Theory Division

Dark sectors are ubiquitous in physics beyond the Standard Model (SM), and may play a role  in explaining many of the long-standing problems of the SM such as the existence of dark matter or the electroweak hierarchy problem.  By definition, dark sectors are not charged under any of the known forces. Discovering their possible existence... More »

Neutrinoless double-beta decay, as a lepton-number violating process, has been the focus of numerous experimental and theoretical investigations in recent years. While it proves that neutrinos are Majorana particles once observed, the underlying new physics responsible for this process can only be constrained if the theoretical predictions of the rate are substantially refined. This talk... More »

Laser spectroscopy of muonic hydrogen [1,2] yielded a proton rms charge radius which is 4% (or ~6 sigmas) smaller than the CODATA value [3]. This discrepancy is now called the “proton radius puzzle” [4]. Also the deuteron charge radius from muonic deuterium [5] is 6 sigmas smaller than the CODATA value, but consistent with the... More »

When a particle is accelerated, as in a scattering event, it will radiate gravitons and, if electrically charged, photons. The infrared tail of the spectrum of this radiation has a divergence: an arbitrarily small amount of total energy is divided into an arbitrarily large number of radiated bosons. Each of these in turn carries a... More »