NMR signal analysis for deuteron polarization determination in a COMPASS large polarized 6LiD target

The internal structure of nucleons is an ongoing research topic of great importance. At COMPASS, in the 2021-2022 period, we adopted 6LiD as a polarized target and measured the azimuthal distribution of the cross-section for the production of π mesons when muons are injected. We investigated the Sivers asymmetry and Collins asymmetry. The polarization and its error of the target are crucial parameters for determining the Sivers asymmetry and Collins asymmetry. The polarized target is the largest ever with a length of 120 cm. To reduce systematic errors for the asymmetry, the target is divided into three cells, and the adjacent cells are polarized in the opposite direction to perform scattering experiments. Each cell of the target is equipped with 3 or 4 coils, and the intensity of Nuclear Magnetic Resonance (NMR) signals obtained from a total of 10 coils was measured. The polarization was determined by calibrating the NMR signals with the signals obtained in the thermal equilibrium state (TE). The NMR signals at TE were measured over several days under various conditions, including target temperatures of 1.0 K, 1.3 K, 1.5 K, with a magnetic field of 2.5 T. Dynamic Nuclear Polarization (DNP) was used as a means to polarize the target. DNP was performed over several days while varying the frequency and power of the microwaves irradiated into each cell. In this presentation, we provide details on the analysis of NMR signals for determining the polarization of deuterons at COMPASS.