Neutron Skin in CsI and Low-Energy Effective Weak Mixing Angle from COHERENT Data. (arXiv:1902.07625v1 [hep-ph])

Neutron Skin in CsI and Low-Energy Effective Weak Mixing Angle from COHERENT Data. (arXiv:1902.07625v1 [hep-ph])
<a href="http://arxiv.org/find/hep-ph/1/au:+Huang_X/0/1/0/all/0/1">Xu-Run Huang</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Chen_L/0/1/0/all/0/1">Lie-Wen Chen</a>

Both the neutron skin thickness $Delta R_{np}$ of atomic nuclei and the
low-energy neutrino-nucleon ($nu N$) 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 (CE$nu$NS) provides a clean way
to extract their information. The new physics beyond the SM may cause
effectively a shift of the SM weak mixing angle $theta_W$ in low-energy $nu
N$ interactions, leading to an effective weak mixing angle $theta^*_W$. By
analyzing the CE$nu$NS data of the COHERENT experiment, we find that while a
one-parameter fit to the COHERENT data produces an unrealistically large
central value of $Delta R^{rm{CsI}}_{np} simeq 0.7$ fm for CsI when the
low-energy $sin^2 theta^*_W$ is fixed at the low-energy SM value of
$sin^2theta_W^{rm{SM}} = 0.23857(5)$, a two-dimensional fit gives
significantly smaller central values of $Delta R^{rm{CsI}}_{np} simeq 0.25$
fm and $sin^2 theta^*_W simeq 0.21$, although their uncertainties are large.
The implication of the substantial deviation of the low-energy effective
$sin^2 theta^*_W$ from $sin^2theta_W^{rm{SM}}$ on the new physics
scenarios in neutrino physics is discussed.

Both the neutron skin thickness $Delta R_{np}$ of atomic nuclei and the
low-energy neutrino-nucleon ($nu N$) 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 (CE$nu$NS) provides a clean way
to extract their information. The new physics beyond the SM may cause
effectively a shift of the SM weak mixing angle $theta_W$ in low-energy $nu
N$ interactions, leading to an effective weak mixing angle $theta^*_W$. By
analyzing the CE$nu$NS data of the COHERENT experiment, we find that while a
one-parameter fit to the COHERENT data produces an unrealistically large
central value of $Delta R^{rm{CsI}}_{np} simeq 0.7$ fm for CsI when the
low-energy $sin^2 theta^*_W$ is fixed at the low-energy SM value of
$sin^2theta_W^{rm{SM}} = 0.23857(5)$, a two-dimensional fit gives
significantly smaller central values of $Delta R^{rm{CsI}}_{np} simeq 0.25$
fm and $sin^2 theta^*_W simeq 0.21$, although their uncertainties are large.
The implication of the substantial deviation of the low-energy effective
$sin^2 theta^*_W$ from $sin^2theta_W^{rm{SM}}$ on the new physics
scenarios in neutrino physics is discussed.

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