14,807 research outputs found
Stability of P11 Resonance Extracted from pi-N Data
We address a question about how much resonance poles and residues extracted
from data depend on a model used for the extraction, and on the precision of
data. We focus on the P11 pi-N scattering and use the dynamical coupled-channel
(DCC) model developed in Excited Baryon Analysis Center (EBAC) at JLab. We
examine the model-dependence of the poles by varying parameters largely within
the EBAC-DCC model. We find that two poles associated with the Roper resonance
are fairly stable against the variation. We also study the stability of the
Roper poles against different analytic structure of the P11 amplitude below
pi-N threshold by using a bare nucleon model. We again find a good stability of
the Roper poles.Comment: 4 pages, 4 figures, Contribution to the proceedings of 12th
International Conference on Meson-Nucleon Physics and the Structure of the
Nucleon (MENU2010), Williamsburg, USA, May 31-June 4 201
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
Neutrino Induced 4He Break-up Reaction -- Application of the Maximum Entropy Method in Calculating Nuclear Strength Function
The maximum entropy method is examined as a new tool for solving the
ill-posed inversion problem involved in the Lorentz integral transformation
(LIT) method. As an example, we apply the method to the spin-dipole strength
function of 4He. We show that the method can be successfully used for inversion
of LIT, provided the LIT function is available with a sufficient accuracy.Comment: 5 pages, 2 figures. Poster presented by TM at the International
Workshop on Neutrino-Nucleus Interaction in the Few-GeV Region (NuInt15),
Novenber 16-21 2015, Osaka, Japa
Bridging over p-wave pi-production and weak processes in few-nucleon systems with chiral perturbation theory
I study an aspect of chiral perturbation theory (\chi PT) which enables one
to ``bridge'' different reactions. That is, an operator fixed in one of the
reactions can then be used to predict the other. For this purpose, I calculate
the partial wave amplitude for the p-wave pion production (pp\to pn\pi^+) using
the pion production operator from the lowest and the next nonvanishing orders.
The operator includes a contact operator whose coupling has been fixed using a
matrix element of a low-energy weak process (pp\to de^+\nu_e). I find that this
operator does not reproduce the partial wave amplitude extracted from
experimental data, showing that the bridging over the reactions with
significantly different kinematics is not necessarily successful. I study the
dependence of the amplitude on the various inputs such as the NN potential, the
\pi N\Delta coupling, and the cutoff. I argue the importance of a higher order
calculation. In order to gain an insight into a higher order calculation, I add
a higher order counter term to the operator used above, and fit the couplings
to both the low-energy weak process and the pion production. The energy
dependence of the partial wave amplitude for the pion production is described
by the operator consistently with the data. However, I find a result which
tells us to be careful about the convergence of the chiral expansion for the
pp\to pn\pi^+ reaction.Comment: 30 pages, 13 figures, figures changed, compacted tex
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