Joint with theory seminar
The mass of the W boson, a mediator of the weak force between elementary particles, is tightly constrained by the symmetries of the standard model of particle physics. The Higgs boson was the last missing component of the model. After observation of the Higgs boson, a measurement of the W boson mass provides a stringent test of the model. We measure the W boson mass, MW, using data corresponding to 8.8 inverse femtobarns of integrated luminosity collected in proton-antiproton collisions at a 1.96 tera–electron volt center-of-mass energy with the CDF II detector at the Fermilab Tevatron collider. A sample of approximately 4 million W boson candidates is used to obtain, MW=80,433.5±6.4stat±6.9syst=80,433.5±9.4 MeV/c2 the precision of which exceeds that of all previous measurements combined (stat, statistical uncertainty; syst, systematic uncertainty; MeV, mega–electron volts; c, speed of light in a vacuum). This measurement is in significant tension with the standard model expectation.
and pointing the way for improving these event generators.
Next generation searches for beyond standard model physics such as nEDM and neutron spin rotation rely on exquisitely uniform magnetic fields. Recent advances in theory and computation have yielded a streamlined pipeline to design coils satisfying increasingly stringent design requirements. nEDM@LANL is a natural progression of nEDM measurements, and we expect it will ultimately be limited by the well-known systematic of magnetic gradients, which ultimately induce a false EDM. In spite of our best efforts to design and build a perfect magnetically shielded room (MSR) and B0 coils, we will need a coil package capable of shimming away specific unwanted gradients. We are designing our gradient correction coils in two generations. The focus of this talk will be on the second-generation coils. We are pursuing coils designed with modern CAD tooling: I'll discuss stream-function generated coils as well as a family of continuously wound coils designed with a nod to the weakly perturbed scalar potential method before introducing the fabrication and validation of these coils and their implementation as a full gradient correction package.
There exists a class of ultralight Dark Matter (DM) models which could form a Bose-Einstein condensate (BEC) in the early universe and behave as a single coherent wave instead of individual particles in galaxies. We show that a generic BEC DM halo intervening along the line of sight of a gravitational wave (GW) signal could induce an observable change in the speed of GW, with the effective refractive index depending only on the mass and self-interaction of the constituent DM particles and the GW frequency. Hence, we propose to use the deviation in the speed of GW as a new probe of the BEC DM parameter space. With a multi-messenger approach to GW astronomy and/or with extended sensitivity to lower GW frequencies, the entire BEC DM parameter space can be effectively probed by our new method in the near future.
We will discuss a simple model of low-energy baryon number violation in order to simultaneously explain the observed matter-antimatter asymmetry and dark matter relic density in the universe. The stability of dark matter is related to the stability of the proton. The model predicts a sizeable rate for the neutron-antineutron oscillation at low energy and a new type of monojet signal at the LHC. There exists an interesting complementarity between the observed baryon asymmetry, ratio of dark matter and baryon abundances, neutron-antineutron oscillation lifetime and the LHC monojet signal.
Nab, an experiment that allows studying unpolarized neutron beta decay at the Spallation Neutron Source at Oak Ridge National Lab, aims to determine a, the neutrino-electron correlation coefficient, and b, the Fierz interference term, with high precision. Such measurements provide opportunities to search for evidence of extensions to the Standard Model. Nab is presently being constructed. The spectrometer magnet is supposed to arrive in the week I am giving this seminar. Beam readiness planned for end of summer 2018. I will discuss the experiment’s motivation and design, the planned modes of operation, and the performance of its components.