Neutron skin in CsI and low-energy effective weak mixing angle from COHERENT data

• Published in: Physical review. D 2019-10, Vol.100 (7), p.071301-1, Article 071301
• Main Authors: Huang, Xu-Run, Chen, Lie-Wen
• Format: Article
• Language: English
• Subjects: Astrophysics; Coherent scattering; Elastic scattering; Neutrinos; Nuclei (nuclear physics); Nucleons; Particle physics; Physics
• ISSN: 2470-0010; 2470-0029
• DOI: 10.1103/PhysRevD.100.071301

Both the neutron skin thickness ΔRnp of atomic nuclei and the low-energy neutrino-nucleon (νN) interactions are of fundamental importance in nuclear and particle physics, astrophysics as well as new physics beyond the standard model (SM) but largely uncertain currently, and the coherent elastic neutrino-nucleus scattering (CEνNS) provides a clean way to extract their information. New physics beyond the SM may cause effectively a shift of the SM weak mixing angle θW in low-energy νN interactions, leading to an effective weak mixing angle θW*. By analyzing the CEνNS data of the COHERENT experiment, we find that while a one-parameter fit to the COHERENT data by varying ΔRnp produces ΔRnpCsI ≃ 0.68−1.13+0.91 fm for CsI with an unrealistically large central value by fixing sin2θW* at the low-energy SM value of sin2θWSM = 0.23857, a two-dimensional fit by varying ΔRnp and sin2θW* leads to a strong positive correlation between ΔRnp and sin2θW* with significantly smaller central values of ΔRnpCsI ≃ 0.24−2.03+2.30 fm and sin2θW* = 0.21−0.10+0.13. Although the uncertainty is too large to claim a determination of ΔRnpCsI and sin2θW*, the present study suggests that the multidimensional fit is important in future analyses of high-precision CEνNS data. The implication of the possible deviation of sin2θW* from sin2θWSM on new physics beyond the SM is also discussed.