Current Schedule

Speaker = Dr. Brenden Robert Longfellow of Lawrence Livermore National Laboratory (LLNL)

Host = Joseph Chung-Jung jungj@frib.msu.edu

When = 2025-01-29 Wednesday 15:30 (note the new time!)

Where = FRIB 1300

Please feel free to sign up below, but note that some slots may need to be re-assigned to accommodate those with a specific need to meet the speaker. If this happens, the Admin or Speaker Host will reach out to you via email.

Title = From Tensor Current Limits to Solar Neutrinos: 8Li and 8B Studies with the Beta-decay Paul Trap

Abstract

The precision measurement program on 8Li and 8B beta decay with the Beta-decay Paul Trap (BPT) at Argonne National Laboratory will be presented. Recent BPT results represent the two most stringent limits on beyond standard model tensor currents in the low-energy regime and were used to reconstruct the 8B neutrino energy spectrum, a vital ingredient for solar neutrino astrophysics.

The vector – axial vector form of the electroweak interaction was established through pioneering beta-decay experiments in the 1960s and incorporated into the standard model of particle physics. However, there is no a priori reason that the other currents, scalar and tensor, could not be present. The Gamow-Teller beta decays of 8Li and 8B have extremely large Q values and the daughter nucleus in both cases, 8Be, is alpha unbound making these systems exemplary probes of the presence of any tensor contribution affecting the beta-neutrino angular correlation. The improvements from over a decade of high-statistics experiments on 8Li and 8B performed at Argonne National Laboratory using the Beta-decay Paul Trap (BPT) will be presented. In these measurements, the energies of the alpha and beta particles were determined using four 32×32 double-sided silicon strip detectors surrounding the BPT to precisely reconstruct the decay kinematics. The latest iteration of experiments has set the two world-leading limits on tensor currents from single beta-decay measurements. The combined BPT limits from 8Li and 8B for tensor coupling to right-handed neutrinos are comparable to a recent global evaluation of all other precision beta decay studies and are consistent with the standard model, relieving some existing tension. In addition, the high-energy neutrinos observed in solar neutrino astrophysics experiments on Earth predominately originate from 8B beta decay in the Sun. Results on determining the 8B neutrino energy spectrum, an important input for the astrophysics community, from the same data set will be discussed.

Relevant background:

• Kinematic shifts of beta -delayed particles as a probe of beta - nu angular correlations
• Improved Limit on Tensor Currents in the Weak Interaction from 8Li 𝛽 Decay
• Improved Tensor Current Limit from 8B 𝛽 Decay Including New Recoil-Order Calculations
• Determination of the 8B neutrino energy spectrum using trapped ions
• Solar Neutrino Problem
• Mirror Nuclei