15,726 research outputs found
A Feynman graph selection tool in GRACE system
We present a Feynman graph selection tool {\tt grcsel}, which is an
interpreter written in C language. In the framework of {\tt GRACE}, it enables
us to get a subset of Feynman graphs according to given conditions.Comment: 3 pages, 2 figures, Latex, ACAT200
Neutrino Oscillations in Intermediate States.II -- Wave Packets
We analyze oscillations of intermediate neutrinos in terms of the scattering
of particles described by Gaussian wave packets. We study a scalar model as in
a previous paper (I) but in realistic situations, where the two particles of
the initial state and final state are wave packets and neutrinos are in the
intermediate state. The oscillation of the intermediate neutrino is found from
the time evolution of the total transition probability between the initial
state and final state. The effect of a finite lifetime and a finite relaxation
time are also studied. We find that the oscillation pattern depends on the
magnitude of wave packet sizes of particles in the initial state and final
state and the lifetime of the initial particle. For eV, the oscillation probability deviates from that of the standard
formula if the wave packet sizes are around m for 0.4 MeV neutrino.Comment: 29 pages, 11 figures. typos corrected, appendix adde
Operation of Faddeev-Kernel in Configuration Space
We present a practical method to solve Faddeev three-body equations at
energies above three-body breakup threshold as integral equations in coordinate
space. This is an extension of previously used method for bound states and
scattering states below three-body breakup threshold energy. We show that
breakup components in three-body reactions produce long-range effects on
Faddeev integral kernels in coordinate space, and propose numerical procedures
to treat these effects. Using these techniques, we solve Faddeev equations for
neutron-deuteron scattering to compare with benchmark solutions.Comment: 20 pages, 8 figures, to be published in Few-Body System
photoproduction off the deuteron and low-energy -nucleon interaction
We study photoproduction off the deuteron () at a
special kinematics: GeV of the photon beam energy and of the scattering angle of the proton. This kinematics is ideal to
extract the low-energy -nucleon scattering parameters such as (scattering length) and (effective range) because the
-nucleon elastic scattering is significantly enhanced. We show that if a
ratio , the cross section divided by the cross section convoluted with the proton momentum distribution in
the deuteron, is measured with 5% error, () can be determined at the precision of 0.1 fm
(0.5 fm), significantly narrowing down the currently estimated range
of the parameters. The measurement is ongoing at the Research Center for
Electron Photon Science (ELPH), Tohoku University.Comment: 4 pages, 5 figures, Contribution to the Proceedings for 8th
International Conference on Quarks and Nuclear Physics (QNP2018), November
13-17, 2018, Tsukuba, Japa
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