐷푠(2317) → ± 0 ∗ ± ∗± 퐷푠 휋 ) was investigated, but no hint for the existence of 퐷푠(2317) → 퐷푠 훾 was found. 1 Introduction The spectroscopy of heavy-light mesons can mostly be described successfully with non-relativistic quark potential models in the limit of Heavy Quark Effective Theory (HQET), in which the mesons can be considered as a hydrogen atom. The limit requires that 푚Q → ∞, which is the mass of the ⃗ meson’s heavy quark. In that case the spin of the heavy quark 푆Q is decoupled from the orbital angular momentum 푙 ⃗ between the quarks and states in the spectrum are identified by the quantum numbers 푗 푗 = 퐿 + 푠q, 퐿 and 퐽. Therefore the 푃-wave (퐿 = 1) states are expected to be doubly degenerated in the spin of the heavy quark. Moreover new symmetries called Heavy Flavour Symmetry and Heavy Spin Symmetry come along with the HQET that make it possible to estimate several mass states and branching fractions.