Constraints on axial two-body currents from solar neutrino data

We briefly review recent calculations of neutrino-deuteron cross sections within the effective field theory and traditional potential model approaches. We summarize recent efforts to determine the counter term describing axial two-body currents, $L_{1A}$, in the effective field theory approach. We determine the counterterm directly from the solar neutrino data and find several, slightly different, ranges of $L_{1A}$ under different sets of assumptions. Our most conservative fit value with the largest uncertainty is $L_{1A}={4.5}_{-12}^{+18}{\text{fm}}^3$. We show that the contribution of the uncertainty of $L_{1A}$ to the analysis and interpretation of the solar neutrino data measured at the Sudbury Neutrino Observatory is significantly less than the uncertainty coming from the lack of having a better knowledge of ${\theta }_{13}$.

Figure 1

(Color online) The change in the allowed region of the neutrino parameter space using solar neutrino data measured at SNO as the value of $L_{1A}$ changes. In the calculations leading to this figure the neutrino mixing angle ${\theta }_{13}$ is taken to be zero (see text). The shaded areas are the $90\%$ confidence level region; $95\%$ (solid line), $99\%$ (long-dashed line), and $99.73\%$ (dotted line) confidence levels are also shown.

Figure 2

(Color online) Projection of the global $\Delta {\chi }^2$ function on the parameter $L_{1A}$. In the calculations leading to this figure ${\theta }_{13}$ is taken to be zero. ${\theta }_{12}$, $\delta m_{12}^2$, and the parameter $f_B$ (the multiplier of the ${}^8\mathrm{B}$ flux) are varied. The solid line represents the case where all these three are unconstrained. The long-dashed line is when the ${}^8\mathrm{B}$ flux is fixed as described in the text, but the other two are unconstrained. The dotted line is when ${\theta }_{12}$ and $\delta m_{12}^2$ are also taken to be the best fit values to the SNO energy spectra.

Figure 3

(Color online) Values of $L_{1A}$ obtained from different analyses. The values labeled Balantekin-Yuksel are calculated using the dashed and the dotted lines of Fig. 2 as described in the text. Helioseismology limit is from Ref. 20. Reactor antineutrino limit is from Ref. 18. The limit obtained by CHS [23] is also shown.

Figure 4

(Color online) Allowed parameter space when ${\theta }_{12}$ and $\delta m_{12}^2$ are fixed to give the minimum ${\chi }^2$ values to reproduce the SNO day-night spectrum (left-hand panel) and all solar neutrino experiments along with the KamLAND experiment (right-hand panel). The shaded areas are the $90\%$ confidence level region; $95\%$ (solid line), $99\%$ (long-dashed line), and $99.73\%$ (dotted line) confidence levels are also shown. The dark-shaded region corresponds to the case when the ${}^8\mathrm{B}$ flux is fixed to be the standard solar model value. The light-shaded region corresponds to the case when that flux is unconstrained.