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 DH: Mini-Symposium on the Three-nucleon Force in Few-Body Scattering and Reactions II |
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Chair: June Matthews, Massachusetts Institute of Technology Room: Kings 3 |
Thursday, October 15, 2009 7:00PM - 7:30PM |
DH.00001: Three-nucleon force effects in 3N hadronic reactions Invited Speaker: Results on three-nucleon scattering below the pion production threshold will be presented with emphasis on the need of a three-nucleon force (3NF). The large discrepancies between a theory based on numerical solutions of 3N Faddeev equations with modern NN interactions and data clearly point to the action of 3NF's. Successes and failures in the description of high precision 3N data using in addition to the pairwise interactions present day 3N forces will be discussed. The large theoretically predicted 3NF effects for different 3N polarization observables nourish the hope to pin down the proper spin structure of 3NF's. Especially interesting in this respect are higher energy data which, however, require to study magnitude of relativistic effects. Importance of relativity in 3N continuum, in particular of boost and Wigner spin rotation, on observables in elastic scattering and breakup will be discussed. The boost effects turn out to be significant for the elastic scattering cross section mostly 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, mostly restricted to the backward angles. At energies below $\sim$20 MeV boost and Wigner spin rotation lower the maximum of vector analyzing power increasing the discrepancy between theory and data. This calls for even larger 3NF effects to explain low energy analyzing power puzlle. Higher energy elastic scattering spin observables are only slightly modified by relativity. The selectivity of the breakup singles out this reaction as a tool to look for localized effects which when averaged are difficult to see in elastic scattering. At higher energies this selectivity of breakup allows to find the configurations with large relativistic and/or 3NF effects. [Preview Abstract] |
Thursday, October 15, 2009 7:30PM - 7:45PM |
DH.00002: Three-nucleon force effects in three-nucleon continuum states Souichi Ishikawa The introduction of the two-pion exchange three-nucleon force (2$\pi$E-3NF) into nuclear Hamiltonian is known to be unsuccessful in explaining the existing discrepancies between calculations with two-nucleon forces and experimental data for some polarization observables, such as $A_y(\theta)$ and $T_{21}(\theta)$ in nucleon-deuteron scattering. A phenomenological 3NF to reproduce such observables at a low energy is examined for those at higher energies. For proton-deuteron scattering, effects of the long-range proton-proton Coulomb potential are properly included by solving a Coulomb-modified Faddeev integral equation in coordinate space. Also studies of searching for realistic mechanisms to produce the same effects as the phenomenological 3NF will be reported. [Preview Abstract] |
Thursday, October 15, 2009 7:45PM - 8:00PM |
DH.00003: Universal Correlations in ``Pion-less'' Effective Field Theory: 3, 4 and 6 Nucleons Harald W. Griesshammer, Johannes Kirscher, Deepshikha Shukla, Hartmut M. Hofmann In a feasibility study for chiral EFT and heavier systems, we analyse bound and scattering properties of 3-, 4- and 6-nucleon systems in the Effective Field Theory ``without pions'' at next-to-leading order using the Refined Renormalisation Group Method with full Coulomb treatment, with 3N-interactions, phase-equivalent potentials and a range of cut-offs for convergence checks. For correlations between the triton binding energy $B_{3H}$, its charge radius and the binding energy of ${}^4$He, convergence is consistent with an expansion parameter $\approx\frac{1}{3}$. No 4N-interaction is needed for renormalisation. With the correlation between $B_{3H}$ and the $^3$He binding energy iso-spin symmetric at NLO, the model-independent difference at the physical $B_{3H}$, $[0.10\mp 0.03]$MeV, is the same both in magnitude and uncertainty as estimates from charge-symmetry breaking. In the first scattering calculation for $A\ge4$, we found a correlation between $B_{3H}$ and the real part of the singlet scattering length of ${}^3$He--n scattering similar to the Tjon line. Finally, we address convergence of ``pion-less'' EFT in the halo nucleus ${}^6$He. [Preview Abstract] |
Thursday, October 15, 2009 8:00PM - 8:15PM |
DH.00004: Measurement of tensor analyzing powers of $pd$ capture at RCNP Kenshi Sagara, Yuji Tameshige, Kichiji Hatanaka, Atsushi Tamii, Sho Kuroita, Hiroaki Matsubara, Hiroyuki Okamura, Kimiko Sekiguchi, Yasuyuki Sakemi, Kunihiro Fujita, Tomotsugu Wakasa, Takahiro Kawabata, Yohei Shimizu, Yukie Maeda Tensor analyzing powers $A_{xx}$, $A_{yy}$ and $A_{zz}$ of $pd$ radiative capture at $E_d=$ 196 MeV were measured again at RCNP. Results are basically consistent with our previous data, i.e., $A_{xx}$ and $A_{zz}$ are about twice larger in their absolute values than theoretical predictions. Similar discrepancy has been found also at $E_d=$ 137 MeV. [Preview Abstract] |
Thursday, October 15, 2009 8:15PM - 8:30PM |
DH.00005: Precision Measurement of the n-$^3$He Incoherent Scattering Length Using Neutron Interferometry Fred Wietfeldt, Michael Huber, Timothy Black, Muhammad Arif, Wangchun Chen, Tom Gentile, Dan Hussey, Dimitry Pushin, Liang Yang The low energy neutron-$^3$He scattering lengths are important for testing nuclear potential models that include three nucleon forces, effective field theories for few-body nuclear systems,and neutron scattering measurements of quantum excitations in liquid helium. We report the first measurement of the $n$-$^3$He incoherent scattering length using neutron interferometry: $b_i' = (-2.512\pm 0.012\mbox{ statistical} \pm0.014\mbox{ systematic})$ fm.This is in good agreement with a recent calculation using the AV18+UIX potential [1], but disagrees with a previous measurement using pseudomagnetic spin rotation [2]. This work also demonstrates the first use of a polarized nuclear target in a neutron interferometer.\\[4pt] [1] H.~M.~Hofmann and G.~M.~Hale, Phys. Rev. C {\bf 68}, 021002(R) (2003).\\[0pt] [2] O. Zimmer {\em et al.}, EPJdirect C {\bf A1}, 1 (2002). [Preview Abstract] |
Thursday, October 15, 2009 8:30PM - 8:45PM |
DH.00006: Three-Nucleon Scattering with a Possible Long-Range Force Shinsho Oryu, Yasuhisa Hiratsuka, Shuichi Gojuki, Tetsuo Sawada, Takashi Watanabe Three-nucleon scattering problems have been intensely investigated during almost a half century in an effort to constrain models of the nuclear force. However, we still see discrepancies between theoretical predictions based on certain nuclear forces and the experimental data. Two decades ago, one of the authers (T.S.), in search of a possible long range force between hadrons, analysed S-wave phase shift data for proton-proton scattering. He found that it is consistent with a potential corresponding to a strong Van der Waals force. Here, we try to reproduce modern nuclear phase shifts by replaceing the $\sigma$-meson term of the Paris potential with a Van der Waals potential $C'/r(r+a)^5$ having two parameters, the range $a$ and the depth $C'$. We obtained a reasonable fit to the phase shifts $^1S_0$, $^3S_1$-$^3D_1$, $^1P_1$, $^1D_2$,$^1F_3$,$^1G_4$,$^3P_1$,$^3D_2$,$^3F_3$,$^3G_4$ and $^3D_3-^3G_3$ by using the GSE method. Preliminary calculations for three-body $pd$ elastic scattering were performed to obtain sample physical observables using the new potentials plus other states from the original Paris (PEST) potentials. We found differences in the three-body observables compared with the original nuclear force results. [Preview Abstract] |
Thursday, October 15, 2009 8:45PM - 9:00PM |
DH.00007: Long Range Component of the Nuclear Potential Tetsuo Sawada Possible long range force of the strong Van der Waals type is searched in the nuclear potential. For the case of the short range potential, the amplitude $A(s,t)$ is regular at $t=0$, on the other hand, when the potential is long range, namely $V(r) \sim -C/r^{\alpha}$, the extra branch point $ A(s,t)= C' (-t)^{\gamma}+ \cdots$ with $\gamma=(\alpha-3)/2$ appears at $t=0$. Therefore if we try the polynomial fit to the amplitude, it must deviate rather abruptly from the fit in the small neighborhood of $t=0$. In terms of the partial wave, the extra branch point of the once subtracted S-wave amplitude $(a_{0}(\nu)-a_{0}(0))/\nu$ becomes a cusp $ C'' \sqrt{\nu}$ when the long range potential is the Van der Waals of the London type, namely $\alpha=6$, where $\nu$ is the center of mass momentum squared. In order to see the cusp as clearly as possible, we must subtract the near-by unitarity cut (in $\nu \geq 0$) and the one-pion exchage cut (in $\nu \leq -\mu^2/4$). By fitting to the cusp, the parameters of the long range potential are determined: $\alpha=6.09$ and $C=0.170$, in which the Compton wave length of the charged pion is used as the unit of the length. [Preview Abstract] |
Thursday, October 15, 2009 9:00PM - 9:15PM |
DH.00008: Applications of local chiral N$^2$LO three-nucleon interaction to nuclear structure and reactions Petr Navratil, Sofia Quaglioni We overview recent results obtained with the three-nucleon (NNN) interaction derived within the chiral effective field theory at the N$^2$LO order regulated with a magnitude of the momentum transfer [1]. The regulated NNN interaction is then local in the coordinate space, which is an advantage for some many-body techniques. This interaction in combination with a chiral N$^3$LO nucleon-nucleon potential [2] proved to be successful in describing $A$=3 and 4 binding energies, radii [3,4] and scattering lengths [4], the structure of mid-$p$-shell nuclei [3], photo-disintegration of $^4$He [5], and $n-^3$H and A=3 scattering [6,7]. [1] P. Navratil, Few Body Syst. 41, 117 (2007). [2] D. R. Entem and R. Machleidt, Phys. Rev. C 68, 041001(R) (2003). [3] P. Navratil, V. G. Gueorguiev, J. P. Vary, W. E. Ormand, A. Nogga, Phys. Rev. Lett. 99, 042501 (2007). [4] A. Kievsky {\it et al.}, J. Phys. G 35, 063101 (2008). [5] S. Quaglioni and P. Navratil, Phys Lett B 652, 370 (2007). [6] M. Viviani {\it et al.}, arXiv:0812.3547 [nucl-th]. [7] L. E. Marcucci {\it et al.}, arXiv:0905.3306 [nucl-th]. [Preview Abstract] |
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