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Optimization of Neutrino Oscillation Parameters Using Differential Evolution

Communications in Theoretical Physics 2013年第3期59卷 324-330页

作者： Ghulam Mustafa Faisal Akram Bilal Masud Centre for High Energy Physics University of the PunjabLahore(54590)Pakistan

We show how the traditional grid based method for finding neutrino oscillation parameters △m2 and tan2θ can be combined with an optimization technique, Differential Evolution （DE）, to get a significant decrease in computer processing time required to obtain minimal chi-square （χ2） in four different regions of the parameter space. We demonstrate efficiency for the two-neutrinos case. For this, the χ2 function for neutrino oscillations is evaluated for grids with different density of points in standard allowed regions of the parameter space of △m2 and tan2θ using experimental and theoretical total event rates of ehlorine （Homestake）, Gallex＋GNO, SAGE, Superkamiokande, and SNO detectors. We find that using DE in combination with the grid based method with smail density of points can produce the results comparable with the one obtained using high density grid, in much lesser computation time.

关键词： solar neutrinos neutrino masses and mixing numerical optimization

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Re-examination of constraints on the Maxwell-Boltzmann distribution by Helioseismology

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Chinese Physics C 2013年第10期37卷 19-21页

作者：何建军张立勇侯素青徐世伟 Institute of Modern Physics Chinese Academy of Sciences School of Nuclear Science and Technology Lanzhou University University of Chinese Academy of Sciences

Nuclear reactions in stars occur between nuclei in the high-energy tail of the energy distribution and are sensitive to possible deviations from the standard equilibrium thermal-energy distribution, the well-known Maxwell- Boltzmann Distribution （MBD）. Strong constraints on such deviations were made previously with the detailed he- lioseismic information of the solar structure. With a small deviation parameterized with a factor exp[-8（E/kT）2], it was shown 8 restricted between -0.005 and ~0.002. These constraints have been carefully re-examined in the present work. We find that a normalization factor was missed in the previous modified MBD. In this work, the nor- realization factor c is calculated as a function of 8. It shows the factor c is almost unity within the range 0〈8~.〈0.002, which supports the previous conclusion. However, it demonstrates that 8 cannot take a negative value from the normalization point of view. As a result, a stronger constraint on 8 is defined as 0~〈 8 40.002. The astrophysical implication on the solar neutrino fluxes is simply discussed based on a positive 8 value of 0.003. The reduction of the 7Be and SB neutrino fluxes expected from the modified MBD can possibly shed alternative light on the solar neutrino problem. In addition, the resonant reaction rates for the 14N（p, /）150 reaction are calculated with a standard MBD and a modified MBD, respectively. It shows that the rates demonstrates the importance and necessity of experimental temperatures. are quite sensitive even to a very small 8. This work verification or testing of the well-known MBD at high

关键词： solar interior helioseismology statistical mechanics solar neutrinos

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