Bulletin of the American Physical Society
2007 Annual Meeting of the Division of Nuclear Physics
Volume 52, Number 10
Wednesday–Saturday, October 10–13, 2007; Newport News, Virginia
Session HF: Electroweak Interactions |
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Chair: Rocco Schiavilla, Jefferson Laboratory/Old Dominion University Room: Newport News Marriott at City Center Pearl Salon II |
Saturday, October 13, 2007 9:00AM - 9:12AM |
HF.00001: Beta-Neutrino Correlation in Laser-Trapped $^{21}$Na P.A. Vetter, J. Abo-Shaeer, B.K. Fujikawa, S.J. Freedman, R. Maruyama We have re-measured $a_{\beta-\nu}$ in $^{21}$Na in a magneto-optic trap. We measure the momentum spectrum of the recoil nuclei by time- of-flight, using low-energy electrons shaken off by the recoil as a start signal. This scheme is a factor of 25 more efficient than our previous experiment (N.D. Scielzo {\it et al.}, PRL {\bf 93}, 102501 (2004)). We also detect autoionized Na$_{2}$, formed via photoassociation in our MOT. We believe that our previous measurement was erroneous because of contributions to the data from beta decays occuring in molecular Na. We have characterized the molecule formation rate as a function of trap population, and detected autoionized $^{21}$Na$_{2}^{+}$. We have acquired data using much smaller trapped samples, for which the molecular fraction of the decay events is an order of magnitude smaller, and we have taken data using a dark MOT, in which molecule formation is suppressed by three orders of magnitude. Our new result is inconsistent with our previous measurement, agrees with the calculated value of $a_{\beta-\nu}=0.554(2)$, with absolute uncertainty about 0.006. [Preview Abstract] |
Saturday, October 13, 2007 9:12AM - 9:24AM |
HF.00002: Precision measurement of $^{23}$Al beta-decay Yongjun Zhai, V.E. Iacob, J.C. Hardy, T. Al-Abdullah, A. Banu, C. Fu, V.V. Golovko, M. McCleskey, N. Nica, H.I. Park, G. Tabacaru, R.E. Tribble, L. Trache The beta-decay of $^{23}$Al (See [1]) was re-measured with higher statistics and better accuracy at Texas A{\&}M University. Using MARS we produced and separated pure $^{23}$Al at 4000 pps, with a 48 MeV/u $^{24}$Mg beam via the $^{24}$Mg (p, 2n)$^{ 23}$Al reaction on a H$_{2}$ cryogenic target. New $\beta $ and $\beta -\gamma $ coincidence measurements were made with a scintillator, an HPGe detector with BGO shielding and the fast tape transport system. The BGO Compton shield very much improved the quality of the $\gamma $ spectra around the transition from the IAS state at 7803 keV. From the measured $\beta $ singles and $\beta -\gamma $ coincidence decay spectra we obtained an improved $\beta $-decay scheme and a more precise lifetime: t=447(4) ms. We use the method of detailed balance to obtain absolute $\beta $-branching ratios and absolute log\textit{ft} values for transitions to final states in $^{23}$Mg. For this method, precise efficiency calibration of the HPGe detector up to about 8 MeV is needed. We extended our previous efficiency calibration to the range E$_{\gamma }$=3.5-8 MeV using the $\beta $-decay of $^{24}$Al. \newline [1] V.E. Iacob, Y. Zhai et al., Phys. Rev. C 74, 045810 (2006). [Preview Abstract] |
Saturday, October 13, 2007 9:24AM - 9:36AM |
HF.00003: Confirmation of Precise Branching Ratio Measurement in the $\beta $ Decay of $^{34}$Ar V.E. Iacob, J.C. Hardy, V. Golovko Precise \textit{ft}-values for superallowed $0^+\to 0^+ \quad \beta ^{+}$-decays yield a demanding test of the Standard Model via the unitarity of the Cabibbo-Kobayashi-Maskawa matrix. One of the ingredients of an \textit{ft}-value is the transition branching ratio which, to be relevant for the unitarity test, must be measured with a precision of $\sim $0.1{\%} or better. After a preliminary report of such a measurement for $^{34}$Ar [1], we have verified our methods and tested for any possible systematic effects by measuring the decay of $^{10}$C under similar conditions. This nucleus is very well suited for a test of the data reduction method: it has a simple decay scheme without a ground-state branch, and all decay branches generate a 718 keV gamma ray. As with the $^{34}$Ar measurement, an implanted $^{10}$C source was placed between a plastic scintillator for $\beta $ particles and a HPGe detector that is efficiency calibrated with high precision (0.2{\%} between 50 and 1400 keV). Both $\beta $ singles and $\beta -\gamma $ coincidences were then recorded, and the collect/move/detect cycle was repeated until the desired statistical accuracy was obtained. We determined experimentally that the percentage of $^{10}$C decays leading to a 718 keV gamma ray is statistically consistent with the expected 100{\%}. This result validates our methods and reinforces the branching-ratio value previously obtained for the $^{34}$Ar decay. [1] V. Iacob \textit{et al.}, Bulletin APS 52, (37) Apr-Meeting 2007 [Preview Abstract] |
Saturday, October 13, 2007 9:36AM - 9:48AM |
HF.00004: The Search for a Non-Superallowed Branch in the $\beta$ decay of $^{38m}$K Kyle Leach, D. Bandyopadhyay, P. Finlay, P.E. Garrett, G.F. Grinyer, A.A. Phillips, M.A. Schumaker, C.E. Svensson, J. Wong, G.C. Ball, E. Bassiachvilli, S. Ettenauer, G. Hackman, A.C. Morton, S. Mythili, O. Newman, C.J. Pearson, M.R. Pearson, H. Savajols, J.R. Leslie, D. Melconian, R.A.E. Austin, C. Barton The study presented is part of an experimental program exploring the properties of superallowed Fermi $\beta$ decays conducted at the Isotope Separator and Accelerator (ISAC) facility at TRIUMF in Vancouver, B.C. Canada. Using the 8$\pi$ $\gamma$-ray spectrometer and the Scintillating Electron Positron Tagging Array (SCEPTAR), it was possible to set a new upper limit on an unobserved non-analogue branch in the decay of $^{38m}$K. This branch is expected to be extremely weak, and the removal of contaminant isobaric decays and background radiation in the spectra was thus exceedingly important during the analysis. Our work has reduced the previous upper limit by approximately a factor of two and is approaching the theoretically predicted branching ratio. [Preview Abstract] |
Saturday, October 13, 2007 9:48AM - 10:00AM |
HF.00005: Isospin mixing in the nucleon and $^4$He and the nucleon strange electric form factor Michele Viviani, Rocco Schiavilla In order to isolate the contribution of the nucleon strange electric form factor to the parity-violating asymmetry measured in $^4{\rm He}(\vec e,e^\prime){}^4{\rm He}$ experiments, it is crucial to have a reliable estimate of the magnitude of isospin-symmetry-breaking (ISB) corrections in both the nucleon and $^4{\rm He}$. Isospin admixtures in the nucleon are studied by B.\ Kubis and R.\ Lewis in Ref. Phys.\ Rev.\ C {\bf 74}, 015204 (2006) in chiral perturbation theory. We examine in the present contribution the issue of isospin admixtures in $^4{\rm He}$ derived from ISB components in the nuclear and electromagnetic interactions. A careful analysis of the model dependence in the resulting predictions for the nucleon and nuclear ISB contributions to the asymmetry is carried out. We conclude that, at the low momentum transfers of interest in recent measurements reported by the HAPPEX collaboration at Jefferson Lab, these contributions are of comparable magnitude to those associated with strangeness components in the nucleon electric form factor. [Preview Abstract] |
Saturday, October 13, 2007 10:00AM - 10:12AM |
HF.00006: Transverse Beam Spin Asymmetries in Backward-Angle Elastic Electron-Proton and Quasielastic Electron-Deuteron Scattering Juliette Mammei There has been considerable recent interest in the two-photon exchange contribution to electron scattering, largely driven by the role the real part of this amplitude plays in the discrepancy between the Rosenbluth and polarization transfer measurements of the elastic form factor ratio $G^{p}_E/G^{p}_M$. The transverse beam spin asymmetry measured in the elastic scattering of electrons from unpolarized nucleons provides a measurement of the imaginary part of the two photon exchange amplitude. The $G^{0}$ collaboration at Jefferson Lab has taken data of this type during its backward-angle phase with an average laboratory electron scattering angle of $110^{\circ}$. Beam-normal single-spin asymmetry data were obtained under these conditions: elastic $\vec{e}$-p at beam energies of 362 MeV ($Q^2 = 0.23\hbox{GeV}^2$) and 687 MeV ($Q^2 = 0.64\ \hbox{GeV}^2$) and quasi-elastic $\vec{e}$-d at a beam energy of 362 MeV ($Q^2 = 0.23\ \hbox{GeV}^2$). The status of the analysis for these sets of data will be presented. [Preview Abstract] |
Saturday, October 13, 2007 10:12AM - 10:24AM |
HF.00007: A first measurement of neutrino nucleon elastic scattering in MiniBooNE D. Christopher Cox Neutrino nucleon elastic scattering $\nu\ N \rightarrow\ \nu\ N$ is a fundamental process of the weak interaction, and provides insight into the structure of the nucleon. In MiniBooNE, a neutrino oscillation experiment at Fermilab, this process comprises about 15\% of all neutrino interactions, making it MiniBooNE's third largest scattering process with over two hundred thousand events expected in the current data sample. First cross section results will be presented. [Preview Abstract] |
Saturday, October 13, 2007 10:24AM - 10:36AM |
HF.00008: SciBooNE experiment, the neutrino cross section measurement Teppei Katori The SciBooNE experiment will measure muon neutrino and antineutrino cross sections on carbon near 1 GeV with unprecedented precision. SciBooNE uses the Booster Neutrino Beam at Fermilab and the SciBar vertex detector formerly used in the K2K experiment at KEK. SciBooNE started its data run in antineutrino mode in June, 2007. Physics potential of the experiment and first data will be shown. [Preview Abstract] |
Saturday, October 13, 2007 10:36AM - 10:48AM |
HF.00009: Neutrino Interactions in the MINOS Near Detector Michael Kordosky The Main Injector Neutrino Oscillation Search (MINOS) is a long baseline neutrino oscillation experiment that uses a muon-neutrino beam produced by the Neutrinos at the Main Injector (NuMI) facility at Fermi National Accelerator Laboratory (FNAL). The experiment is conducted with a pair of functionally identical detectors, located at two sites, the Near Detector at FNAL and the Far Detector in the Soudan Underground Laboratory in Minnesota. The high intensity NuMI beam provides a large neutrino event sample in the Near Detector which can be used to characterise neutrino-nucleus interactions. I will describe the experimental procedure for deducing the neutrino flux and follow with prospects for measuring the energy dependence of the inclusive muon neutrino and anti-neutrino charged-current cross-section. I will close with a discussion of the experiment's ability to measure the $Q^{2}$ dependence of the quasi-elastic scattering cross-section as well as the structure functions $F_{2}$ and $xF_{3}$ at low $Q^{2}$ and high $x$. [Preview Abstract] |
Saturday, October 13, 2007 10:48AM - 11:00AM |
HF.00010: Lorentz and CPT violation test in BNL muon g-2 data Xiaobo Huang V.A. Kosteleck\'{y} et. al. proposed an extension of the standard model of the particle physics which allows Lorentz and CPT violation by introducing additional terms to the Lagrangian of the standard model. In this extended standard model, the muon anomalous precession frequency, $\omega_{a}$, is evaluated. There are two Lorentz and CPT violation signatures predicted: nonzero $\Delta\omega_{a}$ (=$\omega_{a}^{\mu^{+}}-\omega_{a}^{\mu^{-}}$) and sidereal variation of $\omega_{a}^{\mu^{\pm}}$. A Lorentz and CPT invariance test, using the BNL muon g-2 data, is done. No significant effect was found. The limit of Lorentz and CPT violation is set to be at the level of $10^{-24}$ GeV. [Preview Abstract] |
Saturday, October 13, 2007 11:00AM - 11:12AM |
HF.00011: Everything from nearly `Nothing' A Topologically Substructured Spin-dominated Superstring Concept and its Universal Physical and Cosmological Implications Paul W. Buecking The present concept of a string is too simple. It does not have the necessary level of complexity needed to express the `Everything'. On string level no defined unique structure exists that inherently can make the world the way it is in a self-consistent way. The idea of a vacuum deflates string theory. In the new concept (NC) a superstring (SS) is the most elementary \textit{structure with functionality}. It consists of more basic substructural entities that do not have, but enable functionality. In the NC these entities are anti-commuting spacetime topologies. Their emergence in primordial spacetime breaks its isotropic hydrodynamic symmetry. By quantization of three plane simply connected cobording topologies and their compactification to three-layered toric SS with spin functionality, globally an entagled SS-fluid is restored. Its constituents are mutually repulsing (--$>\Lambda )$ dark SS stem particles in a supersymmetric state. Breaking of this symmetry generates all particles of physics. This diversification decouples physics, taking place in spacetime, from its broken topology. All particle decays and changes of flavors include the conservation of this symmetry. The NC seems to solve many enigmas and finds explanations for the `Why'. By this it reveals the awe-inspiring genius of nature in its fundamental aspiration to conserve symmetries. [Preview Abstract] |
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