Bulletin of the American Physical Society
3rd Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 54, Number 10
Tuesday–Saturday, October 13–17, 2009; Waikoloa, Hawaii
Session CH: Mini-Symposium on the Three-nucleon Force in Few-Body Scattering and Reactions I |
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Chair: Shinsho Oryu, Tokyo University of Science Room: Kings 3 |
Thursday, October 15, 2009 9:00AM - 9:30AM |
CH.00001: Few Nucleon Scattering and Three Nucleon Force Invited Speaker: One recent topic of the few-nucleon system studies to explore the properties of three nucleon forces (3NFs) that appear in the system more than two nucleons. The 3NFs arise naturally in the standard meson exchange picture as well as in the more recent concept of chiral effective field theory. These forces are considered to be one key element to understand the nuclear phenomena in a consistent way. However there had been little knowledge with which to constrain the 3NFs. That is due to the fact that 3NFs are relatively weak compared to the nucleon--nucleon (NN) forces and then their effects are easily masked. Few nucleon scattering is one of the most promising tool for the 3NF study, because this system provides a rich set of energy dependent spin observables and differential cross sections. In the end of 1990's two theory groups reported the rigorous numerical Faddeev calculations incorporating 2$\pi$-exchange 3NFs in elastic $Nd$ scattering at intermediate energies ($E/A \sim 100~\rm MeV$), and they suggested that the difference found in the cross section minima is the signature of 3NF effects. Since then experimental studies of intermediate-energy $pd$/$nd$ elastic scattering and $pd$ breakup reactions have been performed by groups at RIKEN, RCNP, KVI, IUCF and Uppsala. Theoretically 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. The importance of 3NFs has also been noted in other instances; e.g. descriptions of the binding energies of light mass nuclei and the empirical saturation point of symmetric nuclear matter. It is clear that the testing of 3NF models has just begun. In the presentation, recent progress in the 3NF study with few nucleon scattering at intermediate energies will be given. [Preview Abstract] |
Thursday, October 15, 2009 9:30AM - 9:45AM |
CH.00002: Three-nucleon forces in neutron-deuteron elastic and inelastic scattering J.L. Matthews, M. Chtangeev, W.A. Franklin, T. Akdogan, E. Ertan, M.A. Kovash, M. Yuly The sensitivity to three-nucleon forces (3NF) of nucleon-deuteron elastic scattering at large center-of-mass angles is by now well known. Previous p-d experiments (differential cross sections and spin observables) have tended to agree better with calculations that include 3NF, although at energies 200 MeV and above both p-d and n-d cross sections exceed theoretical predictions. We have undertaken a measurement of the dependence on incident neutron energy of the differential cross section for n-d elastic scattering and will report data in the range 130-250 MeV. The sensitivity of the inelastic process d(N,Nnp) to 3NF is not as clear from the calculations; effects are seen to be generally small and to depend strongly on kinematics and on the form of the 3NF used. The theoretical inelastic cross sections in quasi-free kinematics exhibit almost no sensitivity to 3NF, but are not able to reproduce the only data available (d(p,np)p at 200 MeV) in the intermediate energy region. To investigate this problem and to motivate further theoretical work, we have undertaken a measurement of the energy dependence of the d(n,np)n cross section in the incident energy range 100-400 MeV. [Preview Abstract] |
Thursday, October 15, 2009 9:45AM - 10:00AM |
CH.00003: Cross section enhancement in \mbox{\boldmath $pd$} breakup at \mbox{\boldmath $E_p=$} 250 MeV Sho Kuroita, Kenshi Sagara, Yuichiro Eguchi, Keisuke Yashima, Takuro Shishido, Tatsuya Yabe, Masanori Dozono, Yukiko Yamada, Tomotsugu Wakasa, Tetsuo Noro, Hiroaki Matsubara, Juzo Zenihiro, Atsushi Tamii, Hiroyuki Okamura, Kichiji Hatanaka, Toru Saito, Yukie Maeda, Hiroyuki Kamada, Yuji Tameshige Up to a few times enhancement of $pd$ breakup cross section was found in our inclusive experiment of $^2$H$(p,p_1)pn$ at $E_p=$ 250 MeV. The enhancement around $E_{p_1}=$ 150 MeV has been investigated in our exclusive experiment $^2$H$(p,p_1p_2)n$ at the same incident energy in the range of $\theta _2= 35^{\circ}-80^{\circ}$. We found that the exclusive cross section enhancement depend on $\theta _2$. Enhancement of $pd$ elastic scattering cross section has been found also at the incident energy. [Preview Abstract] |
Thursday, October 15, 2009 10:00AM - 10:15AM |
CH.00004: Systematic measurement of quasi-free scattering in \textit{pd} breakup Yuichiro Eguchi, Kenshi Sagara, Sho Kuroita, Keisuke Yashima, Takuro Shishido, Tatsuya Yabe, Souichi Ishikawa Space-star anomaly in \textit{Nd }breakup cross section is well known. There were reports on anomaly in quasi-free scattering (QFS) cross section in \textit{nd }breakup reaction. We measured QFS cross section in \textit{pd} breakup reaction, and compared the data with recent \textit{pd} calculations. It was found that experimental QFS cross sections in \textit{nd}/\textit{pd} breakup reaction are higher/lower than calculations, respectively. [Preview Abstract] |
Thursday, October 15, 2009 10:15AM - 10:30AM |
CH.00005: Quantum Monte Carlo Calculations of Nucleon-Nucleus Scattering R.B. Wiringa, Kenneth M. Nollett, Steven C. Pieper, I. Brida We report recent quantum Monte Carlo (variational and Green's function) calculations of elastic nucleon-nucleus scattering. We are adding the cases of proton-$^{4}$He, neutron-$^{3}$H and proton-$^{3}$He scattering to a previous GFMC study of neutron-$^{4}$He scattering [1]. To do this requires generalizing our methods to include long-range Coulomb forces and to treat coupled channels. The two four-body cases can be compared to other accurate four-body calculational methods such as the AGS equations and hyperspherical harmonic expansions. We will present results for the Argonne v$_{18}$ interaction alone and with Urbana and Illinois three-nucleon potentials. \\[4pt] [1] K.M. Nollett, S. C. Pieper, R.B. Wiringa, J. Carlson, and G.M. Hale, Phys. Rev. Lett. 99, 022502 (2007) [Preview Abstract] |
Thursday, October 15, 2009 10:30AM - 10:45AM |
CH.00006: Calculation of the $nd$ Scattering Lengths by a Realistic Nonlocal Gaussian Potential Kenji Fukukawa, Yoshikazu Fujiwara The calculation of the quartet and doublet $nd$ scattering length, $^{4}a_{nd}$ and $^{2}a_{nd}$, is very difficult because of the deuteron distortion effect, especially for $^{2} a_{nd}$. Even for $^{4}a_{nd}$, it is not easy to keep the numerical accracy since the many channels couple. The well- known corellation between the triton binding energy and $^{2}a_{nd}$ is not completely understood in the calculations including three-body forces. Motivated by the successful application of the our quark-model baryon-baryon interaction fss2 to the triton binding energy without the three-body forces, we reexamine $^{2}a_{nd}$ and $^ {4}a_{nd}$ to study the effect of the nonlocality. We use a nonlocal Gaussian potential based on fss2, which is constructed to make few-baryon calculations much easier than the original interaction. We calculate the eigen-phase shift ${\delta}$ and plot $k\cot{\delta}$ versus $k^{2}$. The charge independence breaking is ignored. The energy region examined is from $E_ {c.m.}$=50 keV to 1 MeV. For the quartet scattering length, $k\cot{\delta}$ is almost linear with respect to $k^{2}$ above $E_{c.m.}$=100 keV. Below 100 keV, the numerical accuracy seems not to be maintained. We have obtained $^{4}a_{nd}$=6.3 fm, which is close to the experimental value $^{4}a^{\rm exp}_{nd}=6.34 \pm $ 0.03 fm. For the doublet scattering length, $^{2}a_{nd}$ is expected to be about 0.8 fm (vs. $^{2}a^{\rm exp}_{nd}=0.65 \pm 0.03$ fm), but we need much wider model space than $J_{\rm max} =2$ and fine mesh points to keep the numerical accuracy of the eigen-phase shifts. [Preview Abstract] |
Thursday, October 15, 2009 10:45AM - 11:00AM |
CH.00007: Neutron-Neutron Scattering Length Determinations Using nd Breakup in Different Nucleon Detection Geometries C.R. Howell, A.S. Crowell, J. Deng, J.H. Esterline, M.R. Kiser, R.A. Macri, S. Tajima, W. Tornow, B.J. Crowe III, R.S. Pedroni, W. Von Witsch, H. Wita{\l}a Significant differences in the value for the $^1S_0$ neutron-neutron ({\it nn}) scattering length($a_{nn}$) have been obtained with neutron-deuteron (nd) breakup measurements made using different detection geometries [1,2]. We report the results of a new determination of $a_{nn}$ made using the nd breakup reaction in recoil proton geometry. The measurements were made at the Triangle Universities Nuclear Laboratory (TUNL) with a neutron beam energy of 19.0 MeV. The momenta of the recoil proton and one of the outgoing neutrons were measured at mean angles of $\theta_p = 45.0^\circ$ and $\theta_n = 52.1^{\circ}$, respectively. Details of the experiment and analysis will be presented, and results will be discussed. \\[4pt] [1] D.E.~Gon$\acute a$lez Trotter {\em et al.}, Phys. Rev. C {\bf 73}, 034001 (2006).\\[0pt] [2] V.~Huhn {\em et al.}, Phys. Rev. Lett. {\bf 85}, 1190 (2000). [Preview Abstract] |
Thursday, October 15, 2009 11:00AM - 11:15AM |
CH.00008: Study of the 1H(d, pp) and 2H(p, pp) breakup reaction in the off-plane star configuration at 13 MeV Yukie Maeda, Hiroki Shimoda, Kenshi Sagara, Yuichiro Eguchi, Noriyuki Fujita, Kichiji Hatanaka, Daisuke Ishikawa, Sho Kuroita, Atsushi Nonaka, Hiroyuki Okamura, Takehiro Sueta, Atsushi Tamii, Keisuke Yashima Recently the data of the differential cross sections for the 1H (d,pp)n breakup reactions in the off-plane star configurations at Ed = 19 MeV are reported. This study covers the kinematical configurations in which all three nucleons in the final state scattered with equal magnitudes of momenta in the c.m. system. The comparison of the data with the Faddeev calculations showed large discrepancies, which we call ``off-plane star anomaly.'' To clarify the cause of this anomaly, we carried out the measurement of the 1H(d, pp)n reactions at Ed = 26MeV at RCNP and that of the 2H(p, pp)n reactions at Ep = 13 MeV at KUTL. By carrying out these experiments, we obtained the data for the almost full angular range of the alpha. We are going to show the preliminary results of the differential cross sections along the S-curve and compare these results to the Faddeev calculations. Our data is well reproduced by the calculations including the Coulomb, which is different from the results of Koln at 19 MeV. [Preview Abstract] |
Thursday, October 15, 2009 11:15AM - 11:30AM |
CH.00009: A novel treatment of the proton-proton Coulomb force in elastic pd scattering and breakup reaction Henryk Witala, Roman Skibinski, Jacek Golak, Walter Gloeckle A novel approach to incorporate the proton-proton Coulomb force into the three-nucleon Faddeev calculations is presented. The main new ingredient is a 3-dimensional screened proton-proton Coulomb t-matrix obtained by a numerical solution of the 3-dimensional Lippmann-Schwinger equation. It is demonstrated numerically that the elastic proton-deuteron observables can be determined directly from the resulting on shell three-nucleon amplitude increasing the screening radius. The screening limit exists without the need of renormalization. Applying renormalization to the proton-proton half-shell t-matrix also breakup observables can be derived as is demonstrated for some exclusive breakup configurations. [Preview Abstract] |
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