Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session J13: Few Body Physics III |
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Sponsoring Units: GFB Chair: Wayne Polyzou, University of Iowa Room: Plaza Court 3 |
Sunday, May 3, 2009 1:30PM - 1:42PM |
J13.00001: Know Your Target: Toward A Better Understanding of the 3He System Elena Long The Hall A E05-102 collaboration of Jefferson Lab is seeking to better understand the polarized 3He system. Polarized 3He is often used as an effective neutron target for purposes such as measuring the neutron asymmetry A1n. These measurements have reached a level where the errors from the understanding of the 3He system are comparable in some cases to the statistical errors. In order to improve our understanding, double-polarized asymmetries in the quasi-elastic 3He(e,e'd) reaction will be measured. Faddeev calculations of the Bochum/Krakow and Hannover groups result in distinct descriptions of the Ax and Az asymmetries. These descriptions will be compared to asymmetries measured as a function of missing momentum and will allow for a better understanding of the 3He system. This development has important implications for all experiments using polarized 3He as an effective neutron target. Details of the experiment will be discussed. [Preview Abstract] |
Sunday, May 3, 2009 1:42PM - 1:54PM |
J13.00002: How Small are FSI Corections at High $Q^2$ Aidan Kelleher, Misak Sargsian For analysis of precision experiments recently performed at Jefferson Lab, as well as experiments proposed for the 12 GeV upgraded facility, it is important to accurately relate the processes measured using light nuclei to equivalent free nucleons. It is widely accepted that Final State Interactions (FSI) and Meson Exchange Currents (MEC) diminish for quasi-elastic kinematics at high $Q^2$. The subject of this study is the exact value due to FSI and MEC for quasi-elastic measurements at high $Q^2$. The Generalized Eikonal Approximation allows a potentially infinite number of re-scattering diagrams to be summed into the final set of Feynman diagrams.\footnote{Sargsian, M M, arXiv: nucl-th/0110053} In this talk, I will discuss results of calculations made in the framework of recent theoretical models for FSI relevant to data taken for Jefferson Lab E02-013, a high precision measurement of the Sach's form factor $G_E^n$ at $Q^2$ up to 3.5 GeV$^2$ via quasi-elastic scattering from a polarized $^3$He target. [Preview Abstract] |
Sunday, May 3, 2009 1:54PM - 2:06PM |
J13.00003: Photo-disintegration of $^3$He below E$_\gamma$ = 15 MeV at HI$\vec{\gamma}$S B.A. Perdue, M.W. Ahmed, S.S. Henshaw, J. Li, S. Mikhailov, S. Stave, H.R. Weller, Y. Wu, P.P. Martel, A. Teymurazyan Differential cross sections of the $^3$He($\gamma$,n)pp reaction have been measured at HI$\vec{\gamma}$S. Measurements were taken at E$_{\gamma}$ = 11.4, 12.8, 13.5, and 14.7 MeV. The breakup neutrons were detected using liquid scintillator detectors placed at 75 cm from the target center and at the scattering angles of $\theta$ = 50$^{\circ}$, 75$^{\circ}$, 90$^{\circ}$, 105$^{\circ}$, 130$^{\circ}$, and 160$^{\circ}$. At a given scattering angle, theory\footnote{Deltuva {\it et.~al.~} Phys. Rev. \textbf{C72} 054004 (2005)} predicts that $\frac{d^3\sigma}{dE_n d\Omega_n}(E_n)$ peaks near $E_n^{max}$. This peaking in the energy distribution is predicted to begin around E$_{\gamma}$ = 10 MeV and becomes more pronounced as the incident $\gamma$-ray energy is increased. Below E$_{\gamma}$ = 10 MeV and at a given scattering angle the predicted neutron energy distribution is consistent with a {\it phase space only} neutron energy distribution. The measured differential cross sections for E$_{\gamma}$ = 11.4 and 12.8 MeV do not show peaking in the neutron energy distribution as predicted by theory, and the shape of the energy distribution at a given scattering angle is consistent with the shape of a phase space distribution. The peaking near $E_n^{max}$ of the energy distribution is observed at E$_{\gamma}$ = 13.5 and 14.7 MeV. [Preview Abstract] |
Sunday, May 3, 2009 2:06PM - 2:18PM |
J13.00004: Subtractive renormalization of the chiral potentials up to next-to-next-to-leading order I: Higher NN partial waves Chieh Jen Yang, Charlotte Elster, Daniel Phillips We develop a subtractive renormalization scheme to evaluate the p-wave NN scattering phase shifts using chiral effective theory (ChiET) potentials. This allows us to consider arbitrarily high cutoffs when solving the Lippmann-Schwinger equation. We employ NN potentials computed up to next-to-next-to-leading order (NNLO) in ChiET, using both dimensional regularization and spectral-function regularization. When used in our subtracted p-wave Lippmann-Schwinger equation the NNLO potential yields cutoff-independent predictions. This shows that renormalization of the NNLO potential can be achieved by using the generalized NN scattering lengths as input---an alternative to fitting the constant that multiplies the p-wave contact interaction in the ChiET NN force. However, in order to obtain the best fit to the NN data at NNLO the generalized scattering lengths must be varied away from the values extracted from the so-called high-precision potentials. The situation at NNLO is in contrast to the situation with the LO and NLO ChiET potentials, where only two p-waves require renormalization. Attempts to incorporate the contact interactions that occur in the NLO potential then lead to difficulties at cutoffs larger than 1-1.2 GeV. [Preview Abstract] |
Sunday, May 3, 2009 2:18PM - 2:30PM |
J13.00005: Subtractive renormalization of the NN interaction from chiral effective theory up to next-to-next-to-leading order II: S-waves Daniel Phillips, Chieh Jen Yang, Charlotte Elster We develop a subtractive renormalization scheme to evaluate the 1S0 and 3S1-3D1 NN scattering phase shifts up to next-to-next-to-leading order (NNLO) in the chiral effective theory. We show that for the 1S0 channel, the phase shift can be obtained by performing two subtractions on the Lippmann-Schwinger equation and using the knowledge of the scattering length and the 1S0 phase shift at a particular energy. For the triplet channel, the renormalization can be achieved by 2 subtractions---which use knowledge of the 3S1 scattering length and the 3S1-3D1 generalized scattering length---and then making a fit to one additional piece of NN scattering data. This method allows us to use arbitrarily high cutoffs in the Lippmann-Schwinger equation. Our results show that use of an energy-dependent short-distance potential in the 1S0 channel creates scattering resonances at certain cutoffs---in conflict with NN data. This facilitates an analysis of the cutoff at which an the non-perturbative treatment of higher-order pieces of the ChiET potential becomes questionable. [Preview Abstract] |
Sunday, May 3, 2009 2:30PM - 2:42PM |
J13.00006: $_{\Lambda}^9 $Be $(\frac{3}{2}^+,\frac{5}{2}^+)$ spin-orbit splitting within three-body cluster model Vladimir Suslov, Igor Filikhin, Branislav Vlahovic The configuration-space Faddeev equations have been applied to study spin-flip spacing for the first excited states of $_{\Lambda}^9 $Be hypernucleus considered as a three-body cluster system $\alpha \alpha \Lambda $[1]. In this model the phenomenological potentials for inter-cluster interactions are used [2]. Calculated are the binding energy for the ground and first excited states and $(\frac{3}{2}^+,\frac{5}{2}^+)$ spin-orbit splitting for different types of $\alpha \Lambda$ and $\alpha \alpha$ potentials. The overbinding of the system when Ali-Bodmer type $\alpha \alpha$ potential is used and dependence of the interaction on the orbital quantum number $\alpha \Lambda$ are discussed. The spin-orbit component of $\alpha \Lambda$ interaction is taken by the potential [3] having one range Gaussian form. Our results are in a qualitative agreement with those obtained with the combined RGM and Faddeev cluster calculations [3]. Cluster model that includes a repulsive three cluster $\alpha \alpha \Lambda$ potential [4] was also studied. 1. O. Hashimoto, H. Tamura, Prog.Part. Nucl. Phys. 57, 564 (2006); 2. E. Cravo, A.C. Fonseca, Y. Koike, PRC 66 (2002) 014001; 3. http://xxx.lanl.gov/find/nucl-th/1/au:+Fujiwara\_Y/0/1/0/all/0/1 Y. Fujiwara, at al. PRC70, 047002 (2004); 4. M. Shoeb, PRC74, 064316 (2006). [Preview Abstract] |
Sunday, May 3, 2009 2:42PM - 2:54PM |
J13.00007: Four-electron quantum dot molecule in a magnetic field Shalva Tsiklauri, Roman Kezerashvili In the present paper we report calculations of four-electron quantum dot and four-electron quantum dot molecule in a magnetic field by using Hyperspherical Functions Method. The obtained results are compared with those obtained by several approximate methods.The ground state properties and the spin and angular momentum transitions for different electron interaction strengths and magnetic fields are obtained. [Preview Abstract] |
Sunday, May 3, 2009 2:54PM - 3:06PM |
J13.00008: Multiparticle dynamics: nonlinearity and long-range forces Vladimir Hizhnyakov, Mati Haas, Aleksander Shelkan, Imbi Tehver, Mihhail Klopov Nonlinear vibration interactions are well localized; as a consequence, intrinsic localized modes (ILMs) and other types of nonlinear modes can exist. On the contrary, linear interactions in 3D systems depend on long range forces (LRF), which make unsatisfactory MD simulations based on a cluster consideration. In [1-2], an analytical theory of ILMs was developed, which takes LRF into account. Here we present a method of MD simulations, which also includes LRF. It was found that LRF can qualitatively change the results: instead of ILMs with the frequency in the gap of the phonon spectrum one may obtain modes with the frequency above the spectrum. This allows one to conclude that the nonlinearity-induced localization of vibrational energy may exist much more widely than it was believed on the basis of the previous theories which neglect LRF. 1. V. Hizhnyakov et al, Phys. Rev. B, 73, 224302 (2006). 2. V. Hizhnyakov, A. Shelkan, M. Klopov, Physics Letters A, 357, 393 (2006). 3. A. Shelkan, V. Hizhnyakov, M. Klopov, Phys. Rev. B, 75, 134304 (2007). [Preview Abstract] |
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