New insights into nuclear physics and weak mixing angle using electroweak probes

Using the new results on coherent elastic neutrino-nucleus scattering data in cesium-iodide provided by the COHERENT experiment, we determine a new measurement of the average neutron rms radius of Cs-133 and I-127. In combination with the atomic parity violation (APV) experimental result, we derive the most precise measurement of the neutron rms radii of Cs-133 and I-127, disentangling for the first time the contributions of the two nuclei. By exploiting these measurements we determine the corresponding neutron skin values for Cs-133 and I-127. These results suggest a preference for models which predict large neutron skin values, as corroborated by the only other electroweak measurements of the neutron skin of Pb-208 performed by PREX experiments. Moreover, for the first time, we obtain a data-driven APV+COHERENT measurement of the low-energy weak mixing angle with a percent uncertainty, independent of the value of the average neutron rms radius of Cs-133 and I-127, that is allowed to vary freely in the fit. The value of the low-energy weak mixing angle that we found is slightly larger than the standard model prediction.

Automated summary

Utilizing new data from the COHERENT experiment, we determined a new measurement of the average neutron rms radius of Cs-133 and I-127, further obtaining corresponding neutron skin values for the isotopes. The preference for models predicting large neutron skin values is supported by the results, and the slightly higher value of the low-energy weak mixing angle compared to the standard model prediction was observed for the first time.