Parity violation in atomic ytterbium: experimental sensitivity and systematics K. Tsigutkin, 1, ∗ D. Dounas-Frazer, 1 A. Family, 1 J. E. Stalnaker, 1, † V. V. Yashchuk, 2 and D. Budker 1, 3 $^{1}$Department of Physics, University of California at Berkeley, Berkeley, CA 94720-7300 $^{2}$Advanced Light Source Division, Lawrence Berkeley National Laboratory, Berkeley CA 94720 $^{3}$Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (Dated: October 30, 2018) We present a detailed description of the observation of parity violation in the 6s $^{2 1}$S$_{0}$ → 5d6s $^{3}$D$_{1}$ 408-nm forbidden transition of ytterbium, a brief report of which appeared earlier. Linearly polarized 408-nm light interacts with Yb atoms in crossed E - and B -fields. The probability of the 408- nm transition contains a parity violating term, proportional to ( E · B )[( E × E ) · B ], arising from interference between the parity violating amplitude and the Stark amplitude due to the E-field ( E is the electric field of the light). The transition probability is detected by measuring the population of the $^{3}$P$_{0}$ state, to which 65% of the atoms excited to the $^{3}$D$_{1}$ state spontaneously decay. The population of the $^{3}$P$_{0}$ state is determined by resonantly exciting the atoms with 649-nm light to the 6s7s $^{3}$S$_{1}$ state and collecting the fluorescence resulting from its decay. Systematic corrections due to E-field and B-field imperfections are determined in auxiliary experiments. The statistical uncertainty is dominated by parasitic frequency excursions of the 408-nm excitation light due to imperfect stabilization of the optical reference with respect to the atomic resonance. The present uncertainties are 9% statistical and 8% systematic. Methods of improving the accuracy for the future experiments are discussed. PACS numbers: 11.30.Er, 32.90.+a I. INTRODUCTION In an earlier paper [1], we reported on observa- tion of the atomic parity violation (PV) effect in the 6s $^{2 1}$S$_{0}$ → 5d6s $^{3}$D$_{1}$ 408-nm forbidden transition of $^{174}$Yb. We measured the PV induced transition matrix element to be 8 . 7 ± 1 . 4 × 10 − 10 ea$_{0}$, which confirms the theoretically anticipated PV enhancement in Yb [2] and constitutes the largest atomic parity violation effect ob- served so far. However, the measurement accuracy is not yet sufficient for the observation of the isotopic and hyperfine differences in the PV amplitude, the study of which is the main goal of the present experiments. Here we describe the impact of the apparatus imperfections and systematic effects on the accuracy of the measure- ments and discuss ways of improving it. During the initial stage of the experiment, an effort was invested into measuring various spectroscopic prop- erties of the Yb system of direct relevance to the PV measurement, including determination of radiative life- times, measurement of the Stark-induced amplitudes, hy- perfine structure, isotope shifts, and dc-Stark shifts of the 6s $^{2 1}$S$_{0}$ → 5d6s $^{3}$D$_{1}$ transition [3]. In addition, the 6s $^{2 1}$S$_{0}$ → $^{3}$D$_{2}$ transition at 404 nm has been observed, and the electric quadrupole transition amplitude and ten- sor transition polarizability have been measured [4]. The forbidden magnetic-dipole (M1) amplitude of the 408 nm transition was measured to be 1 . 33 × 10 − 4 µ$_{B}$ using the M1-(Stark-induced)E1 interference technique [5]. The ytterbium atomic system, where transition amplitudes and interferences are well understood, has proven use- ful for gaining insight into the Jones-dichroism effects that had been studied in condensed-matter systems at extreme conditions and whose origin had been a matter of debate (see Ref. [6] and references therein). An experimental and theoretical study of the dynamic (ac) Stark effect on the 6s $^{2 1}$S$_{0}$ → 5d6s $^{3}$D$_{1}$ forbid- den transition was also undertaken [7]. A model was de- veloped to calculate spectral line shapes resulting from resonant excitation of atoms in an intense standing light wave in the presence of off-resonant ac-Stark shifts. A bi- product of this work was an independent determination (from the saturation behavior of the 408-nm transition) of the Stark transition polarizability, which was found to be in agreement with the earlier measurement [4]. The present Yb APV experiment involves a measure- ment using an atomic beam. An alternative approach would involve working with a heat-pipe-like vapor cell. Various aspects of such an experiment were investigated, including measurements of collisional perturbations of relevant Yb states [8], nonlinear optical processes in a dense Yb vapor with pulsed UV-laser excitation [9], and an altogether different scheme for measuring APV via optical rotation on a transition between excited states [10]. The present paper addresses the issues of sensitivity and systematics in the Yb APV experiment. In Sec- tions II and III the experimental technique and its ap- plication in the present experiment are discussed. In Section IV a method of analyzing the impact of various apparatus imperfections is described based on theoret- arXiv:1001.0587v1 [physics.atom-ph] 4 Jan 2010 $^{∗}$Electronic address: tsigutkin@berkeley.edu $^{†}$Present address: Department of Physics and Astronomy, Oberlin College, Oberlin, OH 44074