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 JH: Light Ions and Inverse Reactions |
Hide Abstracts |
Chair: Werner Tornow, Duke University Room: Newport News Marriott at City Center Blue Point I |
Saturday, October 13, 2007 2:00PM - 2:12PM |
JH.00001: Direct Measurement of the $^1S_0$ Neutron-Neutron Scattering Length at the YAGUAR Reactor S.L. Stephenson, B.E. Crawford, D. Kawamura, M.R. Schmidt, D.A. Yager-Elorriaga, C.R. Howell, W. Tornow, G.E. Mitchell, W.I. Furman, A.R. Krylov, E.V. Lychagin, A. Yu. Muzichka, G.V. Nekhaev, E.I. Sharapov, V.N. Shvetsov, A.V. Strelkov, B.G. Levakov, A.E. Lyzhin, Yu. I. Chernukhin, Ya. Z. Kandiev A direct measurement of the $^1S_0$ neutron-neutron ({\it nn}) scattering length ($a_{nn}$) provides a unique contribution to understanding charge symmetry breaking in the nuclear force. The current status of the experiment at the pulsed aperiodic YAGUAR reactor facility, with a neutron density flux of over $10^{18}$ cm$^{-2}$ s$^{-1}$, will be presented. [Preview Abstract] |
Saturday, October 13, 2007 2:12PM - 2:24PM |
JH.00002: A study of proton-deuteron scattering in configuration space Vladimir Suslov, Mikhail Braun, Igor Filikhin, Branislav Vlahovic A new computational method for solving the configuration-space Faddeev equations for the breakup scattering problem [1] has been applied to consider the pd scattering below and above the deuteron threshold. To perform numerical calculations for arbitrary nuclear potential and with arbitrary number of partial waves retained we use approach proposed in [2]. The calculations of the inelasticity and phase-shift for various lab energies were performed with the charge independent AV14 potential. The results are compared with those of other authors [3, 4]. 1. V.M. Suslov and B. Vlahovic, Phys. Rev. C69, 044003 (2004). 2. S.P. Merkuriev, C. Gignoux and A. Laverne, Ann. Phys. 99, 30 (1976). 3. A.Kievsky, J.L Friar, G.L. Payne, S. Rosati, M. Viviani, Phys. Rev. C63, 064004 (2001). 4. A. Deltuva, A.C. Fonseca, A.Kievsky, S. Rosati, P.U. Sauer, and M. Viviani, Phys. Rev. C74, 064003 (2005). [Preview Abstract] |
Saturday, October 13, 2007 2:24PM - 2:36PM |
JH.00003: Neutron-Helium-3 Analyzing Powers between 1.60 and 5.54 MeV J.H. Esterline, A.S. Crowell, B.A. Fallin, C.R. Howell, A. Hutcheson, M.F. Kidd, M.R. Kiser, R.A. Macri, S. Tajima, W. Tornow, B.J. Crowe, R.S. Pedroni, G.J. Weisel As part of a broader investigation of the four-nucleon system, the analyzing power for neutron-helium-3 scattering was measured at Triangle Universities Nuclear Laboratory (TUNL) at five neutron energies between 1.60 and 5.54 MeV. Measurements were made at around thirty angles for each energy using neutron beams, produced by the T(p,n)$^{3}$He and D(d,n)$^{3}$He source reactions, with polarizations ranging from 0.3 to 0.5. The data, recently corrected for finite geometry and multiple scattering effects, are compared to earlier experimental results as well as new \emph{ab initio} calculations, as from [1]. [1] A. Deltuva and A.C. Fonseca, Phys. Rev. C \textbf{75}, 014005 (2007). [Preview Abstract] |
Saturday, October 13, 2007 2:36PM - 2:48PM |
JH.00004: Ab initio no-core shell model and microscopic light-ion reactions Sofia Quaglioni, Petr Navratil We report on recent results of our work in the direction of building an {\em ab initio} method for low-energy light-ion reactions by augmenting the no-core shell model (NCSM)$^{1,2}$ to include clustering and resonant and non-resonant continuum. For this purpose, we adapt the resonating group method$^{3}$, a microscopic technique in which the many-body problem is mapped onto various channels of nucleon clusters and their relative motion. In our approach we use NCSM wave functions for the clusters involved, and NCSM effective interactions derived from realistic nucleon-nucleon and three-nucleon interactions. In particular, we will present our first results for the scattering of low-energy neutrons on $^4$He. This work was performed under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. Support from U.S. DOE/SC/NP (Work Proposal Number SCW0498) is acknowledged.\\ {\bf References }\\ 1. P.~Navr{\'a}til et al, Phys. Rev. Lett. {\bf 84}, 5728 (2000); Phys. Rev. C {\bf 62}, 054311 (2000).\\ 2. P.~Navr{\'a}til and W.~E. Ormand, Phys. Rev. Lett. {\bf 88}, 152502 (2002); Phys. Rev. C {\bf 68}, 034305 (2003).\\ 3. K.~Wildermuth and Y.~C.~Tang , A Unified Theory of the Nucleus., Vieweg, Braunschweig (1977). [Preview Abstract] |
Saturday, October 13, 2007 2:48PM - 3:00PM |
JH.00005: Nuclear Structure Measurements for (0$\nu $2$\beta )$ Decay of $^{76}$Ge J.P. Schiffer, S.J. Freeman, A.C.C. Villari, J.A. Clark, C. Deibel, S. Gros, C.R. Fitzpatrick, A. Heinz, D. Hirata, C.L. Jiang, B.P. Kay, A. Parikh, P.D. Parker, J. Qian, K.E. Rehm, X.D. Tang, V. Werner, C. Wrede There are considerable uncertainties in the theoretical matrix elements for neutrinoless double beta decay. To narrow down the possibilities, we have measured the occupation of valence orbitals, with particular attention to the \textit{differences} between $^{76}$Ge and $^{76}$Se. Neutron adding and removing transfer reactions were measured at the Yale ESTU tandem, with careful attention to absolute, and especially relative, cross sections. All significant components with a given angular momentum were identified, then sum rules were used to obtain occupation numbers in a consistent manner. Our results indicate that the Fermi surface is considerably more diffuse than those in QRPA used to calculate the 0$\nu $2$\beta $ matrix elements. The differences in neutron occupations appear to be spread over more orbits. \textit{This work was supported in part by the U.S. Department of Energy, Office of Nuclear Physics, under Contracts No. }\textit{DE-AC02-06CH1135 and DE-FG02-91ER-40609}$.$ [Preview Abstract] |
Saturday, October 13, 2007 3:00PM - 3:12PM |
JH.00006: Updates for Gadolinium neutron capture measurements at DANCE Dugersuren Dashdorj, G.E. Mitchell, B. Baramsai, R. Chankova, A. Chyzh, C. Walker, U. Agvaanluvsan, J.A. Becker, W. Parker, C.Y. Wu, T. Bredeweg, A. Couture, R. Haight, M. Jandel, J. O'Donnell, R. Rundberg, J. Wouters, J. Ullmann, D. Vieira, F. Becvar, M. Krticka Neutron capture reactions for several isotopes of Gadolinium have been measured at DANCE array in Los Alamos Neutron Science Center. Progress on the analysis is discussed. The detector response function of DANCE array is presented in connection with the statistical gamma-ray decay cascade simulation. In the region of separated neutron resonances, the statistical gamma-ray decay cascade is simulated using the DICEBOX code. Various models for the photon strength function and level density are used as input. The output of simulations is compared with DANCE data. [Preview Abstract] |
Saturday, October 13, 2007 3:12PM - 3:24PM |
JH.00007: $^{241}$Am(n,$\gamma$) absolute cross sections measured with DANCE M. Jandel, T.A. Bredeweg, M.M. Fowler, E.M. Bond, M.B. Chadwick, R.R. Clement, A. Couture, J.M. O'Donnell, R. Reifarth, R.S. Rundberg, J.L. Ullmann, D.J. Vieira, J.B. Wilhelmy, J.M. Wouters, U. Agvaanluvsan, R.A. Macri, S.A. Sheets, C.Y. Wu, J.A. Becker $^{241}$Am is present in plutonium due to the beta decay of $^{241}$Pu (t$_{1/2}$=14.38 years). As such $^{241}$Am can be used as a detector for nuclear forensics. A precise measurement of $^{241}$Am(n,$\gamma$) cross section is thus needed for this application. The measurement is also of interest for advanced reactor design as part of the Global Nuclear Energy Partnership (GNEP). The Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory (LANL) was used for neutron capture cross section measurement on $^{241}$Am. The high granularity of DANCE (160 BaF$_{2}$ detectors in a 4$\Pi$ geometry) enables the efficient detection of prompt gamma-rays following a neutron capture. DANCE is located on the 20.26 m neutron flight path 14(FP14) at the Manuel Lujan Jr. Neutron Scattering Center at the Los Alamos Neutron Science Center (LANSCE). The absolute $^{241}$Am(n,$\gamma$) cross sections were obtained in the range of neutron energies from 0.02 eV to 320 keV. The results will be compared to existing evaluations in detail. [Preview Abstract] |
Saturday, October 13, 2007 3:24PM - 3:36PM |
JH.00008: Benchmarking a surrogate reaction for neutron capture using $^{171,173}$Yb($d,p\gamma$) R. Hatarik, J.A. Cizewski, P.D. O'Malley, T. Swan, L.A. Bernstein, J.T. Burke, J. Gibelin, L. Phair The surrogate reaction technique is an indirect way to determine cross sections by measuring a reaction that proceeds through the same compound nucleus. A neutron transfer reaction, such as ($d,p$) has the advantage over a direct ($n,\gamma$) measurement since it can be measured in inverse kinematics. To test the feasibility of using a ($d,p\gamma$) reaction as a surrogate for neutron capture, a benchmark experiment has been carried out with the goal to reproduce the known [1] neutron capture cross section ratio of $^{171}$Yb and $^{173}$Yb. The $^{171,173}$Yb($d,p\gamma$) reactions were measured using an 18.5 MeV deuteron beam from the 88-Inch Cyclotron at LBNL. The reaction protons were measured using the Si detector array STARS and coincident $\gamma$-rays were detected using 6 Ge Clover detectors (LiBerACE). Preliminary results comparing surrogate ratio with the measured ($n,\gamma$) cross section will be presented.\newline\newline [1] K. Wisshak et al, Phys. Rev. C \textbf{61}, (2000) 065801. [Preview Abstract] |
Saturday, October 13, 2007 3:36PM - 3:48PM |
JH.00009: Photodisintegration Cross Section Measurements for $^{142}$Nd and $^{150}$Nd and Low-energy E1 $\gamma$-ray Strength Functions C.T. Angell, H. Utsunomiya, S. Goko, A. Makinaga, T. Kaihori, H. Toyokawa, Y.W. Lui The photo-neutron disintegration cross sections were measured near threshold for $^{142}$Nd, and, for the first time, $^{150}$Nd. The measurements were made using the monoenergetic $\gamma$-ray beam at the AIST TERAS facility in Tsukuba, Japan. The $\gamma$-ray beam was produced via laser inverse-Compton scattering. The neutrons were detected using a composite detector consisting of $^{3}$He proportional counters embedded in a polyethylene block. The technique and facility will be overviewed, highlighting the advantages of a monoenergetic $\gamma$-ray beam to absolute cross section measurements. The results will be compared to theoretical calculations using the Quasi-particle Random Phase Approximation (QRPA). Finally, the neutron number dependence of the low-energy E1 $\gamma$-ray strength function will be discussed. [Preview Abstract] |
Saturday, October 13, 2007 3:48PM - 4:00PM |
JH.00010: Is ALPHA the Odometer of the Universe? Shantilal Goradia The answer seems to be affirmative. ALPHA may be an odometer with sixty decimal points, the last digit moving up one integer every Planck time, displaying the information of the age of the universe. We can only measure it to the ninth decimal point. ALPHA is greater than or equal to the reciprocal of the natural logarithm of the age of the universe in Planck times, sixty orders of magnitude. Eddington spent good portion of his life trying to come up with a value of ALPHA based on multiplicity. Gamow had the insight about the four nucleotides of genetic tape. His deeper 1967 insight was a link between ALPHA and cosmology. Evolution mandates variation of ALPHA. In terms of the entropy equation on Boltzmann's tomb, ALPHA seems to be the Maxwell's demon, decreasing the entropy of invisible compartments within which electromagnetic interactions take place. Nature potentially knows only the Planck units. I will discuss the implications for the second law of thermodynamics drafted in physics/0210040 v3. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700