234 research outputs found
Electroweak Interactions and Fundamental Symmetries in Light Nuclei with Short-range Effective Field Theories
Effective field theories(EFTs) are powerful tools to study nuclear systems that display separation of scales. In this dissertation, we present halo EFT results for the -delayed proton emission from Be, and pionless EFT results for three-nucleon systems. Halo nuclei are simply described by a tightly bound core and loosely bound valence nucleons. Using the halo EFT, we calculate the rate of the rare decay Be, which is a well-known halo nucleus, into . We assume a shallow resonance in the Be system with an energy consistent with a recent experiment by Ayyad {\it et al.} and obtain a branching ratio and a resonance width of this decay. Our calculation shows that the experimental branching ratio and resonance parameters of Ayyad {\it et al.} are consistent with each other. Thus, no exotic mechanism (such as beyond the standard model physics) is needed to explain the experimental decay rate. Electric dipole moments (EDMs) of nucleons receive negligible contributions from the CKM mechanism and are thus, extremely sensitive probes of CP-violation beyond the Standard Model. Using the pionless EFT, we calculate the EDMs of three-nucleon systems at leading order. Neglecting the Coulomb interaction, we consider the triton and He, and also investigate them in the Wigner-SU(4) symmetric limit. We also calculate the electric dipole form factor and find numerically that the momentum dependence of the electric dipole form factor in the Wigner limit is, up to an overall constant (and numerical accuracy), the same as the momentum dependence of the charge form factor. At last, under the same framework, charge form factors with Coulomb interactions are considered both perturbatively and non-perturbatively to NLO. The third Zemach moment of He is evaluated and compared to experimental results
Agree to Disagree: Measuring Hidden Dissents in FOMC Meetings
Based on a record of dissents on FOMC votes and transcripts of the meetings
from 1976 to 2017, we develop a deep learning model based on self-attention
modules to create a measure of the level of disagreement for each member in
each meeting. While dissents are rare, we find that members often have
reservations with the policy decision. The level of disagreement is mostly
driven by current or predicted macroeconomic data, and personal characteristics
of the members play almost no role. We also use our model to evaluate speeches
made by members between meetings, and we find a weak correlation between the
level of disagreement revealed in them and that of the following meeting.
Finally, we find that the level of disagreement increases whenever monetary
policy action is more aggressive
- …