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 KC: Nuclear Reactions: Hadrons/Light Ions |
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Chair: Hiroyoshi Sakurai, RIKEN Room: Kohala 1 |
Saturday, October 17, 2009 9:00AM - 9:15AM |
KC.00001: Study of charged pion photoproduction on deuteron and proton Yuncheng Han Pion photoproduction on nucleon and nuclei is an important tool to explore hadron structure and meson-baryon interaction. Charged pion production $\gamma $d$\to \pi ^{-}$ pp and $\gamma $d$\to \pi ^{+}\pi ^{-}$np with $E_{\gamma }$from 0.67 to 1.1 GeV, and $\gamma $p$\to \pi ^{+}\pi ^{-}$ p with$ E_{\gamma }$from 0.67 to 0.92 GeV were measured with the second generation of Neutral Kaon Spectrometer, and tagged photon facility at the Laboratory of Nuclear Science, Tohoku University. The aim is to investigate the pion photoproduction process on the nucleus in the second and third resonance regions. The quasi-free process on bound proton and neutron inside deuteron and also non-quasi-free contributions were derived individually. The study on the proton follows our previous research with $E_{\gamma }$from 0.8 to 1.1 GeV.The excitation function of $\gamma $d$\to \pi ^{-}$pp will be reported with an energy bin of 6 MeV. This will be an improvement on the world data with the energy resolution of 10 MeV. A new method of the tagged photon energy calibration using the kinematically complete measurement of d($\gamma $, $\pi ^{- }$pp) will be introduced. The $\pi ^{+}\pi ^{-}$ photoproduction on bound proton in deuteron will be reported. The cross sections for $\gamma $d$\to \pi ^{+}\pi ^{-}$np reaction with intermediate double delta channel were derived. This reaction is one of the important non-quasi-free processes, and is expected to be relevant to the ABC effect. [Preview Abstract] |
Saturday, October 17, 2009 9:15AM - 9:30AM |
KC.00002: Feeding of the 1$^{-}$ isomer in $^{176}$Lu in neutron induced reactions N. Fotiades, M. Devlin, R.O. Nelson The ($n,n^{\prime}\gamma$) reaction was used to measure $\gamma$-ray excitation functions in $^{175,176}$Lu with a $^{nat}$Lu target. The data were taken using the GEANIE spectrometer comprised of 26 Ge detectors. The pulsed neutron source of the LANSCE/WNR facility provided neutrons with incident energies from 1 to 300~MeV, determined using the time-of-flight technique. The excitation functions for 111 $\gamma$-rays from several reaction channels were determined, among them two transitions feeding directly the 1$^{-}$, 3.664h isomer, and one transition feeding directly the 7$^{-}$, 3.76${\times}10^{10}y$ ground state in $^{176}$Lu. Both states $\beta$-decay to $^{176}$Hf. The Lu-Hf radioactive decay system, with a half-life of $\sim$37 billion years from the ground state, is a chronometer for dynamic processes on a stellar time scale. Recent anomalies have questioned the accuracy of this chronometer, one possible explanation being that astrophysical ($n,n^{\prime}$) reactions populate the 1$^{-}$ isomer and reduce the effective half-life of $^{176}$Lu. The excitation functions for the three $^{176}$Lu transitions from the present experiment can be compared to nuclear reaction model calculations that predict the $^{176g}$Lu($n,n^{\prime}\gamma$)$^{176m}$Lu cross section, thus providing an important check for such models. Attempts to improve the experimental results to obtain absolute partial $\gamma$-ray cross sections for more $\gamma$-rays feeding the isomer and ground state of $^{176}$Lu in future GEANIE experiments will be discussed. This work was supported by U.S. DOE DE-AC52-06NA25396. [Preview Abstract] |
Saturday, October 17, 2009 9:30AM - 9:45AM |
KC.00003: Proton pairing correlation studies A. Roberts, J.J. Kolata, A. Villano, F.D. Becchetti, J.P. Schiffer, J.A. Clark, B.P. Kay, K.E. Rehm, S.J. Freeman, A.M. Howard A program to study proton pairing correlations in nuclei relevant for neutrinoless double $\beta$ decay has been initiated at Notre Dame. The results will complement neutron-pairing studies [S.J. Freeman, et al., Phys. Rev. C75, 05301R (2007)], helping to constrain theoretical calculations of this decay mode. High-precision measurements of the ($^3$He,n) reaction using a pulsed beam and a large neutron detector are in progress. The necessary 250 keV resolution at a neutron energy of 25 MeV is well within reach. Recent results obtained with a $^{26}$Mg target will be presented. This well-studied system serves as a calibration for measurements on $^{74,76}$Ge and other targets. Ground-state cross sections will be obtained with relative precison of $<$5\% and absolute accuracy of $<$10\%. Proton pairing vibrations (if any) will be identified and measured. [Preview Abstract] |
Saturday, October 17, 2009 9:45AM - 10:00AM |
KC.00004: Fission cross section measurements at LANSCE Fredrik Tovesson, Tony Hill Neutron induced fission cross sections of actinides are measured at the Los Alamos Neutron Science Center (LANSCE) in support of the Advanced Fuel Cycle Initiative (AFCI) and the National Nuclear Security Administration (NNSA). Nuclear technologies are increasingly dependent on advanced simulations for design and licensing requirements, and nuclear cross section data are important input parameters for the simulation tools. Fast nuclear reactor and stockpile stewardship applications often share nuclear data needs and requirements, and the LANSCE neutron source is ideal for measuring many of these data. The fission cross section measurements are guided by sensitivity studies performed in support of the AFCI program, as well as requests from NNSA. Recent results for the Pu-239 and Pu-241 fission cross sections from 0.01 eV to 200 MeV will be presented, and the discrepancy with current evaluations of the Pu-241 fission cross section discussed. Ongoing activities to extend the fission program will be presented, such as the development of a Time Projection Chamber (TPC) to significantly improve the experimental accuracies in fission cross section measurements. [Preview Abstract] |
Saturday, October 17, 2009 10:00AM - 10:15AM |
KC.00005: Study of medium effect in NN interaction by using (p,pn) reactions Yukiko Yamada, Tetsuo Noro, Takumi Imamura, Tomotsugu Wakasa, Masanori Dozono, Yoshihide Matsuda, Midori Okamoto, Sho Kuroita, Yuichiro Eguchi, Keisuke Yashima, Tatsuya Yabe, Harutaka Sakaguchi, Kichiji Hatanaka, Hiroyuki Okamura, Atsushi Tamii, Yusuke Yasuda, Juzo Zenihiro, Hiroaki Matsubara, Daiki Ishikawa, Yukie Maeda, Atsusi Nonaka, Noriyuki Fujita, Toru Saito, Yasuhiro Sakemi, Hidetomo P. Yoshida Exclusive measurement of nucleon quasifree scattering is a direct tool to investigate how nucleon-nucleon ($NN$) interaction changes in the nuclear medium. We measured analyzing powers ($A_y$) for 1s$_{1/2}$-knockout ($p$,$pn$) reactions on light nuclei aiming at studying such modification. The experiment was performed at RCNP with a 392 MeV proton beam. It is found that the $^{12}$C($p$,$pn$) exclusive $A_y$ data are mostly consistent with impulse calculations based on the $p$-$n$ interaction in free space, in contrast to the ($p$,2$p$) case, where a strong suppression of $A_y$ is observed. This large imbalance between the ($p$,$pn$) and ($p$,2$p$) results is difficult to explain in conventional models. [Preview Abstract] |
Saturday, October 17, 2009 10:15AM - 10:30AM |
KC.00006: Hadronic description for the $\phi$-photoproduction near the threshold Huiyoung Ryu, Atsushi Hosaka, Hyun-Chul Kim The Pomeron-exchange plays an important role in the $\phi$-photoproduction from the nucleon. It describes well the increasing behavior of the production rate at high energies, a consequence of the Regge theory with the Pomeron trajectory $\alpha(t)$. Recently LEPS has reported a bump-like structure in $d\sigma/d t$ near the threshold energy. Within the Regge theory, the second Pomeron is examined, but it is difficult to reproduce such a narrow bump structure. Besides the Pomeron-exchange, we could expect hadronic processes relevant in the threshold region. In this work, we attempt a hadronic description for the $\phi$-photoproduction. Since the OZI mechanism suppresses Born diagrams at the tree level, we consider loop contributions. We pay special attention to the gauge invariant set of diagrams and momentum ($s, t$ and $u$) dependence of the amplitude. We discuss that some features of momentum dependence may help to understand the underlying reaction mechanism. We also discuss that some correlated loops may express effectively a meson exchange diagram, for instance, in the $t$-channel. [Preview Abstract] |
Saturday, October 17, 2009 10:30AM - 10:45AM |
KC.00007: Capabilities of the Recent Absolute Total \textit{np} and \textit{pp} Cross Section Determinations to Predict Experimental Observables A.B. Laptev, R.C. Haight, R.A. Arndt, W.J. Briscoe, M.W. Paris, I.I. Strakovsky, R.L. Workman The absolute total cross sections for \textit{np} and \textit{pp} scattering below 1000 MeV are determined based on partial-wave analyses (PWAs) of nucleon-nucleon scattering data. These cross sections are compared with most recent ENDF/B and JENDL data files, and the Nijmegen PWA. Systematic deviations from the ENDF/B and JENDL evaluations are found to exist in the low-energy region. Comparison of the \textit{np} evaluation with the result of most recent \textit{np} total cross section measurement made at LANL in the energy range from 9 to 500 MeV will be discussed. This measurement was not used in the evaluation database. A comparison was done to check a quality of evaluation and its prediction capabilities. Excellent agreement was found between the new experimental data and our PWA prediction. [Preview Abstract] |
Saturday, October 17, 2009 10:45AM - 11:00AM |
KC.00008: Systematic measurement of ``star anomaly'' in pd breakup around 10 MeV K. Yashima, K. Sagara, Y. Maeda, S. Kuroita, H. Shimoda, T. Sueta, Y. Eguchi, T. Shishido, T. Yabe In 3-nucleon breakup around 10 MeV, there is cross section anomaly when three outgoing nucleons form an equilateral triangle (star configuration) perpendicular to the beam axis. We have measured pd breakup cross section at various star configurations which are inclined to the beam axis, and compared the data with recent pd breakup calculations. Angular dependence and energy dependence of star anomaly will be discussed. [Preview Abstract] |
Saturday, October 17, 2009 11:00AM - 11:15AM |
KC.00009: Neutron density distributions of $^{204,206,208}$Pb observed via polarized proton elastic scattering Juzo Zenihiro, Harutaka Sakaguchi, Masaru Yosoi, Yusuke Yasuda, Satoru Terashima, Tetsuya Murakami, Satoshi Kishi, Masatoshi Itoh, Hidetomo Yoshida, Makoto Uchida, Hiroyuki Takeda, Yohei Nakatsugawa Cross sections and analyzing powers of polarized proton elastic scattering from $^{204,206,208}$Pb at $E_p=$295 MeV have been measured with the high-resolution magnetic spectrometer ``Grand Raiden'' at RCNP. For the data analysis, special cares for trigger efficiencies, charge collections of Faraday Cups, and so on, have been paid to deduce absolute values of the cross sections in the measurement and data reduction. We have used relativistic impulse approximation (RIA) with medium-modified nucleon-nucleon interaction and realistic point proton density distributions unfolded from charge distributions obtained by electron scattering data. We will show preliminary results of the deduced neutron density distributions of $^{204,206,208}$Pb and their error envelopes. [Preview Abstract] |
Saturday, October 17, 2009 11:15AM - 11:30AM |
KC.00010: Measurement of deep hole states in $^{39}$K by $^{40}$Ca$(\overrightarrow{p},2p)$ reaction at 392~MeV Yusuke Yasuda, Harutaka Sakaguchi, Kichiji Hatanaka, Masaru Yosoi, Juzo Zenihiro, Tetsuo Noro, Tomotsugu Wakasa, Kunihiro Fujita, Takahiro Kawabata, Yasuhiro Sakemi, Masatoshi Itoh, Hidetomo Yoshida, Takashi Ishida, Hiroyuki Takeda, Makoto Uchida, Satoru Terashima, Yohei Shimizu, Yuji Tameshige The spectroscopic factor and the width of 1s$_{1/2}$ state in $^{40}$Ca have been deduced from $^{40}$Ca($p,2p$) reaction experiment. In the experiment the cross sections and analyzing powers of the $^{40}$Ca($\overrightarrow{p},2p$) reaction at $392$~MeV have been measured. The strength distributions of the single-hole states in $^{39}$K were successfully obtained by multipole decomposition analysis on the basis of the angular momentum $L$. The central value and the width (FWHM) of the obtained strength distribution of 1s$_{1/2}$ are 52~MeV and 22~MeV. The obtained spectroscopic factor of 1s$_{1/2}$ state is about 60\% of the $2J+1$. This value will be compared with the theoretical calculations that include short-range correlations and tensor correlations. [Preview Abstract] |
Saturday, October 17, 2009 11:30AM - 11:45AM |
KC.00011: Updates on neutron induced measurements on Gadolinium isotopes at the DANCE array Dugersuren Dashdorj, Gary Mitchell, Bayarbadrakh Baramsai, Andrii Chyzh, Carrie Walker The gadolinium isotopes are important for practical applications such as reactor applications, medicine and astrophysics. Decay gamma rays following neutron capture on Gd isotopes are detected by the DANCE array, which is located at flight path 14 at the Lujan Neutron Scattering Center at Los Alamos National Laboratory. The high segmentation and close packing of the detector array enable gamma-ray multiplicity measurements. The singles ?-ray spectrum for each multiplicity can be separated by their DANCE cluster multiplicity. The gamma- ray multiplicities and energy spectra for different multiplicities can be measured and analyzed for spin and parity determination of the resolved resonances. [Preview Abstract] |
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