Elastic scattering of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mmultiscripts><mml:mi>He</mml:mi><mml:mprescripts/><mml:none/><mml:mn>3</mml:mn></mml:mmultiscripts><mml:mo>+</mml:mo><mml:mmultiscripts><mml:mi>He</mml:mi><mml:mprescripts/><mml:none/><mml:mn>4</mml:mn></mml:mmultiscripts></mml:mrow></mml:math> with the SONIK scattering chamber
S. N. Paneru, C. R. Brune, D. Connolly, Daniel Odell, Maheshwor Poudel, Daniel R. Phillips, J. Karpesky, B. Davids, C. Ruiz, A. Lennarz, U. Greife, M. Alcorta, R. Giri, M. Lovely, M. Bowry, M. Delgado, N. E. Esker, A. B. Garnsworthy, C. Seeman, P. Machule, J. Fallis, A. A. Chen, F. Laddaran, A. Firmino, C. Weinerman
Abstract
Measurements of the elastic scattering cross section of $^{3}\mathrm{He}$ and $^{4}\mathrm{He}$ are important in order to improve constraints on theoretical models of $^{4}\mathrm{He}(^{3}\mathrm{He},\ensuremath{\gamma})^{7}\mathrm{Be}$, a key reaction in Big Bang nucleosynthesis and solar neutrino production. The astrophysical $S$ factor for this reaction is a significant source of uncertainty in the standard-solar-model prediction of the $^{7}\mathrm{Be}$ and $^{8}\mathrm{B}$ solar neutrino fluxes. The elastic scattering measurements reported in the literature do not extend to low energies and lack proper uncertainty quantification. A new measurement of the $^{4}\mathrm{He}(^{3}\mathrm{He},^{3}\mathrm{He})^{4}\mathrm{He}$ reaction has been made at center-of-mass energies ${E}_{\text{c.m.}}=0.38\ensuremath{-}3.13$ MeV using the Scattering of Nuclei in Inverse Kinematics (SONIK) scattering chamber: a windowless, extended gas target surrounded by an array of 30 collimated silicon charged particle detectors situated at TRIUMF. This is the first elastic scattering measurement of $^{3}\mathrm{He}+^{4}\mathrm{He}$ made below 500 keV and it has greater angular range and better precision than previous measurements. The elastic scattering data were analyzed using both $R$-matrix and halo effective field theory frameworks, and values of the $s$-wave scattering length and effective range were extracted. The resulting improvement in knowledge of the $s$-wave effective-range function at low energies reduces the overall uncertainty in ${S}_{34}$ at solar energies.