5 research outputs found
Convergence of all-order many-body methods: coupled-cluster study for Li
We present and analyze results of the relativistic coupled-cluster
calculation of energies, hyperfine constants, and dipole matrix elements for
the , , and states of Li atom. The calculations are
complete through the fourth order of many-body perturbation theory for energies
and through the fifth order for matrix elements and subsume certain chains of
diagrams in all orders. A nearly complete many-body calculation allows us to
draw conclusions on the convergence pattern of the coupled-cluster method. Our
analysis suggests that the high-order many-body contributions to energies and
matrix elements scale proportionally and provides a quantitative ground for
semi-empirical fits of {\em ab inito} matrix elements to experimental energies.Comment: 4 pages, 3 figure
Precision determination of electroweak coupling from atomic parity violation and implications for particle physics
We carry out high-precision calculation of parity violation in cesium atom,
reducing theoretical uncertainty by a factor of two compared to previous
evaluations. We combine previous measurements with our calculations and extract
the weak charge of the 133Cs nucleus, Q_W = -73.16(29)_exp(20)_th. The result
is in agreement with the Standard Model (SM) of elementary particles. This is
the most accurate to-date test of the low-energy electroweak sector of the SM.
In combination with the results of high-energy collider experiments, we confirm
the energy-dependence (or "running") of the electroweak force over an energy
range spanning four orders of magnitude (from ~10 MeV to ~100 GeV).
Additionally, our result places constraints on a variety of new physics
scenarios beyond the SM. In particular, we increase the lower limit on the
masses of extra -bosons predicted by models of grand unification and string
theories.Comment: 4 pages/3 figs /1 tabl
Standard Model tests with trapped radioactive atoms
We review the use of laser cooling and trapping for Standard Model tests,
focusing on trapping of radioactive isotopes. Experiments with neutral atoms
trapped with modern laser cooling techniques are testing several basic
predictions of electroweak unification. For nuclear decay, demonstrated
trap techniques include neutrino momentum measurements from beta-recoil
coincidences, along with methods to produce highly polarized samples. These
techniques have set the best general constraints on non-Standard Model scalar
interactions in the first generation of particles. They also have the promise
to test whether parity symmetry is maximally violated, to search for tensor
interactions, and to search for new sources of time reversal violation. There
are also possibilites for exotic particle searches. Measurements of the
strength of the weak neutral current can be assisted by precision atomic
experiments using traps of small numbers of radioactive atoms, and sensitivity
to possible time-reversal violating electric dipole moments can be improved.Comment: 45 pages, 17 figures, v3 includes clarifying referee comments,
especially in beta decay section, and updated figure