Bulletin of the American Physical Society
2005 2nd Joint Meeting of the Nuclear Physics Divisions of the APS and The Physical Society of Japan
Sunday–Thursday, September 18–22, 2005; Maui, Hawaii
Session KB: Mini-symposium on Low Energy Tests of the Standard Model and Low Energy Searches for New Physics III |
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Sponsoring Units: DNP JPS Chair: Dave Mack, Thomas Jefferson National Accelerator Facility Room: Ritz-Carlton Hotel Salon 3 |
Thursday, September 22, 2005 2:00PM - 2:30PM |
KB.00001: Weak Interaction Parameters from Superallowed Beta Decay Invited Speaker: A critical survey of world data on superallowed beta decay, which closed in late 2004, has confirmed two tenets of the Conserved Vector Current hypothesis with improved precision: a) G$_{V}$ is demonstrated to be constant to three parts in 10$^{4}$; and b) the induced scalar current is limited to $f_{s}<$ 0.0013 in electron rest-mass units. An improved value is also obtained for the up-down quark-mixing element, $V_{ud}$, of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. This is a key result for testing CKM unitarity and probing the possible existence of right-hand currents. The precision obtained for the parameters extracted from superallowed decays is currently limited by the small theoretical correction terms applied to the data. One can test the terms that are nuclear-structure dependent experimentally by determining their detailed effectiveness in removing the nucleus-to-nucleus variations in the measured\textit{ ft} values. This is the focus of modern experiments, which aim to improve the precision of known \textit{ft} values or to extend measurements to new cases with large predicted corrections. The results included in the survey strongly support the calculated corrections terms but a new measurement of the $^{46}$V decay energy by Savard \textit{et al.} (Phys. Rev. Lett., to be published) does raise some interesting questions. In collaboration withI.S. Towner, Cyclotron Institute, Texas A\&M University, College Station TX 77843. [Preview Abstract] |
Thursday, September 22, 2005 2:30PM - 2:45PM |
KB.00002: Progress towards Precision Measurement of the Neutron Lifetime using Magnetically Trapped Ultracold Neutrons (UCN) L. Yang, J.M. Doyle, F.H. DuBose, E. Korobkina, R. Golub, C.M. O'Shaughnessy, G.L. Palmquist, P.-N. Seo, P.R. Huffman, K.J. Coakley, H.P. Mumm, A.K. Thompson, G.L. Yang, S.K. Lamoreaux Measuring the neutron lifetime using magnetically trapped ultracold neutrons promises to improve the current experimental limit by at least an order of magnitude. Such a trap can be loaded through inelastic scattering of 0.89 nm neutrons with phonons in superfluid Helium-4. Trapped neutrons are detected when they beta decay; energetic decay electrons ionize helium atoms in the superfluid resulting in efficient conversion of electron kinetic energy into light (scintillation). The primary advantages of this technique over previous bottle and beam experiments are continuous detection of scintillation light from decay electrons allowing direct determination of the decay curve, and the elimination of wall losses. Our recent measurement is limited by statistics to 40 seconds. We are currently upgrading our experiment with a larger and deeper magnetic trap. The new apparatus will trap 20 times more neutrons than the previous one, making it possible to reduce the statistical error to below 1 s. Recent experimental data, our studies of systematic uncertainties such as above-threshold neutrons, and the development of the new magnetic trap will be discussed. [Preview Abstract] |
Thursday, September 22, 2005 2:45PM - 3:00PM |
KB.00003: A New Measurement of the Strength of the Superallowed Fermi Branch in the Beta Decay of $\mathrm{^{10}C}$\ with GAMMASPHERE B.K. Fujikawa, T.I. Banks, S.J. Freedman, P.A. Vetter, W.T. Winter, S.J. Asztalos, J.T. Burke, J.P. Greene, N.D. Scielzo We report a new measurement of the strength of the superallowed \mbox{$\mathrm{0^{+}\rightarrow0^{+}}$} transition in the $\beta$-decay of $\mathrm{^{10}C}$. The experiment was done at the LBNL 88-inch cyclotron using eighty-three GAMMASPHERE germanium detectors. This measurement is similar to an earlier experiment performed at GAMMASPHERE but with a significantly higher statistical precision. Precise knowledge of this branching ratio is necessary to compute the superallowed Fermi \mbox{$\mathit{f}$t-value} which in turn gives the weak vector coupling constant and the u to d element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix. [Preview Abstract] |
Thursday, September 22, 2005 3:00PM - 3:15PM |
KB.00004: Beta decays in mass 8 system and test of conserved vector current hypothesis T. Sumikama, T. Nagatomo, M. Ogura, T. Iwakoshi, Y. Nakashima, H. Fujiwara, K. Matsuta, T. Minamisono, M. Fukuda, M. Mihara, K. Minamisono, T. Yamaguchi We observed the alignment correlation terms in the $\beta$-ray angular distribution for $^8$Li and $^8$B. The alignment correlation terms are useful probes to test the conserved vector current (CVC) hypothesis or the $G$-parity conservation in the $\beta$-decay process. The experiment was performed using the Van de Graaff accelerator at Osaka University. The pure nuclear-spin alignments were successfully produced by applying the $\beta$-NMR techniques and the alignment correlation terms were extracted from the $\beta$-ray angular distribution as a function of the $\beta$-ray energy. Under the assumption of the $G$-parity conservation, not only the weak magnetism (WM) but also the second-forbidden matrix element (M$_2$) of the vector current was obtained both from the present alignment correlation terms and the previous $\beta$-$\alpha$ angular correlation terms. The WM and M$_2$ are related by the CVC hypothesis to the M1 and E2 analog $\gamma$-decays from the isobaric analog state of $^8$Be. It is found that the M$_2$ is inconsistent with the previously observed E2 $\gamma$-decay. [Preview Abstract] |
Thursday, September 22, 2005 3:15PM - 3:30PM |
KB.00005: $\gamma$-rays following the $\beta$-decay of $^{62}$Ga and the strength of the superallowed transition J.R. Leslie, I.S. Towner, C. Andreoiu, P.E. Garrett, B.H. Hyland, A.A. Phillips, M.A. Schumaker, C.E. Svensson, J.J. Valiente-Dobin, A. Andreyev, G.C. Ball, P. Bricault, M. Dombsky, G. Hackman, D. Melconian, A.C. Morton, C.J. Pearson, D. Cross, J.A. Becker As part of an ongoing study of superallowed $\beta$-decay at TRIUMF, we have measured the intensity and energy of $\gamma$- rays following the $\beta$-decay of $^{62}$Ga. During a beam on period of 10 s., a total of approximately 3$\times$10$^{8}$ atoms of $^{62}$Ga, from the Resonant Laser Ionisation Source at the ISAC facility, was implanted into a collector tape at the centre of the SCEPTAR/8$\pi$ arrays. Before and after the beam on period, 2 s. of data were taken to assess backgrounds and the build up of long-lived activities. After each counting cycle the tape was moved in order to transport the implanted atoms to a shielded location. Substantial reduction in the Bremsstrahlung induced background were achieved by vetoing events in which the $\beta$-rays and $\gamma$-rays were observed in corresponding detectors. Singles $\beta$ and coincident $\beta$-$\gamma$ events were recorded. The intensities of $\beta$-rays feeding of low lying states in $^{62}$Zn and a $\gamma$-decay scheme of $^ {62}$Zn are proposed. The data are compared to shell model predictions of energies and transition strengths. Predictions of charge dependent effects are tested against the deduced superallowed transition probability. [Preview Abstract] |
Thursday, September 22, 2005 3:30PM - 3:45PM |
KB.00006: Precise Half Life Measurement for the Superallowed $\beta ^{+}$ Emitter$^{34}$Ar V.E. Iacob, J.C. Hardy, C.A. Gagliardi, V.E. Mayes, N. Nica, G. Tabacaru, L. Trache, R.E. Tribble The half-life of the superallowed $\beta ^{+}$ emitter $^{34}$Ar was measured as part of our program to test the Standard Model via the unitarity of the CKM matrix, which requires 0.1{\%} precision or better. A 25$\cdot A$ MeV $^{35}$Cl beam from the Texas A{\&}M cyclotron initiated the $^{1}$H($^{35}$Cl, pn)$^{ 34}$Ar reaction, with recoils then passing through the MARS recoil separator. After being degraded, $^{34}$Ar ions were implanted as a 99.7{\%} pure source in the tape of a fast transport system. After a short collect time (0.7s or 1.0s), the beam was turned off and the implanted source moved in 175 ms to the center of a shielded 4$\pi $ proportional gas counter. Decay positrons were then multi-scaled for 12 s. The cycle was repeated until more than half a billion combined $^{34}$Ar and $^{34}$Cl decay events had been recorded. Critical detection parameters were changed periodically to expose any possible systematic effects; none were found. The extraction of a precise half-life for $^{34}$Ar presents a special challenge as its daughter $^{34}$Cl is itself $\beta ^{+}$ unstable with a half-life only 1.8-times longer. This results in an observed spectrum that is almost indistinguishable from pure $^{34}$Cl decay. A special method was developed to extract a precise half-life for the shorter-lived component in such a decay curve. Our preliminary result for the half-life of $^{34}$Ar is 843.8(7) ms. [Preview Abstract] |
Thursday, September 22, 2005 3:45PM - 4:00PM |
KB.00007: Neutrinoless double beta decay and lepton flavor violation Vincenzo Cirigliano, Andriy Kurylov, Michael Ramsey-Musolf, Petr Vogel We point out that extensions of the Standard Model with low scale ($\sim$ TeV) lepton number violation (LNV) generally lead to a pattern of lepton flavor violation (LFV) experimentally distinguishable from the one implied by models with GUT scale LNV. As a consequence, muon LFV processes provide a powerful diagnostic tool to determine whether or not the effective neutrino mass can be deduced from the rate of neutrinoless double beta decay. We discuss the role of $\mu \to e \gamma$ and $\mu \to e$ conversion in nuclei, which will be studied with high sensitivity in forthcoming experiments. [Preview Abstract] |
Thursday, September 22, 2005 4:00PM - 4:15PM |
KB.00008: Double beta decay of $^{48}$Ca in CANDLES III - Construction and first run - Kayoko Ichihara, Tadafumi Kishimoto, Izumi Ogawa, Ryuta Hazama, Sei Yoshida, Saori Umehara, Yoshiyuki Hirano Experiments of neutrino oscillation show that neutrinos have mass. The absolute mass scale and Majorana nature of neutrino are of current interests. The measurement of neutrino-less double beta decay can establish the Majorana nature of neutrino and is the realistic experiment to measure the effective mass in the range of meV, so far. We have been studying double beta decay of $^{48}$Ca. The highest Q-value of $^{48}$Ca among double beta decay nuclei makes it possible to realize background free measurement. CANDLES (\underline {CA}lcium fluoride for the study of \underline {N}eutrino and \underline {D}ark matter by \underline {L}ow \underline {E}nergy \underline {S}pectrometer) system was proposed, in order to achieve the sensitivity of order of meV neutrino mass. In this system, CaF$_{2}$ crystals are immersed in liquid scintillator. We started studying of neutrino-less double beta decay by using CANDLES III that consists of 60 undoped CaF$_{2}$crystals with total mass of 191kg. The present status of construction and performance of CANDLES III in the first run will be reported. [Preview Abstract] |
Thursday, September 22, 2005 4:15PM - 4:30PM |
KB.00009: Double beta decay of 48Ca in CANDLES III -development of the calibration system- Yoshiyuki Hirano, Tdafumi Kishimoto, Izumi Ogawa, Ryuta Hazama, Sei Yoshida, Saori Umehara, Kayoko Ichihara We have been studying double beta decay of 48Ca. The observation of neutrino-less double beta decay is important since it establishes lepton number non-conservation and the Majorana nature of neutrinos. The detector system CANDLES were developed for the study of neutrino-less double beta decay. We are now constructing CANDLES III, which consists of 40 large PMTs and 60 undoped CaF2 crystals immersed in a liquid scintillator acts as an active veto. And the detector has to be in law background environment because double beta decay is quite rare event. The Q-value (4.27MeV) of 48Ca is the highest among the double beta nuclei. Therefore, the least background rate is expected because the Q-value is higher than the natural gamma ray energy. With regarding to the energy calibration, there are no commercially available sources with gamma ray energy around the Q-value. Consequently, we use sum energy (4.11MeV) of 1.36 MeV and 2.75 MeV emitted from 24Na, which is activated by neutron source. According to a simulation, it is applicable for CANDLES by making use of the 4 pi active shield. I will report CANDLES and it's calibration system. [Preview Abstract] |
Thursday, September 22, 2005 4:30PM - 4:45PM |
KB.00010: Studies of radon nuclear polarization and relaxation Sarah Nuss-Warren, Eric Tardiff, Casey Schnieder-Mizell, Tim Chupp, John Behr, Matthew Pearson, Norbert Pietralla, Georgi Rainovski, Gene Sprouse In preparation for electric dipole moment (EDM) measurements with octupole deformed $^{223}$Rn, a radon source has been developed at the Stony Brook Nuclear Structure Lab, and studies of radon polarization and relaxation are underway. The $^{209}$Rn (29 m) is produced from the decay of $^{209}$Fr (50 s) produced by $^{197}$Au($^{16}$O,4n) at about 100 MeV beam energy. The $^{209}$Fr ionizes at the surface of the heated gold target, is accelerated to 5 keV and implanted in a zirconium foil. To release the radon, the foil is heated. The radon is frozen into a valved measurement cell to which N$_2$ buffer gas is added. The radon is polarized by spin exchange with optically pumped Rb vapor and nuclear orientation is detected by observing anisotopy of $^{209}$At gamma rays populated by beta-decay/electron capture. The EDM measurements require free precession with coherence times of order 100 seconds, which are expected to be limited by wall relaxation in the measurement cell. Spin exchange parameters and wall relaxation will be studied with varying temperatures, wall coatings, and buffer gas compositions. [Preview Abstract] |
Thursday, September 22, 2005 4:45PM - 5:00PM |
KB.00011: Progress towards the measurement of the electric dipole moment of $^{225}$Ra J.R. Guest, N.D. Scielzo, E.C. Schulte, I. Ahmad, K. Bailey, J.P. Greene, R.J. Holt, Z.-T. Lu, T.P. O'Connor, D.H. Potterveld, H. Gould Ongoing searches in many laboratories for a permanent electric dipole moment (EDM) in the atom underscore the importance of this window into physics beyond the Standard Model. The lack of an observed EDM in $^{199}$Hg has set impressive limits on the strength of Parity (P)-and Time (T)-invariance violating interactions in the nucleus. We are in the process of developing a next generation experiment to search for an EDM in laser-cooled and trapped $^{225}$Ra. $^{225}$Ra is predicted to be more than two orders of magnitude more sensitive to these interactions than $^{199}$Hg due to a larger nuclear charge, the octupole deformation in the $^{225}$Ra nucleus, and the collective nature of (P,T)-odd nuclear moments. We will present the challenges associated with $^{225}$Ra, discuss our results from laser spectroscopy on a beam of $^{225}$Ra atoms, and report on our progress towards producing a laser-cooled and trapped sample of these atoms. We will also present a measurement of the lifetime of the 7s7p $^{3}$P$_{1}$ state. [Preview Abstract] |
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