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In-medium $mbox{NN}to mbox{N}Delta$ cross section and its dependence on effective Lagrange parameters in isospin-asymmetric nuclear matter

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 نشر من قبل Yingxun Zhang
 تاريخ النشر 2018
  مجال البحث
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The in-medium $NNrightarrow NDelta$ cross section and its differential cross section in isospin asymmetric nuclear medium are investigated in the framework of the one-boson exchange model by including the isovector mesons, i.e., $delta$ and $rho$ mesons. Our results show that the in-medium $NNrightarrow NDelta$ cross sections are suppressed with density increasing, and the differential cross sections become isotropic with the density increasing at the beam energy around the $Delta$ threshold energy. The isospin splitting on the medium correction factor, $R=sigma_{ NNrightarrow NDelta}^*/sigma_{NNrightarrow NDelta}^{text{free}}$ is observed for different channels of $NNto NDelta$, especially around the threshold energy for all the effective Lagrangian parameters. By analyzing the selected effective Lagrangian parameters, our results show that the larger effective mass is, the weaker medium correction $R$ is.



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In this paper, the in-medium $NNrightarrow NDelta$ cross section is calculated in the framework of the one-boson exchange model by including the isovector mesons, i.e. $delta$ and $rho$ mesons. Due to the isospin exchange in the $NNrightarrow NDelta$ process, the vector self-energies of the outgoing particles are modified relative to the incoming particles in isospin asymmetric nuclear matter, and it leads to the effective energies of the incoming $NN$ pair being different from the outgoing $NDelta$ pair. This effect is investigated in the calculation of the in-medium $NNrightarrow NDelta$ cross section. With the corrected energy conservation, the cross sections of the $Delta^{++}$ and $Delta^+$ channels are suppressed, and the cross sections of the $Delta^0$ and $Delta^-$ channels are enhanced relative to the results obtained without properly considering the potential energy changes. Our results further confirm the dependence of medium correction factor, $R=sigma_{ NNrightarrow NDelta}^*/sigma_{NNrightarrow NDelta}^{text{free}}$, on the charge state of $NNrightarrow NDelta$ especially around the threshold energy, but the isospin splitting of medium correction factor $R$ becomes weak at high beam energies.
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