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 1WG: Workshop 7A: Neutrino Astrophysics |
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Sponsoring Units: DNP JPS Chair: Toshitaka Kajino, National Astronomical Observatory Japan Room: Ritz-Carlton Hotel Plantation 2 |
Sunday, September 18, 2005 9:00AM - 9:30AM |
1WG.00001: Nuclear structure, nuclear force and spin-isospin excitations in stellar processes Invited Speaker: The spin-isospin Nucleon-Nucleon (\textit{NN}) force plays crucial roles in determining shell structure of exotic nuclei. Even magic numbers can be destroyed. We will overview what changes can be expected in exotic nuclei on single-particle properties and spin-isospin excitations, including Gamov-Teller processes. The Gamov-Teller and other weak processes can be well studied by recent shell model calculations with newly determined effective \textit{NN} interactions. We shall survey such new results, and look at possible implications on stellar processes. The calculations include full pf-shell calculations and pf+g$_{9/2}$ calculations. We may discuss the stability of $^{78}$Ni core in exotic Ni isotopes and its implications in the r-process. Within the pf-shell, the Gamov-Teller properties will be assessed in view of their influences on stellar processes. Such studies will provide us with some information on neutrino reactions. [Preview Abstract] |
Sunday, September 18, 2005 9:30AM - 10:00AM |
1WG.00002: Nuclear Reactions with light ion and photon beams: Contributions to Neutrino Astrophysics Invited Speaker: In the star burning, the reaction processes such as charge exchange, inelastic scattering and fusion take place on the basis of the star hierarchy structure with various densities and temperatures. Experimental information from the nuclear reactions has been applied to the astrophysical phenomena observed by telescopes and to understand the isotope composition of meteorites in the solar and galaxy systems. For examples, charge-exchange reaction cross-sections relate closely to$\beta $-decay and electron capture processes. From the observations of isoscalar giant monopole resonances in nuclei provided via inelastic scattering, one can argue the nuclear incompressibility, which is one of the important parameters for the supernova explosions and neutron star structure. Studies of photo-nuclear reactions are deeply related to astrophysics to understand the origin of element synthesis in the galaxy since the nuclear synthesis is made in the environment with ultra high intensity photons in supernovae. In my talk, I would like to show the recent results from the ($^{3}$He,t) and (t,$^{3}$He) and ($\alpha $,$\alpha$$'$) experiments with light ion beams in relation to the neutrino astrophysics. I also show the future possibilities of photoreactions at new facilities in Japan. [Preview Abstract] |
Sunday, September 18, 2005 10:00AM - 10:30AM |
1WG.00003: $^7$Be + p and $^3$He + $^4$He fusion reactions and neutrino astrophysics Invited Speaker: The $^7$Be + p and $^3$He + $^4$He fusion reactions are important steps in the solar p-p chain that lead to the production of neutrinos from decay of $^8$B and $^7$Be in the Sun. Until recently the uncertainty in the $^7$Be + p S-factor was the largest error in the calculated solar model production rate of neutrinos from $^8$B decay, while now it is no longer important [1,2]. The uncertainty in the $^3$He + $^4$He S-factor is now the largest nuclear physics uncertainty in the calculated solar model production rate of neutrinos from both $^8$B and $^7$Be decay [2]. I will discuss the current status of these fusion experiments and the implications for neutrino physics including limits on sterile neutrinos. \newline \newline [1] A. R. Junghans et al., Phys. Rev. C 68, 065803 (2003). \newline [2] J. N. Bahcall and M. H. Pinsonneault, Phys. Rev. Lett. 92, 121301 (2004). [Preview Abstract] |
Sunday, September 18, 2005 10:30AM - 11:00AM |
1WG.00004: New shell model calculations of neutrino-nucleus scattering cross sections Invited Speaker: Neutrino-nucleus reactions induced by charged and neutral currents are investigated by using new shell model Hamiltonians, where nucleon-nucleon interactions in the spin-isospin channel are improved to take into account properly the shell evolution properties. Quenching in the Gamow-Teller transition strength is somewhat weakened and agreement with experimental value is improved in several p-shell nuclei. Better agreement with observed values is systematically obtained for the magnetic moments in p-shell nuclei. Neutrino-nucleus cross sections are calculated for p-shell nuclei, for example, in $^{12}$C and$^{ 11}$B for supernovae and accelerator neutrinos by using the new shell model Hamiltonians. Change of the charged and neutral current cross sections are discussed by comparing with those obtained by conventional shell model Hamiltonians. Reactions on$^{ 4}$He as well as heavy nuclei are also studied. Effects of the spreading in the strength on the cross sections are shown to be important. [Preview Abstract] |
Sunday, September 18, 2005 11:00AM - 11:30AM |
1WG.00005: A Solution to LSND's Second Puzzle Invited Speaker: We present a calculation of the $^{12}C(\nu_{\mu},\mu^{-})^{12}N^{*}$ flux-averaged, inclusive cross section from the Liquid Scintillator Neutrino Detector. The calculation is based upon a relativistic Fermi gas model that has been corrected for long range correlation and binding energy effects. The long range correlation effects are introduced via a non-local, momentum dependent potential in the kinematics of the lepton-nucleon vertex. The potential parameters, most importantly the effective mass $M^{*} = M_{nucleon}/1.4$, have been tuned to match electron scattering data in the appropriate energy range. The binding energy appropriate for $^{12}N$, 27 MeV, is used in stead of the traditional 25 MeV found from the electron data. The result agrees well with the LSND measurement of $10.5\times 10^{-40} cm^{2}$. The calculation makes up for its lack of theoretical rigor in its intuitive simplicity and reliance on well established electron scattering measurements. [Preview Abstract] |
Sunday, September 18, 2005 11:30AM - 12:00PM |
1WG.00006: Neutrino-nucleus cross sections and their role in supernovae Invited Speaker: Interactions between neutrinos and nuclei play a crucial role in core-collapse supernovae. The intense neutrino flux carries away 99\% of the total energy released in the explosion. The dynamics of core collapse and formation (and propagation) of the shock in supernova models are sensitive to the rates used for interactions of neutrinos (and electrons) with nuclei. The distribution of isotopes that are synthesized and ejected into the interstellar medium is also influenced by neutrino-nucleus interactions. Terrestrial measurements of the neutrino spectra from a nearby supernova could give valuable information, but the interpretation of such measurements can be improved by better understanding of the neutrino interactions in the detector material. Neutrino interactions at energies relevant for supernovae (tens of MeV) are quite dependent on the structure of the nucleus. Accurate cross section measurements have been made on only one nucleus, $^{12}$C\@. The reliability of theoretical models for cross sections is uncertain and is likely to depend upon the quality of available nuclear structure information. A collaboration, {\it $\nu$SNS}, has recently proposed to build a facility for measurements of neutrino-nucleus cross sections at the Spallation Neutron Source (SNS), currently under construction at ORNL\@. Detectors for {\it $\nu$SNS} have been designed to be resued for multiple nuclear targets. The charged-current cross section for any particular target could be measured with 10\% accuracy in less than one year of operation with a 20-ton instrument. The role of neutrino-nucleus interactions in supernovae and the proposed experimental program of cross section measurements at the SNS will be presented. [Preview Abstract] |
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