@article{gonzalez_fries_cude-woods_bailey_blatnik_broussard_callahan_choi_clayton_currie_et al._2021, title={Improved Neutron Lifetime Measurement with UCN τ}, volume={127}, ISSN={["1079-7114"]}, DOI={10.1103/PhysRevLett.127.162501}, abstractNote={We report an improved measurement of the free neutron lifetime τ_{n} using the UCNτ apparatus at the Los Alamos Neutron Science Center. We count a total of approximately 38×10^{6} surviving ultracold neutrons (UCNs) after storing in UCNτ's magnetogravitational trap over two data acquisition campaigns in 2017 and 2018. We extract τ_{n} from three blinded, independent analyses by both pairing long and short storage time runs to find a set of replicate τ_{n} measurements and by performing a global likelihood fit to all data while self-consistently incorporating the β-decay lifetime. Both techniques achieve consistent results and find a value τ_{n}=877.75±0.28_{stat}+0.22/-0.16_{syst} s. With this sensitivity, neutron lifetime experiments now directly address the impact of recent refinements in our understanding of the standard model for neutron decay.}, number={16}, journal={PHYSICAL REVIEW LETTERS}, author={Gonzalez, F. M. and Fries, E. M. and Cude-Woods, C. and Bailey, T. and Blatnik, M. and Broussard, L. J. and Callahan, N. B. and Choi, J. H. and Clayton, S. M. and Currie, S. A. and et al.}, year={2021}, month={Oct}, pages={162501} }
@article{saam_petukhov_chastagnier_gentile_golub_swank_2012, title={Comment on "Pressure dependence of wall relaxation in polarized He-3 gaseous cells"}, volume={85}, ISSN={["1094-1622"]}, DOI={10.1103/physreva.85.047401}, abstractNote={Zheng et al. [Zheng, Gao, Ye, and Zhang, Phys. Rev. A 83, 061401(R) (2011)] have measured a strong linear pressure dependence of the nuclear relaxation rate of ${}^{3}$He in glass cells typically used to generate and/or store polarized ${}^{3}$He at room and cryogenic temperatures. Their interpretation is that this linear dependence is a general characteristic of paramagnetic wall relaxation, and they offer a theoretical explanation of the effect based on diffusion theory in the bulk with an incorrect boundary condition. We question the physical basis of the boundary condition and suggest some alternate explanations of the observations. Numerous previous studies support a broadly valid pressure-independent model for wall relaxation.}, number={4}, journal={PHYSICAL REVIEW A}, author={Saam, B. and Petukhov, A. K. and Chastagnier, J. and Gentile, T. R. and Golub, R. and Swank, C. M.}, year={2012}, month={Apr} }
@article{swank_petukhov_golub_2012, title={Correlation functions for restricted Brownian motion from the ballistic through to the diffusive regimes}, volume={376}, ISSN={["1873-2429"]}, DOI={10.1016/j.physleta.2012.05.038}, abstractNote={We calculate the spectra of the correlation functions for fields with arbitrary spatial dependence as seen by Brownian particles in bounded geometries from knowledge of the spectra of the conditional probability density functions in the infinite domain. Our results show a significant difference for the spectra for 1D, 2D and 3D motions. To our knowledge this is the first demonstration of the influence of dimensionality on the form of the correlation functions. Our results also show the different power dependence on frequency for the ballistic and diffusive cases and the treatment of the crossover is unique.}, number={34}, journal={PHYSICS LETTERS A}, author={Swank, C. M. and Petukhov, A. K. and Golub, R.}, year={2012}, month={Jul}, pages={2319–2324} }
@article{zheng_gao_liu_zhang_ye_swank_2011, title={General solution to gradient-induced transverse and longitudinal relaxation of spins undergoing restricted diffusion}, volume={84}, ISSN={["1094-1622"]}, DOI={10.1103/physreva.84.053411}, abstractNote={We develop an approach, by calculating the autocorrelation function of spins, to derive the magnetic field gradient induced transverse ($T_2$) relaxation of spins undergoing restricted diffusion. This approach is an extension to the method adopted by McGregor. McGregor's approach solves the problem only in the fast diffusion limit; however, our approach yields a single analytical solution suitable in all diffusion regimes, including the intermediate regime. This establishes a direct connection between the well-known Torrey's slow diffusion result and the fast diffusion result. We also perform free induction decay measurements on spin-exchange optically polarized $^3$He gas with different diffusion constants. The transverse relaxation profiles are compared with the theory and satisfactory agreement has been found throughout all diffusion regimes. In addition to the transverse relaxation, this approach is also applicable to solving the longitudinal relaxation ($T_1$) regardless of the diffusion limits. It turns out that the longitudinal relaxation in the slow diffusion limit differs by a factor of two, compared with that in the fast diffusion limit.}, number={5}, journal={PHYSICAL REVIEW A}, author={Zheng, W. and Gao, H. and Liu, J-G. and Zhang, Y. and Ye, Q. and Swank, C.}, year={2011}, month={Nov} }
@article{golub_rohm_swank_2011, title={Reexamination of relaxation of spins due to a magnetic field gradient: Identity of the Redfield and Torrey theories}, volume={83}, ISSN={["1094-1622"]}, DOI={10.1103/physreva.83.023402}, abstractNote={There is an extensive literature on magnetic-gradient-induced spin relaxation. Cates, Schaefer, and Happer, in a seminal publication, have solved the problem in the regime where diffusion theory (the Torrey equation) is applicable using an expansion of the density matrix in diffusion equation eigenfunctions and angular momentum tensors. McGregor has solved the problem in the same regime using a slightly more general formulation using the Redfield theory formulated in terms of the autocorrelation function of the fluctuating field seen by the spins and calculating the correlation functions using the diffusion-theory Green's function. The results of both calculations were shown to agree for a special case. In the present work, we show that the eigenfunction expansion of the Torrey equation yields the expansion of the Green's function for the diffusion equation, thus showing the identity of this approach with that of the Redfield theory. The general solution can also be obtained directly from the Torrey equation for the density matrix. Thus, the physical content of the Redfield and Torrey approaches are identical. We then introduce a more general expression for the position autocorrelation function of particles moving in a closed cell, extending the range of applicability of the theory.}, number={2}, journal={PHYSICAL REVIEW A}, author={Golub, R. and Rohm, Ryan M. and Swank, C. M.}, year={2011}, month={Feb} }
@article{o'shaughnessy_golub_schelhammer_swank_seo_huffman_dzhosyuk_mattoni_yang_doyle_et al._2009, title={Measuring the neutron lifetime using magnetically trapped neutrons}, volume={611}, ISSN={["1872-9576"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-71549134894&partnerID=MN8TOARS}, DOI={10.1016/j.nima.2009.07.054}, abstractNote={The neutron beta-decay lifetime plays an important role both in understanding weak interactions within the framework of the Standard Model and in theoretical predictions of the primordial abundance of 4He in Big Bang Nucleosynthesis. In previous work, we successfully demonstrated the trapping of ultracold neutrons in a conservative potential magnetic trap. A major upgrade of the apparatus is nearing completion at the National Institute of Standards and Technology Center for Neutron Research (NCNR). In our approach, a beam of 0.89 nm neutrons is incident on a superfluid 4He target within the minimum field region of an Ioffe-type magnetic trap. A fraction of the neutrons is downscattered in the helium to energies <200neV, and those in the appropriate spin state become trapped. The inverse process is suppressed by the low phonon density of helium at temperatures less than 200 mK, allowing the neutron to travel undisturbed. When the neutron decays the energetic electron ionizes the helium, producing scintillation light that is detected using photomultiplier tubes. Statistical limitations of the previous apparatus will be alleviated by significant increases in field strength and trap volume resulting in twenty times more trapped neutrons.}, number={2-3}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={O'Shaughnessy, C. M. and Golub, R. and Schelhammer, K. W. and Swank, C. M. and Seo, P. -N. and Huffman, P. R. and Dzhosyuk, S. N. and Mattoni, C. E. H. and Yang, L. and Doyle, J. M. and et al.}, year={2009}, month={Dec}, pages={171–175} }
@article{ye_gao_zheng_dutta_dubose_golub_huffman_swank_korobkina_2009, title={Relaxation of spin-polarized He-3 in mixtures of He-3 and He-4 at about 330 mK}, volume={80}, ISSN={["1094-1622"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-68949158555&partnerID=MN8TOARS}, DOI={10.1103/physreva.80.023403}, abstractNote={We report the measurements of depolarization probabilities of polarized $^{3}\text{H}\text{e}$ in a rectangular acrylic cell with a deuterated tetraphenyl butadiene-doped deuterated polystyrene coating filled with superfluid $^{4}\text{H}\text{e}$ at $\ensuremath{\sim}330\text{ }\text{mK}$ with a magnetic holding field of $\ensuremath{\sim}7.3\text{ }\text{G}$. We achieve a wall depolarization probability of $\ensuremath{\sim}1.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$. Such a surface will find application in a new experiment searching for the neutron electric dipole moment and other applications.}, number={2}, journal={PHYSICAL REVIEW A}, author={Ye, Q. and Gao, H. and Zheng, W. and Dutta, D. and Dubose, F. and Golub, R. and Huffman, P. and Swank, C. and Korobkina, E.}, year={2009}, month={Aug} }