The proton-proton ($pp$) fusion cross-section found at the heart of solar models is unconstrained experimentally and relies solely on theoretical calculations. Effective field theory provides an opportunity to constrain the $pp$ cross-section experimentally, however, this method is complicated by the appearance of two-nucleon effects in the form of an unknown parameter $L_{ 1,A}$. We present a method to constrain $L_{ 1,A}$ using the Standard Solar Model and helioseismology. Using this method, we determine a value of $L_{ 1,A}$ = 7.0 fm$^{ 3}$ with a range of 1.6 to 12.4 fm$^{ 3}$. These results are consistent with theoretical estimates of $L_{ 1,A} \approx$ 6 fm$^{ 3}$.
Categories: nucl-th astro-ph