We have measured the isospin mixing of the I pi = 1 / 2 + , E x = 2 . 599 MeV state in nearly doubly magic 47 Ca with the isobaric analog 1 / 2 + state of 47 K. Using the TRIUMF atom trap for 0 decay, we have measured a nonzero asymmetry of the progeny 47 Ca with respect to the initial 47 K spin polarization, which together with the 0 asymmetry implies a nonzero ratio of Fermi to Gamow -Teller matrix elements y = 0 . 098 +/- 0 . 037 for the 1 / 2 + -> 1 / 2 + transition. Interpreting y as mixing between this state and the isobaric analog state implies a Coulomb matrix element magnitude 101 +/- 37 keV. This relatively large matrix element supports a model from the literature of analog-antianalog isospin mixing, which predicts large matrix elements in cases involving excess neutrons over protons occupying more than one major shell. The result supports pursuing a search for time -reversal odd, parity -even, isovector interactions using a correlation in 47 K 0 decay.

We measure the distribution of energy deposited in a 40 x 88 mm plastic scintillator by e+e- pair production of 4.44 MeV y-rays. We observe the double-escape peak of 3.42 MeV from pair production by tagging 511 keV annihilation radiation in two high-Z scintillators. The source is a standard commercial neutron source using a-emitting 241Am encapsulated with 9Be, which has a reaction branch feeding the first Ix = 2+ state of 12C making the 4.44 MeV y-rays. We demonstrate the extraction of the double-escape peak from the large neutron-produced backgound, and explore some of the features and difficulties of this technique with our apparatus.

This is a resource paper concerning enhancement of observable time-reversal breaking effects by nuclear structure, aimed at AMO experimentalists. It's intended to support a white paper by providing some orientation on what can be said about some particular isotopes. Any conclusions are qualitative, and the reader should consult and cite the primary references and reviews rather than this arXiv alone.

We observe the electric-dipole forbidden 7s -> 8s transition in the francium isotopes Fr208-211 and Fr-213 using a two-photon excitation scheme. We collect the atoms online from an accelerator and confine them in a magneto-optical trap for the measurements. In combination with previous measurements of the 7s -> 7(p1/2) transition we perform a King plot analysis. We compare the thus-determined ratio of the field shift constants (1.228 +/- 0.019) to results obtained from new ab initio calculations (1.234 +/- 0.010).

The TRIUMF Neutral Atom Trap (TRINAT) experiment looks at beta decay in radioactive isotopes of alkali metals (Rb and K) and searches for time-reversal symmetry violations on MeV scales. Detection is accomplished by measuring the momenta of three products of the decay – the beta particle, the gamma ray, and the recoiling nucleus. Time reversal is simulated conceptually by flipping the momenta of the three decay products, then smoothly rotating the result to target specific detectors. Asymmetries are present if, when the momenta are flipped, the number of events in the gamma detector changes. Such an observable is not sensitive to spin so, if detected, would point toward new physics different from contributions to the neutron electric dipole moment. Various scintillating materials were tested for their energy resolution, light output, and timing properties while a readout circuit was designed. Two bismuth germanate (BGO) crystals with silicon photomultiplier (SiPM) readout were then tested, calibrated, and mounted symmetrically on the atom trap. Background The excess of matter relative to antimatter points to an asymmetry in baryon generation in the early universe. Sakharov [1] showed that violation of charge-parity symmetry (equivalent to time reversal if CPT is conserved) may result in such an imbalance. The TRINAT experiment looks for a time-reversal violating (TRV) asymmetry in the radiative β decays of K and Rb. This requires determining the momenta of three products of the decay: the recoiling nucleus, the beta particle, and the radiating gamma ray. Such TRV correlations have been searched for in studies of meson decay but never in the first generation of particles [2]. My work this summer focused on constructing and calibrating a pair of detectors to determine the energy spectrum of the gamma ray which is produced in a small fraction (roughly 3% [3]) of decays of Rb. Time reversal modeled by momentum flips The idea of time reversal is simple mathematically: one switches the sign on time, or formally t 7→ −t If we apply such a reversal to momentum, we see that p = m dr dt 7→ m dr d(−t) = −m dt = −p Thus, momentum is a quantity which changes sign when the time reversal operator acts upon it. Now, consider the triple product of the three momenta (the recoiling nucleus, the beta particle, and the gamma ray) measured in the experiment: precoil · (pβ × pγ)

Using Triumf's neutral atom trap, Trinat, for nuclear β decay, we have measured the β asymmetry with respect to the initial nuclear spin in ^{37}K to be A_{β}=-0.5707(13)_{syst}(13)_{stat}(5)_{pol}, a 0.3% measurement. This is the best relative accuracy of any β-asymmetry measurement in a nucleus or the neutron, and is in agreement with the standard model prediction -0.5706(7). We compare constraints on physics beyond the standard model with other β-decay measurements, and improve the value of V_{ud} measured in this mirror nucleus by a factor of 4.

We have measured the non-resonant photoionization cross section of the 7P3/2 state of francium for 442 nm light to be 20.8 ± 7.1 Mb. Atoms were irradiated in a magneto-optical trap, and we deduce the photoionization rate from the change in trap lifetime. The result is consistent with a simple extrapolation of known cross sections for other alkali atoms.

The MTV (Mott Polarimetry for T-Violation) experiment is running at TRIUMF-ISAC (Isotope Separator and ACcelerator), searching for a large T violation in polarized Li-8 beta decay via measurements of the triple vector correlation, R, in the beta decay rate function. The left/right backward scattering asymmetry of Mott scattering from a thin metal foil is measured using an electron tracking detector including a cylindrical drift chamber (CDC). To achieve 10-ppm precision in the Mott scattering asymmetry, we performed multiple studies on the expected systematic effects. The sources of the systematics have been identified and calibration systems have been developed to evaluate the fake effects. The first physics data was collected in 2016 and significantly improved on the result of our previous measurement, which achieved 100-ppm precision in 2010 using the first generation detector (planer drift chamber) at TRIUMF. The data measurement status, together with the results of the systematics studies, is described here. In addition to the T violation, we are preparing to test the Lorentz invariance in the weak sector via our Mott analyzer system. Unexplored Lorentz violating correlations can be tested using the MTV experimental setup. The testing principle and preparation status are also described here.

We report on the status of the FrPNC experiments and summarize our plans for measurements of parity non-conservation (PNC) in a sample of cold francium. The FrPNC collaboration has commissioned a laser cooling apparatus at the TRIUMF accelerator that collects and cools francium atoms for PNC experiments. We have recently demonstrated the robust, high efficiency transfer (50 %) of laser cooled francium atoms to a second laser cooling apparatus, located 0.7 m below the first, where the PNC experiments will be conducted.