# Seasonal Modulation of the $^7$Be Solar Neutrino Rate in Borexino

## TL;DR

This study reports the detection of seasonal variations in the $^7$Be solar neutrino interaction rate using Borexino, confirming its solar origin through multiple analysis methods and rejecting non-seasonal hypotheses with high confidence.

## Contribution

First observation of seasonal modulation of $^7$Be neutrinos in Borexino, demonstrating the detector's sensitivity and confirming solar origin of the neutrino flux variations.

## Key findings

- Seasonal modulation consistent with solar origin.
- Rejection of non-annual modulation at 99.99% confidence.
- Agreement among three different analysis methods.

## Abstract

We detected the seasonal modulation of the $^7$Be neutrino interaction rate with the Borexino detector at the Laboratori Nazionali del Gran Sasso in Italy. The period, amplitude, and phase of the observed time evolution of the signal are consistent with its solar origin, and the absence of an annual modulation is rejected at 99.99\% C.L. The data are analyzed using three methods: the sinusoidal fit, the Lomb-Scargle and the Empirical Mode Decomposition techniques, which all yield results in excellent agreement.