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 CD: Mini-symposium on New Aspects of Nuclear Forces I |
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Sponsoring Units: DNP JPS Chair: Hideyuki Sakai, University of Tokyo Room: Ritz-Carlton Hotel Salon 1 |
Tuesday, September 20, 2005 2:00PM - 2:30PM |
CD.00001: Exploring Three Nucleon Forces via Few Nucleon Systems Invited Speaker: A main interest of nuclear physics is to understand the forces acting between nuclear constituents. Few nucleon systems offer good opportunities to investigate these forces. A recent topic of present day few-nucleon system studies is to explore the properties of three-nucleon forces (3NFs) acting in systems with more than A=2 nucleons. Indication of 3NF for the three-nucleon scattering was first pointed out in the cross section minima for nucleon--deuteron ($Nd$) elastic scattering at intermediate energies ($E/A \sim 100~\rm MeV$) by Witala {\it et al.}$^1$ in 1998. Since then experimental studies of elastic proton--deuteron ($pd$) and neutron--deuteron ($nd$) scattering at intermediate energies have been performed intensively at RIKEN, RCNP, KVI and IUCF and provided precise data of various observables. Cross section data for elastic $pd$ scattering have shown large disagreement between data and rigorous Faddeev calculations with modern NN forces. Combination of these NN forces and 2$\pi$--exchange type 3NFs removes this discrepancy and leads to a good description of the measured cross sections. However spin observables are not always explained by addition of the 3NFs. To describe these spin observables, theoretical approaches, such as addition of 3NFs other than 2$\pi$ exchange types, and/or relativistic treatment, and completely new approach based on chiral effective field theory are now in progress. Measurements for the $Nd$--breakup and radiative capture processes are also underway to provide a solid basis to test current and/or future coming theoretical approaches. In the presentation, an overview of recent advances of 3NF study via few-nucleon systems will be given. In particular, the results of $Nd$ elastic scattering and the $Nd$ breakup reactions obtained at RIKEN will be discussed. \\ 1. H.~Witala, et al., Phys. Rev. Lett. $\bf 81$, 1183 (1998). [Preview Abstract] |
Tuesday, September 20, 2005 2:30PM - 2:45PM |
CD.00002: Neutron-Helium-3 Analyzing Power at 3.14, 4.05, and 5.54 MeV J.H. Esterline, A.S. Crowell, C.R. Howell, A. Hutcheson, R.A. Macri, S. Tajima, W. Tornow, B.J. Crowe, R.S. Pedroni, G.J. Weisel In the interest of resolving differences between calculations and measurements in three-nucleon analyzing powers, the four-nucleon system is being examined due to its sensitivity to the relevant nucleon-nucleon phase shifts. Consequently, the analyzing power for polarized neutron-helion scattering has been measured at Triangle Universities Nuclear Laboratory (TUNL) over a wide angular distribution for incident neutron energies of 3.14, 4.05, and 5.54 MeV. These data were obtained with neutrons generated by the polarization-transfer reactions T(p,n)$^{3}$He for 3.14 MeV neutron energy and D(d,n)$^{3}$He for the higher energies, with neutron polarizations in the range of 0.3 to 0.5, increasing with neutron energy. Statistical uncertainties in the analyzing power were found in preliminary analysis to be less than 0.03 at the cross section minima, corresponding to values of analyzing powers in excess of 0.6. The data are compared to rigorous calculations based on the Yakubovsky equations, with which they are in marked disagreement, and existing proton-triton data corrected for the Coulomb barrier. [Preview Abstract] |
Tuesday, September 20, 2005 2:45PM - 3:00PM |
CD.00003: Relation between Axx and Ayy in pd radiative capture Kenshi Sagara, Takashi Kudoh, Yuji Tameshige, Kichiji Hatanaka, Takanori Yagita We have measured A$_{xx}$ and A$_{yy}$ of \textit{pd} radiative capture at $E_{d}$ = 200 MeV and 140 MeV. A vertically polarized d-beam was incident on a liquid hydrogen target, and $^{3}$He recoils were detected in vertical and horizontal planes to measure A$_{xx}$ and A$_{yy}$, respectively. Polarization of the d-beam was measured during the experiment using the maximum value of A$_{yy}$ in the angular distribution of \textit{dp} scattering. The polarimeter A$_{yy}$ at 200 MeV was calibrate using $^{12}$C($d$,$^{4}$He) reaction at zero degree in a separate experiment. Measured A$_{xx}$ and A$_{yy}$ of \textit{pd} radiative capture have nearly equal values at 200 and 140 MeV, also at 17.5 MeV in our previous experiment. The relation A$_{xx} \quad \sim $ A$_{yy }$in\textit{ pd} capture is curious one because, so far as we know, all the reactions other than \textit{pd} capture (and probably \textit{dd} capture) have the relation A$_{xx} \quad \sim $ - A$_{yy}$. Calculated A$_{xx}$ and A$_{yy}$ of \textit{pd} capture are nearly equal below 50 MeV, and become separate at higher energy. As a result, large difference between the calculation and experiment of A$_{xx}$ is seen at 140-200 MeV. Recently A$_{xx}$ and A$_{yy}$ of \textit{pd} capture have been measured. The relation A$_{xx} \quad \sim $ A$_{yy}$ seems to hold, however, the absolute values of A$_{xx}$ and A$_{yy}$ are different with ours. [Preview Abstract] |
Tuesday, September 20, 2005 3:00PM - 3:15PM |
CD.00004: Spin correlation parameter C$_{yy}$ of $p^{3}$\textit{He} backward elastic scattering at intermediate energy Kichiji Hatanaka, Yohei Shimizu, Alexander Kobushkin, Tatsuya Adachi, Kunihiro Fujita, Hiroaki Matsubara, Yasuhiro Sakemi, Yoshihiro Shimbara, Yuji Tameshige, Atsushi Tamii, Makoto Uchida, Keisuke Itho, Takahiro Kawabata, Yoshiko Sasamoto, Keiji Suda, Tomohiro Uesaka, Takashi Wakui, Takashi Kudoh, Hitomi Ohira, Kenshi Sagara, Hidetomo Yoshida, Mizuho Tomiyama, Tomotsugu Wakasa, Hiroyuki Okamura For several decades considerable efforts have been performed to investigate the structure of the lightest nuclei at short distances between constituent nucleons. Large part of these investigations consists of studies of elastic backward proton-nucleus scattering (EBS). At present there is no theoretical model which quantitatively describes the existing data, even for the simplest reaction, \textit{pd} EBS. Recently there have been several theoretical attempts to understand the $p^{3}$\textit{He} EBS which is studied in much less detail than \textit{pd} EBS. We have measured the cross section and spin correlation parameter C$_{yy}$ of $p^{3}$\textit{He} EBS at 200,300 and 400 MeV. Experimental results are compared to theoretical predictions with two-nucleon pair exchange in the triplet and singlet spin states, pion-exchange and direct mechanism. [Preview Abstract] |
Tuesday, September 20, 2005 3:15PM - 3:30PM |
CD.00005: Relativistic effects in the 3N continuum Henryk Witala, Jacek Golak, Walter Gloeckle, Hiroyuki Kamada We solved the three-nucleon (3N) Faddeev equation including relativistic features. Those features are relativistic kinematics, boost effects and Wigner spin rotations. As dynamical input a relativistic nucleon-nucleon interaction exactly on-shell equivalent to the AV18 nucleon-nucleon potential has been used. The effects of Wigner rotations for elastic scattering observables were found to be small. The boost effects are significant at higher energies. They diminish the transition matrix elements at higher energies and lead in spite of the increased relativistic phase-space factor as compared to the nonrelativistic one to rather small effects in the cross section, which are mostly restricted to the backward angles. [Preview Abstract] |
Tuesday, September 20, 2005 3:30PM - 3:45PM |
CD.00006: Two-and three- body breakup of $ {^3}$He at low energies W. Tornow, A.P. Tonchev, J.H. Esterline, C.R. Howell, H.J. Karwowski, J.H. Kelley, J. Li, S.F. Mikhailov, I.V. Pinayev, Y.K. Wu, H. Witala We report on measurements of the two-body breakup cross section of $^{3}$He for gamma-ray energies between 8 and 16 MeV, and of the analyzing power of the kinematically incomplete three-body breakup at 15 MeV. The monoenergetic gamma-ray beams were produced via Compton backscattering of FEL photons from high-energy electrons at the High-Intensity Gamma-ray Source at Duke University. The $^{3}$He target consisted of a high-pressure gas scintillator. The data are compared to rigorous three-nucleon calculations using realistic nucleon-nucleon and three-nucleon interactions. [Preview Abstract] |
Tuesday, September 20, 2005 3:45PM - 4:00PM |
CD.00007: Measurements of the n+d elastic scattering and the three-nucleon force effects Yukie Maeda, Hideyuki Sakai, Takahiro Kawabata, Kentaro Yako, Kenji Suda, Takaaki Saito, Hironori Kuboki, Masaki Sasano, Michio Hatano, Kichiji Hatanaka, Yasuhiro Sakemi, Atsushi Tamii, Yohei Shimizu, Yuji Tameshige, Jan Blomgren, Philippe Mermod, Henryk Witala, M.B. Greenfield, Keisuke Itoh, Hiroyuki Kamada, Hiroyuki Okamura, Yoshiteru Satou, Kimiko Sekiguchi, Tomotsugu Wakasa, Jun'ichiro Kamiya One of the problem in the precise research of the three-nucleon force (3NF) is the ambiguity coming from the Coulomb force in the comparison between the p+d data and the n+d calculations. It has been remaining theoretical problem for a long time to carry out the calculations including Coulomb force. To answer the question about the effects of the 3NF and about the effects of Coulomb force in the three nucleon system at intermediate energy region, n+d and p+d experiments are carried out at RCNP and Uppsala at 100 and 250MeV. I will mainly introduce 250MeV n+d data and talk about the overview of the recent study of 3NF via the n+d and p+d experiments and discuss on the effects of the 3NF and Coulomb force. Concerning about the data at 250MeV, the relativistic effects will be also presented. [Preview Abstract] |
Tuesday, September 20, 2005 4:00PM - 4:15PM |
CD.00008: Neutron-deuteron scattering and the three-nucleon force M. Chtangeev, T. Akdogan, W.A. Franklin, J.L. Matthews, M.A. Kovash, P.A.M. Gram, S.A. Wender, M. Yuly Differential cross sections for neutron-deuteron elastic scattering were measured at six angles between 65 and 130 degrees (center-of-mass) for incident neutron energies in the range 140 to 240 MeV. A liquid deuterium target was exposed to the pulsed neutron beam provided by the LANSCE/WNR facility at the Los Alamos National Laboratory. Scattered neutrons and recoil deuterons were observed in coincidence using time-of-flight techniques and an array of plastic and CsI scintillation detectors. With liquid hydrogen in the target, elastic neutron-proton scattering cross sections were measured to aid in normalization of the neutron-deuteron data. The results will be compared with theoretical predictions including three-nucleon forces and with the results of previous measurements. [Preview Abstract] |
Tuesday, September 20, 2005 4:15PM - 4:30PM |
CD.00009: Three-nucleon tensor force effects in nucleon-deuteron scattering. Souichi Ishikawa The introduction of three-nucleon (3N) forces arising from the exchange of two pions among three nucleons (2PE-3NF) is known to get rid of the discrepancies between experimental data and only two-nucleon force (2NF) calculations for the 3N binding energies and nucleon-deuteron (ND) differential cross sections. On the other hand, we have shown that tensor components of the 2PE-3NF give undesirable contributions to tensor analyzing powers (TAP's) in ND elastic scattering at energies below the three-body breakup threshold. We made a phenomenological 3NF that reproduces the TAP's by inversing the sign of a tensor component in a 2PE-3NF simulated 3N potential, which consists of scalar and tensor forces in spin space with Gaussian form factors. In this work, we examine 3NF effects on ND scattering observables at energies above the three-body breakup threshold. Our calculations show that the tensor-inversed 2PE-3NF model is also successful in reproducing some polarization observables at higher energies, which are not reproduced by 2NF and 2NF + 2PE-3NF. [Preview Abstract] |
Tuesday, September 20, 2005 4:30PM - 4:45PM |
CD.00010: Search for three-nucleon force effects in elastic proton-deuteron scattering Nasser Kalantar-Nayestanaki Three-body forces are, though small, very important in nature. The effect of these forces have far-reaching consequences in many fields of physics. A relatively good understanding of most phenomena in nuclear physics has been arrived at by only considering two-nucleon forces. However, high precision data emerging are revealing the shortcomings of these forces. At KVI, a program has been set up to study the effects of three-nucleon forces in elastic proton-deuteron scattering. High-precision cross sections, analyzing powers and spin-transfer coefficients have been measured at various incident proton or deuteron beam energies between 100 and 200 MeV for a large range of scattering angles. Calculations based on two-body forces only are clearly unable to predict the data. The inclusion of three-body forces brings the results generally closer to the data. However, there are still clear deficiencies in the calculations. The result of these recent measurements along with several calculations will be discussed. Furthermore, future plans to study the break-up reaction in the same system for an almost 4p geometry will be outlined. [Preview Abstract] |
Tuesday, September 20, 2005 4:45PM - 5:00PM |
CD.00011: Two-Body Photodisintegration of $^{3}$He, $^{4}$He, and $^{2}$He up to 1.5 GeV Barry L. Berman We have obtained data on all of the photoreaction channels of $^{3}$He and $^{4}$He, from 0.35 to 1.5 GeV, using liquid targets, the Photon Tagger, and the CLAS in Hall B at Jefferson Lab. Our data for the three-body photodisintegration of $^{3}$He and its evidence for three-body mechanisms have been published.$^{1}$ Here we report preliminary results for three other reaction channels as well as a more detailed analysis of the data of Ref. 1. Cross sections for the $^{3}$He($\gamma $,dp) and $^{4}$He($\gamma $,tp) reactions are compared with the model predictions of Laget$^{2}$ to throw further light on three-body mechanisms and reaffirm their importance. The angular distribution for $^{4}$He($\gamma $,dd) shows no evidence for dipole reactions and the breaking of isospin symmetry, in contrast with earlier results at lower energies. And selecting only those $^{3}$He($\gamma $,pp)n events where the neutron is a spectator enables us to study the two-body photodisintegration of $^{2}$He, with surprising results, in preparation for an upcoming experiment$^{3}$ on hard-pp quark-exchange processes.\newline \newline $^{1}$ S. Niccolai \textit{et al}., Phys. Rev. C \textbf{70}, 064003 (2004)\newline $^{2}$ J-M. Laget, Pr. Comm. (2004)\newline $^{3}$ R. Gilman \textit{et al}., JLab Expt. E03-101 (2003) [Preview Abstract] |
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